ICOS in scientific publications

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ICOS related publications are publications that used ICOS data or knowledge based on ICOS data, or is based on science that is relevant for ICOS and to which persons from the large ICOS community have contributed.

This list is updated only a few times per year. Last update: 10 July 2020.

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Bastos A, Ciais P, Friedlingstein P, Sitch S, Pongratz J, Fan L, Wigneron JP, Weber U, Reichstein M, Fu Z, Anthoni P, Arneth A, Haverd V, Jain AK, Joetzjer E, Knauer J, Lienert S, Loughran T, McGuire PC, Tian H, Viovy N and Zaehle S (2020), "Direct and seasonal legacy effects of the 2018 heat wave and drought on European ecosystem productivity", Science Advances., jun, 2020. Vol. 6(24), pp. eaba2724.
Abstract: In summer 2018, central and northern Europe were stricken by extreme drought and heat (DH2018). The DH2018 differed from previous events in being preceded by extreme spring warming and brightening, but moderate rainfall deficits, yet registering the fastest transition between wet winter conditions and extreme summer drought. Using 11 vegetation models, we show that spring conditions promoted increased vegetation growth, which, in turn, contributed to fast soil moisture depletion, amplifying the summer drought. We find regional asymmetries in summer ecosystem carbon fluxes: increased (reduced) sink in the northern (southern) areas affected by drought. These asymmetries can be explained by distinct legacy effects of spring growth and of water-use efficiency dynamics mediated by vegetation composition, rather than by distinct ecosystem responses to summer heat/drought. The asymmetries in carbon and water exchanges during spring and summer 2018 suggest that future land-management strategies could influence patterns of summer heat waves and droughts under long-term warming.
BibTeX:
@article{Bastos2020,
  author = {Bastos, A. and Ciais, P. and Friedlingstein, P. and Sitch, S. and Pongratz, J. and Fan, L. and Wigneron, J. P. and Weber, U. and Reichstein, M. and Fu, Z. and Anthoni, P. and Arneth, A. and Haverd, V. and Jain, A. K. and Joetzjer, E. and Knauer, J. and Lienert, S. and Loughran, T. and McGuire, P. C. and Tian, H. and Viovy, N. and Zaehle, S.},
  title = {Direct and seasonal legacy effects of the 2018 heat wave and drought on European ecosystem productivity},
  journal = {Science Advances},
  year = {2020},
  volume = {6},
  number = {24},
  pages = {eaba2724},
  url = {https://advances.sciencemag.org/lookup/doi/10.1126/sciadv.aba2724},
  doi = {10.1126/sciadv.aba2724}
}
Becker M, Olsen A, Landschützer P, Omar A, Rehder G, Rödenbeck C and Skjelvan I (2020), "The northern European shelf as increasing net sink for CO2", Biogeosciences Discussions., jan, 2020. , pp. 1-28. Copernicus GmbH.
BibTeX:
@article{Becker2020,
  author = {Becker, Meike and Olsen, Are and Landschützer, Peter and Omar, Abdirhaman and Rehder, Gregor and Rödenbeck, Christian and Skjelvan, Ingunn},
  title = {The northern European shelf as increasing net sink for CO2},
  journal = {Biogeosciences Discussions},
  publisher = {Copernicus GmbH},
  year = {2020},
  pages = {1--28},
  doi = {10.5194/bg-2019-480}
}
Bowring SP, Lauerwald R, Guenet B, Zhu D, Guimberteau M, Regnier P, Tootchi A, Ducharne A and Ciais P (2020), "ORCHIDEE MICT-LEAK (r5459), a global model for the production, transport, and transformation of dissolved organic carbon from Arctic permafrost regions - Part 2: Model evaluation over the Lena River basin", Geoscientific Model Development., feb, 2020. Vol. 13(2), pp. 507-520. Copernicus GmbH.
Abstract: In this second part of a two-part study, we performed a simulation of the carbon and water budget of the Lena catchment with the land surface model ORCHIDEE MICT-LEAK, enabled to simulate dissolved organic carbon (DOC) production in soils and its transport and fate in high-latitude inland waters. The model results are evaluated for their ability to reproduce the fluxes of DOC and carbon dioxide (CO2) along the soil-inland-water continuum and the exchange of CO2 with the atmosphere, including the evasion outgassing of CO2 from inland waters. We present simulation results over the years 1901-2007 and show that the model is able to broadly reproduce observed state variables and their emergent properties across a range of interacting physical and biogeochemical processes. These include (1) net primary production (NPP), respiration and riverine hydrologic amplitude, seasonality, and inter-annual variation; (2) DOC concentrations, bulk annual flow, and their volumetric attribution at the sub-catchment level; (3) high headwater versus downstream CO2 evasion, an emergent phenomenon consistent with observations over a spectrum of high-latitude observational studies. These quantities obey emergent relationships with environmental variables like air temperature and topographic slope that have been described in the literature. This gives us confidence in reporting the following additional findings: of the ĝ'1/434TgCyr-1 left over as input to soil matter after NPP is diminished by heterotrophic respiration, 7TgCyr-1 is leached and transported into the aquatic system. Of this, over half (3.6TgCyr-1) is evaded from the inland water surface back into the atmosphere and the remainder (3.4TgCyr-1) flushed out into the Arctic Ocean, mirroring empirically derived studies. These riverine DOC exports represent ĝ'1/41.5% of NPP. DOC exported from the floodplains is dominantly sourced from recent more "labile" terrestrial production in contrast to DOC leached from the rest of the watershed with runoff and drainage, which is mostly sourced from recalcitrant soil and litter. All else equal, both historical climate change (a spring-summer warming of 1.8ĝ' C over the catchment) and rising atmospheric CO2 (+85.6ppm) are diagnosed from factorial simulations to contribute similar significant increases in DOC transport via primary production, although this similarity may not hold in the future.
BibTeX:
@article{Bowring2020,
  author = {Bowring, Simon P.K. and Lauerwald, Ronny and Guenet, Bertrand and Zhu, Dan and Guimberteau, Matthieu and Regnier, Pierre and Tootchi, Ardalan and Ducharne, Agnes and Ciais, Philippe},
  title = {ORCHIDEE MICT-LEAK (r5459), a global model for the production, transport, and transformation of dissolved organic carbon from Arctic permafrost regions - Part 2: Model evaluation over the Lena River basin},
  journal = {Geoscientific Model Development},
  publisher = {Copernicus GmbH},
  year = {2020},
  volume = {13},
  number = {2},
  pages = {507--520},
  doi = {10.5194/gmd-13-507-2020}
}
Carrière SD, Martin-StPaul NK, Cakpo CB, Patris N, Gillon M, Chalikakis K, Doussan C, Olioso A, Babic M, Jouineau A, Simioni G and Davi H (2020), "The role of deep vadose zone water in tree transpiration during drought periods in karst settings – Insights from isotopic tracing and leaf water potential", Science of the Total Environment., jan, 2020. Vol. 699, pp. 134332. Elsevier BV.
Abstract: Karst environments are unusual because their dry, stony and shallow soils seem to be unfavorable to vegetation, and yet they are often covered with forests. How can trees survive in these environments? Where do they find the water that allows them to survive? This study uses midday and predawn water potentials and xylem water isotopes of branches to assess tree water status and the origin of transpired water. Monitoring was conducted during the summers of 2014 and 2015 in two dissimilar plots of Mediterranean forest located in karst environments. The results show that the three monitored tree species (Abies alba Mill, Fagus sylvatica L, and Quercus ilex L.) use deep water resources present in the karst vadose zone (unsaturated zone) more intensively during drier years. Quercus ilex, a species well- adapted to water stress, which grows at the drier site, uses the deep water resource very early in the summer season. Conversely, the two other species exploit the deep water resource only during severe drought. These results open up new perspectives to a better understanding of ecohydrological equilibrium and to improved water balance modeling in karst forest settings.
BibTeX:
@article{Carriere2020a,
  author = {Carrière, Simon Damien and Martin-StPaul, Nicolas K. and Cakpo, Coffi Belmys and Patris, Nicolas and Gillon, Marina and Chalikakis, Konstantinos and Doussan, Claude and Olioso, Albert and Babic, Milanka and Jouineau, Arnaud and Simioni, Guillaume and Davi, Hendrik},
  title = {The role of deep vadose zone water in tree transpiration during drought periods in karst settings – Insights from isotopic tracing and leaf water potential},
  journal = {Science of the Total Environment},
  publisher = {Elsevier BV},
  year = {2020},
  volume = {699},
  pages = {134332},
  doi = {10.1016/j.scitotenv.2019.134332}
}
Carrière SD, Ruffault J, Pimont F, Doussan C, Simioni G, Chalikakis K, Limousin JM, Scotti I, Courdier F, Cakpo CB, Davi H and Martin-StPaul NK (2020), "Impact of local soil and subsoil conditions on inter-individual variations in tree responses to drought: insights from Electrical Resistivity Tomography", Science of the Total Environment., jan, 2020. Vol. 698, pp. 134247. Elsevier BV.
Abstract: • Inter-individual variability of tree drought responses within a stand has received little attention. Here we explore whether the spatial variations in soil/subsoil properties assessed through Electrical Resistivity Tomography (ERT) could explain variations in drought response traits among trees. • We used ERT to compute the percent variation in resistivity (PVR) between dry and wet conditions as an indicator of spatial variability in total available water content. PVR was computed in two different depth ranges (0–2 and 2–5 m) for eleven Quercus ilex stools in a Mediterranean forest stand. PVR values were compared to biological traits, including tree water status (predawn water potential (Ψ)), leaf traits (δ13C, leaf mass area (LMA)), and canopy defoliation measured after intense drought. • We found significant correlations between PVR and biological variables. For Ψ, the nature and strength of the correlations vary according to the level of drought intensity. The correlation between Ψ and PVR was positive during well-watered conditions in the upper layer (0–2 m) and during water-limited conditions in the deeper layer (2–5 m). During most severe droughts, however, the Ψ was negatively correlated with PVR in the upper layer. Trees with lower PVR in the upper layer were also associated with water use efficiency (higher δ13C), higher LMA, and a lower level of defoliation after extreme drought. • Overall, our results indicate that local differences in soil/subsoil properties affect tree response to drought and suggest that less favorable soil/subsoil conditions (lower PVR) can lead to lower water stress during the driest period and to lower defoliation after extreme drought. Plausible explanations for this better acclimation include higher stomatal regulation and improved deep soil and subsoil water exploration by trees located in more adverse conditions. We encourage the development of ERT in ecological studies to further explore the interrelated relationships between soil/subsoil, climate, and tree functioning.
BibTeX:
@article{Carriere2020,
  author = {Carrière, S. D. and Ruffault, J. and Pimont, F. and Doussan, C. and Simioni, G. and Chalikakis, K. and Limousin, J. M. and Scotti, I. and Courdier, F. and Cakpo, C. B. and Davi, H. and Martin-StPaul, N. K.},
  title = {Impact of local soil and subsoil conditions on inter-individual variations in tree responses to drought: insights from Electrical Resistivity Tomography},
  journal = {Science of the Total Environment},
  publisher = {Elsevier BV},
  year = {2020},
  volume = {698},
  pages = {134247},
  doi = {10.1016/j.scitotenv.2019.134247}
}
Chave J, Piponiot C, Maréchaux I, de Foresta H, Larpin D, Fischer FJ, Derroire G, Vincent G and Hérault B (2020), "Slow rate of secondary forest carbon accumulation in the Guianas compared with the rest of the Neotropics", Ecological Applications., oct, 2020. Vol. 30(1) Wiley.
Abstract: Secondary forests are a prominent component of tropical landscapes, and they constitute a major atmospheric carbon sink. Rates of carbon accumulation are usually inferred from chronosequence studies, but direct estimates of carbon accumulation based on long-term monitoring of stands are rarely reported. Recent compilations on secondary forest carbon accumulation in the Neotropics are heavily biased geographically as they do not include estimates from the Guiana Shield. We analysed the temporal trajectory of aboveground carbon accumulation and floristic composition at one 25-ha secondary forest site in French Guiana. The site was clear-cut in 1976, abandoned thereafter, and one large plot (6.25 ha) has been monitored continuously since. We used Bayesian modeling to assimilate inventory data and simulate the long-term carbon accumulation trajectory. Canopy change was monitored using two aerial lidar surveys conducted in 2009 and 2017. We compared the dynamics of this site with that of a surrounding old-growth forest. Finally, we compared our results with that from secondary forests in Costa Rica, which is one of the rare long-term monitoring programs reaching a duration comparable to our study. Twenty years after abandonment, aboveground carbon stock was 64.2 (95% credibility interval 46.4, 89.0) Mg C/ha, and this stock increased to 101.3 (78.7, 128.5) Mg C/ha 20 yr later. The time to accumulate one-half of the mean aboveground carbon stored in the nearby old-growth forest (185.6 [155.9, 200.2] Mg C/ha) was estimated at 35.0 [20.9, 55.9] yr. During the first 40 yr, the contribution of the long-lived pioneer species Xylopia nitida, Goupia glabra, and Laetia procera to the aboveground carbon stock increased continuously. Secondary forest mean-canopy height measured by lidar increased by 1.14 m in 8 yr, a canopy-height increase consistent with an aboveground carbon accumulation of 7.1 Mg C/ha (or 0.89 Mg Ctextperiodcenteredha−1textperiodcenteredyr−1) during this period. Long-term AGC accumulation rate in Costa Rica was almost twice as fast as at our site in French Guiana. This may reflect higher fertility of Central American forest communities or a better adaptation of the forest tree community to intense and frequent disturbances. This finding may have important consequences for scaling-up carbon uptake estimates to continental scales.
BibTeX:
@article{Chave2020,
  author = {Chave, Jérôme and Piponiot, Camille and Maréchaux, Isabelle and de Foresta, Hubert and Larpin, Denis and Fischer, Fabian Jörg and Derroire, Géraldine and Vincent, Grégoire and Hérault, Bruno},
  title = {Slow rate of secondary forest carbon accumulation in the Guianas compared with the rest of the Neotropics},
  journal = {Ecological Applications},
  publisher = {Wiley},
  year = {2020},
  volume = {30},
  number = {1},
  doi = {10.1002/eap.2004}
}
Ciais P, Wang Y, Andrew R, Bréon FM, Chevallier F, Broquet G, Nabuurs GJ, Peters G, McGrath M, Meng W, Zheng B and Tao S (2020), "Biofuel burning and human respiration bias on satellite estimates of fossil fuel CO 2 emissions", Environmental Research Letters., jul, 2020. Vol. 15(7), pp. 074036.
BibTeX:
@article{Ciais2020,
  author = {Ciais, P and Wang, Y and Andrew, R and Bréon, F M and Chevallier, F and Broquet, G and Nabuurs, G J and Peters, G and McGrath, M and Meng, W and Zheng, B and Tao, S},
  title = {Biofuel burning and human respiration bias on satellite estimates of fossil fuel CO 2 emissions},
  journal = {Environmental Research Letters},
  year = {2020},
  volume = {15},
  number = {7},
  pages = {074036},
  url = {https://iopscience.iop.org/article/10.1088/1748-9326/ab7835},
  doi = {10.1088/1748-9326/ab7835}
}
Cristofanelli P, Arduini J, Calzolari F, Giostra U, Bonasoni P and Maione M (2020), "First Evidences of Methyl Chloride (CH3Cl) Transport from the Northern Italy Boundary Layer during Summer 2017", Atmosphere., feb, 2020. Vol. 11(3), pp. 238.
Abstract: Methyl Chloride (CH3Cl) is a chlorine-containing trace gas in the atmosphere contributing significantly to stratospheric ozone depletion. While the atmospheric CH3Cl emissions are predominantly caused by natural sources on the global budget, significant uncertainties still remain for the anthropogenic CH3Cl emission strengths. In summer 2007 an intensive field campaign within the ACTRIS-2 Project was hosted at the Mt. Cimone World Meteorological Organization/Global Atmosphere Watch global station (CMN, 44.17° N, 10.68° E, 2165 m a.s.l.). High-frequency and high precision in situ measurements of atmospheric CH3Cl revealed significant high-frequency variability superimposed on the seasonally varying regional background levels. The high-frequency CH3Cl variability was characterized by an evident cycle over 24 h with maxima during the afternoon which points towards a systematic role of thermal vertical transport of air-masses from the regional boundary layer. The temporal correlation analysis with specific tracers of anthropogenic activity (traffic, industry, petrochemical industry) together with bivariate analysis as a function of local wind regime suggested that, even if the role of natural marine emissions appears as predominant, the northern Italy boundary layer could potentially represent a non-negligible source of CH3Cl during summer. Since industrial production and use of CH3Cl have not been regulated under the Montreal Protocol (MP) or its successor amendments, continuous monitoring of CH3Cl outflow from the Po Basin is important to properly assess its anthropogenic emissions.
BibTeX:
@article{Cristofanelli2020,
  author = {Cristofanelli, Paolo and Arduini, Jgor and Calzolari, Francescopiero and Giostra, Umberto and Bonasoni, Paolo and Maione, Michela},
  title = {First Evidences of Methyl Chloride (CH3Cl) Transport from the Northern Italy Boundary Layer during Summer 2017},
  journal = {Atmosphere},
  year = {2020},
  volume = {11},
  number = {3},
  pages = {238},
  url = {https://www.mdpi.com/2073-4433/11/3/238},
  doi = {10.3390/atmos11030238}
}
De Gruyter J, Weedon JT, Bazot S, Dauwe S, Fernandez-Garberí P-R, Geisen S, De La Motte LG, Heinesch B, Janssens IA, Leblans N, Manise T, Ogaya R, Löfvenius MO, Peñuelas J, Sigurdsson BD, Vincent G and Verbruggen E (2020), "Patterns of local, intercontinental and interseasonal variation of soil bacterial and eukaryotic microbial communities", FEMS Microbiology Ecology., mar, 2020. Vol. 96(3)
Abstract: Although ongoing research has revealed some of the main drivers behind global spatial patterns of microbial communities, spatio-temporal dynamics of these communities still remain largely unexplored. Here, we investigate spatio-temporal variability of both bacterial and eukaryotic soil microbial communities at local and intercontinental scales. We compare how temporal variation in community composition scales with spatial variation in community composition, and explore the extent to which bacteria, protists, fungi and metazoa have similar patterns of temporal community dynamics. All soil microbial groups displayed a strong correlation between spatial distance and community dissimilarity, which was related to the ratio of organism to sample size. Temporal changes were variable, ranging from equal to local between-sample variation, to as large as that between communities several thousand kilometers apart. Moreover, significant correlations were found between bacterial and protist communities, as well as between protist and fungal communities, indicating that these microbial groups change in tandem, potentially driven by interactions between them. We conclude that temporal variation can be considerable in soil microbial communities, and that future studies need to consider temporal variation in order to reliably capture all drivers of soil microbiome changes.
BibTeX:
@article{DeGruyter2020,
  author = {De Gruyter, Johan and Weedon, James T and Bazot, Stéphane and Dauwe, Steven and Fernandez-Garberí, Pere-Roc and Geisen, Stefan and De La Motte, Louis Gourlez and Heinesch, Bernard and Janssens, Ivan A and Leblans, Niki and Manise, Tanguy and Ogaya, Romà and Löfvenius, Mikaell Ottosson and Peñuelas, Josep and Sigurdsson, Bjarni D and Vincent, Gaëlle and Verbruggen, Erik},
  title = {Patterns of local, intercontinental and interseasonal variation of soil bacterial and eukaryotic microbial communities},
  journal = {FEMS Microbiology Ecology},
  year = {2020},
  volume = {96},
  number = {3},
  url = {https://academic.oup.com/femsec/article/doi/10.1093/femsec/fiaa018/5719567},
  doi = {10.1093/femsec/fiaa018}
}
Flechard CR, Ibrom A, Skiba UM, de Vries W, van Oijen M, Cameron DR, Dise NB, Korhonen JFJ, Buchmann N, Legout A, Simpson D, Sanz MJ, Aubinet M, Loustau D, Montagnani L, Neirynck J, Janssens IA, Pihlatie M, Kiese R, Siemens J, Francez A-J, Augustin J, Varlagin A, Olejnik J, Juszczak R, Aurela M, Berveiller D, Chojnicki BH, Dämmgen U, Delpierre N, Djuricic V, Drewer J, Dufrêne E, Eugster W, Fauvel Y, Fowler D, Frumau A, Granier A, Gross P, Hamon Y, Helfter C, Hensen A, Horváth L, Kitzler B, Kruijt B, Kutsch WL, Lobo-do-Vale R, Lohila A, Longdoz B, Marek MV, Matteucci G, Mitosinkova M, Moreaux V, Neftel A, Ourcival J-M, Pilegaard K, Pita G, Sanz F, Schjoerring JK, Sebastià M-T, Tang YS, Uggerud H, Urbaniak M, van Dijk N, Vesala T, Vidic S, Vincke C, Weidinger T, Zechmeister-Boltenstern S, Butterbach-Bahl K, Nemitz E and Sutton MA (2020), "Carbon-nitrogen interactions in European forests and semi-natural vegetation; Part 1: Fluxes and budgets of carbon, nitrogen and greenhouse gases from ecosystem monitoring and modelling", Biogeosciences., mar, 2020. Vol. 17(6), pp. 1583-1620.
Abstract: 3 g N m−2 yr−1. Such large levels of Nr loss likely indicate that different stages of N saturation occurred at a number of sites. The joint analysis of the C and N budgets provided further hints that N saturation could be detected in altered patterns of forest growth. Net ecosystem productivity increased with Nr deposition up to 2–2.5 g N m−2 yr−1, with large scatter associated with a wide range in carbon sequestration efficiency (CSE, defined as the NEP ∕ GPP ratio). At elevated Ndep levels (textgreater 2.5 g N m−2 yr−1), where inorganic Nr losses were also increasingly large, NEP levelled off and then decreased. The apparent increase in NEP at low to intermediate Ndep levels was partly the result of geographical cross-correlations between Ndep and climate, indicating that the actual mean dC∕dN response at individual sites was significantly lower than would be suggested by a simple, straightforward regression of NEP vs. Ndep.]]textgreater
BibTeX:
@article{Flechard2020,
  author = {Flechard, Chris R. and Ibrom, Andreas and Skiba, Ute M. and de Vries, Wim and van Oijen, Marcel and Cameron, David R. and Dise, Nancy B. and Korhonen, Janne F. J. and Buchmann, Nina and Legout, Arnaud and Simpson, David and Sanz, Maria J. and Aubinet, Marc and Loustau, Denis and Montagnani, Leonardo and Neirynck, Johan and Janssens, Ivan A. and Pihlatie, Mari and Kiese, Ralf and Siemens, Jan and Francez, André-Jean and Augustin, Jürgen and Varlagin, Andrej and Olejnik, Janusz and Juszczak, Radosław and Aurela, Mika and Berveiller, Daniel and Chojnicki, Bogdan H. and Dämmgen, Ulrich and Delpierre, Nicolas and Djuricic, Vesna and Drewer, Julia and Dufrêne, Eric and Eugster, Werner and Fauvel, Yannick and Fowler, David and Frumau, Arnoud and Granier, André and Gross, Patrick and Hamon, Yannick and Helfter, Carole and Hensen, Arjan and Horváth, László and Kitzler, Barbara and Kruijt, Bart and Kutsch, Werner L. and Lobo-do-Vale, Raquel and Lohila, Annalea and Longdoz, Bernard and Marek, Michal V. and Matteucci, Giorgio and Mitosinkova, Marta and Moreaux, Virginie and Neftel, Albrecht and Ourcival, Jean-Marc and Pilegaard, Kim and Pita, Gabriel and Sanz, Francisco and Schjoerring, Jan K. and Sebastià, Maria-Teresa and Tang, Y. Sim and Uggerud, Hilde and Urbaniak, Marek and van Dijk, Netty and Vesala, Timo and Vidic, Sonja and Vincke, Caroline and Weidinger, Tamás and Zechmeister-Boltenstern, Sophie and Butterbach-Bahl, Klaus and Nemitz, Eiko and Sutton, Mark A.},
  title = {Carbon-nitrogen interactions in European forests and semi-natural vegetation; Part 1: Fluxes and budgets of carbon, nitrogen and greenhouse gases from ecosystem monitoring and modelling},
  journal = {Biogeosciences},
  year = {2020},
  volume = {17},
  number = {6},
  pages = {1583--1620},
  url = {https://www.biogeosciences.net/17/1583/2020/},
  doi = {10.5194/bg-17-1583-2020}
}
Flechard CR, van Oijen M, Cameron DR, de Vries W, Ibrom A, Buchmann N, Dise NB, Janssens IA, Neirynck J, Montagnani L, Varlagin A, Loustau D, Legout A, Ziembliʼnska K, Aubinet M, Aurela M, Chojnicki BH, Drewer J, Eugster W, Francez A-J, Juszczak R, Kitzler B, Kutsch WL, Lohila A, Longdoz B, Matteucci G, Moreaux V, Neftel A, Olejnik J, Sanz MJ, Siemens J, Vesala T, Vincke C, Nemitz E, Zechmeister-Boltenstern S, Butterbach-Bahl K, Skiba UM and Sutton MA (2020), "Carbon-nitrogen interactions in European forests and semi-natural vegetation; Part 2: Untangling climatic, edaphic, management and nitrogen deposition effects on carbon sequestration potentials", Biogeosciences., mar, 2020. Vol. 17(6), pp. 1621-1654.
Abstract: 2.5–3 g N m−2 yr−1) but accompanied by increasingly large ecosystem N losses by leaching and gaseous emissions. The reduced increase in productivity per unit N deposited at high Ndep levels implies that the forecast increased Nr emissions and increased Ndep levels in large areas of Asia may not positively impact the continent's forest CO2 sink. The large level of unexplained variability in observed carbon sequestration efficiency (CSE) across sites further adds to the uncertainty in the dC∕dN response.]]textgreater
BibTeX:
@article{Flechard2020a,
  author = {Flechard, Chris R. and van Oijen, Marcel and Cameron, David R. and de Vries, Wim and Ibrom, Andreas and Buchmann, Nina and Dise, Nancy B. and Janssens, Ivan A. and Neirynck, Johan and Montagnani, Leonardo and Varlagin, Andrej and Loustau, Denis and Legout, Arnaud and Ziembliʼnska, Klaudia and Aubinet, Marc and Aurela, Mika and Chojnicki, Bogdan H. and Drewer, Julia and Eugster, Werner and Francez, André-Jean and Juszczak, Radosław and Kitzler, Barbara and Kutsch, Werner L. and Lohila, Annalea and Longdoz, Bernard and Matteucci, Giorgio and Moreaux, Virginie and Neftel, Albrecht and Olejnik, Janusz and Sanz, Maria J. and Siemens, Jan and Vesala, Timo and Vincke, Caroline and Nemitz, Eiko and Zechmeister-Boltenstern, Sophie and Butterbach-Bahl, Klaus and Skiba, Ute M. and Sutton, Mark A.},
  title = {Carbon-nitrogen interactions in European forests and semi-natural vegetation; Part 2: Untangling climatic, edaphic, management and nitrogen deposition effects on carbon sequestration potentials},
  journal = {Biogeosciences},
  year = {2020},
  volume = {17},
  number = {6},
  pages = {1621--1654},
  url = {https://www.biogeosciences.net/17/1621/2020/},
  doi = {10.5194/bg-17-1621-2020}
}
Haverd V, Smith B, Canadell JG, Cuntz M, Mikaloff‐Fletcher S, Farquhar G, Woodgate W, Briggs PR and Trudinger CM (2020), " Higher than expected CO 2 fertilization inferred from leaf to global observations ", Global Change Biology., feb, 2020. Vol. 26(4), pp. 2390-2402. Wiley.
Abstract: Several lines of evidence point to an increase in the activity of the terrestrial biosphere over recent decades, impacting the global net land carbon sink (NLS) and its control on the growth of atmospheric carbon dioxide (ca). Global terrestrial gross primary production (GPP)—the rate of carbon fixation by photosynthesis—is esti- mated to have risen by (31 ± 5)% since 1900, but the relative contributions of differ- ent putative drivers to this increase are not well known. Here we identify the rising atmospheric CO2 concentration as the dominant driver. We reconcile leaf-level and global atmospheric constraints on trends in modeled biospheric activity to reveal a global CO2 fertilization effect on photosynthesis of 30% since 1900, or 47% for a doubling of ca above the pre-industrial level. Our historic value is nearly twice as high as current estimates (17 ± 4)% that do not use the full range of available constraints. Consequently, under a future low-emission scenario, we project a land carbon sink (174 PgC, 2006–2099) that is 57 PgC larger than if a lower CO2 fertilization effect comparable with current estimates is assumed. These findings suggest a larger ben- eficial role of the land carbon sink in modulating future excess anthropogenic CO2 consistent with the target of the Paris Agreement to stay below 2°C warming, and underscore the importance of preserving terrestrial carbon sinks.
BibTeX:
@article{Haverd2020,
  author = {Haverd, Vanessa and Smith, Benjamin and Canadell, Josep G. and Cuntz, Matthias and Mikaloff‐Fletcher, Sara and Farquhar, Graham and Woodgate, William and Briggs, Peter R. and Trudinger, Cathy M.},
  title = { Higher than expected CO 2 fertilization inferred from leaf to global observations },
  journal = {Global Change Biology},
  publisher = {Wiley},
  year = {2020},
  volume = {26},
  number = {4},
  pages = {2390--2402},
  doi = {10.1111/gcb.14950}
}
Janssens-Maenhout G, Pinty B, Dowell M, Zunker H, Andersson E, Balsamo G, Bézy J-L, Brunhes T, Bösch H, Bojkov B, Brunner D, Buchwitz M, Crisp D, Ciais P, Counet P, Dee D, Denier van der Gon H, Dolman H, Drinkwater M, Dubovik O, Engelen R, Fehr T, Fernandez V, Heimann M, Holmlund K, Houweling S, Husband R, Juvyns O, Kentarchos A, Landgraf J, Lang R, Löscher A, Marshall J, Meijer Y, Nakajima M, Palmer P, Peylin P, Rayner P, Scholze M, Sierk B, Tamminen J and Veefkind P (2020), "Towards an operational anthropogenic CO2 emissions monitoring and verification support capacity", Bulletin of the American Meteorological Society., feb, 2020. Vol. preprint(2020)
Abstract: Under the Paris Agreement progress of emission reduction efforts is tracked on the basis of regular updates to national Greenhouse Gas (GHG) inventories, referred to as bottom-up estimates. However, only top-down atmospheric measurements can provide observation-based evidence of emission trends. Today there is no internationally agreed, operational capacity to monitor anthropogenic GHG emission trends using atmospheric measurements to complement national bottom-up inventories.
BibTeX:
@article{JanssensMaenhout2020,
  author = {Janssens-Maenhout, G. and Pinty, B. and Dowell, M. and Zunker, H. and Andersson, E. and Balsamo, G. and Bézy, J.-L. and Brunhes, T. and Bösch, H. and Bojkov, B. and Brunner, D. and Buchwitz, M. and Crisp, D. and Ciais, P. and Counet, P. and Dee, D. and Denier van der Gon, H. and Dolman, H. and Drinkwater, M. and Dubovik, O. and Engelen, R. and Fehr, T. and Fernandez, V. and Heimann, M. and Holmlund, K. and Houweling, S. and Husband, R. and Juvyns, O. and Kentarchos, A. and Landgraf, J. and Lang, R. and Löscher, A. and Marshall, J. and Meijer, Y. and Nakajima, M. and Palmer, P.I. and Peylin, P. and Rayner, P. and Scholze, M. and Sierk, B. and Tamminen, J. and Veefkind, P.},
  title = {Towards an operational anthropogenic CO2 emissions monitoring and verification support capacity},
  journal = {Bulletin of the American Meteorological Society},
  year = {2020},
  volume = {preprint},
  number = {2020},
  url = {https://journals.ametsoc.org/bams/article/345576/Towards-an-operational-anthropogenic-CO2-emissions},
  doi = {10.1175/BAMS-D-19-0017.1}
}
Jung M, Schwalm C, Migliavacca M, Walther S, Camps-Valls G, Koirala S, Anthoni P, Besnard S, Bodesheim P, Carvalhais N, Chevallier F, Gans F, Goll DS, Haverd V, Köhler P, Ichii K, Jain AK, Liu J, Lombardozzi D, Nabel JEMS, Nelson JA, O&apos, Sullivan M, Pallandt M, Papale D, Peters W, Pongratz J, Rödenbeck C, Sitch S, Tramontana G, Walker A, Weber U and Reichstein M (2020), "Scaling carbon fluxes from eddy covariance sites to globe: synthesis and evaluation of the FLUXCOM approach", Biogeosciences., mar, 2020. Vol. 17(5), pp. 1343-1365.
Abstract: 0.94 at 1∘ spatial resolution) while the majority of DGVMs show, for 70 % of the land surface, values outside the FLUXCOM range. Global mean GPP magnitudes for 2008–2010 from FLUXCOM members vary within 106 and 130 PgC yr−1 with the largest uncertainty in the tropics. Seasonal variations in independent SIF estimates agree better with FLUXCOM GPP (mean global pixel-wise R2∼0.75) than with GPP from DGVMs (mean global pixel-wise R2∼0.6). Seasonal variations in FLUXCOM NEE show good consistency with atmospheric inversion-based net land carbon fluxes, particularly for temperate and boreal regions (R2textgreater0.92). Interannual variability of global NEE in FLUXCOM is underestimated compared to inversions and DGVMs. The FLUXCOM version which also uses meteorological inputs shows a strong co-variation in interannual patterns with inversions (R2=0.87 for 2001–2010). Mean regional NEE from FLUXCOM shows larger uptake than inversion and DGVM-based estimates, particularly in the tropics with discrepancies of up to several hundred grammes of carbon per square metre per year. These discrepancies can only partly be reconciled by carbon loss pathways that are implicit in inversions but not captured by the flux tower measurements such as carbon emissions from fires and water bodies. We hypothesize that a combination of systematic biases in the underlying eddy covariance data, in particular in tall tropical forests, and a lack of site history effects on NEE in FLUXCOM are likely responsible for the too strong tropical carbon sink estimated by FLUXCOM. Furthermore, as FLUXCOM does not account for CO2 fertilization effects, carbon flux trends are not realistic. Overall, current FLUXCOM estimates of mean annual and seasonal cycles of GPP as well as seasonal NEE variations provide useful constraints of global carbon cycling, while interannual variability patterns from FLUXCOM are valuable but require cautious interpretation. Exploring the diversity of Earth observation data and of machine learning concepts along with improved quality and quantity of flux tower measurements will facilitate further improvements of the FLUXCOM approach overall.]]textgreater
BibTeX:
@article{Jung2020,
  author = {Jung, Martin and Schwalm, Christopher and Migliavacca, Mirco and Walther, Sophia and Camps-Valls, Gustau and Koirala, Sujan and Anthoni, Peter and Besnard, Simon and Bodesheim, Paul and Carvalhais, Nuno and Chevallier, Frédéric and Gans, Fabian and Goll, Daniel S. and Haverd, Vanessa and Köhler, Philipp and Ichii, Kazuhito and Jain, Atul K. and Liu, Junzhi and Lombardozzi, Danica and Nabel, Julia E. M. S. and Nelson, Jacob A. and O'Sullivan, Michael and Pallandt, Martijn and Papale, Dario and Peters, Wouter and Pongratz, Julia and Rödenbeck, Christian and Sitch, Stephen and Tramontana, Gianluca and Walker, Anthony and Weber, Ulrich and Reichstein, Markus},
  title = {Scaling carbon fluxes from eddy covariance sites to globe: synthesis and evaluation of the FLUXCOM approach},
  journal = {Biogeosciences},
  year = {2020},
  volume = {17},
  number = {5},
  pages = {1343--1365},
  url = {https://www.biogeosciences.net/17/1343/2020/},
  doi = {10.5194/bg-17-1343-2020}
}
Kaikkonen L, Enberg S, Blomster J, Luhtanen A-M, Autio R and Rintala J-M (2020), "Autumn to spring microbial community in the northern Baltic Sea: temporal variability in bacterial, viral and nanoflagellate abundance during the cold-water season", Polar Biology., jun, 2020.
BibTeX:
@article{Kaikkonen2020,
  author = {Kaikkonen, Laura and Enberg, Sara and Blomster, Jaanika and Luhtanen, Anne-Mari and Autio, Riitta and Rintala, Janne-Markus},
  title = {Autumn to spring microbial community in the northern Baltic Sea: temporal variability in bacterial, viral and nanoflagellate abundance during the cold-water season},
  journal = {Polar Biology},
  year = {2020},
  url = {http://link.springer.com/10.1007/s00300-020-02700-8},
  doi = {10.1007/s00300-020-02700-8}
}
Kammer J, Décuq C, Baisnée D, Ciuraru R, Lafouge F, Buysse P, Bsaibes S, Henderson B, Cristescu SM, Benabdallah R, Chandra V, Durand B, Fanucci O, Petit JE, Truong F, Bonnaire N, Sarda-Estève R, Gros V and Loubet B (2020), "Characterization of particulate and gaseous pollutants from a French dairy and sheep farm", Science of the Total Environment., apr, 2020. Vol. 712, pp. 135598. Elsevier BV.
Abstract: Agricultural activities highly contribute to atmospheric pollution, but the diversity and the magnitude of their emissions are still subject to large uncertainties. A field measurement campaign was conducted to characterize gaseous and particulate emissions from an experimental farm in France containing a sheep pen and a dairy stable. During the campaign, more than four hundred volatile organic compounds (VOCs) were characterized using an original combination of online and off-line measurements. Carbon dioxide (CO2) and ammonia (NH3) were the most concentrated compounds inside the buildings, followed by methanol, acetic acid and acetaldehyde. A CO2 mass balance model was used to estimate NH3 and VOC emission rates. To our knowledge, this study constitutes the first evaluation of emission rates for most of the identified VOCs. The measurements show that the dairy stable emitted more VOCs than the sheep pen. Despite strong VOC and NH3 emissions, the chemical composition of particles indicates that gaseous farm emissions do not affect the loading of fine particles inside the farm and is mainly explained by the low residence time inside the buildings. The experimental dataset obtained in this work will help to improve emissions inventories for agricultural activities.
BibTeX:
@article{Kammer2020,
  author = {Kammer, Julien and Décuq, Céline and Baisnée, Dominique and Ciuraru, Raluca and Lafouge, Florence and Buysse, Pauline and Bsaibes, Sandy and Henderson, Ben and Cristescu, Simona M. and Benabdallah, Rachid and Chandra, Varunesh and Durand, Brigitte and Fanucci, Oliver and Petit, Jean Eudes and Truong, Francois and Bonnaire, Nicolas and Sarda-Estève, Roland and Gros, Valerie and Loubet, Benjamin},
  title = {Characterization of particulate and gaseous pollutants from a French dairy and sheep farm},
  journal = {Science of the Total Environment},
  publisher = {Elsevier BV},
  year = {2020},
  volume = {712},
  pages = {135598},
  doi = {10.1016/j.scitotenv.2019.135598}
}
Koebsch F, Sonnentag O, Järveoja J, Peltoniemi M, Alekseychik P, Aurela M, Arslan AN, Dinsmore K, Gianelle D, Helfter C, Jackowicz-Korczynski M, Korrensalo A, Leith F, Linkosalmi M, Lohila A, Lund M, Maddison M, Mammarella I, Mander Ü, Minkkinen K, Pickard A, Pullens JW, Tuittila ES, Nilsson MB and Peichl M (2020), "Refining the role of phenology in regulating gross ecosystem productivity across European peatlands", Global Change Biology., dec, 2020. Vol. 26(2), pp. 876-887. Wiley.
Abstract: The role of plant phenology as a regulator for gross ecosystem productivity (GEP) in peatlands is empirically not well constrained. This is because proxies to track vegetation development with daily coverage at the ecosystem scale have only recently become available and the lack of such data has hampered the disentangling of biotic and abiotic effects. This study aimed at unraveling the mechanisms that regulate the seasonal variation in GEP across a network of eight European peatlands. Therefore, we described phenology with canopy greenness derived from digital repeat photography and disentangled the effects of radiation, temperature and phenology on GEP with commonality analysis and structural equation modeling. The resulting relational network could not only delineate direct effects but also accounted for possible effect combinations such as interdependencies (mediation) and interactions (moderation). We found that peatland GEP was controlled by the same mechanisms across all sites: phenology constituted a key predictor for the seasonal variation in GEP and further acted as a distinct mediator for temperature and radiation effects on GEP. In particular, the effect of air temperature on GEP was fully mediated through phenology, implying that direct temperature effects representing the thermoregulation of photosynthesis were negligible. The tight coupling between temperature, phenology and GEP applied especially to high latitude and high altitude peatlands and during phenological transition phases. Our study highlights the importance of phenological effects when evaluating the future response of peatland GEP to climate change. Climate change will affect peatland GEP especially through changing temperature patterns during plant phenologically sensitive phases in high latitude and high altitude regions.
BibTeX:
@article{Koebsch2020,
  author = {Koebsch, Franziska and Sonnentag, Oliver and Järveoja, Järvi and Peltoniemi, Mikko and Alekseychik, Pavel and Aurela, Mika and Arslan, Ali Nadir and Dinsmore, Kerry and Gianelle, Damiano and Helfter, Carole and Jackowicz-Korczynski, Marcin and Korrensalo, Aino and Leith, Fraser and Linkosalmi, Maiju and Lohila, Annalea and Lund, Magnus and Maddison, Martin and Mammarella, Ivan and Mander, Ülo and Minkkinen, Kari and Pickard, Amy and Pullens, Johannes W.M. and Tuittila, Eeva Stiina and Nilsson, Mats B. and Peichl, Matthias},
  title = {Refining the role of phenology in regulating gross ecosystem productivity across European peatlands},
  journal = {Global Change Biology},
  publisher = {Wiley},
  year = {2020},
  volume = {26},
  number = {2},
  pages = {876--887},
  doi = {10.1111/gcb.14905}
}
Languille B, Gros V, Petit JE, Honoré C, Baudic A, Perrussel O, Foret G, Michoud V, Truong F, Bonnaire N, Sarda-Estève R, Delmotte M, Feron A, Maisonneuve F, Gaimoz C, Formenti P, Kotthaus S, Haeffelin M and Favez O (2020), "Wood burning: A major source of Volatile Organic Compounds during wintertime in the Paris region", Science of the Total Environment., apr, 2020. Vol. 711, pp. 135055. Elsevier BV.
Abstract: Wood burning is widely used for domestic heating and has been identified as a ubiquitous pollution source in urban areas, especially during cold months. The present study is based on a three and a half winter months field campaign in the Paris region measuring Volatile Organic Compounds (VOCs) by Proton Transfer Reaction Mass Spectrometry (PTR-MS) in addition to Black Carbon (BC). Several VOCs were identified as strongly wood burning-influenced (e.g., acetic acid, furfural), or traffic-influenced (e.g., toluene, C8-aromatics). Methylbutenone, benzenediol and butandione were identified for the first time as wood burning-related in ambient air. A Positive Matrix Factorization (PMF) analysis highlighted that wood burning is the most important source of VOCs during the winter season. (47%). Traffic was found to account for about 22% of the measured VOCs during the same period, whereas solvent use plus background accounted altogether for the remaining fraction. The comparison with the regional emission inventory showed good consistency for benzene and xylenes but revisions of the inventory should be considered for several VOCs such as acetic acid, C9-aromatics and methanol. Finally, complementary measurements acquired simultaneously at other sites in Île-de-France (the Paris region) enabled evaluation of spatial variabilities. The influence of traffic emissions on investigated pollutants displayed a clear negative gradient from roadside to suburban stations, whereas wood burning pollution was found to be fairly homogeneous over the region.
BibTeX:
@article{Languille2020,
  author = {Languille, Baptiste and Gros, Valérie and Petit, Jean Eudes and Honoré, Cécile and Baudic, Alexia and Perrussel, Olivier and Foret, Gilles and Michoud, Vincent and Truong, François and Bonnaire, Nicolas and Sarda-Estève, Roland and Delmotte, Marc and Feron, Anaïs and Maisonneuve, Franck and Gaimoz, Cécile and Formenti, Paola and Kotthaus, Simone and Haeffelin, Martial and Favez, Olivier},
  title = {Wood burning: A major source of Volatile Organic Compounds during wintertime in the Paris region},
  journal = {Science of the Total Environment},
  publisher = {Elsevier BV},
  year = {2020},
  volume = {711},
  pages = {135055},
  doi = {10.1016/j.scitotenv.2019.135055}
}
Le Quéré C, Jackson RB, Jones MW, Smith AJP, Abernethy S, Andrew RM, De-Gol AJ, Willis DR, Shan Y, Canadell JG, Friedlingstein P, Creutzig F and Peters GP (2020), "Temporary reduction in daily global CO2 emissions during the COVID-19 forced confinement", Nature Climate Change., jul, 2020. Vol. 10(7), pp. 647-653.
BibTeX:
@article{LeQuere2020,
  author = {Le Quéré, Corinne and Jackson, Robert B. and Jones, Matthew W. and Smith, Adam J. P. and Abernethy, Sam and Andrew, Robbie M. and De-Gol, Anthony J. and Willis, David R. and Shan, Yuli and Canadell, Josep G. and Friedlingstein, Pierre and Creutzig, Felix and Peters, Glen P.},
  title = {Temporary reduction in daily global CO2 emissions during the COVID-19 forced confinement},
  journal = {Nature Climate Change},
  year = {2020},
  volume = {10},
  number = {7},
  pages = {647--653},
  url = {http://www.nature.com/articles/s41558-020-0797-x},
  doi = {10.1038/s41558-020-0797-x}
}
Lian X, Piao S, Li LZ, Li Y, Huntingford C, Ciais P, Cescatti A, Janssens IA, Peñuelas J, Buermann W, Chen A, Li X, Myneni RB, Wang X, Wang Y, Yang Y, Zeng Z, Zhang Y and McVicar TR (2020), "Summer soil drying exacerbated by earlier spring greening of northern vegetation", Science Advances., jan, 2020. Vol. 6(1), pp. eaax0255. American Association for the Advancement of Science (AAAS).
Abstract: Earlier vegetation greening under climate change raises evapotranspiration and thus lowers spring soil moisture, yet the extent and magnitude of this water deficit persistence into the following summer remain elusive. We provide observational evidence that increased foliage cover over the Northern Hemisphere, during 1982–2011, triggers an additional soil moisture deficit that is further carried over into summer. Climate model simulations independently support this and attribute the driving process to be larger increases in evapotranspiration than in precipitation. This extra soil drying is projected to amplify the frequency and intensity of summer heatwaves. Most feedbacks operate locally, except for a notable teleconnection where extra moisture transpired over Europe is transported to central Siberia. Model results illustrate that this teleconnection offsets Siberian soil moisture losses from local spring greening. Our results highlight that climate change adaptation planning must account for the extra summer water and heatwave stress inherited from warming-induced earlier greening.
BibTeX:
@article{Lian2020,
  author = {Lian, Xu and Piao, Shilong and Li, Laurent Z.X. and Li, Yue and Huntingford, Chris and Ciais, Philippe and Cescatti, Alessandro and Janssens, Ivan A. and Peñuelas, Josep and Buermann, Wolfgang and Chen, Anping and Li, Xiangyi and Myneni, Ranga B. and Wang, Xuhui and Wang, Yilong and Yang, Yuting and Zeng, Zhenzhong and Zhang, Yongqiang and McVicar, Tim R.},
  title = {Summer soil drying exacerbated by earlier spring greening of northern vegetation},
  journal = {Science Advances},
  publisher = {American Association for the Advancement of Science (AAAS)},
  year = {2020},
  volume = {6},
  number = {1},
  pages = {eaax0255},
  doi = {10.1126/sciadv.aax0255}
}
Louarn G, Chabbi A and Gastal F (2020), "Nitrogen concentration in the upper leaves of the canopy is a reliable indicator of plant N nutrition in both pure and mixed grassland swards", Grass and Forage Science., jan, 2020. Vol. 75(1), pp. 127-133. Wiley.
Abstract: Effective indicators of plant nitrogen (N) nutrition are needed to improve N management in grasslands. This is particularly the case for mixtures that rely on N fixation by legumes as a major N input, because no reference tool such as the nitrogen nutrition index (NNI) exists under these conditions. The aims of this study were to test the reliability of a plant-based index, the N concentration of upper leaves in the canopy (Nup), as a possible alternative for NNI in both pure and mixed grasslands. Data were gathered from four experiments covering a range of pure and mixed grasslands under different N fertilization levels. A cross-validation of Nup predictions against NNI in pure stands, and against two NNI-derived indices in mixtures, was performed. The Nup values appeared to be linearly related to NNI in pure stands of both grasses and legumes. The relationship was identical for the two groups of species and explained up to 86% of NNI variability. In mixtures, Nup also displayed a linear relationship with the two other tested indices, explaining 65% and 78% of variability. The conclusions of the three indices diverged with respect to strongly unbalanced mixtures, where the assumptions regarding the computation of NNI-derived indices were not met. Excluding these situations, the overall relationship between Nup and NNI proved to be identical for mixtures and pure stands. The results suggest that Nup is a valid criterion for plant N nutrition which applies to a broad range of grassland species and to mixture conditions.
BibTeX:
@article{Louarn2020,
  author = {Louarn, Gaëtan and Chabbi, Abad and Gastal, François},
  title = {Nitrogen concentration in the upper leaves of the canopy is a reliable indicator of plant N nutrition in both pure and mixed grassland swards},
  journal = {Grass and Forage Science},
  publisher = {Wiley},
  year = {2020},
  volume = {75},
  number = {1},
  pages = {127--133},
  doi = {10.1111/gfs.12466}
}
Macovei VA, Hartman SE, Schuster U, Torres-Valdés S, Moore CM and Sanders RJ (2020), "Impact of physical and biological processes on temporal variations of the ocean carbon sink in the mid-latitude North Atlantic (2002–2016)", Progress in Oceanography., jan, 2020. Vol. 180, pp. 102223. Elsevier BV.
Abstract: The ocean is currently a significant net sink for anthropogenically remobilised CO2, taking up around 24% of global emissions. Numerical models predict a diversity of responses of the ocean carbon sink to increased atmospheric concentrations in a warmer world. Here, we tested the hypothesis that increased atmospheric forcing is causing a change in the ocean carbon sink using a high frequency observational dataset derived from underway pCO2 (carbon dioxide partial pressure) instruments on ships of opportunity (SOO) and a fixed-point mooring between 2002 and 2016. We calculated an average carbon flux of 0.013 Pg yr−1 into the ocean at the Porcupine Abyssal Plain (PAP) site, consistent with past estimates. In spite of the increase in atmospheric pCO2, monthly average seawater pCO2 did not show a statistically significant increasing trend, but a higher annual variability, likely due to the decreasing buffer capacity of the system. The increasing ΔpCO2 led to an increasing trend in the estimated CO2 flux into the ocean of 0.19 ± 0.03 mmol m−2 day−1 per year across the entire 15 year time series, making the study area a stronger carbon sink. Seawater pCO2 variability is mostly influenced by temperature, alkalinity and dissolved inorganic carbon (DIC) changes, with 77% of the annual seawater pCO2 changes explained by these terms. DIC is in turn influenced by gas exchange and biological production. In an average year, the DIC drawdown by biological production, as determined from nitrate uptake, was higher than the DIC increase due to atmospheric CO2 dissolution into the surface ocean. This effect was enhanced in years with high nutrient input or shallow mixed layers. Using the rate of change of DIC and nitrate, we observed Redfieldian carbon consumption during the spring bloom at a C:N ratio of 6.2 ± 1.6. A comparison between SOO and PAP sustained observatory data revealed a strong agreement for pCO2 and DIC. This work demonstrates that the study area has continued to absorb atmospheric CO2 in recent years with this sink enhancing over time. Furthermore, the change in pCO2 per unit nitrate became larger as surface buffer capacity changed.
BibTeX:
@article{Macovei2020,
  author = {Macovei, Vlad A. and Hartman, Susan E. and Schuster, Ute and Torres-Valdés, Sinhué and Moore, C. Mark and Sanders, Richard J.},
  title = {Impact of physical and biological processes on temporal variations of the ocean carbon sink in the mid-latitude North Atlantic (2002–2016)},
  journal = {Progress in Oceanography},
  publisher = {Elsevier BV},
  year = {2020},
  volume = {180},
  pages = {102223},
  doi = {10.1016/j.pocean.2019.102223}
}
Pastorello G, Trotta C, Canfora E, Chu H, Christianson D, Cheah Y-W, Poindexter C, Chen J, Elbashandy A, Humphrey M, Isaac P, Polidori D, Ribeca A, van Ingen C, Zhang L, Amiro B, Ammann C, Arain MA, Ardö J, Arkebauer T, Arndt SK, Arriga N, Aubinet M, Aurela M, Baldocchi D, Barr A, Beamesderfer E, Marchesini LB, Bergeron O, Beringer J, Bernhofer C, Berveiller D, Billesbach D, Black TA, Blanken PD, Bohrer G, Boike J, Bolstad PV, Bonal D, Bonnefond J-M, Bowling DR, Bracho R, Brodeur J, Brümmer C, Buchmann N, Burban B, Burns SP, Buysse P, Cale P, Cavagna M, Cellier P, Chen S, Chini I, Christensen TR, Cleverly J, Collalti A, Consalvo C, Cook BD, Cook D, Coursolle C, Cremonese E, Curtis PS, D'Andrea E, da Rocha H, Dai X, Davis KJ, De Cinti B, de Grandcourt A, De Ligne A, De Oliveira RC, Delpierre N, Desai AR, Di Bella CM, di Tommasi P, Dolman H, Domingo F, Dong G, Dore S, Duce P, Dufrêne E, Dunn A, Dušek J, Eamus D, Eichelmann U, ElKhidir HAM, Eugster W, Ewenz CM, Ewers B, Famulari D, Fares S, Feigenwinter I, Feitz A, Fensholt R, Filippa G, Fischer M, Frank J, Galvagno M, Gharun M, Gianelle D, Gielen B, Gioli B, Gitelson A, Goded I, Goeckede M, Goldstein AH, Gough CM, Goulden ML, Graf A, Griebel A, Gruening C, Grünwald T, Hammerle A, Han S, Han X, Hansen BU, Hanson C, Hatakka J, He Y, Hehn M, Heinesch B, Hinko-Najera N, Hörtnagl L, Hutley L, Ibrom A, Ikawa H, Jackowicz-Korczynski M, Janouš D, Jans W, Jassal R, Jiang S, Kato T, Khomik M, Klatt J, Knohl A, Knox S, Kobayashi H, Koerber G, Kolle O, Kosugi Y, Kotani A, Kowalski A, Kruijt B, Kurbatova J, Kutsch WL, Kwon H, Launiainen S, Laurila T, Law B, Leuning R, Li Y, Liddell M, Limousin J-M, Lion M, Liska AJ, Lohila A, López-Ballesteros A, López-Blanco E, Loubet B, Loustau D, Lucas-Moffat A, Lüers J, Ma S, Macfarlane C, Magliulo V, Maier R, Mammarella I, Manca G, Marcolla B, Margolis HA, Marras S, Massman W, Mastepanov M, Matamala R, Matthes JH, Mazzenga F, McCaughey H, McHugh I, McMillan AMS, Merbold L, Meyer W, Meyers T, Miller SD, Minerbi S, Moderow U, Monson RK, Montagnani L, Moore CE, Moors E, Moreaux V, Moureaux C, Munger JW, Nakai T, Neirynck J, Nesic Z, Nicolini G, Noormets A, Northwood M, Nosetto M, Nouvellon Y, Novick K, Oechel W, Olesen JE, Ourcival J-M, Papuga SA, Parmentier F-J, Paul-Limoges E, Pavelka M, Peichl M, Pendall E, Phillips RP, Pilegaard K, Pirk N, Posse G, Powell T, Prasse H, Prober SM, Rambal S, Rannik Ü, Raz-Yaseef N, Reed D, de Dios VR, Restrepo-Coupe N, Reverter BR, Roland M, Sabbatini S, Sachs T, Saleska SR, Sánchez-Cañete EP, Sanchez-Mejia ZM, Schmid HP, Schmidt M, Schneider K, Schrader F, Schroder I, Scott RL, Sedlák P, Serrano-Ortíz P, Shao C, Shi P, Shironya I, Siebicke L, Šigut L, Silberstein R, Sirca C, Spano D, Steinbrecher R, Stevens RM, Sturtevant C, Suyker A, Tagesson T, Takanashi S, Tang Y, Tapper N, Thom J, Tiedemann F, Tomassucci M, Tuovinen J-P, Urbanski S, Valentini R, van der Molen M, van Gorsel E, van Huissteden K, Varlagin A, Verfaillie J, Vesala T, Vincke C, Vitale D, Vygodskaya N, Walker JP, Walter-Shea E, Wang H, Weber R, Westermann S, Wille C, Wofsy S, Wohlfahrt G, Wolf S, Woodgate W, Li Y, Zampedri R, Zhang J, Zhou G, Zona D, Agarwal D, Biraud S, Torn M and Papale D (2020), "The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data", Scientific Data., dec, 2020. Vol. 7(1), pp. 225.
BibTeX:
@article{Pastorello2020,
  author = {Pastorello, Gilberto and Trotta, Carlo and Canfora, Eleonora and Chu, Housen and Christianson, Danielle and Cheah, You-Wei and Poindexter, Cristina and Chen, Jiquan and Elbashandy, Abdelrahman and Humphrey, Marty and Isaac, Peter and Polidori, Diego and Ribeca, Alessio and van Ingen, Catharine and Zhang, Leiming and Amiro, Brian and Ammann, Christof and Arain, M. Altaf and Ardö, Jonas and Arkebauer, Timothy and Arndt, Stefan K. and Arriga, Nicola and Aubinet, Marc and Aurela, Mika and Baldocchi, Dennis and Barr, Alan and Beamesderfer, Eric and Marchesini, Luca Belelli and Bergeron, Onil and Beringer, Jason and Bernhofer, Christian and Berveiller, Daniel and Billesbach, Dave and Black, Thomas Andrew and Blanken, Peter D. and Bohrer, Gil and Boike, Julia and Bolstad, Paul V. and Bonal, Damien and Bonnefond, Jean-Marc and Bowling, David R. and Bracho, Rosvel and Brodeur, Jason and Brümmer, Christian and Buchmann, Nina and Burban, Benoit and Burns, Sean P. and Buysse, Pauline and Cale, Peter and Cavagna, Mauro and Cellier, Pierre and Chen, Shiping and Chini, Isaac and Christensen, Torben R. and Cleverly, James and Collalti, Alessio and Consalvo, Claudia and Cook, Bruce D. and Cook, David and Coursolle, Carole and Cremonese, Edoardo and Curtis, Peter S. and D'Andrea, Ettore and da Rocha, Humberto and Dai, Xiaoqin and Davis, Kenneth J. and De Cinti, Bruno and de Grandcourt, Agnes and De Ligne, Anne and De Oliveira, Raimundo C. and Delpierre, Nicolas and Desai, Ankur R. and Di Bella, Carlos Marcelo and di Tommasi, Paul and Dolman, Han and Domingo, Francisco and Dong, Gang and Dore, Sabina and Duce, Pierpaolo and Dufrêne, Eric and Dunn, Allison and Dušek, Jiří and Eamus, Derek and Eichelmann, Uwe and ElKhidir, Hatim Abdalla M. and Eugster, Werner and Ewenz, Cacilia M. and Ewers, Brent and Famulari, Daniela and Fares, Silvano and Feigenwinter, Iris and Feitz, Andrew and Fensholt, Rasmus and Filippa, Gianluca and Fischer, Marc and Frank, John and Galvagno, Marta and Gharun, Mana and Gianelle, Damiano and Gielen, Bert and Gioli, Beniamino and Gitelson, Anatoly and Goded, Ignacio and Goeckede, Mathias and Goldstein, Allen H. and Gough, Christopher M. and Goulden, Michael L. and Graf, Alexander and Griebel, Anne and Gruening, Carsten and Grünwald, Thomas and Hammerle, Albin and Han, Shijie and Han, Xingguo and Hansen, Birger Ulf and Hanson, Chad and Hatakka, Juha and He, Yongtao and Hehn, Markus and Heinesch, Bernard and Hinko-Najera, Nina and Hörtnagl, Lukas and Hutley, Lindsay and Ibrom, Andreas and Ikawa, Hiroki and Jackowicz-Korczynski, Marcin and Janouš, Dalibor and Jans, Wilma and Jassal, Rachhpal and Jiang, Shicheng and Kato, Tomomichi and Khomik, Myroslava and Klatt, Janina and Knohl, Alexander and Knox, Sara and Kobayashi, Hideki and Koerber, Georgia and Kolle, Olaf and Kosugi, Yoshiko and Kotani, Ayumi and Kowalski, Andrew and Kruijt, Bart and Kurbatova, Julia and Kutsch, Werner L. and Kwon, Hyojung and Launiainen, Samuli and Laurila, Tuomas and Law, Bev and Leuning, Ray and Li, Yingnian and Liddell, Michael and Limousin, Jean-Marc and Lion, Marryanna and Liska, Adam J. and Lohila, Annalea and López-Ballesteros, Ana and López-Blanco, Efrén and Loubet, Benjamin and Loustau, Denis and Lucas-Moffat, Antje and Lüers, Johannes and Ma, Siyan and Macfarlane, Craig and Magliulo, Vincenzo and Maier, Regine and Mammarella, Ivan and Manca, Giovanni and Marcolla, Barbara and Margolis, Hank A. and Marras, Serena and Massman, William and Mastepanov, Mikhail and Matamala, Roser and Matthes, Jaclyn Hatala and Mazzenga, Francesco and McCaughey, Harry and McHugh, Ian and McMillan, Andrew M. S. and Merbold, Lutz and Meyer, Wayne and Meyers, Tilden and Miller, Scott D. and Minerbi, Stefano and Moderow, Uta and Monson, Russell K. and Montagnani, Leonardo and Moore, Caitlin E. and Moors, Eddy and Moreaux, Virginie and Moureaux, Christine and Munger, J. William and Nakai, Taro and Neirynck, Johan and Nesic, Zoran and Nicolini, Giacomo and Noormets, Asko and Northwood, Matthew and Nosetto, Marcelo and Nouvellon, Yann and Novick, Kimberly and Oechel, Walter and Olesen, Jørgen Eivind and Ourcival, Jean-Marc and Papuga, Shirley A. and Parmentier, Frans-Jan and Paul-Limoges, Eugenie and Pavelka, Marian and Peichl, Matthias and Pendall, Elise and Phillips, Richard P. and Pilegaard, Kim and Pirk, Norbert and Posse, Gabriela and Powell, Thomas and Prasse, Heiko and Prober, Suzanne M. and Rambal, Serge and Rannik, Üllar and Raz-Yaseef, Naama and Reed, David and de Dios, Victor Resco and Restrepo-Coupe, Natalia and Reverter, Borja R. and Roland, Marilyn and Sabbatini, Simone and Sachs, Torsten and Saleska, Scott R. and Sánchez-Cañete, Enrique P. and Sanchez-Mejia, Zulia M. and Schmid, Hans Peter and Schmidt, Marius and Schneider, Karl and Schrader, Frederik and Schroder, Ivan and Scott, Russell L. and Sedlák, Pavel and Serrano-Ortíz, Penélope and Shao, Changliang and Shi, Peili and Shironya, Ivan and Siebicke, Lukas and Šigut, Ladislav and Silberstein, Richard and Sirca, Costantino and Spano, Donatella and Steinbrecher, Rainer and Stevens, Robert M. and Sturtevant, Cove and Suyker, Andy and Tagesson, Torbern and Takanashi, Satoru and Tang, Yanhong and Tapper, Nigel and Thom, Jonathan and Tiedemann, Frank and Tomassucci, Michele and Tuovinen, Juha-Pekka and Urbanski, Shawn and Valentini, Riccardo and van der Molen, Michiel and van Gorsel, Eva and van Huissteden, Ko and Varlagin, Andrej and Verfaillie, Joseph and Vesala, Timo and Vincke, Caroline and Vitale, Domenico and Vygodskaya, Natalia and Walker, Jeffrey P. and Walter-Shea, Elizabeth and Wang, Huimin and Weber, Robin and Westermann, Sebastian and Wille, Christian and Wofsy, Steven and Wohlfahrt, Georg and Wolf, Sebastian and Woodgate, William and Li, Yuelin and Zampedri, Roberto and Zhang, Junhui and Zhou, Guoyi and Zona, Donatella and Agarwal, Deb and Biraud, Sebastien and Torn, Margaret and Papale, Dario},
  title = {The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data},
  journal = {Scientific Data},
  year = {2020},
  volume = {7},
  number = {1},
  pages = {225},
  url = {http://www.nature.com/articles/s41597-020-0534-3},
  doi = {10.1038/s41597-020-0534-3}
}
Penuelas J, Janssens IA, Ciais P, Obersteiner M and Sardans J (2020), "Anthropogenic global shifts in biospheric N and P concentrations and ratios and their impacts on biodiversity, ecosystem productivity, food security, and human health", Global Change Biology., feb, 2020. Vol. 26(4), pp. 1962-1985. Wiley.
Abstract: The availability of carbon (C) from high levels of atmospheric carbon dioxide (CO2 ) and anthropogenic release of nitrogen (N) is increasing, but these increases are not paralleled by increases in levels of phosphorus (P). The current unstoppable changes in the stoichiometries of C and N relative to P have no historical precedent. We describe changes in P and N fluxes over the last five decades that have led to asymmetrical increases in P and N inputs to the biosphere. We identified widespread and rapid changes in N:P ratios in air, soil, water, and organisms and important consequences to the structure, function, and biodiversity of ecosystems. A mass-balance approach found that the combined limited availability of P and N was likely to reduce C storage by natural ecosystems during the remainder of the 21st Century, and projected crop yields of the Millennium Ecosystem Assessment indicated an increase in nutrient deficiency in developing regions if access to P fertilizer is limited. Imbalances of the N:P ratio would likely negatively affect human health, food security, and global economic and geopolitical stability, with feedbacks and synergistic effects on drivers of global environmental change, such as increasing levels of CO2 , climatic warming, and increasing pollution. We summarize potential solutions for avoiding the negative impacts of global imbalances of N:P ratios on the environment, biodiversity, climate change, food security, and human health.
BibTeX:
@article{Penuelas2020,
  author = {Penuelas, Josep and Janssens, Ivan A. and Ciais, Philippe and Obersteiner, Michael and Sardans, Jordi},
  title = {Anthropogenic global shifts in biospheric N and P concentrations and ratios and their impacts on biodiversity, ecosystem productivity, food security, and human health},
  journal = {Global Change Biology},
  publisher = {Wiley},
  year = {2020},
  volume = {26},
  number = {4},
  pages = {1962--1985},
  doi = {10.1111/gcb.14981}
}
Piao S, Wang X, Wang K, Li X, Bastos A, Canadell JG, Ciais P, Friedlingstein P and Sitch S (2020), "Interannual variation of terrestrial carbon cycle: Issues and perspectives", Global Change Biology., nov, 2020. Vol. 26(1), pp. 300-318. Wiley.
Abstract: With accumulation of carbon cycle observations and model developments over the past decades, exploring interannual variation (IAV) of terrestrial carbon cycle offers the opportunity to better understand climate–carbon cycle relationships. However, despite growing research interest, uncertainties remain on some fundamental issues, such as the contributions of different regions, constituent fluxes and climatic factors to carbon cycle IAV. Here we overviewed the literature on carbon cycle IAV about current understanding of these issues. Observations and models of the carbon cycle unanimously show the dominance of tropical land ecosystems to the signal of global carbon cycle IAV, where tropical semiarid ecosystems contribute as much as the combination of all other tropical ecosystems. Vegetation photosynthesis contributes more than ecosystem respiration to IAV of the global net land carbon flux, but large uncertainties remain on the contribution of fires and other disturbance fluxes. Climatic variations are the major drivers to the IAV of net land carbon flux. Although debate remains on whether the dominant driver is temperature or moisture variability, their interaction,that is, the dependence of carbon cycle sensitivity to temperature on moisture conditions, is emerging as key regulators of the carbon cycle IAV. On timescales from the interannual to the centennial, global carbon cycle variability will be increasingly contributed by northern land ecosystems and oceans. Therefore, both improving Earth system models (ESMs) with the progressive understanding on the fast processes manifested at interannual timescale and expanding carbon cycle observations at broader spatial and longer temporal scales are critical to better prediction on evolution of the carbon–climate system.
BibTeX:
@article{Piao2020,
  author = {Piao, Shilong and Wang, Xuhui and Wang, Kai and Li, Xiangyi and Bastos, Ana and Canadell, Josep G. and Ciais, Philippe and Friedlingstein, Pierre and Sitch, Stephen},
  title = {Interannual variation of terrestrial carbon cycle: Issues and perspectives},
  journal = {Global Change Biology},
  publisher = {Wiley},
  year = {2020},
  volume = {26},
  number = {1},
  pages = {300--318},
  doi = {10.1111/gcb.14884}
}
Silyakova A, Jansson P, Serov P, Ferré B, Pavlov AK, Hattermann T, Graves CA, Platt SM, Myhre CL, Gründger F and Niemann H (2020), "Physical controls of dynamics of methane venting from a shallow seep area west of Svalbard", Continental Shelf Research., feb, 2020. Vol. 194, pp. 104030. Elsevier BV.
Abstract: We investigate methane seepage on the shallow shelf west of Svalbard during three consecutive years, using discrete sampling of the water column, echosounder-based gas flux estimates, water mass properties, and numerical dispersion modelling. The results reveal three distinct hydrographic conditions in spring and summer, showing that the methane content in the water column is controlled by a combination of free gas seepage intensity and lateral water mass movements, which disperse and displace dissolved methane horizontally away from the seeps. Horizontal dispersion and displacement of dissolved methane are promoted by eddies originating from the West Spitsbergen Current and passing over the shallow shelf, a process that is more intense in winter and spring than in the summer season. Most of the methane injected from seafloor seeps resides in the bottom layer even when the water column is well mixed, implying that the controlling effect of water column stratification on vertical methane transport is small. Only small concentrations of methane are found in surface waters, and thus the escape of methane into the atmosphere above the site of seepage is also small. The magnitude of the sea to air methane flux is controlled by wind speed, rather than by the concentration of dissolved methane in the surface ocean.
BibTeX:
@article{Silyakova2020,
  author = {Silyakova, Anna and Jansson, Pär and Serov, Pavel and Ferré, Benedicte and Pavlov, Alexey K. and Hattermann, Tore and Graves, Carolyn A. and Platt, Stephen M. and Myhre, Cathrine Lund and Gründger, Friederike and Niemann, Helge},
  title = {Physical controls of dynamics of methane venting from a shallow seep area west of Svalbard},
  journal = {Continental Shelf Research},
  publisher = {Elsevier BV},
  year = {2020},
  volume = {194},
  pages = {104030},
  doi = {10.1016/j.csr.2019.104030}
}
Simioni G, Marie G, Davi H, Martin-St Paul N and Huc R (2020), "Natural forest dynamics have more influence than climate change on the net ecosystem production of a mixed Mediterranean forest", Ecological Modelling., jan, 2020. Vol. 416, pp. 108921. Elsevier BV.
Abstract: Climate models predict increased drought conditions for the Mediterranean region, putting forests under increasing risk from direct or indirect effects of droughts. On the other hand, increasing CO2 and longer growing seasons could compensate the negative impacts of more intense droughts on forest productivity and carbon sequestration. Furthermore, large areas of Mediterranean forests are relatively young and unmanaged, and maturing usually tends to decrease carbon sequestration. We conducted a simulation study to explore the interplay between climate, CO2, and maturing, on forest net primary production (NPP) and net ecosystem production (NEP) over the 2000–2100 period. We used the Not Only Tree/Grass (NOTG) model, which is individual-based, process-oriented, and spatially explicit. We applied the model to the Font-Blanche experimental site, a typical mixed Mediterranean forest dominated by Aleppo pines and holm oaks. Simulations under three climate scenarios (current, moderate change, severe change) suggest that NPP could be enhanced by climate change, both due to higher CO2 and longer growing seasons. On the other hand NEP would only be temporarily enhanced by climate change. The largest effect, however, was a decrease of NEP over time for all scenarios, due to forest maturing, with heterotrophic respiration progressively catching up with NPP. This implies that, regardless of climate change, the sink capacity of large unmanaged forest areas in southern Europe could strongly diminish during the 21st century.
BibTeX:
@article{Simioni2020,
  author = {Simioni, Guillaume and Marie, Guillaume and Davi, Hendrik and Martin-St Paul, Nicolas and Huc, Roland},
  title = {Natural forest dynamics have more influence than climate change on the net ecosystem production of a mixed Mediterranean forest},
  journal = {Ecological Modelling},
  publisher = {Elsevier BV},
  year = {2020},
  volume = {416},
  pages = {108921},
  doi = {10.1016/j.ecolmodel.2019.108921}
}
Spank U, Hehn M, Keller P, Koschorreck M and Bernhofer C (2020), "A Season of Eddy-Covariance Fluxes Above an Extensive Water Body Based on Observations from a Floating Platform", Boundary-Layer Meteorology., dec, 2020. Vol. 174(3), pp. 433-464. Springer Science and Business Media LLC.
Abstract: The eddy-covariance (EC) technique is used to determine mass and energy fluxes between the Earth's surface and the lower atmosphere at high temporal resolution. Despite the frequent and successful use of the EC technique at terrestrial sites, its application over water surfaces is rare. We present one season of EC measurements conducted on the Rappbode Reservoir, Germany's largest drinking water reservoir. A floating observation platform in the centre of the reservoir is used for observations of fluxes that were unaffected by surrounding land surfaces and therefore representative of the actual water–atmosphere exchange. The temporal patterns of sensible heat flux are inverted compared to land sites, since the maxima and the minima occur at night and day respectively. The latent heat flux and the evaporation are unexpectedly low for a site where evaporation is not limited by the availability of water. The daily totals in summer and autumn are only 50% and 75% of the potential evaporation assessed by the FAO grass-reference evaporation, respectively. Measurement uncertainties and the effects of the energy balance closure are ruled out as potential factors, so that low values appear to be a general feature of large water surfaces. The observed carbon dioxide fluxes are characterized by distinctive diurnal variations in a typical range for lakes and reservoirs. However, the methane fluxes are low compared to other inland waters.
BibTeX:
@article{Spank2020,
  author = {Spank, Uwe and Hehn, Markus and Keller, Philipp and Koschorreck, Matthias and Bernhofer, Christian},
  title = {A Season of Eddy-Covariance Fluxes Above an Extensive Water Body Based on Observations from a Floating Platform},
  journal = {Boundary-Layer Meteorology},
  publisher = {Springer Science and Business Media LLC},
  year = {2020},
  volume = {174},
  number = {3},
  pages = {433--464},
  doi = {10.1007/s10546-019-00490-z}
}
Stocker M, Darroch L, Krahl R, Habermann T, Devaraju A, Schwardmann U, D'Onofrio C and Häggström I (2020), "Persistent Identification of Instruments", Data Science Journal., may, 2020. Vol. 19
BibTeX:
@article{Stocker2020,
  author = {Stocker, Markus and Darroch, Louise and Krahl, Rolf and Habermann, Ted and Devaraju, Anusuriya and Schwardmann, Ulrich and D'Onofrio, Claudio and Häggström, Ingemar},
  title = {Persistent Identification of Instruments},
  journal = {Data Science Journal},
  year = {2020},
  volume = {19},
  url = {http://datascience.codata.org/articles/10.5334/dsj-2020-018/},
  doi = {10.5334/dsj-2020-018}
}
Tagesson T, Schurgers G, Horion S, Ciais P, Tian F, Brandt M, Ahlström A, Wigneron JP, Ardö J, Olin S, Fan L, Wu Z and Fensholt R (2020), "Recent divergence in the contributions of tropical and boreal forests to the terrestrial carbon sink", Nature Ecology and Evolution., jan, 2020. Vol. 4(2), pp. 202-209. Springer Science and Business Media LLC.
Abstract: Anthropogenic land use and land cover changes (LULCC) have a large impact on the global terrestrial carbon sink, but this effect is not well characterized according to biogeographical region. Here, using state-of-the-art Earth observation data and a dynamic global vegetation model, we estimate the impact of LULCC on the contribution of biomes to the terrestrial carbon sink between 1992 and 2015. Tropical and boreal forests contributed equally, and with the largest share of the mean global terrestrial carbon sink. CO2 fertilization was found to be the main driver increasing the terrestrial carbon sink from 1992 to 2015, but the net effect of all drivers (CO2 fertilization and nitrogen deposition, LULCC and meteorological forcing) caused a reduction and an increase, respectively, in the terrestrial carbon sink for tropical and boreal forests. These diverging trends were not observed when applying a conventional LULCC dataset, but were also evident in satellite passive microwave estimates of aboveground biomass. These datasets thereby converge on the conclusion that LULCC have had a greater impact on tropical forests than previously estimated, causing an increase and decrease of the contributions of boreal and tropical forests, respectively, to the growing terrestrial carbon sink.
BibTeX:
@article{Tagesson2020,
  author = {Tagesson, Torbern and Schurgers, Guy and Horion, Stéphanie and Ciais, Philippe and Tian, Feng and Brandt, Martin and Ahlström, Anders and Wigneron, Jean Pierre and Ardö, Jonas and Olin, Stefan and Fan, Lei and Wu, Zhendong and Fensholt, Rasmus},
  title = {Recent divergence in the contributions of tropical and boreal forests to the terrestrial carbon sink},
  journal = {Nature Ecology and Evolution},
  publisher = {Springer Science and Business Media LLC},
  year = {2020},
  volume = {4},
  number = {2},
  pages = {202--209},
  doi = {10.1038/s41559-019-1090-0}
}
Vezy R, le Maire G, Christina M, Georgiou S, Imbach P, Hidalgo HG, Alfaro EJ, Blitz-Frayret C, Charbonnier F, Lehner P, Loustau D and Roupsard O (2020), "DynACof: A process-based model to study growth, yield and ecosystem services of coffee agroforestry systems", Environmental Modelling and Software., feb, 2020. Vol. 124, pp. 104609. Elsevier BV.
Abstract: The DynACof model was designed to model coffee agroforestry systems and study the trade-offs to e.g. optimize the system facing climate changes. The model simulates net primary productivity (NPP), growth, yield, mortality, energy and water balance of coffee agroforestry systems according to shade tree species and management. Several plot-scale ecosystem services are simulated by the model, such as production, canopy cooling effect, or potential C sequestration. DynACof uses metamodels derived from a detailed 3D process-based model (MAESPA) to account for complex spatial effects, while running fast. It also includes a coffee flower bud and fruit cohort module to better distribute fruit carbon demand over the year, a key feature to obtain a realistic competition between sinks. The model was parameterized and evaluated using a highly comprehensive database on a coffee agroforestry experimental site in Costa Rica. The fluxes simulated by the model were close to the measurements over a 5-year period (nRMSE = 26.27 for gross primary productivity; 28.22 for actual evapo-transpiration, 53.91 for sensible heat flux and 15.26 for net radiation), and DynACof satisfactorily simulated the yield, NPP, mortality and carbon stock for each coffee organ type over a 35-year rotation.
BibTeX:
@article{Vezy2020,
  author = {Vezy, Rémi and le Maire, Guerric and Christina, Mathias and Georgiou, Selena and Imbach, Pablo and Hidalgo, Hugo G. and Alfaro, Eric J. and Blitz-Frayret, Céline and Charbonnier, Fabien and Lehner, Peter and Loustau, Denis and Roupsard, Olivier},
  title = {DynACof: A process-based model to study growth, yield and ecosystem services of coffee agroforestry systems},
  journal = {Environmental Modelling and Software},
  publisher = {Elsevier BV},
  year = {2020},
  volume = {124},
  pages = {104609},
  doi = {10.1016/j.envsoft.2019.104609}
}
Vitale D, Fratini G, Bilancia M, Nicolini G, Sabbatini S and Papale D (2020), "A robust data cleaning procedure for eddy covariance flux measurements", Biogeosciences., mar, 2020. Vol. 17(6), pp. 1367-1391.
BibTeX:
@article{Vitale2020,
  author = {Vitale, Domenico and Fratini, Gerardo and Bilancia, Massimo and Nicolini, Giacomo and Sabbatini, Simone and Papale, Dario},
  title = {A robust data cleaning procedure for eddy covariance flux measurements},
  journal = {Biogeosciences},
  year = {2020},
  volume = {17},
  number = {6},
  pages = {1367--1391},
  url = {https://www.biogeosciences.net/17/1367/2020/},
  doi = {10.5194/bg-17-1367-2020}
}
Wigneron JP, Fan L, Ciais P, Bastos A, Brandt M, Chave J, Saatchi S, Baccini A and Fensholt R (2020), "Tropical forests did not recover from the strong 2015–2016 El Niño event", Science Advances., feb, 2020. Vol. 6(6), pp. eaay4603. American Association for the Advancement of Science (AAAS).
Abstract: Severe drought and extreme heat associated with the 2015–2016 El Niño event have led to large carbon emissions from the tropical vegetation to the atmosphere. With the return to normal climatic conditions in 2017, tropical forest aboveground carbon (AGC) stocks are expected to partly recover due to increased productivity, but the intensity and spatial distribution of this recovery are unknown. We used low-frequency microwave satellite data (L-VOD) to feature precise monitoring of AGC changes and show that the AGC recovery of tropical ecosystems was slow and that by the end of 2017, AGC had not reached predrought levels of 2014. From 2014 to 2017, tropical AGC stocks decreased by 1.31.51.2 Pg C due to persistent AGC losses in Africa (−0.9−0.8−1.1 Pg C) and America (−0.5−0.4−0.6 Pg C). Pantropically, drylands recovered their carbon stocks to pre–El Niño levels, but African and American humid forests did not, suggesting carryover effects from enhanced forest mortality.
BibTeX:
@article{Wigneron2020,
  author = {Wigneron, Jean Pierre and Fan, Lei and Ciais, Philippe and Bastos, Ana and Brandt, Martin and Chave, Jérome and Saatchi, Sassan and Baccini, Alessandro and Fensholt, Rasmus},
  title = {Tropical forests did not recover from the strong 2015–2016 El Niño event},
  journal = {Science Advances},
  publisher = {American Association for the Advancement of Science (AAAS)},
  year = {2020},
  volume = {6},
  number = {6},
  pages = {eaay4603},
  doi = {10.1126/sciadv.aay4603}
}
Zhang H, Goll DS, Wang YP, Ciais P, Wieder WR, Abramoff R, Huang Y, Guenet B, Prescher AK, Viscarra Rossel RA, Barré P, Chenu C, Zhou G and Tang X (2020), "Microbial dynamics and soil physicochemical properties explain large-scale variations in soil organic carbon", Global Change Biology., feb, 2020. Vol. 26(4), pp. 2668-2685. Wiley.
Abstract: First-order organic matter decomposition models are used within most Earth System Models (ESMs) to project future global carbon cycling; these models have been criticized for not accurately representing mechanisms of soil organic carbon (SOC) stabilization and SOC response to climate change. New soil biogeochemical models have been developed, but their evaluation is limited to observations from laboratory incubations or few field experiments. Given the global scope of ESMs, a comprehensive evaluation of such models is essential using in situ observations of a wide range of SOC stocks over large spatial scales before their introduction to ESMs. In this study, we collected a set of in situ observations of SOC, litterfall and soil properties from 206 sites covering different forest and soil types in Europe and China. These data were used to calibrate the model MIMICS (The MIcrobial-MIneral Carbon Stabilization model), which we compared to the widely used first-order model CENTURY. We show that, compared to CENTURY, MIMICS more accurately estimates forest SOC concentrations and the sensitivities of SOC to variation in soil temperature, clay content and litter input. The ratios of microbial biomass to total SOC predicted by MIMICS agree well with independent observations from globally distributed forest sites. By testing different hypotheses regarding (using alternative process representations) the physicochemical constraints on SOC deprotection and microbial turnover in MIMICS, the errors of simulated SOC concentrations across sites were further decreased. We show that MIMICS can resolve the dominant mechanisms of SOC decomposition and stabilization and that it can be a reliable tool for predictions of terrestrial SOC dynamics under future climate change. It also allows us to evaluate at large scale the rapidly evolving understanding of SOC formation and stabilization based on laboratory and limited filed observation.
BibTeX:
@article{Zhang2020,
  author = {Zhang, Haicheng and Goll, Daniel S. and Wang, Ying Ping and Ciais, Philippe and Wieder, William R. and Abramoff, Rose and Huang, Yuanyuan and Guenet, Bertrand and Prescher, Anne Katrin and Viscarra Rossel, Raphael A. and Barré, Pierre and Chenu, Claire and Zhou, Guoyi and Tang, Xuli},
  title = {Microbial dynamics and soil physicochemical properties explain large-scale variations in soil organic carbon},
  journal = {Global Change Biology},
  publisher = {Wiley},
  year = {2020},
  volume = {26},
  number = {4},
  pages = {2668--2685},
  doi = {10.1111/gcb.14994}
}
Zhang H, Väliranta M, Piilo S, Amesbury MJ, Aquino‐López MA, Roland TP, Salminen‐Paatero S, Paatero J, Lohila A and Tuittila E (2020), "Decreased carbon accumulation feedback driven by climate‐induced drying of two southern boreal bogs over recent centuries", Global Change Biology., feb, 2020. Vol. 26(4), pp. 2435-2448. Wiley.
Abstract: textlessptextgreaterNorthern boreal peatlands are important ecosystems in modulating global biogeochemical cycles, yet their biological communities and related carbon dynamics are highly sensitive to changes in climate. Despite this, the strength and recent direction of these feedbacks are still unclear. The response of boreal peatlands to climate warming has received relatively little attention compared with other northern peatland types, despite forming a large northern hemisphere‐wide ecosystem. Here we studied the response of two ombrotrophic boreal peatlands to climate variability over the last textlessitextgreaterctextless/itextgreater. 200 years for which local meteorological data are available. We used remains from plants and testate amoebae to study historical changes in peatland biological communities. These data were supplemented by peat property (bulk density, carbon and nitrogen content), textlesssuptextgreater14textless/suptextgreaterC, textlesssuptextgreater210textless/suptextgreaterPb and textlesssuptextgreater137textless/suptextgreaterCs analyses and were used to infer changes in peatland hydrology and carbon dynamics. In total, six peat cores, three per study site, were studied that represent different microhabitats: low hummock, high lawn and low lawn. The data show a consistent drying trend over recent centuries, represented mainly as a change from wet habitat textlessitextgreaterSphagnumtextless/itextgreater spp. to dry habitat textlessitextgreaterS. fuscumtextless/itextgreater. Summer temperature and precipitation appeared to be important drivers shaping peatland community and surface moisture conditions. Data from the driest microhabitat studied, low hummock, revealed a clear and strong negative linear correlation (Rtextlesssuptextgreater2textless/suptextgreater = 0.5031, textlessitextgreaterptextless/itextgreater textless 0.001) between carbon accumulation rate and peat surface moisture conditions: under dry conditions, less carbon was accumulated. This suggests that at the dry end of the moisture gradient, availability of water regulates carbon accumulation. It can be further linked to the decreased abundance of mixotrophic testate amoebae under drier conditions (Rtextlesssuptextgreater2textless/suptextgreater = 0.4207, textlessitextgreaterptextless/itextgreater textless 0.001). Our study implies that if effective precipitation decreases in the future, the carbon uptake capacity of boreal bogs may be threatened.textless/ptextgreater
BibTeX:
@article{Zhang2020a,
  author = {Zhang, Hui and Väliranta, Minna and Piilo, Sanna and Amesbury, Matthew J. and Aquino‐López, Marco A. and Roland, Thomas P. and Salminen‐Paatero, Susanna and Paatero, Jussi and Lohila, Annalea and Tuittila, Eeva‐Stiina},
  title = {Decreased carbon accumulation feedback driven by climate‐induced drying of two southern boreal bogs over recent centuries},
  journal = {Global Change Biology},
  publisher = {Wiley},
  year = {2020},
  volume = {26},
  number = {4},
  pages = {2435--2448},
  doi = {10.1111/gcb.15005}
}
Acosta M, Dušek J, Chamizo S, Serrano-Ortiz P and Pavelka M (2019), "Autumnal fluxes of CH4 and CO2 from Mediterranean reed wetland based on eddy covariance and chamber methods", Catena., dec, 2019. Vol. 183, pp. 104191. Elsevier BV.
Abstract: Atmospheric methane (CH4) and carbon dioxide (CO2) concentration have been increasing during the last several centuries due to changes in agricultural practices and other anthropogenic activities. Both greenhouse gases (GHGs), have a significant impact on the Earth's radiative balance. GHG effluxes of CH4 and CO2 were measured in a warm Mediterranean wetland in south of Spain. The dominant vegetation cover at the site was by common reed (Phragmites australis) and the measurements were done during short measurement campaign in early autumn 2015. Gas-flux measurements were carried out applying two methods, the eddy covariance (EC) technique and the chamber method (CM). These two methods representing different ecosystem subsets, with EC representing the plant/ecosystem subset and CM representing the water/soil subset. In our measurement campaigns using CM, CH4 emissions ranged from 7.2 to 17.7 mg CH4-C m−2 d−1 and CO2 emissions from 0.53 to 1.27 g CO2-C m−2 d−1. When using EC, the average fluxes of CH4 and CO2 were 31.4 mg CH4-C m−2 d−1 and 1.32 g CO2-C m−2 d−1, respectively. Relationships between gas fluxes (CO2 and CH4) measured by the EC method were quite closely correlated with photosynthetically active solar radiation. Our results showed higher CO2 carbon released from the water/soil ecosystem subset in comparison to plants subset. On the other hand, the estimated CH4 carbon balance for the plant/ecosystem subset was about twice that of the water/soil ecosystem subset. Overall, we showed that EC and CM methods cover different areas making EC advantageous for integrated measurements over larger areas, while the CM approach is suitable for local and spatially well constrained flux measurements. Hence, EC and CM methods should be seen as complementary rather than fully comparable methods.
BibTeX:
@article{Acosta2019,
  author = {Acosta, Manuel and Dušek, Jiří and Chamizo, S. and Serrano-Ortiz, Penelope and Pavelka, Marian},
  title = {Autumnal fluxes of CH4 and CO2 from Mediterranean reed wetland based on eddy covariance and chamber methods},
  journal = {Catena},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {183},
  pages = {104191},
  doi = {10.1016/j.catena.2019.104191}
}
Agustí-Panareda A, Diamantakis M, Massart S, Chevallier F, Muñoz-Sabater J, Barré J, Curcoll R, Engelen R, Langerock B, Law RM, Loh Z, Morguí JA, Parrington M, Peuch VH, Ramonet M, Roehl C, Vermeulen AT, Warneke T and Wunch D (2019), "Modelling CO2 weather-why horizontal resolution matters", Atmospheric Chemistry and Physics., jun, 2019. Vol. 19(11), pp. 7347-7376.
Abstract: Climate change mitigation efforts require information on the current greenhouse gas atmospheric concentrations and their sources and sinks. Carbon dioxide (CO2) is the most abundant anthropogenic greenhouse gas. Its variability in the atmosphere is modulated by the synergy between weather and CO2 surface fluxes, often referred to as CO2 weather. It is interpreted with the help of global or regional numerical transport models, with horizontal resolutions ranging from a few hundreds of kilometres to a few kilometres. Changes in the model horizontal resolution affect not only atmospheric transport but also the representation of topography and surface CO2 fluxes. This paper assesses the impact of horizontal resolution on the simulated atmospheric CO2 variability with a numerical weather prediction model. The simulations are performed using the Copernicus Atmosphere Monitoring Service (CAMS) CO2 forecasting system at different resolutions from 9 to 80 km and are evaluated using in situ atmospheric surface measurements and atmospheric column-mean observations of CO2, as well as radiosonde and SYNOP observations of the winds. The results indicate that both diurnal and day-to-day variability of atmospheric CO2 are generally better represented at high resolution, as shown by a reduction in the errors in simulated wind and CO2. Mountain stations display the largest improvements at high resolution as they directly benefit from the more realistic orography. In addition, the CO2 spatial gradients are generally improved with increasing resolution for both stations near the surface and those observing the total column, as the overall inter-station error is also reduced in magnitude. However, close to emission hotspots, the high resolution can also lead to a deterioration of the simulation skill, highlighting uncertainties in the high-resolution fluxes that are more diffuse at lower resolutions. We conclude that increasing horizontal resolution matters for modelling CO2 weather because it has the potential to bring together improvements in the surface representation of both winds and CO2 fluxes, as well as an expected reduction in numerical errors of transport. Modelling applications like atmospheric inversion systems to estimate surface fluxes will only be able to benefit fully from upgrades in horizontal resolution if the topography, winds and prior flux distribution are also upgraded accordingly. It is clear from the results that an additional increase in resolution might reduce errors even further. However, the horizontal resolution sensitivity tests indicate that the change in the CO2 and wind modelling error with resolution is not linear, making it difficult to quantify the improvement beyond the tested resolutions. Finally, we show that the high-resolution simulations are useful for the assessment of the small-scale variability of CO2 which cannot be represented in coarser-resolution models. These representativeness errors need to be considered when assimilating in situ data and high-resolution satellite data such as Greenhouse gases Observing Satellite (GOSAT), Orbiting Carbon Observatory-2 (OCO-2), the Chinese Carbon Dioxide Observation Satellite Mission (TanSat) and future missions such as the Geostationary Carbon Observatory (GeoCarb) and the Sentinel satellite constellation for CO2. For these reasons, the high-resolution CO2 simulations provided by the CAMS in real time can be useful to estimate such small-scale variability in real time, as well as providing boundary conditions for regional modelling studies and supporting field experiments.
BibTeX:
@article{AgustiPanareda2019,
  author = {Agustí-Panareda, Anna and Diamantakis, Michail and Massart, Sébastien and Chevallier, Frédéric and Muñoz-Sabater, Joaquín and Barré, Jérôme and Curcoll, Roger and Engelen, Richard and Langerock, Bavo and Law, Rachel M. and Loh, Zoë and Morguí, Josep Anton and Parrington, Mark and Peuch, Vincent Henri and Ramonet, Michel and Roehl, Coleen and Vermeulen, Alex T. and Warneke, Thorsten and Wunch, Debra},
  title = {Modelling CO2 weather-why horizontal resolution matters},
  journal = {Atmospheric Chemistry and Physics},
  year = {2019},
  volume = {19},
  number = {11},
  pages = {7347--7376},
  url = {https://www.atmos-chem-phys.net/19/7347/2019/},
  doi = {10.5194/acp-19-7347-2019}
}
Alice Courtois E, Stahl C, Burban B, Van Den Berge J, Berveiller D, Bréchet L, Larned Soong J, Arriga N, Peñuelas J and August Janssens I (2019), "Automatic high-frequency measurements of full soil greenhouse gas fluxes in a tropical forest", Biogeosciences., feb, 2019. Vol. 16(3), pp. 785-796. Copernicus GmbH.
Abstract: Measuring in situ soil fluxes of carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) continuously at high frequency requires appropriate technology. We tested the combination of a commercial automated soil CO 2 flux chamber system (LI-8100A) with a CH 4 and N 2 O analyzer (Picarro G2308) in a tropical rainforest for 4 months. A chamber closure time of 2 min was sufficient for a reliable estimation of CO 2 and CH 4 fluxes (100% and 98.5% of fluxes were above minimum detectable flux - MDF, respectively). This closure time was generally not suitable for a reliable estimation of the low N 2 O fluxes in this ecosystem but was sufficient for detecting rare major peak events. A closure time of 25 min was more appropriate for reliable estimation of most N 2 O fluxes (85.6% of measured fluxes are above MDF±0.002 nmolm -2 s -1 ). Our study highlights the importance of adjusted closure time for each gas.
BibTeX:
@article{AliceCourtois2019,
  author = {Alice Courtois, Elodie and Stahl, Clément and Burban, Benoit and Van Den Berge, Joke and Berveiller, Daniel and Bréchet, Laëtitia and Larned Soong, Jennifer and Arriga, Nicola and Peñuelas, Josep and August Janssens, Ivan},
  title = {Automatic high-frequency measurements of full soil greenhouse gas fluxes in a tropical forest},
  journal = {Biogeosciences},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {16},
  number = {3},
  pages = {785--796},
  doi = {10.5194/bg-16-785-2019}
}
Araujo M, Noriega C, Medeiros C, Lefèvre N, Ibánhez JSP, Flores Montes M, da Silva AC and Santos MdL (2019), "On the variability in the CO2 system and water productivity in the western tropical Atlantic off North and Northeast Brazil", Journal of Marine Systems., jan, 2019. Vol. 189, pp. 62-77. Elsevier BV.
Abstract: A high-resolution nutrient biochemistry and carbonate system surface synoptic data set from the N-NE Brazilian continental shelf was reanalyzed to fill a gap in the time series of the carbonate system in the region and to allow us to perform a historical analysis of its evolution in recent years. We used data collected from 7 oceanographic cruises (n = 852) undertaken between March 1995 and September 2001 during the Brazilian Program “REVIZEE” in the North (N) and Northeast (NE) Economical Exclusive Zones of Brazil. Measured temperature and salinity data, which exhibited strong fluctuations (25.5 °C – 29.5 °C and 13.2–37.4 units, respectively), showed significant differences between the N and NE campaigns. The concentrations of dissolved inorganic nitrogen (DIN), PO4− and SiO2− were higher in the N region than in the NE region, mainly due to fluvial transport, and nitrogen: phosphorus (N:P) ratios of textless16 and oxygen supersaturation were observed within the Amazon plume. The concentrations of riverine nutrients in the N region support primary production occurring in the offshore plume area. The calculated total alkalinity (1031–2437 μmol kg−1) values showed strong spatial variations that were mainly associated with the Amazon plume. The calculated pCO2 values reached 423 μatm offshore in the NE region during boreal winter. The calculated sea-air CO2 fluxes (average: +0.3 ± 1.7 mmol m−2 d−1; range: −1.2 to +2.0 mmol m−2 d−1) showed spatial and temporal variations, with negative values (sink) in the region of the Amazon River plume and positive values (source) offshore in the NE region (4°S to 12°S). The variability in the sea-air CO2 fluxes in the N and NE regions was explained by variations in biological activity and the thermodynamic effect of temperature, respectively. The analysis of available data, complemented with those presented here, indicated that the surface water pCO2 values showed a positive temporal trend (+1.10 ± 0.2 μatm yr−1) in the NE region during the period of 1987–2010. This rate of increase is lower than that verified to have occurred in the atmosphere (+1.72 ± 0.01 μatm yr−1) during the same period.
BibTeX:
@article{Araujo2019,
  author = {Araujo, Moacyr and Noriega, Carlos and Medeiros, Carmen and Lefèvre, Nathalie and Ibánhez, J. Severino P. and Flores Montes, Manuel and da Silva, Alex Costa and Santos, Maria de Lourdes},
  title = {On the variability in the CO2 system and water productivity in the western tropical Atlantic off North and Northeast Brazil},
  journal = {Journal of Marine Systems},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {189},
  pages = {62--77},
  doi = {10.1016/j.jmarsys.2018.09.008}
}
Ariza-Carricondo C, Di Mauro F, De Beeck MO, Roland M, Gielen B, Vitale D, Ceulemans R and Papale D (2019), "A comparison of different methods for assessing leaf area index in four canopy types", Central European Forestry Journal., jun, 2019. Vol. 65(2), pp. 67-80. Walter de Gruyter GmbH.
Abstract: The agreement of Leaf Area Index (LAI) assessments from three indirect methods, i.e. the LAI-2200 Plant Canopy Analyzer, the SS1 SunScan Canopy Analysis System and Digital Hemispherical Photography (DHP) was evaluated for four canopy types, i.e. a short rotation coppice plantation (SRC) with poplar, a Scots pine stand, a Pedunculate oak stand and a maize field. In the SRC and in the maize field, the indirect measurements were compared with direct measurements (litter fall and harvesting). In the low LAI range (0 to 2) the discrepancies of the SS1 were partly explained by the inability to properly account for clumping and the uncertainty of the ellipsoidal leaf angle distribution parameter. The higher values for SS1 in the medium (2 to 6) to high (6 to 8) ranges might be explained by gap fraction saturation for LAI-2200 and DHP above certain values. Wood area index-understood as the woody light-blocking elements from the canopy with respect to diameter growth-accounted for overestimation by all indirect methods when compared to direct methods in the SRC. The inter-comparison of the three indirect methods in the four canopy types showed a general agreement for all methods in the medium LAI range (2 to 6). LAI-2200 and DHP revealed the best agreement among the indirect methods along the entire range of LAI (0 to 8) in all canopy types. SS1 showed some discrepancies with the LAI-2200 and DHP at low (0 to 2) and high ranges of LAI (6 to 8).
BibTeX:
@article{ArizaCarricondo2019,
  author = {Ariza-Carricondo, Cristina and Di Mauro, Francesca and De Beeck, Maarten Op and Roland, Marilyn and Gielen, Bert and Vitale, Domenico and Ceulemans, Reinhart and Papale, Dario},
  title = {A comparison of different methods for assessing leaf area index in four canopy types},
  journal = {Central European Forestry Journal},
  publisher = {Walter de Gruyter GmbH},
  year = {2019},
  volume = {65},
  number = {2},
  pages = {67--80},
  doi = {10.2478/forj-2019-0011}
}
Baeten L, Bruelheide H, van der Plas F, Kambach S, Ratcliffe S, Jucker T, Allan E, Ampoorter E, Barbaro L, Bastias CC, Bauhus J, Benavides R, Bonal D, Bouriaud O, Bussotti F, Carnol M, Castagneyrol B, Charbonnier Y, Chećko E, Coomes DA, Dahlgren J, Dawud SM, De Wandeler H, Domisch T, Finér L, Fischer M, Fotelli M, Gessler A, Grossiord C, Guyot V, Hättenschwiler S, Jactel H, Jaroszewicz B, Joly FX, Koricheva J, Lehtonen A, Müller S, Muys B, Nguyen D, Pollastrini M, Radoglou K, Raulund-Rasmussen K, Ruiz-Benito P, Selvi F, Stenlid J, Valladares F, Vesterdal L, Verheyen K, Wirth C, Zavala MA and Scherer-Lorenzen M (2019), "Identifying the tree species compositions that maximize ecosystem functioning in European forests", Journal of Applied Ecology., dec, 2019. Vol. 56(3), pp. 733-744. Wiley.
Abstract: Forest ecosystem functioning generally benefits from higher tree species richness, but variation within richness levels is typically large. This is mostly due to the contrasting performances of communities with different compositions. Evidence-based understanding of composition effects on forest productivity, as well as on multiple other functions will enable forest managers to focus on the selection of species that maximize functioning, rather than on diversity per se. We used a dataset of 30 ecosystem functions measured in stands with different species richness and composition in six European forest types. First, we quantified whether the compositions that maximize annual above-ground wood production (productivity) generally also fulfil the multiple other ecosystem functions (multifunctionality). Then, we quantified the species identity effects and strength of interspecific interactions to identify the “best” and “worst” species composition for multifunctionality. Finally, we evaluated the real-world frequency of occurrence of best and worst mixtures, using harmonized data from multiple national forest inventories. The most productive tree species combinations also tended to express relatively high multifunctionality, although we found a relatively wide range of compositions with high- or low-average multifunctionality for the same level of productivity. Monocultures were distributed among the highest as well as the lowest performing compositions. The variation in functioning between compositions was generally driven by differences in the performance of the component species and, to a lesser extent, by particular interspecific interactions. Finally, we found that the most frequent species compositions in inventory data were monospecific stands and that the most common compositions showed below-average multifunctionality and productivity. Synthesis and applications. Species identity and composition effects are essential to the development of high-performing production systems, for instance in forestry and agriculture. They therefore deserve great attention in the analysis and design of functional biodiversity studies if the aim is to inform ecosystem management. A management focus on tree productivity does not necessarily trade-off against other ecosystem functions; high productivity and multifunctionality can be combined with an informed selection of tree species and species combinations.
BibTeX:
@article{Baeten2019,
  author = {Baeten, Lander and Bruelheide, Helge and van der Plas, Fons and Kambach, Stephan and Ratcliffe, Sophia and Jucker, Tommaso and Allan, Eric and Ampoorter, Evy and Barbaro, Luc and Bastias, Cristina C. and Bauhus, Jürgen and Benavides, Raquel and Bonal, Damien and Bouriaud, Olivier and Bussotti, Filippo and Carnol, Monique and Castagneyrol, Bastien and Charbonnier, Yohan and Chećko, Ewa and Coomes, David A. and Dahlgren, Jonas and Dawud, Seid Muhie and De Wandeler, Hans and Domisch, Timo and Finér, Leena and Fischer, Markus and Fotelli, Mariangela and Gessler, Arthur and Grossiord, Charlotte and Guyot, Virginie and Hättenschwiler, Stephan and Jactel, Hervé and Jaroszewicz, Bogdan and Joly, François Xavier and Koricheva, Julia and Lehtonen, Aleksi and Müller, Sandra and Muys, Bart and Nguyen, Diem and Pollastrini, Martina and Radoglou, Kalliopi and Raulund-Rasmussen, Karsten and Ruiz-Benito, Paloma and Selvi, Federico and Stenlid, Jan and Valladares, Fernando and Vesterdal, Lars and Verheyen, Kris and Wirth, Christian and Zavala, Miguel A. and Scherer-Lorenzen, Michael},
  editor = {Mori, Akira},
  title = {Identifying the tree species compositions that maximize ecosystem functioning in European forests},
  journal = {Journal of Applied Ecology},
  publisher = {Wiley},
  year = {2019},
  volume = {56},
  number = {3},
  pages = {733--744},
  doi = {10.1111/1365-2664.13308}
}
Balzarolo M, Valdameri N, Fu YH, Schepers L, Janssens IA and Campioli M (2019), "Different determinants of radiation use efficiency in cold and temperate forests", Global Ecology and Biogeography., aug, 2019. Vol. 28(11), pp. 1649-1667. Wiley.
Abstract: Aim: To verify which vegetation and environmental factors are the most important in determining the spatial and temporal variability of average and maximum values of radiation use efficiency (RUEann and RUEmax, respectively) of cold and temperate forests. Location: Forty-eight cold and temperate forests distributed across the Northern Hemisphere. Major taxa studied: Evergreen and deciduous trees. Time period: 2000–2011. Methods: We analysed the impact of 17 factors as potential determinants of mean RUE (at 8 days interval, annual and interannual level) and RUEmax (at annual and interannual level) in cold and temperate forests by using linear regression and random forests models. Results: Mean annual RUE (RUEann, c. 1.1 gC/MJ) and RUEmax (c. 0.8 gC/MJ) did not differ between cold and temperate forests. However, for cold forests, RUEann was affected by temperature-related variables, while for temperate forests RUEann was affected by drought-related variables. Leaf area index (LAI) was important for both forest types, while N deposition only for cold forests and cloud cover only for temperate forest. RUEmax of cold forests was mainly driven by N deposition and LAI, whereas for temperate forests only a weak relationship between RUEmax and CO2 concentration was found. Short-term variability of RUE was strongly related to the meteorological variables and varied during the season and was stronger in summer than spring or autumn. Interannual variability of RUEann and RUEmax was only weakly related to the interannual variability of the environmental drivers. Main conclusions: Cold and temperate forests show different relationships with the environment and vegetation properties. Among the RUE drivers observed, the least anticipated was N deposition. RUE is strongly related to short-term and seasonal changes in meteorological variables among seasons and among sites. Our results should be considered in the formulation of climate zone-specific tools for remote sensing and global models.
BibTeX:
@article{Balzarolo2019,
  author = {Balzarolo, Manuela and Valdameri, Nadia and Fu, Yongshuo H. and Schepers, Lennert and Janssens, Ivan A. and Campioli, Matteo},
  editor = {Kerkhoff, Andrew},
  title = {Different determinants of radiation use efficiency in cold and temperate forests},
  journal = {Global Ecology and Biogeography},
  publisher = {Wiley},
  year = {2019},
  volume = {28},
  number = {11},
  pages = {1649--1667},
  doi = {10.1111/geb.12985}
}
Bange HW, Arévalo-Martínez DL, de la Paz M, Farías L, Kaiser J, Kock A, Law CS, Rees AP, Rehder G, Tortell PD, Upstill-Goddard RC and Wilson ST (2019), "A harmonized nitrous oxide (N 2 O) ocean observation network for the 21st century", Frontiers in Marine Science., apr, 2019. Vol. 6(APR) Frontiers Media SA.
Abstract: Nitrous oxide (N 2 O) is an important atmospheric trace gas involved in tropospheric warming and stratospheric ozone depletion. Estimates of the global ocean contribution to N 2 O emissions average 21% (range: 10 to 53%). Ongoing environmental changes such as warming, deoxygenation and acidification are affecting oceanic N 2 O cycling and emissions to the atmosphere. International activities over the last decades aimed at improving estimates of global N 2 O emissions, including (i) the MarinE MethanE and NiTrous Oxide database (MEMENTO) for archiving of quality-controlled data, and (ii) a recent large-scale inter-laboratory comparison by Working Group 143 of the Scientific Committee on Ocean Research (SCOR). To reduce uncertainties in oceanic N 2 O emission estimates and to characterize the spatial and temporal variability in N 2 O distributions in a changing ocean, we propose the establishment of a harmonized N 2 O Observation Network (N 2 O-ON) combining discrete and continuous data from various platforms. The network will integrate observations obtained by calibrated techniques, using time series measurements at fixed stations and repeated hydrographic sections on voluntary observing ships and research vessels. In addition to exploiting existing oceanographic infrastructure, we propose the establishment of central calibration facilities in selected international laboratories to improve accuracy, and ensure standardization and comparability of N 2 O measurements. Final data products will include a harmonized global N 2 O concentration and emission fields for use in model validation and projections of future oceanic N 2 O emissions, to inform the global research community and policy makers.
BibTeX:
@article{Bange2019,
  author = {Bange, Hermann W. and Arévalo-Martínez, Damian L. and de la Paz, Mercedes and Farías, Laura and Kaiser, Jan and Kock, Annette and Law, Cliff S. and Rees, Andrew P. and Rehder, Gregor and Tortell, Philippe D. and Upstill-Goddard, Robert C. and Wilson, Samuel T.},
  title = {A harmonized nitrous oxide (N 2 O) ocean observation network for the 21st century},
  journal = {Frontiers in Marine Science},
  publisher = {Frontiers Media SA},
  year = {2019},
  volume = {6},
  number = {APR},
  doi = {10.3389/fmars.2019.00157}
}
Bastos A, Ciais P, Chevallier F, Rödenbeck C, Ballantyne AP, Maignan F, Yin Y, Fernández-Martínez M, Friedlingstein P, Peñuelas J, Piao SL, Sitch S, Smith WK, Wang X, Zhu Z, Haverd V, Kato E, Jain AK, Lienert S, Lombardozzi D, Nabel JE, Peylin P, Poulter B and Zhu D (2019), "Contrasting effects of CO2 fertilization, land-use change and warming on seasonal amplitude of Northern Hemisphere CO2 exchange", Atmospheric Chemistry and Physics., oct, 2019. Vol. 19(19), pp. 12361-12375. Copernicus GmbH.
Abstract: Continuous atmospheric CO2 monitoring data indicate an increase in the amplitude of seasonal CO2-cycle exchange (SCANBP) in northern high latitudes. The major drivers of enhanced SCANBP remain unclear and intensely debated, with land-use change, CO2 fertilization and warming being identified as likely contributors. We integrated CO2-flux data from two atmospheric inversions (consistent with atmospheric records) and from 11 state-of-the-art land-surface models (LSMs) to evaluate the relative importance of individual contributors to trends and drivers of the SCANBP of CO2 fluxes for 1980-2015. The LSMs generally reproduce the latitudinal increase in SCANBP trends within the inversions range. Inversions and LSMs attribute SCANBP increase to boreal Asia and Europe due to enhanced vegetation productivity (in LSMs) and point to contrasting effects of CO2 fertilization (positive) and warming (negative) on SCANBP. Our results do not support land-use change as a key contributor to the increase in SCANBP. The sensitivity of simulated microbial respiration to temperature in LSMs explained biases in SCANBP trends, which suggests that SCANBP could help to constrain model turnover times.
BibTeX:
@article{Bastos2019,
  author = {Bastos, Ana and Ciais, Philippe and Chevallier, Frédéric and Rödenbeck, Christian and Ballantyne, Ashley P. and Maignan, Fabienne and Yin, Yi and Fernández-Martínez, Marcos and Friedlingstein, Pierre and Peñuelas, Josep and Piao, Shilong L. and Sitch, Stephen and Smith, William K. and Wang, Xuhui and Zhu, Zaichun and Haverd, Vanessa and Kato, Etsushi and Jain, Atul K. and Lienert, Sebastian and Lombardozzi, Danica and Nabel, Julia E.M.S. and Peylin, Philippe and Poulter, Benjamin and Zhu, Dan},
  title = {Contrasting effects of CO2 fertilization, land-use change and warming on seasonal amplitude of Northern Hemisphere CO2 exchange},
  journal = {Atmospheric Chemistry and Physics},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {19},
  number = {19},
  pages = {12361--12375},
  doi = {10.5194/acp-19-12361-2019}
}
Bechtold M, De Lannoy GJ, Koster RD, Reichle RH, Mahanama SP, Bleuten W, Bourgault MA, Brümmer C, Burdun I, Desai AR, Devito K, Grünwald T, Grygoruk M, Humphreys ER, Klatt J, Kurbatova J, Lohila A, Munir TM, Nilsson MB, Price JS, Röhl M, Schneider A and Tiemeyer B (2019), "PEAT-CLSM: A Specific Treatment of Peatland Hydrology in the NASA Catchment Land Surface Model", Journal of Advances in Modeling Earth Systems., jul, 2019. Vol. 11(7), pp. 2130-2162.
Abstract: Peatlands are poorly represented in global Earth system modeling frameworks. Here we add a peatland-specific land surface hydrology module (PEAT-CLSM) to the Catchment Land Surface Model (CLSM) of the NASA Goddard Earth Observing System (GEOS) framework. The amended TOPMODEL approach of the original CLSM that uses topography characteristics to model catchment processes is discarded, and a peatland-specific model concept is realized in its place. To facilitate its utilization in operational GEOS efforts, PEAT-CLSM uses the basic structure of CLSM and the same global input data. Parameters used in PEAT-CLSM are based on literature data. A suite of CLSM and PEAT-CLSM simulations for peatland areas between 40°N and 75°N is presented and evaluated against a newly compiled data set of groundwater table depth and eddy covariance observations of latent and sensible heat fluxes in natural and seminatural peatlands. CLSM's simulated groundwater tables are too deep and variable, whereas PEAT-CLSM simulates a mean groundwater table depth of −0.20 m (snow-free unfrozen period) with moderate temporal fluctuations (standard deviation of 0.10 m), in significantly better agreement with in situ observations. Relative to an operational CLSM version that simply includes peat as a soil class, the temporal correlation coefficient is increased on average by 0.16 and reaches 0.64 for bogs and 0.66 for fens when driven with global atmospheric forcing data. In PEAT-CLSM, runoff is increased on average by 38% and evapotranspiration is reduced by 19%. The evapotranspiration reduction constitutes a significant improvement relative to eddy covariance measurements.
BibTeX:
@article{Bechtold2019,
  author = {Bechtold, M. and De Lannoy, G. J.M. and Koster, R. D. and Reichle, R. H. and Mahanama, S. P. and Bleuten, W. and Bourgault, M. A. and Brümmer, C. and Burdun, I. and Desai, A. R. and Devito, K. and Grünwald, T. and Grygoruk, M. and Humphreys, E. R. and Klatt, J. and Kurbatova, J. and Lohila, A. and Munir, T. M. and Nilsson, M. B. and Price, J. S. and Röhl, M. and Schneider, A. and Tiemeyer, B.},
  title = {PEAT-CLSM: A Specific Treatment of Peatland Hydrology in the NASA Catchment Land Surface Model},
  journal = {Journal of Advances in Modeling Earth Systems},
  year = {2019},
  volume = {11},
  number = {7},
  pages = {2130--2162},
  url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2018MS001574},
  doi = {10.1029/2018MS001574}
}
Berger C, Bieri M, Bradshaw K, Brümmer C, Clemen T, Hickler T, Kutsch WL, Lenfers UA, Martens C, Midgley GF, Mukwashi K, Odipo V, Scheiter S, Schmullius C, Baade J, du Toit JCO, Scholes RJ, Smit IPJ, Stevens N and Twine W (2019), "Linking scales and disciplines: an interdisciplinary cross-scale approach to supporting climate-relevant ecosystem management", Climatic Change. Vol. 156(1), pp. 139-150.
Abstract: Southern Africa is particularly sensitive to climate change, due to both ecological and socio-economic factors, with rural land users among the most vulnerable groups. The provision of information to support climate-relevant decision-making requires an understanding of the projected impacts of change and complex feedbacks within the local ecosystems, as well as local demands on ecosystem services. In this paper, we address the limitation of current approaches for developing management relevant socio-ecological information on the projected impacts of climate change and human activities. We emphasise the need for linking disciplines and approaches by expounding the methodology followed in our two consecutive projects. These projects combine disciplines and levels of measurements from the leaf level (ecophysiology) to the local landscape level (flux measurements) and from the local household level (socio-economic surveys) to the regional level (remote sensing), feeding into a variety of models at multiple scales. Interdisciplinary, multi-scaled, and integrated socio-ecological approaches, as proposed here, are needed to compliment reductionist and linear, scale-specific approaches. Decision support systems are used to integrate and communicate the data and models to the local decision-makers.
BibTeX:
@article{Berger2019,
  author = {Berger, Christian and Bieri, Mari and Bradshaw, Karen and Brümmer, Christian and Clemen, Thomas and Hickler, Thomas and Kutsch, Werner Leo and Lenfers, Ulfia A. and Martens, Carola and Midgley, Guy F. and Mukwashi, Kanisios and Odipo, Victor and Scheiter, Simon and Schmullius, Christiane and Baade, Jussi and du Toit, Justin C. O. and Scholes, Robert J. and Smit, Izak P. J. and Stevens, Nicola and Twine, Wayne},
  title = {Linking scales and disciplines: an interdisciplinary cross-scale approach to supporting climate-relevant ecosystem management},
  journal = {Climatic Change},
  year = {2019},
  volume = {156},
  number = {1},
  pages = {139--150},
  url = {https://doi.org/10.1007/s10584-019-02544-0}
}
Berhanu TA, Hoffnagle J, Rella C, Kimhak D, Nyfeler P and Leuenberger M (2019), "High-precision atmospheric oxygen measurement comparisons between a newly built CRDS analyzer and existing measurement techniques", Atmospheric Measurement Techniques., dec, 2019. Vol. 12(12), pp. 6803-6826. Copernicus GmbH.
Abstract: Carbon dioxide and oxygen are tightly coupled in land biosphere CO2-O2 exchange processes, whereas they are not coupled in oceanic exchange. For this reason, atmospheric oxygen measurements can be used to constrain the global carbon cycle, especially oceanic uptake. However, accurately quantifying small (∼ 1-100 ppm) variations in O2 is analytically challenging due to the very large atmospheric background which constitutes about 20.9%(209500 ppm) of atmospheric air. Here we present a detailed description of a newly developed high-precision oxygen mixing ratio and isotopic composition analyzer (Picarro G2207) that is based on cavity ring-down spectroscopy (CRDS) as well as to its operating principles; we also demonstrate comprehensive laboratory and field studies using the abovementioned instrument. From the laboratory tests, we calculated a shortterm precision (standard error of 1 min O2 mixing ratio measurements) of textless 1 ppm for this analyzer based on measurements of eight standard gases analyzed for 2 h, respectively. In contrast to the currently existing techniques, the instrument has an excellent long-term stability; therefore, calibration every 12 h is sufficient to get an overall uncertainty of textless 5 ppm. Measurements of ambient air were also conducted at the Jungfraujoch high-altitude research station and the Beromünster tall tower in Switzerland. At both sites, we observed opposing and diurnally varying CO2 and O2 profiles due to different processes such as combustion, photosynthesis, and respiration. Based on the combined measurements at Beromünster tower, we determined height-dependent O2 V CO2 oxidation ratios varying between -0:98 and -1:60; these ratios increased with the height of the tower inlet, possibly due to different source contributions such as natural gas combustion, which has a high oxidation ratio, and biological processes, which have oxidation ratios that are relatively lower.
BibTeX:
@article{Berhanu2019,
  author = {Berhanu, Tesfaye A. and Hoffnagle, John and Rella, Chris and Kimhak, David and Nyfeler, Peter and Leuenberger, Markus},
  title = {High-precision atmospheric oxygen measurement comparisons between a newly built CRDS analyzer and existing measurement techniques},
  journal = {Atmospheric Measurement Techniques},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {12},
  number = {12},
  pages = {6803--6826},
  doi = {10.5194/amt-12-6803-2019}
}
Berhongaray G, Cotrufo FM, Janssens IA and Ceulemans R (2019), "Below-ground carbon inputs contribute more than above-ground inputs to soil carbon accrual in a bioenergy poplar plantation", Plant and Soil., oct, 2019. Vol. 434(1-2), pp. 363-378. Springer Science and Business Media LLC.
Abstract: Background and aims: Soil organic carbon (SOC) accrual is central to the discussion on active atmospheric CO 2 removal strategies, but it requires a clear understanding of the mechanisms driving new SOC formation. SOC is formed from the decomposition of above- and below-ground plant inputs, yet their accurate quantification remains a major challenge. In the current study the in-growth soil core and δ 13 C methods were combined to quantify the net C input from single or combined above- and below-ground parts of a poplar (Populus) bioenergy plantation. Methods: Three different mesh sizes were used for the in-growth cores in four different treatments designed to estimate the relative contributions of above-ground litter fall, fine roots and mycorrhizae (C3 input from the poplar) to the new C formation in cores filled with a C4 soil, by applying a mass balance equation. Results: Soil C formation was higher in the treatments with roots as compared to the treatments with above-ground C inputs only (29 vs 16 g C m −2 ), despite the disproportionally lower root inputs as compared to above-ground C inputs (34 vs 175 g C m −2 y −1 ). Soil C formation from different sources (above- and below-ground) was additive; i.e. the observed soil C formation in the combined treatment was the sum of those in the single soil C input treatments. As a result, below-ground C-inputs had a high conversion efficiency to SOC of 76%. Above-ground plant inputs had a very low SOC formation efficiency of 9%, and were presumably mainly mineralized by microorganisms. Conclusion: The higher soil C accumulation rates from below-ground C inputs are particularly important in bioenergy plantations where the above-ground biomass is frequently removed for biomass and energy production.
BibTeX:
@article{Berhongaray2019,
  author = {Berhongaray, Gonzalo and Cotrufo, Francesca M. and Janssens, Ivan A. and Ceulemans, Reinhart},
  title = {Below-ground carbon inputs contribute more than above-ground inputs to soil carbon accrual in a bioenergy poplar plantation},
  journal = {Plant and Soil},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {434},
  number = {1-2},
  pages = {363--378},
  doi = {10.1007/s11104-018-3850-z}
}
Besnard S, Carvalhais N, Altaf Arain M, Black A, Brede B, Buchmann N, Chen J, Clevers JG, Dutrieux LP, Gans F, Herold M, Jung M, Kosugi Y, Knohl A, Law BE, Paul-Limoges E, Lohila A, Merbold L, Roupsard O, Valentini R, Wolf S, Zhang X and Reichstein M (2019), "Memory effects of climate and vegetation affecting net ecosystem CO2 fluxes in global forests", PLoS ONE., feb, 2019. Vol. 14(2), pp. e0211510. Public Library of Science (PLoS).
Abstract: Forests play a crucial role in the global carbon (C) cycle by storing and sequestering a substantial amount of C in the terrestrial biosphere. Due to temporal dynamics in climate and vegetation activity, there are significant regional variations in carbon dioxide (CO2) fluxes between the biosphere and atmosphere in forests that are affecting the global C cycle. Current forest CO2 flux dynamics are controlled by instantaneous climate, soil, and vegetation conditions, which carry legacy effects from disturbances and extreme climate events. Our level of understanding from the legacies of these processes on net CO2 fluxes is still limited due to their complexities and their long-term effects. Here, we combined remote sensing, climate, and eddy-covariance flux data to study net ecosystem CO2 exchange (NEE) at 185 forest sites globally. Instead of commonly used non-dynamic statistical methods, we employed a type of recurrent neural network (RNN), called Long Short-Term Memory network (LSTM) that captures information from the vegetation and climate's temporal dynamics. The resulting data-driven model integrates interannual and seasonal variations of climate and vegetation by using Landsat and climate data at each site. The presented LSTM algorithm was able to effectively describe the overall seasonal variability (Nash-Sutcliffe efficiency, NSE = 0.66) and across-site (NSE = 0.42) variations in NEE, while it had less success in predicting specific seasonal and interannual anomalies (NSE = 0.07). This analysis demonstrated that an LSTM approach with embedded climate and vegetation memory effects outperformed a non-dynamic statistical model (i.e. Random Forest) for estimating NEE. Additionally, it is shown that the vegetation mean seasonal cycle embeds most of the information content to realistically explain the spatial and seasonal variations in NEE. These findings show the relevance of capturing memory effects from both climate and vegetation in quantifying spatio-temporal variations in forest NEE.
BibTeX:
@article{Besnard2019,
  author = {Besnard, Simon and Carvalhais, Nuno and Altaf Arain, M. and Black, Andrew and Brede, Benjamin and Buchmann, Nina and Chen, Jiquan and Clevers, Jan G.P.W. and Dutrieux, Loïc P. and Gans, Fabian and Herold, Martin and Jung, Martin and Kosugi, Yoshiko and Knohl, Alexander and Law, Beverly E. and Paul-Limoges, Eugénie and Lohila, Annalea and Merbold, Lutz and Roupsard, Olivier and Valentini, Riccardo and Wolf, Sebastian and Zhang, Xudong and Reichstein, Markus},
  editor = {Hui, Dafeng},
  title = {Memory effects of climate and vegetation affecting net ecosystem CO2 fluxes in global forests},
  journal = {PLoS ONE},
  publisher = {Public Library of Science (PLoS)},
  year = {2019},
  volume = {14},
  number = {2},
  pages = {e0211510},
  doi = {10.1371/journal.pone.0211510}
}
Bigeard G, Coudert B, Chirouze J, Er-Raki S, Boulet G, Ceschia E and Jarlan L (2019), "Ability of a soil-vegetation-atmosphere transfer model and a two-source energy balance model to predict evapotranspiration for several crops and climate conditions", Hydrology and Earth System Sciences., dec, 2019. Vol. 23(12), pp. 5033-5058. Copernicus GmbH.
Abstract: The heterogeneity of Agroecosystems, in terms of hydric conditions, crop types and states, and meteorological forcing, is difficult to characterize precisely at the field scale over an agricultural landscape. This study aims to perform a sensitivity study with respect to the uncertain model inputs of two classical approaches used to map the evapotranspiration of agroecosystems: (1) a surface energy balance (SEB) model, the Two-Source Energy Balance (TSEB) model, forced with thermal infrared (TIR) data as a proxy for the crop hydric conditions, and (2) a soil-vegetation-atmosphere transfer (SVAT) model, the SEtHyS model, where hydric conditions are computed from a soil water budget. To this end, the models skill was compared using a large and unique in situ database covering different crops and climate conditions, which was acquired over three experimental sites in southern France and Morocco. On average, the models provide 30 min estimations of latent heat flux (LE) with a RMSE of around 55Wm-2 for TSEB and 47Wm-2 for SEtHyS, and estimations of sensible heat flux (H) with a RMSE of around 29Wm-2 for TSEB and 38Wm-2 for SEtHyS. A sensitivity analysis based on realistic errors aimed to estimate the potential decrease in performance induced by the spatialization process. For the SVAT model, the multi-objective calibration iterative procedure (MCIP) is used to determine and test different sets of parameters. TSEB is run with only one set of parameters and provides acceptable performance for all crop stages apart from the early growing season (LAItextless0.2m2 m-2) and when hydric stress occurs. An in-depth study on the Priestley- Taylor key parameter highlights its marked diurnal cycle and the need to adjust its value to improve flux partitioning between the sensible and latent heat fluxes (1.5 and 1.25 for France and Morocco, respectively). Optimal values of 1.8-2 were highlighted under cloudy conditions, which is of particular interest due to the emergence of low-altitude drone acquisition. Under developed vegetation (LAItextgreater0.8m2 m-2) and unstressed conditions, using sets of parameters that only differentiate crop types is a valuable trade-off for SEtHyS. This study provides some scientific elements regarding the joint use of both approaches and TIR imagery, via the development of new data assimilation and calibration strategies..
BibTeX:
@article{Bigeard2019,
  author = {Bigeard, Guillaume and Coudert, Benoit and Chirouze, Jonas and Er-Raki, Salah and Boulet, Gilles and Ceschia, Eric and Jarlan, Lionel},
  title = {Ability of a soil-vegetation-atmosphere transfer model and a two-source energy balance model to predict evapotranspiration for several crops and climate conditions},
  journal = {Hydrology and Earth System Sciences},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {23},
  number = {12},
  pages = {5033--5058},
  doi = {10.5194/hess-23-5033-2019}
}
Billesbach DP, Chan SW, Cook DR, Papale D, Bracho-Garrillo R, Verfallie J, Vargas R and Biraud SC (2019), "Effects of the Gill-Solent WindMaster-Pro “w-boost” firmware bug on eddy covariance fluxes and some simple recovery strategies", Agricultural and Forest Meteorology., feb, 2019. Vol. 265, pp. 145-151. Elsevier BV.
Abstract: In late 2015 and early 2016, work done by the AmeriFlux Management Project Technical Team (amerilfux.lbl.gov) helped to uncover an issue with Gill WindMaster and WindMaster Pro sonic anemometers used by many researchers for eddy covariance flux measurements. Gill has addressed this issue and has since sent out a notice that the vertical wind speed component (a critical piece of all eddy covariance fluxes) was being erroneously computed and reported. The problem (known as the “w-boost” bug) resulted in positive (upward) wind speeds being under-reported by 16.6% and negative (downward) wind speeds being under-reported by 28.9%. This has the potential to cause similar under estimates in fluxes derived from measurements using these instruments. Additionally, the bug affects corrections for angle of attack as derived by Nakai and Shimoyama, rendering them invalid. While the manufacturer has offered a firmware upgrade for existing instruments that will fix this issue, many existing data sets have been affected by it and are currently in use by the scientific community. To address the issue of affected data, currently in use, we analyzed multi-year and short-term data sets from a variety of ecosystems to assess methods of correcting existing flux data. We found that simple multiplicative correction factors (∼1.18) may be used to remove most of the “w-boost” bias from fluxes in existing data sets that do not include angle of attack corrections.
BibTeX:
@article{Billesbach2019,
  author = {Billesbach, D. P. and Chan, S. W. and Cook, D. R. and Papale, D. and Bracho-Garrillo, R. and Verfallie, J. and Vargas, R. and Biraud, S. C.},
  title = {Effects of the Gill-Solent WindMaster-Pro “w-boost” firmware bug on eddy covariance fluxes and some simple recovery strategies},
  journal = {Agricultural and Forest Meteorology},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {265},
  pages = {145--151},
  doi = {10.1016/j.agrformet.2018.11.010}
}
Bowring SP, Lauerwald R, Guenet B, Zhu D, Guimberteau M, Tootchi A, Ducharne A and Ciais P (2019), "ORCHIDEE MICT-LEAK (r5459), a global model for the production, transport, and transformation of dissolved organic carbon from Arctic permafrost regions - Part 1: Rationale, model description, and simulation protocol", Geoscientific Model Development., aug, 2019. Vol. 12(8), pp. 3503-3521. Copernicus GmbH.
Abstract: Few Earth system models adequately represent the unique permafrost soil biogeochemistry and its respective processes; this significantly contributes to uncertainty in estimating their responses, and that of the planet at large, to warming. Likewise, the riverine component of what is known as the "boundless carbon cycle" is seldom recognised in Earth system modelling. The hydrological mobilisation of organic material from a ∼ 1330-1580 PgC carbon stock to the river network results in either sedimentary settling or atmospheric "evasion", processes widely expected to increase with amplified Arctic climate warming. Here, the production, transport, and atmospheric release of dissolved organic carbon (DOC) from high-latitude permafrost soils into inland waters and the ocean are explicitly represented for the first time in the land surface component (ORCHIDEE) of a CMIP6 global climate model (Institut Pierre Simon Laplace - IPSL). The model, ORCHIDEE MICT-LEAK, which represents the merger of previously described ORCHIDEE versions MICT and LEAK, mechanistically represents (a) vegetation and soil physical processes for high-latitude snow, ice, and soil phenomena and (b) the cycling of DOC and CO2, including atmospheric evasion, along the terrestrial-aquatic continuum from soils through the river network to the coast at 0.5 to 2° resolution. This paper, the first in a two-part study, presents the rationale for including these processes in a high-latitude-specific land surface model, then describes the model with a focus on novel process implementations, followed by a summary of the model configuration and simulation protocol. The results of these simulation runs, conducted for the Lena River basin, are evaluated against observational data in the second part of this study.
BibTeX:
@article{Bowring2019,
  author = {Bowring, Simon P.K. and Lauerwald, Ronny and Guenet, Bertrand and Zhu, Dan and Guimberteau, Matthieu and Tootchi, Ardalan and Ducharne, Agnès and Ciais, Philippe},
  title = {ORCHIDEE MICT-LEAK (r5459), a global model for the production, transport, and transformation of dissolved organic carbon from Arctic permafrost regions - Part 1: Rationale, model description, and simulation protocol},
  journal = {Geoscientific Model Development},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {12},
  number = {8},
  pages = {3503--3521},
  doi = {10.5194/gmd-12-3503-2019}
}
Box JE, Colgan WT, Christensen TR, Schmidt NM, Lund M, Parmentier FJW, Brown R, Bhatt US, Euskirchen ES, Romanovsky VE, Walsh JE, Overland JE, Wang M, Corell RW, Meier WN, Wouters B, Mernild S, Mård J, Pawlak J and Olsen MS (2019), "Key indicators of Arctic climate change: 1971-2017", Environmental Research Letters., apr, 2019. Vol. 14(4), pp. 45010. IOP Publishing.
Abstract: Key observational indicators of climate change in the Arctic, most spanning a 47 year period (1971-2017) demonstrate fundamental changes among nine key elements of the Arctic system. We find that, coherent with increasing air temperature, there is an intensification of the hydrological cycle, evident from increases in humidity, precipitation, river discharge, glacier equilibrium line altitude and land ice wastage. Downward trends continue in sea ice thickness (and extent) and spring snow cover extent and duration, while near-surface permafrost continues to warm. Several of the climate indicators exhibit a significant statistical correlation with air temperature or precipitation, reinforcing the notion that increasing air temperatures and precipitation are drivers of major changes in various components of the Arctic system. To progress beyond a presentation of the Arctic physical climate changes, we find a correspondence between air temperature and biophysical indicators such as tundra biomass and identify numerous biophysical disruptions with cascading effects throughout the trophic levels. These include: increased delivery of organic matter and nutrients to Arctic near-coastal zones; condensed flowering and pollination plant species periods; timing mismatch between plant flowering and pollinators; increased plant vulnerability to insect disturbance; increased shrub biomass; increased ignition of wildfires; increased growing season CO2 uptake, with counterbalancing increases in shoulder season and winter CO2 emissions; increased carbon cycling, regulated by local hydrology and permafrost thaw; conversion between terrestrial and aquatic ecosystems; and shifting animal distribution and demographics. The Arctic biophysical system is now clearly trending away from its 20th Century state and into an unprecedented state, with implications not only within but beyond the Arctic. The indicator time series of this study are freely downloadable at AMAP.no.
BibTeX:
@article{Box2019,
  author = {Box, Jason E. and Colgan, William T. and Christensen, Torben Røjle and Schmidt, Niels Martin and Lund, Magnus and Parmentier, Frans Jan W. and Brown, Ross and Bhatt, Uma S. and Euskirchen, Eugénie S. and Romanovsky, Vladimir E. and Walsh, John E. and Overland, James E. and Wang, Muyin and Corell, Robert W. and Meier, Walter N. and Wouters, Bert and Mernild, Sebastian and Mård, Johanna and Pawlak, Janet and Olsen, Morten Skovgård},
  title = {Key indicators of Arctic climate change: 1971-2017},
  journal = {Environmental Research Letters},
  publisher = {IOP Publishing},
  year = {2019},
  volume = {14},
  number = {4},
  pages = {45010},
  doi = {10.1088/1748-9326/aafc1b}
}
Brændholt A, Ibrom A, Ambus P, Larsen KS and Pilegaard K (2019), "Combining a quantum cascade laser spectrometer with an automated closed-chamber system for δ13C measurements of forest soil, tree stem and tree root CO2 fluxess", Forests., may, 2019. Vol. 10(5), pp. 432. MDPI AG.
Abstract: Recent advances in laser spectroscopy have allowed for real-time measurements of the 13C/12C isotopic ratio in CO2, thereby providing new ways to investigate carbon cycling in natural ecosystems. In this study, we combined an Aerodyne quantum cascade laser spectrometer for CO2 isotopes with a LI-COR LI-8100A/8150 automated chamber system to measure the δ13C of CO2 during automated closed-chamber measurements. The isotopic composition of the CO2 flux was determined for each chamber measurement by applying the Keeling plot method. We found that the δ13C measured by the laser spectrometer was influenced by water vapour and CO2 concentration of the sample air and we developed a method to correct for these effects to yield accurate measurements of δ13C. Overall, correcting for the CO2 concentration increased the δ13C determined from the Keeling plots by 3.4%‰ compared to 2.1%‰ for the water vapour correction. We used the combined system to measure δ13C of the CO2 fluxes automatically every two hours from intact soil, trenched soil, tree stems and coarse roots during a two-month campaign in a Danish beech forest. The mean δ13C was -29.8 ± 0.32%‰ for the intact soil plots, which was similar to the mean δ13C of -29.8 ± 1.2%‰ for the trenched soil plots. The lowest δ13C was found for the root plots with a mean of -32.6 ± 0.78%‰. The mean δ13C of the stems was -30.2 ± 0.74%‰, similar to the mean δ13C of the soil plots. In conclusion, the study showed the potential of using a quantum cascade laser spectrometer to measure δ13C of CO2 during automated closed-chamber measurements, thereby allowing for measurements of isotopic ecosystem CO2 fluxes at a high temporal resolution. It also highlighted the importance of proper correction for cross-sensitivity with water vapour and CO2 concentration of the sample air to get accurate measurements of δ13C.
BibTeX:
@article{Brendholt2019,
  author = {Brændholt, Andreas and Ibrom, Andreas and Ambus, Per and Larsen, Klaus Steenberg and Pilegaard, Kim},
  title = {Combining a quantum cascade laser spectrometer with an automated closed-chamber system for δ13C measurements of forest soil, tree stem and tree root CO2 fluxess},
  journal = {Forests},
  publisher = {MDPI AG},
  year = {2019},
  volume = {10},
  number = {5},
  pages = {432},
  doi = {10.3390/f10050432}
}
Buchen C, Roobroeck D, Augustin J, Behrendt U, Boeckx P and Ulrich A (2019), "High N2O consumption potential of weakly disturbed fen mires with dissimilar denitrifier community structure", Soil Biology and Biochemistry., mar, 2019. Vol. 130, pp. 63-72.
BibTeX:
@article{Buchen2019,
  author = {Buchen, C. and Roobroeck, D. and Augustin, J. and Behrendt, U. and Boeckx, P. and Ulrich, A.},
  title = {High N2O consumption potential of weakly disturbed fen mires with dissimilar denitrifier community structure},
  journal = {Soil Biology and Biochemistry},
  year = {2019},
  volume = {130},
  pages = {63--72},
  url = {https://linkinghub.elsevier.com/retrieve/pii/S0038071718304115},
  doi = {10.1016/j.soilbio.2018.12.001}
}
Campbell JL and Laudon H (2019), "Carbon response to changing winter conditions in northern regions: Current understanding and emerging research needs", Environmental Reviews., dec, 2019. Vol. 27(4), pp. 545-566.
Abstract: Winter is an important period for ecological processes in northern regions; however, compared to other seasons, the impacts of winter climate on ecosystems are poorly understood. In this review we evaluate the influence of winter climate on carbon dynamics based on the current state of knowledge and highlight emerging topics and future research challenges. Studies that have addressed this topic include plot-scale snow cover manipulation experiments that alter soil temperatures, empirical investigations along natural climatic gradients, laboratory temperature incubation experiments aimed at isolating influential factors in controlled environments, and time series of climate and carbon data that evaluate long-term natural variation and trends. Combined, these studies have demonstrated how winter climate can influence carbon in complex ways that in some cases are consistent across studies and in other cases are difficult to predict. Despite advances in our understanding, there is a great need for studies that further explore: (i) carry-over effects from one season to another, (ii) ecosystem processes in the fall–winter and winter–spring shoulder seasons, (iii) the impacts of extreme events, (iv) novel experimental approaches, and (v) improvements to models to include ecological effects of winter climate. We also call for the establishment of an international winter climate change research network that enhances collaboration and coordination among studies, which could provide a more thorough understanding of how the snow-covered period influences carbon cycling, thereby improving our ability to predict future responses to climate change.
BibTeX:
@article{Campbell2019,
  author = {Campbell, John L. and Laudon, Hjalmar},
  title = {Carbon response to changing winter conditions in northern regions: Current understanding and emerging research needs},
  journal = {Environmental Reviews},
  year = {2019},
  volume = {27},
  number = {4},
  pages = {545--566},
  url = {http://www.nrcresearchpress.com/doi/10.1139/er-2018-0097},
  doi = {10.1139/er-2018-0097}
}
Campeau A, Bishop K, Amvrosiadi N, Billett MF, Garnett MH, Laudon H, Öquist MG and Wallin MB (2019), "Current forest carbon fixation fuels stream CO 2 emissions", Nature Communications., dec, 2019. Vol. 10(1), pp. 1876.
Abstract: Stream CO 2 emissions contribute significantly to atmospheric climate forcing. While there are strong indications that groundwater inputs sustain these emissions, the specific biogeochemical pathways and timescales involved in this lateral CO 2 export are still obscure. Here, via an extensive radiocarbon ( 14 C) characterisation of CO 2 and DOC in stream water and its groundwater sources in an old-growth boreal forest, we demonstrate that the 14 C-CO 2 is consistently in tune with the current atmospheric 14 C-CO 2 level and shows little association with the 14 C-DOC in the same waters. Our findings thus indicate that stream CO 2 emissions act as a shortcut that returns CO 2 recently fixed by the forest vegetation to the atmosphere. Our results expose a positive feedback mechanism within the C budget of forested catchments, where stream CO 2 emissions will be highly sensitive to changes in forest C allocation patterns associated with climate and land-use changes.
BibTeX:
@article{Campeau2019,
  author = {Campeau, A. and Bishop, K. and Amvrosiadi, N. and Billett, M. F. and Garnett, M. H. and Laudon, H. and Öquist, M. G. and Wallin, M. B.},
  title = {Current forest carbon fixation fuels stream CO 2 emissions},
  journal = {Nature Communications},
  year = {2019},
  volume = {10},
  number = {1},
  pages = {1876},
  url = {http://www.nature.com/articles/s41467-019-09922-3},
  doi = {10.1038/s41467-019-09922-3}
}
Cernusak LA, Haverd V, Brendel O, Le Thiec D, Guehl JM and Cuntz M (2019), "Robust Response of Terrestrial Plants to Rising CO2", Trends in Plant Science., jul, 2019. Vol. 24(7), pp. 578-586. Elsevier BV.
Abstract: Human-caused CO2 emissions over the past century have caused the climate of the Earth to warm and have directly impacted on the functioning of terrestrial plants. We examine the global response of terrestrial gross primary production (GPP) to the historic change in atmospheric CO2. The GPP of the terrestrial biosphere has increased steadily, keeping pace remarkably in proportion to the rise in atmospheric CO2. Water-use efficiency, namely the ratio of CO2 uptake by photosynthesis to water loss by transpiration, has increased as a direct leaf-level effect of rising CO2. This has allowed an increase in global leaf area, which has conspired with stimulation of photosynthesis per unit leaf area to produce a maximal response of the terrestrial biosphere to rising atmospheric CO2 and contemporary climate change.
BibTeX:
@article{Cernusak2019,
  author = {Cernusak, Lucas A. and Haverd, Vanessa and Brendel, Oliver and Le Thiec, Didier and Guehl, Jean Marc and Cuntz, Matthias},
  title = {Robust Response of Terrestrial Plants to Rising CO2},
  journal = {Trends in Plant Science},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {24},
  number = {7},
  pages = {578--586},
  doi = {10.1016/j.tplants.2019.04.003}
}
Chen JM, Ju W, Ciais P, Viovy N, Liu R, Liu Y and Lu X (2019), "Vegetation structural change since 1981 significantly enhanced the terrestrial carbon sink", Nature Communications., sep, 2019. Vol. 10(1) Springer Science and Business Media LLC.
Abstract: Satellite observations show that leaf area index (LAI) has increased globally since 1981, but the impact of this vegetation structural change on the global terrestrial carbon cycle has not been systematically evaluated. Through process-based diagnostic ecosystem modeling, we find that the increase in LAI alone was responsible for 12.4% of the accumulated terrestrial carbon sink (95 ± 5 Pg C) from 1981 to 2016, whereas other drivers of CO2 fertilization, nitrogen deposition, and climate change (temperature, radiation, and precipitation) contributed to 47.0%, 1.1%, and −28.6% of the sink, respectively. The legacy effects of past changes in these drivers prior to 1981 are responsible for the remaining 65.5% of the accumulated sink from 1981 to 2016. These results refine the attribution of the land sink to the various drivers and would help constrain prognostic models that often have large uncertainties in simulating changes in vegetation and their impacts on the global carbon cycle.
BibTeX:
@article{Chen2019,
  author = {Chen, Jing M. and Ju, Weimin and Ciais, Philippe and Viovy, Nicolas and Liu, Ronggao and Liu, Yang and Lu, Xuehe},
  title = {Vegetation structural change since 1981 significantly enhanced the terrestrial carbon sink},
  journal = {Nature Communications},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {10},
  number = {1},
  doi = {10.1038/s41467-019-12257-8}
}
Chi J, Nilsson MB, Kljun N, Wallerman J, Fransson JE, Laudon H, Lundmark T and Peichl M (2019), "The carbon balance of a managed boreal landscape measured from a tall tower in northern Sweden", Agricultural and Forest Meteorology., aug, 2019. Vol. 274, pp. 29-41.
Abstract: Boreal forests exchange large amounts of carbon dioxide (CO2) with the atmosphere. A managed boreal landscape usually comprises various potential CO2 sinks and sources across forest stands of varying age classes, clear-cut areas, mires, and lakes. Due to this heterogeneity and complexity, large uncertainties exist regarding the net CO2 balance at the landscape scale. In this study, we present the first estimate of the net CO2 exchange over a managed boreal landscape (∼68 km2) in northern Sweden, based on tall tower eddy covariance measurements. Our results suggest that from March 1, 2016 to February 28, 2018, the heterogeneous landscape was a net CO2 sink with a 2-year mean uptake of −87 ± 6 g C m−2 yr−1. Due to an earlier and warmer spring and sunnier autumn, the landscape was a stronger CO2 sink during the first year (−122 ± 8 g C m−2) compared to the second year (−52 ± 9 g C m−2). Footprint analysis shows that 87% of the CO2 flux measurements originated from forests, whereas mires, clear-cuts, lakes, and grassland contributed 11%, 1%, 0.7%, and 0.2%, respectively. Altogether, the CO2 sink strength of the heterogeneous landscape was up to 38% lower compared to the sink strength of a mature stand surrounding the tower. Overall, this study suggests that the managed boreal landscape acted as a CO2 sink and advocates tall tower eddy covariance measurements to improve regional carbon budget estimates.
BibTeX:
@article{Chi2019,
  author = {Chi, Jinshu and Nilsson, Mats B. and Kljun, Natascha and Wallerman, Jörgen and Fransson, Johan E.S. and Laudon, Hjalmar and Lundmark, Tomas and Peichl, Matthias},
  title = {The carbon balance of a managed boreal landscape measured from a tall tower in northern Sweden},
  journal = {Agricultural and Forest Meteorology},
  year = {2019},
  volume = {274},
  pages = {29--41},
  url = {https://linkinghub.elsevier.com/retrieve/pii/S0168192319301509},
  doi = {10.1016/j.agrformet.2019.04.010}
}
Chiesa M, Bignotti L, Finco A, Marzuoli R and Gerosa G (2019), "Size-resolved aerosol fluxes above a broadleaved deciduous forest", Agricultural and Forest Meteorology., dec, 2019. Vol. 279, pp. 107757. Elsevier BV.
Abstract: In order to understand the aerosol exchange dynamics between the atmosphere and a peri-urban forest ecosystem located in the Po Valley, a region characterized by high PM concentrations, eddy covariance (EC) aerosol fluxes were measured between September and December 2017. The aerosol sampling, performed with an Electrical Low Pressure Impactor (ELPI +, DEKATI), involved a wide range of particle sizes including both ultrafine and fine aerosol. The monitoring campaign comprised a period with leaves (PL) and a period without leaves (PNL) to assess their influence on the emission and deposition fluxes. The diurnal profiles of particle number (PN) fluxes associated to the geometric mean diameters (GMD) of 0.02 µm and 0.48 µm were chosen as representative of the behaviour of ultrafine and fine particles, respectively. Fluxes of ultrafine particles showed a net emission pattern both in PL and PNL assuming values up to 5.6 106 m−2 s−1 and 4.5textperiodcentered106 m−2 s−1, respectively. Instead, fine particles fluxes showed a net deposition pattern in PL, assuming values up to −1.1 textperiodcentered 106 m−2 s−1, while in PNL a slight emission up to 4.1 textperiodcentered105 m−2 s−1 occurred. The behaviour of the fluxes of the cumulative classes PM0.1 and PM1 was similar to the one of the PN fluxes of ultrafine and fine aerosol, respectively. Deposition velocities were calculated for PL and PNL depending on the atmospheric stability class. The values emerged from this study (from −0.25 cm s−1 up to 0.12 cm s−1) evidenced that under stable and very stable atmospheric conditions all size classes presented negative or slightly positive deposition velocities both in PL and PNL. Instead under unstable conditions fine particles showed deposition velocities whose direction changed in the two periods (PL and PNL).
BibTeX:
@article{Chiesa2019,
  author = {Chiesa, M. and Bignotti, L. and Finco, A. and Marzuoli, R. and Gerosa, G.},
  title = {Size-resolved aerosol fluxes above a broadleaved deciduous forest},
  journal = {Agricultural and Forest Meteorology},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {279},
  pages = {107757},
  doi = {10.1016/j.agrformet.2019.107757}
}
Collalti A, Thornton PE, Cescatti A, Rita A, Borghetti M, Nolè A, Trotta C, Ciais P and Matteucci G (2019), "The sensitivity of the forest carbon budget shifts across processes along with stand development and climate change", Ecological Applications., feb, 2019. Vol. 29(2) Wiley.
Abstract: The future trajectory of atmospheric CO2 concentration depends on the development of the terrestrial carbon sink, which in turn is influenced by forest dynamics under changing environmental conditions. An in-depth understanding of model sensitivities and uncertainties in non-steady-state conditions is necessary for reliable and robust projections of forest development and under scenarios of global warming and CO2 enrichment. Here, we systematically assessed if a biogeochemical process-based model (3D-CMCC-CNR), which embeds similarities with many other vegetation models, applied in simulating net primary productivity (NPP) and standing woody biomass (SWB), maintained a consistent sensitivity to its 55 input parameters through time, during forest ageing and structuring as well as under climate change scenarios. Overall, the model applied at three contrasting European forests showed low sensitivity to the majority of its parameters. Interestingly, model sensitivity to parameters varied through the course of textgreater100 yr of simulations. In particular, the model showed a large responsiveness to the allometric parameters used for initialize forest carbon and nitrogen pools early in forest simulation (i.e., for NPP up to ˜37%, 256 g Ctextperiodcenteredm−2textperiodcenteredyr−1 and for SWB up to ˜90%, 65 Mg C/ha, when compared to standard simulation), with this sensitivity decreasing sharply during forest development. At medium to longer time scales, and under climate change scenarios, the model became increasingly more sensitive to additional and/or different parameters controlling biomass accumulation and autotrophic respiration (i.e., for NPP up to ˜30%, 167 g Ctextperiodcenteredm−2textperiodcenteredyr−1 and for SWB up to ˜24%, 64 Mg C/ha, when compared to standard simulation). Interestingly, model outputs were shown to be more sensitive to parameters and processes controlling stand development rather than to climate change (i.e., warming and changes in atmospheric CO2 concentration) itself although model sensitivities were generally higher under climate change scenarios. Our results suggest the need for sensitivity and uncertainty analyses that cover multiple temporal scales along forest developmental stages to better assess the potential of future forests to act as a global terrestrial carbon sink.
BibTeX:
@article{Collalti2019,
  author = {Collalti, Alessio and Thornton, Peter E. and Cescatti, Alessandro and Rita, Angelo and Borghetti, Marco and Nolè, Angelo and Trotta, Carlo and Ciais, Philippe and Matteucci, Giorgio},
  title = {The sensitivity of the forest carbon budget shifts across processes along with stand development and climate change},
  journal = {Ecological Applications},
  publisher = {Wiley},
  year = {2019},
  volume = {29},
  number = {2},
  doi = {10.1002/eap.1837}
}
Conil S, Helle J, Langrene L, Laurent O, Delmotte M and Ramonet M (2019), "Continuous atmospheric CO2, CH4 and CO measurements at the Observatoire Pérenne de l'Environnement (OPE) station in France from 2011 to 2018", Atmospheric Measurement Techniques., dec, 2019. Vol. 12(12), pp. 6361-6383. Copernicus GmbH.
Abstract: Located in north-east France, the Observatoire Pérenne de l'Environnement (OPE) station was built during the Integrated Carbon Observation System (ICOS) Demonstration Experiment to monitor the greenhouse gases mole fraction. Its continental rural background setting fills the gaps between oceanic or mountain stations and urban stations within the ICOS network. Continuous measurements of several greenhouse gases using high-precision spectrometers started in 2011 on a tall tower with three sampling inlets at 10, 50 and 120 m above ground level (a.g.l.). Measurement quality is regularly assessed using several complementary approaches based on reference high-pressure cylinders, audits using travelling instruments and sets of travelling cylinders ("cucumber" intercomparison programme). Thanks to the quality assurance strategy recommended by ICOS, measurement uncertainties are within the World Meteorological Organisation compatibility goals for carbon dioxide (CO2), methane (CH4) and carbon monoxide (CO). The time series of mixing ratios from 2011 to the end of 2018 are used to analyse trends and diurnal and seasonal cycles. The CO2 and CH4 annual growth rates are 2.4 ppm yr-1 and 8.8 ppb yr-1 respectively for measurements at 120 m a.g.l. over the investigated period. However, no significant trend has been recorded for CO mixing ratios. The afternoon mean residuals (defined as the differences between midday observations and a smooth fitted curve) of these three compounds are significantly stronger during the cold period when inter-species correlations are high, compared to the warm period. The variabilities of residuals show a close link with air mass backtrajectories.
BibTeX:
@article{Conil2019,
  author = {Conil, Sébastien and Helle, Julie and Langrene, Laurent and Laurent, Olivier and Delmotte, Marc and Ramonet, Michel},
  title = {Continuous atmospheric CO2, CH4 and CO measurements at the Observatoire Pérenne de l'Environnement (OPE) station in France from 2011 to 2018},
  journal = {Atmospheric Measurement Techniques},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {12},
  number = {12},
  pages = {6361--6383},
  doi = {10.5194/amt-12-6361-2019}
}
Conte A, Fares S, Salvati L, Savi F, Matteucci G, Mazzenga F, Spano D, Sirca C, Marras S, Galvagno M, Cremonese E and Montagnani L (2019), "Ecophysiological Responses to Rainfall Variability in Grassland and Forests Along a Latitudinal Gradient in Italy", Frontiers in Forests and Global Change., may, 2019. Vol. 2 Frontiers Media SA.
Abstract: In the Mediterranean region, ecosystems are severely affected by climate variability. The Italian Peninsula is a hot spot for biodiversity thanks to heterogeneous landscape and Mediterranean, Continental, and Alpine climates hosting a broad range of plant functional types along a limited latitudinal range from 40' to 46' N. In this study we applied a comparative approach integrating descriptive statistics, time series analysis, and multivariate techniques to answer the following questions: (i) do the climatic variables affect GPP, Reco, WUE and ET to a similar extent among different sites? (ii) Does a common response pattern exist among ecosystems along a latitudinal gradient in Italy? And, finally (iii) do these ecosystems respond synchronically to meteorological conditions or does a delayed response exists? Six sites along a latitudinal, altitudinal and vegetational gradient from semi-arid (southern Italy) to a mountainous Mediterranean site (central Italy) and sub-humid wet Alpine sites (northern Italy) were considered. For each site, carbon and water fluxes and meteorological data collected during two hydrologically-contrasting years (i.e. a dry and a wet year) were analysed. Principal Component Analysis was adopted to identify temporal and spatial variations in Gross Primary Productivity (GPP), Ecosystem Respiration (Reco), Water Use Efficiency (WUE) and Evapotranspiration (ET). The model outlined differences among Mediterranean semi-arid, Mediterranean mountainous, and Alpine sites in response to contrasting precipitation regimes. GPP, Reco, WUE and ET increased up to 16, 19, 25 and 28 %, respectively in semi-arid Mediterranean sites and up to 15, 32, 15 and 11%, respectively in Alpine sites in the wet year compared to the dry year. Air temperature was revealed to be one of the most important variables affecting GPP, Reco, WUE and ET in all the study sites. While relative air humidity was more important in southern Mediterranean sites, global radiation was more significant in northern Italy. Our work suggests that a realistic prediction of the main responses of Italian forests under climate change should also take in account delayed responses due to acclimation to abiotic stress or changing environmental conditions.
BibTeX:
@article{Conte2019,
  author = {Conte, Adriano and Fares, Silvano and Salvati, Luca and Savi, Flavia and Matteucci, Giorgio and Mazzenga, Francesco and Spano, Donatella and Sirca, Costantino and Marras, Serena and Galvagno, Marta and Cremonese, Edoardo and Montagnani, Leonardo},
  title = {Ecophysiological Responses to Rainfall Variability in Grassland and Forests Along a Latitudinal Gradient in Italy},
  journal = {Frontiers in Forests and Global Change},
  publisher = {Frontiers Media SA},
  year = {2019},
  volume = {2},
  doi = {10.3389/ffgc.2019.00016}
}
Crabbe RA, Janouš D, Dařenová E and Pavelka M (2019), "Exploring the potential of LANDSAT-8 for estimation of forest soil CO 2 efflux", International Journal of Applied Earth Observation and Geoinformation., may, 2019. Vol. 77, pp. 42-52. Elsevier BV.
Abstract: Monitoring forest soil carbon dioxide efflux (FCO 2 ) is important as it contributes significantly to terrestrial ecosystem respiration and is hence a major factor in global carbon cycle. FCO 2 monitoring is usually conducted by the use of soil chambers to sample various point positions, but this method is difficult to replicate at spatially large research sites. Satellite remote sensing is accustomed to monitoring environmental phenomenon at large spatial scale, however its utilisation in FCO 2 monitoring is under-explored. To this end, this study explored the potential of LANDSAT-8 to estimate FCO 2 with the specific aims of deriving land surface temperature (LST) from LANDSAT-8 and then develop FCO 2 model on the basis of LANDSAT-8 LST to account for seasonal and inter-annual variations of FCO 2 . The study was conducted over an old European beech forest (Fagus sylvatica) in Czech Republic. In the end, two kinds of linear mixed effect models were built; Model-1 (inter-annual variations of FCO 2 ) and Model-2 (seasonal variations of FCO 2 ). The difference between Model-1 and Model-2 lies in their random factors; while Model-1 has ‘year' of FCO 2 measurement as a random factor, Model-2 has ‘season' of FCO 2 measurement as a random factor. When modelling without random factors, LANDSAT-8 LST as the fixed predictor in both models was able to account for 26% (marginal R 2 = 0.26) of FCO 2 variability in Model-1 whereas it accounted for 29% in Model-2. However, the parameterisation of random effects improved the performance of both models. Model-1 was the best in that it explained 65% (conditional R 2 = 0.65) of variability in FCO 2 and produced the least deviation from observed FCO 2 (RMSE = 0.38 μmol/m 2 /s). This study adds to the limited number of previous similar studies with the aim of encouraging satellite remote sensing integration in FCO 2 observation.
BibTeX:
@article{Crabbe2019,
  author = {Crabbe, Richard A. and Janouš, Dalibor and Dařenová, Eva and Pavelka, Marian},
  title = {Exploring the potential of LANDSAT-8 for estimation of forest soil CO 2 efflux},
  journal = {International Journal of Applied Earth Observation and Geoinformation},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {77},
  pages = {42--52},
  doi = {10.1016/j.jag.2018.12.007}
}
Dangal SR, Tian H, Xu R, Chang J, Canadell JG, Ciais P, Pan S, Yang J and Zhang B (2019), "Global Nitrous Oxide Emissions From Pasturelands and Rangelands: Magnitude, Spatiotemporal Patterns, and Attribution", Global Biogeochemical Cycles., feb, 2019. Vol. 33(2), pp. 200-222. American Geophysical Union (AGU).
Abstract: The application of manure and mineral nitrogen (N) fertilizer, and livestock excreta deposition are the main drivers of nitrous oxide (N 2 O) emissions in agricultural systems. However, the magnitude and spatiotemporal variations of N 2 O emissions due to different management practices (excreta deposition and manure/fertilizer application) from grassland ecosystems remain unclear. In this study, we used the Dynamic Land Ecosystem Model to simulate the spatiotemporal variation in global N 2 O emissions and their attribution to different sources from both intensively managed (pasturelands) and extensively managed (rangelands) grasslands during 1961–2014. Over the study period, pasturelands and rangelands experienced a significant increase in N 2 O emissions from 1.74 Tg N 2 O-N in 1961 to 3.11 Tg N 2 O-N in 2014 (p textless 0.05). Globally, pasturelands and rangelands were responsible for 54% (2.2 Tg N 2 O-N) of the total agricultural N 2 O emissions (4.1 Tg N 2 O-N) in 2006. Natural and anthropogenic sources contributed 26% (0.64 Tg N 2 O-N/year) and 74% (1.78 Tg N 2 O-N/year) of the net emissions, respectively. Across different biomes, pasturelands (i.e., C3 and C4) were the single largest contributor to N 2 O fluxes, accounting for 86% of the net global emissions from grasslands. Among different sources, livestock excreta deposition contributed 54% of the net emissions, followed by manure N (13%) and mineral N (7%) application. Regionally, southern Asia contributed 38% of the total emissions, followed by Europe (29%) and North America (16%). Our modeling study demonstrates that livestock excreta deposition and manure/fertilizer application have dramatically altered the N cycle in pasturelands, with a substantial impact on the climate system.
BibTeX:
@article{Dangal2019,
  author = {Dangal, Shree R.S. and Tian, Hanqin and Xu, Rongting and Chang, Jinfeng and Canadell, Josep G. and Ciais, Philippe and Pan, Shufen and Yang, Jia and Zhang, Bowen},
  title = {Global Nitrous Oxide Emissions From Pasturelands and Rangelands: Magnitude, Spatiotemporal Patterns, and Attribution},
  journal = {Global Biogeochemical Cycles},
  publisher = {American Geophysical Union (AGU)},
  year = {2019},
  volume = {33},
  number = {2},
  pages = {200--222},
  doi = {10.1029/2018GB006091}
}
Darenova E, Szatniewska J, Acosta M and Pavelka M (2019), "Variability of stem CO2 efflux response to temperature over the diel period", Tree Physiology., dec, 2019. Vol. 39(5), pp. 877-887. Oxford University Press (OUP).
Abstract: This study presents results from continuous measurements of stem CO2 efflux carried out for seven growing seasons in a young Norway spruce forest. The objective of the study was to determine differences in temperature sensitivity of stem CO2 efflux (Q10) during night (when sap flow is zero or nearly zero), during early afternoon (when the maximum rate of sap flow occurs) and during two transition periods between the aforementioned periods. The highest Q10 was recorded during the period of zero sap flow, while the lowest Q10 was observed in period of the highest sap flow. Calculating Q10 using only data from the period of zero sap flow resulted in a Q10 that was higher by as much as 19% compared with Q10 calculated using 24 h data. On the other hand, basing the calculation on data from the period of the highest sap flow yielded 5.6% lower Q10 than if 24 h data were used. Considering that change in CO2 efflux lagged in time behind changing stem temperature, there was only a small effect on calculated Q10 for periods with zero and the highest sap flow. A larger effect of the time lag (by as much as 15%) was observed for the two transition periods. Stem CO2 efflux was modelled based on the night CO2 efflux response to temperature. This model had a tendency to overestimate CO2 efflux during daytime, thus indicating potential daytime depression of stem CO2 efflux compared with the values predicated on the basis of temperature caused by CO2 transport upward in the sap flow. This view was supported by our results inasmuch as the overestimation grew with sap flow that was modelled on the basis of photosynthetically active radiation and vapour pressure deficit.
BibTeX:
@article{Darenova2019,
  author = {Darenova, Eva and Szatniewska, Justyna and Acosta, Manuel and Pavelka, Marian},
  editor = {Ryan, Michael},
  title = {Variability of stem CO2 efflux response to temperature over the diel period},
  journal = {Tree Physiology},
  publisher = {Oxford University Press (OUP)},
  year = {2019},
  volume = {39},
  number = {5},
  pages = {877--887},
  doi = {10.1093/treephys/tpy134}
}
De Marco A, Proietti C, Anav A, Ciancarella L, D'Elia I, Fares S, Fornasier MF, Fusaro L, Gualtieri M, Manes F, Marchetto A, Mircea M, Paoletti E, Piersanti A, Rogora M, Salvati L, Salvatori E, Screpanti A, Vialetto G, Vitale M and Leonardi C (2019), "Impacts of air pollution on human and ecosystem health, and implications for the National Emission Ceilings Directive: Insights from Italy", Environment International., apr, 2019. Vol. 125, pp. 320-333. Elsevier BV.
Abstract: Across the 28 EU member states there were nearly half a million premature deaths in 2015 as a result of exposure to PM2.5, O3 and NO2. To set the target for air quality levels and avoid negative impacts for human and ecosystems health, the National Emission Ceilings Directive (NECD, 2016/2284/EU) sets objectives for emission reduction for SO2, NOx, NMVOCs, NH3 and PM2.5 for each Member State as percentages of reduction to be reached in 2020 and 2030 compared to the emission levels into 2005. One of the innovations of NECD is Article 9, that mentions the issue of “monitoring air pollution impacts” on ecosystems. We provide a clear picture of what is available in term of monitoring network for air pollution impacts on Italian ecosystems, summarizing what has been done to control air pollution and its effects on different ecosystems in Italy. We provide an overview of the impacts of air pollution on health of the Italian population and evaluate opportunities and implementation of Article 9 in the Italian context, as a case study beneficial for all Member States. The results showed that SO42− deposition strongly decreased in all monitoring sites in Italy over the period 1999–2017, while NO3− and NH4+ decreased more slightly. As a consequence, most of the acid-sensitive sites which underwent acidification in the 1980s partially recovered. The O3 concentration at forest sites showed a decreasing trend. Consequently, AOT40 (the metric identified to protect vegetation from ozone pollution) showed a decrease, even if values were still above the limit for forest protection (5000 ppb h−1), while PODy (flux-based metric under discussion as new European legislative standard for forest protection) showed an increase. National scale studies pointed out that PM10 and NO2 induced about 58,000 premature deaths (year 2005), due to cardiovascular and respiratory diseases. The network identified for Italy contains a good number of monitoring sites (6 for terrestrial ecosystem monitoring, 4 for water bodies monitoring and 11 for ozone impact monitoring) distributed over the territory and will produce a high number of monitored parameters for the implementation of the NECD.
BibTeX:
@article{DeMarco2019,
  author = {De Marco, Alessandra and Proietti, Chiara and Anav, Alessandro and Ciancarella, Luisella and D'Elia, Ilaria and Fares, Silvano and Fornasier, Maria Francesca and Fusaro, Lina and Gualtieri, Maurizio and Manes, Fausto and Marchetto, Aldo and Mircea, Mihaela and Paoletti, Elena and Piersanti, Antonio and Rogora, Michela and Salvati, Luca and Salvatori, Elisabetta and Screpanti, Augusto and Vialetto, Giovanni and Vitale, Marcello and Leonardi, Cristina},
  title = {Impacts of air pollution on human and ecosystem health, and implications for the National Emission Ceilings Directive: Insights from Italy},
  journal = {Environment International},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {125},
  pages = {320--333},
  doi = {10.1016/j.envint.2019.01.064}
}
DeCola P, Tarasova O, Brunner D, Maksyutov S, Manning A, Vogel F, Gurney K, Turnbull J, Zavala-Araiza D, Kort E, Robinson R, Canadell P, Ciais P, Vladu F, Houweling S, Lauvaux T, Mueller K, Vermeulen A(LU and Al. E (2019), "An Integrated Global Greenhouse Gas Information System (IG3IS) Science Implementation Plane - GAW Report No. 245". Thesis at: WMO. Geneva , pp. 62.
Abstract: The implementation of the Paris Agreement will require countries and sub-national entities to take actions to reduce emissions of greenhouse gases in an optimal way. To assist the countries in meeting their commitments the World Meteorological Organization (WMO) and its partners have initiated the development of an Integrated Global Greenhouse Gas Information System (IG3IS). IG3IS looks to serve users (decision-makers) who are able and willing to take actions to reduce emissions of greenhouse gases and pollutants that reduce air quality. This service is based on existing and successful methods and use-cases for which the scientific and technical skill is proven or emerging. The Science Implementation Plan presents the suite of the technical solutions that are available to address articulated user needs on different scales (from national to facility). It also paves the way for the development of future solutions where additional research is required. This document presents the main principles of the IG3IS Science Implementation Plan. The choice of the objective to be implemented has to be made by the countries or sub-national implementation bodies/practitioners. For each individual objective, the plan presents the available and proven tools based on measurements and model analyses. It summarizes key elements required to implement individual solutions. The plan describes the approach to the modelling coordination activities to ensure harmonized and quality assured global implementation and compatibility of the products delivered on different scales. The measure of success of the IG3IS implementation is the use of the provided information for valuable and additional emission reduction actions, building user confidence and practitioner skills in the value of atmospheric composition measurements as an essential part of the climate change mitigation and pollution remediation tool kits. The IG3IS team defined four implementation objectives: 1) improve knowledge of national emissions (including reduction of uncertainties of inventory reporting to the United Nations Framework Convention on Climate Change (UNFCCC)); 2) locate and quantify previously unknown emission reduction opportunities such as fugitive methane emissions from industrial sources; 3) provide sub-national entities such as large urban source regions (for example, megacities) with timely and quantified information on the amounts, trends and attribution by sector of their greenhouse gas (GHG) emissions to evaluate and guide progress towards emission reduction goals; and 4) support for the Paris Agreement's global stocktake through the integration of these objectives. This Science Implementation Plan documents the “good-practice” methodological guidelines for how atmospheric measurements and analysis methods can deliver valuable information under each objective area. This plan and the team that prepared it, will serve to guide WMO Members and their partners in the definition and implementation of new IG3IS projects that apply and advance these “good-practice” capabilities. The plan will evolve overtime to respond to new policy challenges and to capture emerging capabilities. Successful application of IG3IS methods depends on intimate dialogue between scientists and users in order to ensure that user requirements are met, and so that users are introduced to previously unknown capabilities that may drive them to address challenges in new ways. IG3IS takes a highly collaborative “Translation Atmospheric Sciences” approach to deliver science-based services to potential stakeholders/users and is well in line with the implementation plan of the Global Atmosphere Watch (GAW) Programme. The plan directly supports implementation of the WMO Strategic Plan for 2020-2023, Objective 3.2 “Advance policy-relevant science”.
BibTeX:
@techreport{DeCola2019,
  author = {DeCola, Phil and Tarasova, Oksana and Brunner, Dominik and Maksyutov, Shamil and Manning, Alistair and Vogel, Felix and Gurney, Kevin and Turnbull, Jocelyn and Zavala-Araiza, Daniel and Kort, Eric and Robinson, Rod and Canadell, Pep and Ciais, Philippe and Vladu, Florin and Houweling, Sander and Lauvaux, Thomas and Mueller, Kim and Vermeulen, Alex (Lund University) and Al., Et},
  title = {An Integrated Global Greenhouse Gas Information System (IG3IS) Science Implementation Plane - GAW Report No. 245},
  school = {WMO},
  year = {2019},
  pages = {62},
  url = {https://library.wmo.int/index.php?lvl=etageresee&id=144.WK2TTBiZNB}
}
Deirmendjian L, Anschutz P, Morel C, Mollier A, Augusto L, Loustau D, Cotovicz LC, Buquet D, Lajaunie K, Chaillou G, Voltz B, Charbonnier C, Poirier D and Abril G (2019), "Importance of the vegetation-groundwater-stream continuum to understand transformation of biogenic carbon in aquatic systems – A case study based on a pine-maize comparison in a lowland sandy watershed (Landes de Gascogne, SW France)", Science of the Total Environment., apr, 2019. Vol. 661, pp. 613-629. Elsevier BV.
Abstract: During land-aquatic transfer, carbon (C) and inorganic nutrients (IN) are transformed in soils, groundwater, and at the groundwater-surface water interface as well as in stream channels and stream sediments. However, processes and factors controlling these transfers and transformations are not well constrained, particularly with respect to land use effect. We compared C and IN concentrations in shallow groundwater and first-order streams of a sandy lowland catchment dominated by two types of land use: pine forest and maize cropland. Contrary to forest groundwater, crop groundwater exhibited oxic conditions all-year round as a result of higher evapotranspiration and better lateral drainage that decreased the water table below the organic-rich soil horizon, prevented the leaching of soil-generated dissolved organic carbon (DOC) in groundwater, and thus limited consumption of dissolved oxygen (O 2 ). In crop groundwater, oxic conditions inhibited denitrification and methanogenesis resulting in high nitrate (NO 3− ; on average 1140 ± 485 μmol L −1 ) and low methane (CH 4 ; 40 ± 25 nmol L −1 ) concentrations. Conversely, anoxic conditions in forest groundwater led to lower NO 3− (25 ± 40 μmol L − 1) and higher CH 4 (1770 ± 1830 nmol L −1 ) concentrations. The partial pressure of carbon dioxide (pCO 2 ; 30,650 ± 11,590 ppmv) in crop groundwater was significantly lower than in forest groundwater (50,630 ± 26,070 ppmv), and was apparently caused by the deeper water table delaying downward diffusion of soil CO 2 to the water table. In contrast, pCO 2 was not significantly different in crop (4480 ± 2680 ppmv) and forest (4900 ± 4500 ppmv) streams, suggesting faster degassing in forest streams resulting from greater water turbulence. Although NO 3− concentrations indicated that denitrification occurred in riparian-forest groundwater, crop streams nevertheless exhibited important signs of spring and summer eutrophication such as the development of macrophytes. Stream eutrophication favored development of anaerobic conditions in crop stream sediments, as evidenced by increased ammonia (NH 4+ ) and CH 4 in stream waters and concomitant decreased in NO 3− concentrations as a result of sediment denitrification. In crop streams, dredging and erosion of streambed sediments during winter sustained high concentration of particulate organic C, NH 4+ and CH 4 . In forest streams, dissolved iron (Fe 2+ ), NH 4+ and CH 4 were negatively correlated with O 2 reflecting the gradual oxygenation of stream water and associated oxidations of Fe 2+ , NH 4+ and CH 4 . The results overall showed that forest groundwater behaved as source of CO 2 and CH 4 to streams, the intensity depending on the hydrological connectivity among soils, groundwater, and streams. CH 4 production was prevented in cropland in soils and groundwater, however crop groundwater acted as a source of CO 2 to streams (but less so than forest groundwater). Conversely, in streams, pCO 2 was not significantly affected by land use while CH 4 production was enhanced by cropland. At the catchment scale, this study found substantial biogeochemical heterogeneity in C and IN concentrations between forest and crop waters, demonstrating the importance of including the full vegetation-groundwater-stream continuum when estimating land-water fluxes of C (and nitrogen) and attempting to understand their spatial and temporal dynamics.
BibTeX:
@article{Deirmendjian2019,
  author = {Deirmendjian, Loris and Anschutz, Pierre and Morel, Christian and Mollier, Alain and Augusto, Laurent and Loustau, Denis and Cotovicz, Luiz Carlos and Buquet, Damien and Lajaunie, Katixa and Chaillou, Gwenaëlle and Voltz, Baptiste and Charbonnier, Céline and Poirier, Dominique and Abril, Gwenaël},
  title = {Importance of the vegetation-groundwater-stream continuum to understand transformation of biogenic carbon in aquatic systems – A case study based on a pine-maize comparison in a lowland sandy watershed (Landes de Gascogne, SW France)},
  journal = {Science of the Total Environment},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {661},
  pages = {613--629},
  doi = {10.1016/j.scitotenv.2019.01.152}
}
Delon C, Galy-Lacaux C, Serça D, Personne E, Mougin E, Adon M, Le Dantec V, Loubet B, Fensholt R and Tagesson T (2019), "Modelling land-atmosphere daily exchanges of NO, NH3, and CO2 in a semi-arid grazed ecosystem in Senegal", Biogeosciences., may, 2019. Vol. 16(9), pp. 2049-2077. Copernicus GmbH.
Abstract: Three different models (STEP-GENDEC-NOflux, Zhang2010, and Surfatm) are used to simulate NO, CO2, and NH3 fluxes at the daily scale for 2 years (2012-2013) in a semi-arid grazed ecosystem at Dahra (15°24′10′ ′ N, 15°25′56′ ′W, Senegal, Sahel). Model results are evaluated against experimental results acquired during three field campaigns. At the end of the dry season, when the first rains re-wet the dry soils, the model STEP-GENDEC-NOflux simulates the sudden mineralization of buried litter, leading to pulses in soil respiration and NO fluxes. The contribution of wet season fluxes of NO and CO2 to the annual mean is respectively 51% and 57 %. NH3 fluxes are simulated by two models: Surfatm and Zhang2010. During the wet season, air humidity and soil moisture increase, leading to a transition between low soil NH3 emissions (which dominate during the dry months) and large NH3 deposition on vegetation during wet months. Results show a great impact of the soil emission potential, a difference in the deposition processes on the soil and the vegetation between the two models with however a close agreement of the total fluxes. The order of magnitude of NO, NH3, and CO2 fluxes is correctly represented by the models, as well as the sharp transitions between seasons, specific to the Sahel region. The role of soil moisture in flux magnitude is highlighted, whereas the role of soil temperature is less obvious. The simultaneous increase in NO and CO2 emissions and NH3 deposition at the beginning of the wet season is attributed to the availability of mineral nitrogen in the soil and also to microbial processes, which distribute the roles between respiration (CO2 emissions), nitrification (NO emissions), volatilization, and deposition (NH3 emission/deposition). The objectives of this study are to understand the origin of carbon and nitrogen compounds exchanges between the soil and the atmosphere and to quantify these exchanges on a longer timescale when only a few measurements have been performed.
BibTeX:
@article{Delon2019,
  author = {Delon, Claire and Galy-Lacaux, Corinne and Serça, Dominique and Personne, Erwan and Mougin, Eric and Adon, Marcellin and Le Dantec, Valérie and Loubet, Benjamin and Fensholt, Rasmus and Tagesson, Torbern},
  title = {Modelling land-atmosphere daily exchanges of NO, NH3, and CO2 in a semi-arid grazed ecosystem in Senegal},
  journal = {Biogeosciences},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {16},
  number = {9},
  pages = {2049--2077},
  doi = {10.5194/bg-16-2049-2019}
}
Djomo SN, De Groote T, Gobin A, Ceulemans R and Janssens IA (2019), "Combining a land surface model with life cycle assessment for identifying the optimal management of short rotation coppice in Belgium", Biomass and Bioenergy., feb, 2019. Vol. 121, pp. 78-88. Elsevier BV.
Abstract: Poplar (Populus spp.) and willow (Salix spp.) short rotation coppice (SRC) are attractive feedstock for conversion to renewable electricity. Site managers typically optimize biomass production at their sites. However, maximum biomass production does not necessarily equate an optimal CO2 balance, water use and energy production. This is because many operational actions consume water and energy and emit CO2, either on-site or off-site. Coupling a land surface model (ORCHIDEE-SRC) with life cycle assessment enabled us to determine the optimal management for SRC in Belgium. We simulated 120 different management scenarios for each of two well-studied Belgian SRC sites (i.e. Boom and Lochristi). Simulated soil carbon changes suggested substantial carbon losses of 20–30 Mg ha−1 over a time period of 20 years, which were within observation-based uncertainty bounds. Results showed that in Belgium, which has a temperate maritime climate, optimal management of SRC has a rotation cycle of two years without irrigation. Energy inputs for this optimal management were 5.2 GJ ha−1 yr−1 for the Boom site and 5.3 GJ ha−1 yr−1 for the Lochristi site, while the biomass yields at Boom and Lochristi were 9.0 Mg ha−1 yr−1 and 9.4 Mg ha−1 yr−1, respectively. The energy ratio (i.e., ratio of bioelectricity output to cumulative energy input) for this optimal management was 12, on average. Planting density turned out to be unimportant, while rotation length turned out to be most important to obtain the highest energy ratio and still maintain high biomass yield. Scenarios with high energy-input generated more bioenergy outputs, but the energy gains did not compensate for the increased energy inputs. Reductions in energy consumption per unit of bioenergy output should target the agricultural stage since it accounted for the largest energy share in the production chain.
BibTeX:
@article{Djomo2019,
  author = {Djomo, S. Njakou and De Groote, T. and Gobin, A. and Ceulemans, R. and Janssens, I. A.},
  title = {Combining a land surface model with life cycle assessment for identifying the optimal management of short rotation coppice in Belgium},
  journal = {Biomass and Bioenergy},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {121},
  pages = {78--88},
  doi = {10.1016/j.biombioe.2018.12.010}
}
Druel A, Ciais P, Krinner G and Peylin P (2019), "Modeling the Vegetation Dynamics of Northern Shrubs and Mosses in the ORCHIDEE Land Surface Model", Journal of Advances in Modeling Earth Systems., jul, 2019. Vol. 11(7), pp. 2020-2035. American Geophysical Union (AGU).
Abstract: Parameterizations of plant competition processes involving shrubs, mosses, grasses, and trees were introduced with the recently implemented shrubs and mosses plant functional types in the ORCHIDEE dynamic global vegetation model in order to improve the representation of high latitude vegetation dynamics. Competition is based on light capture for growth, net primary productivity, and survival to cold-induced mortality during winter. Trees are assumed to outcompete shrubs and grasses for light, and shrubs outcompete grasses. Shrubs are modeled to have a higher survival than trees to extremely cold winters because of thermic protection by snow. The fractional coverage of each plant type is based on their respective net primary productivity and winter mortality of trees and shrubs. Gridded simulations were carried out for the historical period and the 21st century following the RCP4.5 and 8.5 scenarios. We evaluate the simulated present-day vegetation with an observation-based distribution map and literature data of boreal shrubs. The simulation produces a realistic present-day boreal vegetation distribution, with shrubs, mosses north of trees and grasses. Nevertheless, the model underestimated local shrub expansion compared to observations from selected sites in the Arctic during the last 30 years suggesting missing processes (nutrients and microscale effects). The RCP4.5 and RCP8.5 projections show a substantial decrease of bare soil, an increase in tree and moss cover and an increase of shrub net primary productivity. Finally, the impact of new vegetation types and associated processes is discussed in the context of climate feedbacks.
BibTeX:
@article{Druel2019,
  author = {Druel, Arsène and Ciais, Philippe and Krinner, Gerhard and Peylin, Philippe},
  title = {Modeling the Vegetation Dynamics of Northern Shrubs and Mosses in the ORCHIDEE Land Surface Model},
  journal = {Journal of Advances in Modeling Earth Systems},
  publisher = {American Geophysical Union (AGU)},
  year = {2019},
  volume = {11},
  number = {7},
  pages = {2020--2035},
  doi = {10.1029/2018MS001531}
}
Dumortier P, Aubinet M, Lebeau F, Naiken A and Heinesch B (2019), "Point source emission estimation using eddy covariance: Validation using an artificial source experiment", Agricultural and Forest Meteorology. Vol. 266-267, pp. 148-156. Elsevier BV.
Abstract: Eddy covariance is increasingly used to monitor cattle emissions. However, the turbulent flux calculation method and the footprint models upon which calculations are based are insufficiently validated. In addition, available footprint models presume the source to be placed at soil height, which is obviously not the case for cattle. The present study uses a single known artificial point source placed at cow's muzzle height in order to assess the impact of the flux calculation method (averaging method, averaging period, quality filters) and of the footprint model on the emission estimates. The optimal calculation method and footprint model combination (running mean, 15 min averaging periods, no application of the Foken and Wichura (1996) stationarity filter, and the use of the Kormann and Meixner (2001) footprint function) led to estimated emissions between 90 and 113% of the true emission, leading to the conclusion that the use of eddy-covariance for point-source emission estimation is feasible provided an adequate calculation method is selected.
BibTeX:
@article{Dumortier2019,
  author = {Dumortier, Pierre and Aubinet, Marc and Lebeau, Frédéric and Naiken, Alwin and Heinesch, Bernard},
  title = {Point source emission estimation using eddy covariance: Validation using an artificial source experiment},
  journal = {Agricultural and Forest Meteorology},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {266-267},
  pages = {148--156},
  url = {https://doi.org/10.1016%2Fj.agrformet.2018.12.012},
  doi = {10.1016/j.agrformet.2018.12.012}
}
Efren LB, Exbrayat JF, Lund M, Christensen TR, Tamstorf MP, Slevin D, Hugelius G, Bloom AA and Williams M (2019), "Evaluation of terrestrial pan-Arctic carbon cycling using a data-assimilation system", Earth System Dynamics., apr, 2019. Vol. 10(2), pp. 233-255. Copernicus GmbH.
Abstract: There is a significant knowledge gap in the current state of the terrestrial carbon (C) budget. Recent studies have highlighted a poor understanding particularly of C pool transit times and of whether productivity or biomass dominate these biases. The Arctic, accounting for approximately 50% of the global soil organic C stocks, has an important role in the global C cycle. Here, we use the CARbon DAta MOdel (CARDAMOM) data-assimilation system to produce pan-Arctic terrestrial C cycle analyses for 2000-2015. This approach avoids using traditional plant functional type or steady-state assumptions. We integrate a range of data (soil organic C, leaf area index, biomass, and climate) to determine the most likely state of the high-latitude C cycle at a 11 resolution and also to provide general guidance about the controlling biases in transit times. On average, CARDAMOM estimates regional mean rates of photosynthesis of 565 gCm2 yr1 (90% confidence interval between the 5th and 95th percentiles: 428, 741), autotrophic respiration of 270 g Cm2 yr1 (182, 397) and heterotrophic respiration of 219 g Cm2 yr1 (31, 1458), suggesting a pan-Arctic sink of 67 (287, 1160) gCm2 yr1, weaker in tundra and stronger in taiga. However, our confidence intervals remain large (and so the region could be a source of C), reflecting uncertainty assigned to the regional data products. We show a clear spatial and temporal agreement between CARDAMOM analyses and different sources of assimilated and independent data at both pan-Arctic and local scales but also identify consistent biases between CARDAMOM and validation data. The assimilation process requires clearer error quantification for leaf area index (LAI) and biomass products to resolve these biases. Mapping of vegetation C stocks and change over time and soil C ages linked to soil C stocks is required for better analytical constraint. Comparing CARDAMOM analyses to global vegetation models (GVMs) for the same period, we conclude that transit times of vegetation C are inconsistently simulated in GVMs due to a combination of uncertainties from productivity and biomass calculations. Our findings highlight that GVMs need to focus on constraining both current vegetation C stocks and net primary production to improve a process-based understanding of C cycledynamics in the Arctic.
BibTeX:
@article{Efren2019,
  author = {Efren, Lopez Blanco and Exbrayat, Jean Francois and Lund, Magnus and Christensen, Torben R. and Tamstorf, Mikkel P. and Slevin, Darren and Hugelius, Gustaf and Bloom, Anthony A. and Williams, Mathew},
  title = {Evaluation of terrestrial pan-Arctic carbon cycling using a data-assimilation system},
  journal = {Earth System Dynamics},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {10},
  number = {2},
  pages = {233--255},
  doi = {10.5194/esd-10-233-2019}
}
Esquivel-Muelbert A, Baker TR, Dexter KG, Lewis SL, Brienen RJ, Feldpausch TR, Lloyd J, Monteagudo-Mendoza A, Arroyo L, Álvarez-Dávila E, Higuchi N, Marimon BS, Marimon-Junior BH, Silveira M, Vilanova E, Gloor E, Malhi Y, Chave J, Barlow J, Bonal D, Davila Cardozo N, Erwin T, Fauset S, Hérault B, Laurance S, Poorter L, Qie L, Stahl C, Sullivan MJ, ter Steege H, Vos VA, Zuidema PA, Almeida E, Almeida de Oliveira E, Andrade A, Vieira SA, Aragão L, Araujo-Murakami A, Arets E, Aymard C GA, Baraloto C, Camargo PB, Barroso JG, Bongers F, Boot R, Camargo JL, Castro W, Chama Moscoso V, Comiskey J, Cornejo Valverde F, Lola da Costa AC, del Aguila Pasquel J, Di Fiore A, Fernanda Duque L, Elias F, Engel J, Flores Llampazo G, Galbraith D, Herrera Fernández R, Honorio Coronado E, Hubau W, Jimenez-Rojas E, Lima AJN, Umetsu RK, Laurance W, Lopez-Gonzalez G, Lovejoy T, Aurelio Melo Cruz O, Morandi PS, Neill D, Núñez Vargas P, Pallqui Camacho NC, Parada Gutierrez A, Pardo G, Peacock J, Peña-Claros M, Peñuela-Mora MC, Petronelli P, Pickavance GC, Pitman N, Prieto A, Quesada C, Ramírez-Angulo H, Réjou-Méchain M, Restrepo Correa Z, Roopsind A, Rudas A, Salomão R, Silva N, Silva Espejo J, Singh J, Stropp J, Terborgh J, Thomas R, Toledo M, Torres-Lezama A, Valenzuela Gamarra L, van de Meer PJ, van der Heijden G, van der Hout P, Vasquez Martinez R, Vela C, Vieira ICG and Phillips OL (2019), "Compositional response of Amazon forests to climate change", Global Change Biology., nov, 2019. Vol. 25(1), pp. 39-56. Wiley.
Abstract: Most of the planet's diversity is concentrated in the tropics, which includes many regions undergoing rapid climate change. Yet, while climate-induced biodiversity changes are widely documented elsewhere, few studies have addressed this issue for lowland tropical ecosystems. Here we investigate whether the floristic and functional composition of intact lowland Amazonian forests have been changing by evaluating records from 106 long-term inventory plots spanning 30 years. We analyse three traits that have been hypothesized to respond to different environmental drivers (increase in moisture stress and atmospheric CO 2 concentrations): maximum tree size, biogeographic water-deficit affiliation and wood density. Tree communities have become increasingly dominated by large-statured taxa, but to date there has been no detectable change in mean wood density or water deficit affiliation at the community level, despite most forest plots having experienced an intensification of the dry season. However, among newly recruited trees, dry-affiliated genera have become more abundant, while the mortality of wet-affiliated genera has increased in those plots where the dry season has intensified most. Thus, a slow shift to a more dry-affiliated Amazonia is underway, with changes in compositional dynamics (recruits and mortality) consistent with climate-change drivers, but yet to significantly impact whole-community composition. The Amazon observational record suggests that the increase in atmospheric CO 2 is driving a shift within tree communities to large-statured species and that climate changes to date will impact forest composition, but long generation times of tropical trees mean that biodiversity change is lagging behind climate change.
BibTeX:
@article{EsquivelMuelbert2019,
  author = {Esquivel-Muelbert, Adriane and Baker, Timothy R. and Dexter, Kyle G. and Lewis, Simon L. and Brienen, Roel J.W. and Feldpausch, Ted R. and Lloyd, Jon and Monteagudo-Mendoza, Abel and Arroyo, Luzmila and Álvarez-Dávila, Esteban and Higuchi, Niro and Marimon, Beatriz S. and Marimon-Junior, Ben Hur and Silveira, Marcos and Vilanova, Emilio and Gloor, Emanuel and Malhi, Yadvinder and Chave, Jerôme and Barlow, Jos and Bonal, Damien and Davila Cardozo, Nallaret and Erwin, Terry and Fauset, Sophie and Hérault, Bruno and Laurance, Susan and Poorter, Lourens and Qie, Lan and Stahl, Clement and Sullivan, Martin J.P. and ter Steege, Hans and Vos, Vincent Antoine and Zuidema, Pieter A. and Almeida, Everton and Almeida de Oliveira, Edmar and Andrade, Ana and Vieira, Simone Aparecida and Aragão, Luiz and Araujo-Murakami, Alejandro and Arets, Eric and Aymard C, Gerardo A. and Baraloto, Christopher and Camargo, Plínio Barbosa and Barroso, Jorcely G. and Bongers, Frans and Boot, Rene and Camargo, José Luís and Castro, Wendeson and Chama Moscoso, Victor and Comiskey, James and Cornejo Valverde, Fernando and Lola da Costa, Antonio Carlos and del Aguila Pasquel, Jhon and Di Fiore, Anthony and Fernanda Duque, Luisa and Elias, Fernando and Engel, Julien and Flores Llampazo, Gerardo and Galbraith, David and Herrera Fernández, Rafael and Honorio Coronado, Eurídice and Hubau, Wannes and Jimenez-Rojas, Eliana and Lima, Adriano José Nogueira and Umetsu, Ricardo Keichi and Laurance, William and Lopez-Gonzalez, Gabriela and Lovejoy, Thomas and Aurelio Melo Cruz, Omar and Morandi, Paulo S. and Neill, David and Núñez Vargas, Percy and Pallqui Camacho, Nadir C. and Parada Gutierrez, Alexander and Pardo, Guido and Peacock, Julie and Peña-Claros, Marielos and Peñuela-Mora, Maria Cristina and Petronelli, Pascal and Pickavance, Georgia C. and Pitman, Nigel and Prieto, Adriana and Quesada, Carlos and Ramírez-Angulo, Hirma and Réjou-Méchain, Maxime and Restrepo Correa, Zorayda and Roopsind, Anand and Rudas, Agustín and Salomão, Rafael and Silva, Natalino and Silva Espejo, Javier and Singh, James and Stropp, Juliana and Terborgh, John and Thomas, Raquel and Toledo, Marisol and Torres-Lezama, Armando and Valenzuela Gamarra, Luis and van de Meer, Peter J. and van der Heijden, Geertje and van der Hout, Peter and Vasquez Martinez, Rodolfo and Vela, Cesar and Vieira, Ima Célia Guimarães and Phillips, Oliver L.},
  title = {Compositional response of Amazon forests to climate change},
  journal = {Global Change Biology},
  publisher = {Wiley},
  year = {2019},
  volume = {25},
  number = {1},
  pages = {39--56},
  doi = {10.1111/gcb.14413}
}
Fan L, Wigneron JP, Ciais P, Chave J, Brandt M, Fensholt R, Saatchi SS, Bastos A, Al-Yaari A, Hufkens K, Qin Y, Xiao X, Chen C, Myneni RB, Fernandez-Moran R, Mialon A, Rodriguez-Fernandez NJ, Kerr Y, Tian F and Peñuelas J (2019), "Satellite-observed pantropical carbon dynamics", Nature Plants., jul, 2019. Vol. 5(9), pp. 944-951. Springer Science and Business Media LLC.
Abstract: Changes in terrestrial tropical carbon stocks have an important role in the global carbon budget. However, current observational tools do not allow accurate and large-scale monitoring of the spatial distribution and dynamics of carbon stocks1. Here, we used low-frequency L-band passive microwave observations to compute a direct and spatially explicit quantification of annual aboveground carbon (AGC) fluxes and show that the tropical net AGC budget was approximately in balance during 2010 to 2017, the net budget being composed of gross losses of −2.86 PgC yr−1 offset by gross gains of −2.97 PgC yr−1 between continents. Large interannual and spatial fluctuations of tropical AGC were quantified during the wet 2011 La Niña year and throughout the extreme dry and warm 2015–2016 El Niño episode. These interannual fluctuations, controlled predominantly by semiarid biomes, were shown to be closely related to independent global atmospheric CO2 growth-rate anomalies (Pearson's r = 0.86), highlighting the pivotal role of tropical AGC in the global carbon budget.
BibTeX:
@article{Fan2019,
  author = {Fan, Lei and Wigneron, Jean Pierre and Ciais, Philippe and Chave, Jérôme and Brandt, Martin and Fensholt, Rasmus and Saatchi, Sassan S. and Bastos, Ana and Al-Yaari, Amen and Hufkens, Koen and Qin, Yuanwei and Xiao, Xiangming and Chen, Chi and Myneni, Ranga B. and Fernandez-Moran, Roberto and Mialon, Arnaud and Rodriguez-Fernandez, N. J. and Kerr, Yann and Tian, Feng and Peñuelas, Josep},
  title = {Satellite-observed pantropical carbon dynamics},
  journal = {Nature Plants},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {5},
  number = {9},
  pages = {944--951},
  doi = {10.1038/s41477-019-0478-9}
}
Fares S, Alivernini A, Conte A and Maggi F (2019), "Ozone and particle fluxes in a Mediterranean forest predicted by the AIRTREE model", Science of the Total Environment., sep, 2019. Vol. 682, pp. 494-504. Elsevier BV.
Abstract: Mediterranean forests are among the most threatened ecosystems by the concurrent effects of climate change and atmospheric pollution. In this work we parameterized the AIRTREE multi-layer model to predict CO2, water, ozone, and fine particles exchanges between leaves and the atmosphere. AIRTREE consists of four different modules: (1) a canopy environmental module determines the leaf temperature and radiative fluxes at different levels from above to the bottom of the canopy; (2) a hydrological module predicts soil water flow and water availability to the plant's photosynthetic apparatus; (3) a photosynthesis module estimates the net photosynthesis and stomatal conductance, and (4) a deposition module estimates ozone and PM deposition sinks as a function of the resistances to gas diffusion in the atmosphere, and within the canopy and leaf boundary layer. We describe the AIRTREE model framework, accuracy and sensitivity by comparing modeling results against long-term continuous Eddy Covariance measurements of ozone, water, and CO2 fluxes in a Mediterranean Holm oak forest, and we discuss potential application of AIRTREE for ozone-risk assessment in view of availability of a large observational database from ecosystems distributed worldwide.
BibTeX:
@article{Fares2019,
  author = {Fares, Silvano and Alivernini, Alessandro and Conte, Adriano and Maggi, Federico},
  title = {Ozone and particle fluxes in a Mediterranean forest predicted by the AIRTREE model},
  journal = {Science of the Total Environment},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {682},
  pages = {494--504},
  doi = {10.1016/j.scitotenv.2019.05.109}
}
Fernández-Martínez M, Sardans J, Chevallier F, Ciais P, Obersteiner M, Vicca S, Canadell JG, Bastos A, Friedlingstein P, Sitch S, Piao SL, Janssens IA and Peñuelas J (2019), "Global trends in carbon sinks and their relationships with CO2 and temperature", Nature Climate Change., dec, 2019. Vol. 9(1), pp. 73-79. Springer Science and Business Media LLC.
Abstract: Elevated CO2 concentrations increase photosynthesis and, potentially, net ecosystem production (NEP), meaning a greater CO2 uptake. Climate, nutrients and ecosystem structure, however, influence the effect of increasing CO2. Here we analysed global NEP from MACC-II and Jena CarboScope atmospheric inversions and ten dynamic global vegetation models (TRENDY), using statistical models to attribute the trends in NEP to its potential drivers: CO2, climatic variables and land-use change. We found that an increased CO2 was consistently associated with an increased NEP (1995–2014). Conversely, increased temperatures were negatively associated with NEP. Using the two atmospheric inversions and TRENDY, the estimated global sensitivities for CO2 were 6.0 ± 0.1, 8.1 ± 0.3 and 3.1 ± 0.1 PgC per 100 ppm (˜1 °C increase), and −0.5 ± 0.2, −0.9 ± 0.4 and −1.1 ± 0.1 PgC °C−1 for temperature. These results indicate a positive CO2 effect on terrestrial C sinks that is constrained by climate warming.
BibTeX:
@article{FernandezMartinez2019,
  author = {Fernández-Martínez, M. and Sardans, J. and Chevallier, F. and Ciais, P. and Obersteiner, M. and Vicca, S. and Canadell, J. G. and Bastos, A. and Friedlingstein, P. and Sitch, S. and Piao, S. L. and Janssens, I. A. and Peñuelas, J.},
  title = {Global trends in carbon sinks and their relationships with CO2 and temperature},
  journal = {Nature Climate Change},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {9},
  number = {1},
  pages = {73--79},
  doi = {10.1038/s41558-018-0367-7}
}
Fischer FJ, Maréchaux I and Chave J (2019), "Improving plant allometry by fusing forest models and remote sensing", New Phytologist., apr, 2019. Vol. 223(3), pp. 1159-1165. Wiley.
Abstract: Allometry determines how tree shape and function scale with each other, related through size. Allometric relationships help scale processes from the individual to the global scale and constitute a core component of vegetation models. Allometric relationships have been expected to emerge from optimisation theory, yet this does not suitably predict empirical data. Here we argue that the fusion of high-resolution data, such as those derived from airborne laser scanning, with individual-based forest modelling offers insight into how plant size contributes to large-scale biogeochemical processes. We review the challenges in allometric scaling, how they can be tackled by advances in data-model fusion, and how individual-based models can serve as data integrators for dynamic global vegetation models.
BibTeX:
@article{Fischer2019,
  author = {Fischer, Fabian Jörg and Maréchaux, Isabelle and Chave, Jérôme},
  title = {Improving plant allometry by fusing forest models and remote sensing},
  journal = {New Phytologist},
  publisher = {Wiley},
  year = {2019},
  volume = {223},
  number = {3},
  pages = {1159--1165},
  doi = {10.1111/nph.15810}
}
Fitzky AC, Sandén H, Karl T, Fares S, Calfapietra C, Grote R, Saunier A and Rewald B (2019), "The Interplay Between Ozone and Urban Vegetation—BVOC Emissions, Ozone Deposition, and Tree Ecophysiology", Frontiers in Forests and Global Change., sep, 2019. Vol. 2 Frontiers Media SA.
Abstract: Tropospheric ozone (Otextlesssubtextgreater3textless/subtextgreater) is one of the most prominent air pollution problems in Europe and other countries worldwide. Human health is affected by Otextlesssubtextgreater3textless/subtextgreater via the respiratory as well the cardiovascular systems. Even though trees are present in relatively low numbers in urban areas, they can be a dominant factor in the regulation of urban Otextlesssubtextgreater3textless/subtextgreater concentrations. Trees affect the Otextlesssubtextgreater3textless/subtextgreater concentration via emission of biogenic volatile organic compounds (BVOC), which can act as a precursor of Otextlesssubtextgreater3textless/subtextgreater, and by Otextlesssubtextgreater3textless/subtextgreater deposition on leaves. The role of urban trees with regard to Otextlesssubtextgreater3textless/subtextgreater will gain further importance as NOtextlesssubtextgreaterxtextless/subtextgreater concentrations continue declining and climate warming is progressing—rendering especially the urban ozone chemistry more sensitive to BVOC emissions. However, the role of urban vegetation on the local regulation of tropospheric Otextlesssubtextgreater3textless/subtextgreater concentrations is complex and largely influenced by species-specific emission rates of BVOCs and Otextlesssubtextgreater3textless/subtextgreater deposition rates, both highly modified by tree physiological status. In this review, we shed light on processes related to trees that affect tropospheric ozone concentrations in metropolitan areas from rural settings to urban centers, and discuss their importance under present and future conditions. After a brief overview on the mechanisms regulating Otextlesssubtextgreater3textless/subtextgreater concentrations in urban settings, we focus on effects of tree identity and tree physiological status, as affected by multiple stressors, influencing both BVOC emission and Otextlesssubtextgreater3textless/subtextgreater deposition rates. In addition, we highlight differences along the rural-urban gradient affecting tropospheric Otextlesssubtextgreater3textless/subtextgreater concentrations and current knowledge gaps with the potential to improve future models on tropospheric Otextlesssubtextgreater3textless/subtextgreater formation in metropolitan areas.
BibTeX:
@article{Fitzky2019,
  author = {Fitzky, Anne Charlott and Sandén, Hans and Karl, Thomas and Fares, Silvano and Calfapietra, Carlo and Grote, Rüdiger and Saunier, Amélie and Rewald, Boris},
  title = {The Interplay Between Ozone and Urban Vegetation—BVOC Emissions, Ozone Deposition, and Tree Ecophysiology},
  journal = {Frontiers in Forests and Global Change},
  publisher = {Frontiers Media SA},
  year = {2019},
  volume = {2},
  doi = {10.3389/ffgc.2019.00050}
}
Frey M, Sha MK, Hase F, Kiel M, Blumenstock T, Harig R, Surawicz G, Deutscher NM, Shiomi K, Franklin JE, Bösch H, Chen J, Grutter M, Ohyama H, Sun Y, Butz A, Mengistu Tsidu G, Ene D, Wunch D, Cao Z, Garcia O, Ramonet M, Vogel F and Orphal J (2019), "Building the COllaborative Carbon Column Observing Network (COCCON): Long-term stability and ensemble performance of the EM27/SUN Fourier transform spectrometer", Atmospheric Measurement Techniques., mar, 2019. Vol. 12(3), pp. 1513-1530. Copernicus GmbH.
Abstract: In a 3.5-year long study, the long-term performance of a mobile, solar absorption Bruker EM27/SUN spectrometer, used for greenhouse gas observations, is checked with respect to a co-located reference Bruker IFS 125HR spectrometer, which is part of the Total Carbon Column Observing Network (TCCON). We find that the EM27/SUN is stable on timescales of several years; the drift per year between the EM27/SUN and the official TCCON product is 0.02 ppmv for XCO2 and 0.9 ppbv for XCH4, which is within the 1σ precision of the comparison, 0.6 ppmv for XCO2 and 4.3 ppbv for XCH4. The bias between the two data sets is 3.9 ppmv for XCO2 and 13.0 ppbv for XCH4. In order to avoid sensitivity-dependent artifacts, the EM27/SUN is also compared to a truncated IFS 125HR data set derived from full-resolution TCCON interferograms. The drift is 0.02 ppmv for XCO2 and 0.2 ppbv for XCH4 per year, with 1σ precisions of 0.4 ppmv for XCO2 and 1.4 ppbv for XCH4, respectively. The bias between the two data sets is 0.6 ppmv for XCO2 and 0.5 ppbv for XCH4. With the presented long-term stability, the EM27/SUN qualifies as an useful supplement to the existing TCCON network in remote areas. To achieve consistent performance, such an extension requires careful testing of any spectrometers involved by application of common quality assurance measures. One major aim of the COllaborative Carbon Column Observing Network (COCCON) infrastructure is to provide these services to all EM27/SUN operators. In the framework of COCCON development, the performance of an ensemble of 30 EM27/SUN spectrometers was tested and found to be very uniform, enhanced by the centralized inspection performed at the Karlsruhe Institute of Technology prior to deployment. Taking into account measured instrumental line shape parameters for each spectrometer, the resulting average bias across the ensemble with respect to the reference EM27/SUN used in the long-term study in XCO2 is 0.20 ppmv, while it is 0.8 ppbv for XCH4. The average standard deviation of the ensemble is 0.13 ppmv for XCO2 and 0.6 ppbv for XCH4. In addition to the robust metric based on absolute differences, we calculate the standard deviation among the empirical calibration factors. The resulting 2σ uncertainty is 0.6 ppmv for XCO2 and 2.2 ppbv for XCH4. As indicated by the executed long-term study on one device presented here, the remaining empirical calibration factor deduced for each individual instrument can be assumed constant over time. Therefore the application of these empirical factors is expected to further improve the EM27/SUN network conformity beyond the scatter among the empirical calibration factors reported above.
BibTeX:
@article{Frey2019,
  author = {Frey, Matthias and Sha, Mahesh K. and Hase, Frank and Kiel, Matthäus and Blumenstock, Thomas and Harig, Roland and Surawicz, Gregor and Deutscher, Nicholas M. and Shiomi, Kei and Franklin, Jonathan E. and Bösch, Hartmut and Chen, Jia and Grutter, Michel and Ohyama, Hirofumi and Sun, Youwen and Butz, André and Mengistu Tsidu, Gizaw and Ene, Dragos and Wunch, Debra and Cao, Zhensong and Garcia, Omaira and Ramonet, Michel and Vogel, Felix and Orphal, Johannes},
  title = {Building the COllaborative Carbon Column Observing Network (COCCON): Long-term stability and ensemble performance of the EM27/SUN Fourier transform spectrometer},
  journal = {Atmospheric Measurement Techniques},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {12},
  number = {3},
  pages = {1513--1530},
  doi = {10.5194/amt-12-1513-2019}
}
Friedlingstein P, Jones MW, O'Sullivan M, Andrew RM, Hauck J, Peters GP, Peters W, Pongratz J, Sitch S, Le Quéré C, DBakker OC, Canadell1 JG, Ciais1 P, Jackson RB, Anthoni1 P, Barbero L, Bastos A, Bastrikov V, Becker M, Bopp L, Buitenhuis E, Chandra N, Chevallier F, Chini LP, Currie KI, Feely RA, Gehlen M, Gilfillan D, Gkritzalis T, Goll DS, Gruber N, Gutekunst S, Harris I, Haverd V, Houghton RA, Hurtt G, Ilyina T, Jain AK, Joetzjer E, Kaplan JO, Kato E, Goldewijk KK, Korsbakken JI, Landschützer P, Lauvset SK, Lefèvre N, Lenton A, Lienert S, Lombardozzi D, Marland G, McGuire PC, Melton JR, Metzl N, Munro DR, Nabel JE, Nakaoka SI, Neill C, Omar AM, Ono T, Peregon A, Pierrot D, Poulter B, Rehder G, Resplandy L, Robertson E, Rödenbeck C, Séférian R, Schwinger J, Smith N, Tans PP, Tian H, Tilbrook B, Tubiello FN, Van Der Werf GR, Wiltshire AJ and Zaehle S (2019), "Global carbon budget 2019", Earth System Science Data., dec, 2019. Vol. 11(4), pp. 1783-1838.
Abstract: Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere-the "global carbon budget"-is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFF) are based on energy statistics and cement production data, while emissions from land use change (ELUC), mainly deforestation, are based on land use and land use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2009-2018), EFF was 9:5±0:5 GtC yr-1, ELUC 1:5±0:7 GtC yr-1, GATM 4:9±0:02 GtC yr-1 (2:3±0:01 ppm yr-1), SOCEAN 2:5±0:6 GtC yr-1, and SLAND 3:2±0:6 GtC yr-1, with a budget imbalance BIM of 0.4 GtC yr-1 indicating overestimated emissions and/or underestimated sinks. For the year 2018 alone, the growth in EFF was about 2.1% and fossil emissions increased to 10:0±0:5 GtC yr-1, reaching 10 GtC yr-1 for the first time in history, ELUC was 1:5±0:7 GtC yr-1, for total anthropogenic CO2 emissions of 11:5±0:9 GtC yr-1 (42:5±3:3 GtCO2). Also for 2018, GATM was 5:1±0:2 GtC yr-1 (2:4±0:1 ppm yr-1), SOCEAN was 2:6±0:6 GtC yr-1, and SLAND was 3:5±0:7 GtC yr-1, with a BIM of 0.3 GtC. The global atmospheric CO2 concentration reached 407:38±0:1 ppm averaged over 2018. For 2019, preliminary data for the first 6-10 months indicate a reduced growth in EFF of C0:6% (range of.0:2% to 1.5 %) based on national emissions projections for China, the USA, the EU, and India and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. Overall, the mean and trend in the five components of the global carbon budget are consistently estimated over the period 1959-2018, but discrepancies of up to 1 GtC yr-1 persist for the representation of semi-decadal variability in CO2 fluxes. A detailed comparison among individual estimates and the introduction of a broad range of observations shows (1) no consensus in the mean and trend in land use change emissions over the last decade, (2) a persistent low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) an apparent underestimation of the CO2 variability by ocean models outside the tropics. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this data set (Le Quéré et al., 2018a, b, 2016, 2015a, b, 2014, 2013). The data generated by this work are available at https://doi.org/10.18160/gcp-2019 (Friedlingstein et al., 2019).
BibTeX:
@article{Friedlingstein2019,
  author = {Friedlingstein, Pierre and Jones, Matthew W. and O'Sullivan, Michael and Andrew, Robbie M. and Hauck, Judith and Peters, Glen P. and Peters, Wouter and Pongratz, Julia and Sitch, Stephen and Le Quéré, Corinne and DBakker, Orothee C.E. and Canadell1, Josep G. and Ciais1, Philippe and Jackson, Robert B. and Anthoni1, Peter and Barbero, Leticia and Bastos, Ana and Bastrikov, Vladislav and Becker, Meike and Bopp, Laurent and Buitenhuis, Erik and Chandra, Naveen and Chevallier, Frédéric and Chini, Louise P. and Currie, Kim I. and Feely, Richard A. and Gehlen, Marion and Gilfillan, Dennis and Gkritzalis, Thanos and Goll, Daniel S. and Gruber, Nicolas and Gutekunst, Sören and Harris, Ian and Haverd, Vanessa and Houghton, Richard A. and Hurtt, George and Ilyina, Tatiana and Jain, Atul K. and Joetzjer, Emilie and Kaplan, Jed O. and Kato, Etsushi and Goldewijk, Kees Klein and Korsbakken, Jan Ivar and Landschützer, Peter and Lauvset, Siv K. and Lefèvre, Nathalie and Lenton, Andrew and Lienert, Sebastian and Lombardozzi, Danica and Marland, Gregg and McGuire, Patrick C. and Melton, Joe R. and Metzl, Nicolas and Munro, David R. and Nabel, Julia E.M.S. and Nakaoka, Shin Ichiro and Neill, Craig and Omar, Abdirahman M. and Ono, Tsuneo and Peregon, Anna and Pierrot, Denis and Poulter, Benjamin and Rehder, Gregor and Resplandy, Laure and Robertson, Eddy and Rödenbeck, Christian and Séférian, Roland and Schwinger, Jörg and Smith, Naomi and Tans, Pieter P. and Tian, Hanqin and Tilbrook, Bronte and Tubiello, Francesco N. and Van Der Werf, Guido R. and Wiltshire, Andrew J. and Zaehle, Sönke},
  title = {Global carbon budget 2019},
  journal = {Earth System Science Data},
  year = {2019},
  volume = {11},
  number = {4},
  pages = {1783--1838},
  url = {https://www.earth-syst-sci-data.net/11/1783/2019/},
  doi = {10.5194/essd-11-1783-2019}
}
Fröb F, Olsen A, Becker M, Chafik L, Johannessen T, Reverdin G and Omar A (2019), "Wintertime fCO 2 Variability in the Subpolar North Atlantic Since 2004", Geophysical Research Letters., feb, 2019. Vol. 46(3), pp. 1580-1590.
Abstract: Winter data of surface ocean temperature (SST), salinity (SSS) and CO 2 fugacity (fCO 2 ) collected on the VOS M/V Nuka Arctica in the subpolar North Atlantic between 2004 and 2017 are used to establish trends, drivers, and interannual variability. Over the period, waters cooled and freshened, and the fCO 2 increased at a rate similar to the atmospheric CO 2 growth rate. When accounting for the freshening, the inferred increase in dissolved inorganic carbon (DIC) was found to be approximately twice that expected from atmospheric CO 2 alone. This is attributed to the cooling. In the Irminger Sea, fCO 2 exhibited additional interannual variations driven by atmospheric forcing through winter mixing. As winter fCO 2 in the region is close to the atmospheric, the subpolar North Atlantic has varied between being slightly supersaturated and slightly undersaturated over the investigated period.
BibTeX:
@article{Froeb2019,
  author = {Fröb, F. and Olsen, A. and Becker, M. and Chafik, L. and Johannessen, T. and Reverdin, G. and Omar, A.},
  title = {Wintertime fCO 2 Variability in the Subpolar North Atlantic Since 2004},
  journal = {Geophysical Research Letters},
  year = {2019},
  volume = {46},
  number = {3},
  pages = {1580--1590},
  url = {http://doi.wiley.com/10.1029/2018GL080554},
  doi = {10.1029/2018GL080554}
}
Geng MS, Christensen JH and Christensen TR (2019), "Potential future methane emission hot spots in Greenland", Environmental Research Letters., mar, 2019. Vol. 14(3), pp. 35001. IOP Publishing.
Abstract: Climate models have been making significant progress encompassing an increasing number of complex feedback mechanisms from natural ecosystems. Permafrost thaw and subsequent induced greenhouse gas emissions, however, remain a challenge for climate models at large. Deducing permafrost conditions and associated greenhouse gas emissions from parameters that are simulated in climate models would be a helpful step towards estimating emission budgets from permafrost regions. Here we use a regional climate model with a 5 km horizontal resolution to assess future potential methane (CH4) emissions over presently unglaciated areas in Greenland under an RCP8.5 scenario. A simple frost index is applied to estimate permafrost conditions from the model output. CH4 flux measurements from two stations in Greenland; Nuuk representing sub-Arctic and Zackenberg high-Arctic climate, are used to establish a relationship between emissions and near surface air temperature. Permafrost conditions in Greenland change drastically by the end of the 21st century in an RCP8.5 climate. Continuous permafrost remains stable only in North Greenland, the north-west coast, the northern tip of Disko Island, and Nuussuaq. Southern Greenland conditions only sustain sporadic permafrost conditions and largely at high elevations, whereas former permafrost in other regions thaws. The increasing thawed soil leads to increasing CH4 emissions. Especially the area surrounding Kangerlussuaq, Scoresby Land, and the southern coast of Greenland exhibit potentially high emissions during the longer growing season. The constructed maps and budgets combining modelled permafrost conditions with observed CH4 fluxes from CH4 promoting sites represent a useful tool to identify areas in need of additional monitoring as they highlight potential CH4 hot spots.
BibTeX:
@article{Geng2019,
  author = {Geng, Marilena Sophie and Christensen, Jens Hesselbjerg and Christensen, Torben Røjle},
  title = {Potential future methane emission hot spots in Greenland},
  journal = {Environmental Research Letters},
  publisher = {IOP Publishing},
  year = {2019},
  volume = {14},
  number = {3},
  pages = {35001},
  doi = {10.1088/1748-9326/aaf34b}
}
Gonzaga Gomez L, Loubet B, Lafouge F, Ciuraru R, Buysse P, Durand B, Gueudet JC, Fanucci O, Fortineau A, Zurfluh O, Decuq C, Kammer J, Duprix P, Bsaibes S, Truong F, Gros V and Boissard C (2019), "Comparative study of biogenic volatile organic compounds fluxes by wheat, maize and rapeseed with dynamic chambers over a short period in northern France", Atmospheric Environment., oct, 2019. Vol. 214, pp. 116855. Elsevier BV.
Abstract: Biogenic volatile organic compounds (BVOC) are mainly emitted from vegetation. However there is still little information on BVOC exchanges with crops. In this study we measured fluxes of BVOC from wheat, maize and rapeseed crops near Paris at the plant level during a full-week period for each species. We used dynamic automated chambers coupled to a Proton Transfer Reaction, Quadrupole ion guide, Time of Flight mass spectrometer (PTR-Qi-Tof-MS) instrument for online measurements of BVOC. Our results confirm the hypothesis that many unexplored compounds contribute to BVOC exchanges between crops and the atmosphere, although for all plant species methanol was dominating the emissions (55–85% of the sum of the BVOC exchanges fluxes on a mass basis) followed by acetone and acetaldehyde. The 10 most exchanged compounds, excluding methanol, contributed more than 50% of the summed fluxes and the 100 most exchanged contributed to more than 90%. The summed BVOC emission and deposition presented large interspecies variations, but limited intra-species variability, with a summed net flux of 0.11 ± 0.02 μgBVOC gDW−1 h−1 for maize, 1.5 ± 0.7 μgBVOC gDW−1 h−1 for wheat, and 9.1 ± 2.4 μgBVOC gDW−1 h−1 for rapeseed. The 10 most emitted compounds were mostly emitted during the day and were correlated with both photosynthetically active radiation and temperature and anti-correlated with relative humidity. This study provides the first evaluation so far of the biosphere-atmosphere fluxes for several BVOC. In particular we provide a first evaluation of standard emission factor for isoprene and monoterpene for wheat and rapeseed at their respective growth stages. This study is however limited to a week period at a given stage for each species and at the plant level.
BibTeX:
@article{GonzagaGomez2019,
  author = {Gonzaga Gomez, Lais and Loubet, Benjamin and Lafouge, Florence and Ciuraru, Raluca and Buysse, Pauline and Durand, Brigitte and Gueudet, Jean Christophe and Fanucci, Olivier and Fortineau, A. and Zurfluh, Olivier and Decuq, Céline and Kammer, Julien and Duprix, Pascal and Bsaibes, S. and Truong, François and Gros, Valérie and Boissard, Christophe},
  title = {Comparative study of biogenic volatile organic compounds fluxes by wheat, maize and rapeseed with dynamic chambers over a short period in northern France},
  journal = {Atmospheric Environment},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {214},
  pages = {116855},
  doi = {10.1016/j.atmosenv.2019.116855}
}
Gourlez de la Motte L, Dumortier P, Beckers Y, Bodson B, Heinesch B and Aubinet M (2019), "Herd position habits can bias net CO 2 ecosystem exchange estimates in free range grazed pastures", Agricultural and Forest Meteorology., apr, 2019. Vol. 268, pp. 156-168. Elsevier BV.
Abstract: The eddy covariance (EC) technique has been widely used to quantify the net CO 2 ecosystem exchange (NEE) of grasslands, which is an important component of grassland carbon and greenhouse gas budgets. In free range grazed pastures, NEE estimations are supposed to also include cattle respiration. However, cattle respiration measurement by an EC system is challenging as animals act as moving points emitting CO 2 that are more or less captured by the EC tower depending on their presence in the footprint. Often it is supposed that, over the long term, cattle distribution in the pasture is homogeneous so that fluctuations due to moving sources are averaged and NEE estimates are reasonably representative of cattle respiration. In this study, we test this hypothesis by comparing daily cow respiration rate per livestock unit (LU) estimated by postulating a homogeneous cow repartition over the whole pasture with three other estimates based on animal localization data, animal scale carbon budget and confinement experiments. We applied these methods to an intensively managed free range grassland and showed that the NEE estimate based on a homogeneous cow repartition was systematically lower than the three other estimates. The bias was about 60 g C m –2 yr –1 , which corresponded to around 40% of the annual NEE. The sign and the importance of this bias is site specific, as it depends on cow location habits in relation to the footprint of the EC measurements which highlight the importance of testing the hypothesis of homogeneity of cattle distribution on each site. Consequently, in order to allow estimating the validity of this hypothesis but also to improve inter site comparisons, we advocate to compute separately pasture NEE and grazer's respiration. For the former we propose a method based on cattle presence detection using CH 4 fluxes, elimination of data with cattle and gap filling on the basis of data without cattle. For the second we present and discuss three independent methods (animal localization with GPS, animal scale carbon budget, confinement experiments) to estimate the cattle respiration rate.
BibTeX:
@article{GourlezdelaMotte2019,
  author = {Gourlez de la Motte, Louis and Dumortier, Pierre and Beckers, Yves and Bodson, Bernard and Heinesch, Bernard and Aubinet, Marc},
  title = {Herd position habits can bias net CO 2 ecosystem exchange estimates in free range grazed pastures},
  journal = {Agricultural and Forest Meteorology},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {268},
  pages = {156--168},
  doi = {10.1016/j.agrformet.2019.01.015}
}
Grossiord C, Christoffersen B, Alonso-Rodríguez AM, Anderson-Teixeira K, Asbjornsen H, Aparecido LMT, Carter Berry Z, Baraloto C, Bonal D, Borrego I, Burban B, Chambers JQ, Christianson DS, Detto M, Faybishenko B, Fontes CG, Fortunel C, Gimenez BO, Jardine KJ, Kueppers L, Miller GR, Moore GW, Negron-Juarez R, Stahl C, Swenson NG, Trotsiuk V, Varadharajan C, Warren JM, Wolfe BT, Wei L, Wood TE, Xu C and McDowell NG (2019), "Precipitation mediates sap flux sensitivity to evaporative demand in the neotropics", Oecologia., sep, 2019. Vol. 191(3), pp. 519-530. Springer Science and Business Media LLC.
Abstract: Transpiration in humid tropical forests modulates the global water cycle and is a key driver of climate regulation. Yet, our understanding of how tropical trees regulate sap flux in response to climate variability remains elusive. With a progressively warming climate, atmospheric evaporative demand [i.e., vapor pressure deficit (VPD)] will be increasingly important for plant functioning, becoming the major control of plant water use in the twenty-first century. Using measurements in 34 tree species at seven sites across a precipitation gradient in the neotropics, we determined how the maximum sap flux velocity (vmax) and the VPD threshold at which vmax is reached (VPDmax) vary with precipitation regime [mean annual precipitation (MAP); seasonal drought intensity (PDRY)] and two functional traits related to foliar and wood economics spectra [leaf mass per area (LMA); wood specific gravity (WSG)]. We show that, even though vmax is highly variable within sites, it follows a negative trend in response to increasing MAP and PDRY across sites. LMA and WSG exerted little effect on vmax and VPDmax, suggesting that these widely used functional traits provide limited explanatory power of dynamic plant responses to environmental variation within hyper-diverse forests. This study demonstrates that long-term precipitation plays an important role in the sap flux response of humid tropical forests to VPD. Our findings suggest that under higher evaporative demand, trees growing in wetter environments in humid tropical regions may be subjected to reduced water exchange with the atmosphere relative to trees growing in drier climates.
BibTeX:
@article{Grossiord2019,
  author = {Grossiord, Charlotte and Christoffersen, Bradley and Alonso-Rodríguez, Aura M. and Anderson-Teixeira, Kristina and Asbjornsen, Heidi and Aparecido, Luiza Maria T. and Carter Berry, Z. and Baraloto, Christopher and Bonal, Damien and Borrego, Isaac and Burban, Benoit and Chambers, Jeffrey Q. and Christianson, Danielle S. and Detto, Matteo and Faybishenko, Boris and Fontes, Clarissa G. and Fortunel, Claire and Gimenez, Bruno O. and Jardine, Kolby J. and Kueppers, Lara and Miller, Gretchen R. and Moore, Georgianne W. and Negron-Juarez, Robinson and Stahl, Clément and Swenson, Nathan G. and Trotsiuk, Volodymyr and Varadharajan, Charu and Warren, Jeffrey M. and Wolfe, Brett T. and Wei, Liang and Wood, Tana E. and Xu, Chonggang and McDowell, Nate G.},
  title = {Precipitation mediates sap flux sensitivity to evaporative demand in the neotropics},
  journal = {Oecologia},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {191},
  number = {3},
  pages = {519--530},
  doi = {10.1007/s00442-019-04513-x}
}
Haro K, Ouarma I, Nana B, Bere A, Tubreoumya GC, Kam SZ, Laville P, Loubet B and Koulidiati J (2019), "Assessment of CH4 and CO2 surface emissions from Polesgo's landfill (Ouagadougou, Burkina Faso) based on static chamber method", Advances in Climate Change Research., sep, 2019. Vol. 10(3), pp. 181-191. Elsevier BV.
Abstract: Methane (CH4) and carbon dioxide (CO2) surface emissions from Polesgo's landfill (Ouagadougou, Burkina Faso) were measured using the static chamber technique in 2017 and 2018. The Polesgo's landfill was composed of four zones: Phase I, II, Phase III, and SP. The surface of Phase I was fully covered and its conditions are better for surface emission measurements. As results concerning the Phase I zone, the geospatial means flux rates of CH4 (657 mg m−2 h−1 in 2017 and 1210 mg m−2 h−1 in 2018, respectively) are measured higher than the tolerable value reported in literature. The emitted CH4 or CO2 have permitted to locate higher surface emissions which are related to the cover state. The calculated gas collection efficiency (27.4% in 2017 and 23.0% in 2018) is low compared to those reported for landfills integrating landfill gas (LFG) extraction system. The carbon footprint calculations (24,966 tCO2-eq 2017 and 40,025 tCO2-eq in 2018, respectively) shown that Polesgo's landfill is a significant source of greenhouse gases (GHG) and its important potential for organic recovery can contribute to reduce the carbon footprint.
BibTeX:
@article{Haro2019,
  author = {Haro, Kayaba and Ouarma, Issoufou and Nana, Bernard and Bere, Antoine and Tubreoumya, Guy Christian and Kam, Sié Zacharie and Laville, Patricia and Loubet, Benjamin and Koulidiati, Jean},
  title = {Assessment of CH4 and CO2 surface emissions from Polesgo's landfill (Ouagadougou, Burkina Faso) based on static chamber method},
  journal = {Advances in Climate Change Research},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {10},
  number = {3},
  pages = {181--191},
  doi = {10.1016/j.accre.2019.09.002}
}
Hartman SE, Humphreys MP, Kivimäe C, Woodward EM, Kitidis V, McGrath T, Hydes DJ, Greenwood N, Hull T, Ostle C, Pearce DJ, Sivyer D, Stewart BM, Walsham P, Painter SC, McGovern E, Harris C, Griffiths A, Smilenova A, Clarke J, Davis C, Sanders R and Nightingale P (2019), "Seasonality and spatial heterogeneity of the surface ocean carbonate system in the northwest European continental shelf", Progress in Oceanography., oct, 2019. Vol. 177, pp. 101909. Elsevier BV.
Abstract: In 2014–5 the UK NERC sponsored an 18 month long Shelf Sea Biogeochemistry research programme which collected over 1500 nutrient and carbonate system samples across the NW European Continental shelf, one of the largest continental shelves on the planet. This involved the cooperation of 10 different Institutes and Universities, using 6 different vessels. Additional carbon dioxide (CO2) data were obtained from the underway systems on three of the research vessels. Here, we present and discuss these data across 9 ecohydrodynamic regions, adapted from those used by the EU Marine Strategy Framework Directive (MSFD). We observed strong seasonal and regional variability in carbonate chemistry around the shelf in relation to nutrient biogeochemistry. Whilst salinity increased (and alkalinity decreased) out from the near-shore coastal waters offshore throughout the year nutrient concentrations varied with season. Spatial and seasonal variations in the ratio of DIC to nitrate concentration were seen that could impact carbon cycling. A decrease in nutrient concentrations and a pronounced under-saturation of surface pCO2 was evident in the spring in most regions, especially in the Celtic Sea. This decrease was less pronounced in Liverpool Bay and to the North of Scotland, where nutrient concentrations remained measurable throughout the year. The near-shore and relatively shallow ecosystems such as the eastern English Channel and southern North Sea were associated with a thermally driven increase in pCO2 to above atmospheric levels in summer and an associated decrease in pH. Non-thermal processes (such as mixing and the remineralisation of organic material) dominated in winter in most regions but especially in the northwest of Scotland and in Liverpool Bay. The large database collected will improve understanding of carbonate chemistry over the North-Western European Shelf in relation to nutrient biogeochemistry, particularly in the context of climate change and ocean acidification.
BibTeX:
@article{Hartman2019,
  author = {Hartman, S. E. and Humphreys, M. P. and Kivimäe, C. and Woodward, E. M.S. and Kitidis, V. and McGrath, T. and Hydes, D. J. and Greenwood, N. and Hull, T. and Ostle, C. and Pearce, D. J. and Sivyer, D. and Stewart, B. M. and Walsham, P. and Painter, S. C. and McGovern, E. and Harris, C. and Griffiths, A. and Smilenova, A. and Clarke, J. and Davis, C. and Sanders, R. and Nightingale, P.},
  title = {Seasonality and spatial heterogeneity of the surface ocean carbonate system in the northwest European continental shelf},
  journal = {Progress in Oceanography},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {177},
  pages = {101909},
  doi = {10.1016/j.pocean.2018.02.005}
}
Hastie A, Lauerwald R, Ciais P and Regnier P (2019), "Aquatic carbon fluxes dampen the overall variation of net ecosystem productivity in the Amazon basin: An analysis of the interannual variability in the boundless carbon cycle", Global Change Biology., apr, 2019. Vol. 25(6), pp. 2094-2111. Wiley.
Abstract: The river–floodplain network plays an important role in the carbon (C) cycle of the Amazon basin, as it transports and processes a significant fraction of the C fixed by terrestrial vegetation, most of which evades as CO 2 from rivers and floodplains back to the atmosphere. There is empirical evidence that exceptionally dry or wet years have an impact on the net C balance in the Amazon. While seasonal and interannual variations in hydrology have a direct impact on the amounts of C transferred through the river–floodplain system, it is not known how far the variation of these fluxes affects the overall Amazon C balance. Here, we introduce a new wetland forcing file for the ORCHILEAK model, which improves the representation of floodplain dynamics and allows us to closely reproduce data-driven estimates of net C exports through the river–floodplain network. Based on this new wetland forcing and two climate forcing datasets, we show that across the Amazon, the percentage of net primary productivity lost to the river–floodplain system is highly variable at the interannual timescale, and wet years fuel aquatic CO 2 evasion. However, at the same time overall net ecosystem productivity (NEP) and C sequestration are highest during wet years, partly due to reduced decomposition rates in water-logged floodplain soils. It is years with the lowest discharge and floodplain inundation, often associated with El Nino events, that have the lowest NEP and the highest total (terrestrial plus aquatic) CO 2 emissions back to atmosphere. Furthermore, we find that aquatic C fluxes display greater variation than terrestrial C fluxes, and that this variation significantly dampens the interannual variability in NEP of the Amazon basin. These results call for a more integrative view of the C fluxes through the vegetation-soil-river-floodplain continuum, which directly places aquatic C fluxes into the overall C budget of the Amazon basin.
BibTeX:
@article{Hastie2019,
  author = {Hastie, Adam and Lauerwald, Ronny and Ciais, Philippe and Regnier, Pierre},
  title = {Aquatic carbon fluxes dampen the overall variation of net ecosystem productivity in the Amazon basin: An analysis of the interannual variability in the boundless carbon cycle},
  journal = {Global Change Biology},
  publisher = {Wiley},
  year = {2019},
  volume = {25},
  number = {6},
  pages = {2094--2111},
  doi = {10.1111/gcb.14620}
}
Hayes F, Mills G, Alonso R, González-Fernández I, Coyle M, Grünhage L, Gerosa G, Karlsson PE and Marzuoli R (2019), "A Site-Specific Analysis of the Implications of a Changing Ozone Profile and Climate for Stomatal Ozone Fluxes in Europe", Water, Air, and Soil Pollution., dec, 2019. Vol. 230(1) Springer Science and Business Media LLC.
Abstract: In this study, we used eight sites from across Europe to investigate the implications of a future climate (2 °C warmer and 20% drier) and a changing ozone profile (increased background concentrations and reduced peaks) on stomatal ozone fluxes of three widely occurring plant species. A changing ozone profile with small increases in background ozone concentrations over the course of a growing season could have significant impacts on the annual accumulated stomatal ozone uptake, even if peak concentrations of ozone are reduced. Predicted increases in stomatal ozone uptake showed a strong relationship with latitude and were larger at sites from northern and mid-Europe than those from southern Europe. At the sites from central and northern regions of Europe, including the UK and Sweden, climatic conditions were highly conducive to stomatal ozone uptake by vegetation during the summer months and therefore an increase in daily mean ozone concentration of 3–16% during this time of year (from increased background concentrations, reduced peaks) would have a large impact on stomatal ozone uptake. In contrast, during spring and autumn, the climatic conditions can limit ozone uptake for many species. Although small increases in ozone concentration during these seasons could cause a modest increase in ozone uptake, for those species that are active at low temperatures, a 2 °C increase in temperature would increase stomatal ozone uptake even in the absence of further increases in ozone concentration. Predicted changes in climate could alter ozone uptake even with no change in ozone profile. For some southern regions of Europe, where temperatures are close to or above optimum for stomatal opening, an increase in temperature of 2 °C could limit stomatal ozone uptake by enhancing stomatal closure during the summer months, whereas during the spring, when many plants are actively growing, a small increase in temperature would increase stomatal ozone uptake.
BibTeX:
@article{Hayes2019,
  author = {Hayes, Felicity and Mills, Gina and Alonso, Rocio and González-Fernández, Ignacio and Coyle, Mhairi and Grünhage, Ludger and Gerosa, Giacomo and Karlsson, Per Erik and Marzuoli, Riccardo},
  title = {A Site-Specific Analysis of the Implications of a Changing Ozone Profile and Climate for Stomatal Ozone Fluxes in Europe},
  journal = {Water, Air, and Soil Pollution},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {230},
  number = {1},
  doi = {10.1007/s11270-018-4057-x}
}
He Y, Peng S, Liu Y, Li X, Wang K, Ciais P, Arain MA, Fang Y, Fisher JB, Goll D, Hayes D, Huntzinger DN, Ito A, Jain AK, Janssens IA, Mao J, Matteo C, Michalak AM, Peng C, Peñuelas J, Poulter B, Qin D, Ricciuto DM, Schaefer K, Schwalm CR, Shi X, Tian H, Vicca S, Wei Y, Zeng N and Zhu Q (2019), "Global vegetation biomass production efficiency constrained by models and observations", Global Change Biology., sep, 2019. Vol. 26(3), pp. 1474-1484. Wiley.
Abstract: Plants use only a fraction of their photosynthetically derived carbon for biomass production (BP). The biomass production efficiency (BPE), defined as the ratio of BP to photosynthesis, and its variation across and within vegetation types is poorly understood, which hinders our capacity to accurately estimate carbon turnover times and carbon sinks. Here, we present a new global estimation of BPE obtained by combining field measurements from 113 sites with 14 carbon cycle models. Our best estimate of global BPE is 0.41 ± 0.05, excluding cropland. The largest BPE is found in boreal forests (0.48 ± 0.06) and the lowest in tropical forests (0.40 ± 0.04). Carbon cycle models overestimate BPE, although models with carbon–nitrogen interactions tend to be more realistic. Using observation-based estimates of global photosynthesis, we quantify the global BP of non-cropland ecosystems of 41 ± 6 Pg C/year. This flux is less than net primary production as it does not contain carbon allocated to symbionts, used for exudates or volatile carbon compound emissions to the atmosphere. Our study reveals a positive bias of 24 ± 11% in the model-estimated BP (10 of 14 models). When correcting models for this bias while leaving modeled carbon turnover times unchanged, we found that the global ecosystem carbon storage change during the last century is decreased by 67% (or 58 Pg C).
BibTeX:
@article{He2019,
  author = {He, Yue and Peng, Shushi and Liu, Yongwen and Li, Xiangyi and Wang, Kai and Ciais, Philippe and Arain, M. Altaf and Fang, Yuanyuan and Fisher, Joshua B. and Goll, Daniel and Hayes, Daniel and Huntzinger, Deborah N. and Ito, Akihiko and Jain, Atul K. and Janssens, Ivan A. and Mao, Jiafu and Matteo, Campioli and Michalak, Anna M. and Peng, Changhui and Peñuelas, Josep and Poulter, Benjamin and Qin, Dahe and Ricciuto, Daniel M. and Schaefer, Kevin and Schwalm, Christopher R. and Shi, Xiaoying and Tian, Hanqin and Vicca, Sara and Wei, Yaxing and Zeng, Ning and Zhu, Qiuan},
  title = {Global vegetation biomass production efficiency constrained by models and observations},
  journal = {Global Change Biology},
  publisher = {Wiley},
  year = {2019},
  volume = {26},
  number = {3},
  pages = {1474--1484},
  doi = {10.1111/gcb.14816}
}
Helfter C, Mullinger N, Vieno M, O'Doherty S, Ramonet M, Palmer PI and Nemitz E (2019), "Country-scale greenhouse gas budgets using shipborne measurements: A case study for the UK and Ireland", Atmospheric Chemistry and Physics., mar, 2019. Vol. 19(5), pp. 3043-3063. Copernicus GmbH.
Abstract: We present a mass balance approach to estimate the seasonal and annual budgets of carbon dioxide (CO2) and methane (CH4) of the United Kingdom (excluding Scotland) and the Republic of Ireland from concentration measurements taken on a ferry along the east coast of the United Kingdom over a 3-year period (2015-2017). We estimate the annual emissions of CH4 to be 2.55±0.48 Tg, which is consistent with the combined 2.29 Tg reported to the United Nations Framework Convention on Climate Change by the individual countries. The net CO2 budget (i.e. including all anthropogenic and biogenic sources and sinks of CO2) is estimated at 881.0±125.8 Tg, with a net biogenic contribution of 458.7 Tg (taken as the difference between the estimated net emissions and the inventory value, which accounts for anthropogenic emissions only). The largest emissions for both gases were observed in a broad latitudinal band (52.5-54°N), which coincides with densely populated areas. The emissions of both gases were seasonal (maxima in winter and minima in summer), strongly correlated with natural gas usage and, to a lesser extent, also anti-correlated with mean air temperature. Methane emissions exhibited a statistically significant anti-correlation with air temperature at the seasonal timescale in the central region spanning 52.8-54.2°N, which hosts a relatively high density of waste treatment facilities. Methane emissions from landfills have been shown to sometimes increase with decreasing air temperature due to changes in the CH4-oxidising potential of the topsoil, and we speculate that the waste sector contributes significantly to the CH4 budget of this central region. This study brings independent verification of the emission budgets estimated using alternative products (e.g. mass balance budgets by aircraft measurements, inverse modelling, inventorying) and offers an opportunity to investigate the seasonality of these emissions, which is usually not possible.
BibTeX:
@article{Helfter2019,
  author = {Helfter, Carole and Mullinger, Neil and Vieno, Massimo and O'Doherty, Simon and Ramonet, Michel and Palmer, Paul I. and Nemitz, Eiko},
  title = {Country-scale greenhouse gas budgets using shipborne measurements: A case study for the UK and Ireland},
  journal = {Atmospheric Chemistry and Physics},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {19},
  number = {5},
  pages = {3043--3063},
  doi = {10.5194/acp-19-3043-2019}
}
Holding T, Ashton IG, Shutler JD, Land PE, Nightingale PD, Rees AP, Brown I, Piolle JF, Kock A, Bange HW, Woolf DK, Goddijn-Murphy L, Pereira R, Paul F, Girard-Ardhuin F, Chapron B, Rehder G, Ardhuin F and Donlon CJ (2019), "The fluxengine air-sea gas flux toolbox: Simplified interface and extensions for in situ analyses and multiple sparingly soluble gases", Ocean Science., dec, 2019. Vol. 15(6), pp. 1707-1728. Copernicus GmbH.
Abstract: The flow (flux) of climate-critical gases, such as carbon dioxide (textlessspan classCombining double low line"inline-formula"textgreaterCO2textless/spantextgreater), between the ocean and the atmosphere is a fundamental component of our climate and an important driver of the biogeochemical systems within the oceans. Therefore, the accurate calculation of these air-sea gas fluxes is critical if we are to monitor the oceans and assess the impact that these gases are having on Earth's climate and ecosystems. FluxEngine is an open-source software toolbox that allows users to easily perform calculations of air-sea gas fluxes from model, in situ, and Earth observation data. The original development and verification of the toolbox was described in a previous publication. The toolbox has now been considerably updated to allow for its use as a Python library, to enable simplified installation, to ensure verification of its installation, to enable the handling of multiple sparingly soluble gases, and to enable the greatly expanded functionality for supporting in situ dataset analyses. This new functionality for supporting in situ analyses includes user-defined grids, time periods and projections, the ability to reanalyse in situ textlessspan classCombining double low line"inline-formula"textgreaterCO2textless/spantextgreater data to a common temperature dataset, and the ability to easily calculate gas fluxes using in situ data from drifting buoys, fixed moorings, and research cruises. Here we describe these new capabilities and demonstrate their application through illustrative case studies. The first case study demonstrates the workflow for accurately calculating textlessspan classCombining double low line"inline-formula"textgreaterCO2textless/spantextgreater fluxes using in situ data from four research cruises from the Surface Ocean textlessspan classCombining double low line"inline-formula"textgreaterCO2textless/spantextgreater ATlas (SOCAT) database. The second case study calculates air-sea textlessspan classCombining double low line"inline-formula"textgreaterCO2textless/spantextgreater fluxes using in situ data from a fixed monitoring station in the Baltic Sea. The third case study focuses on nitrous oxide (textlessspan classCombining double low line"inline-formula"textgreaterN2Otextless/spantextgreater) and, through a user-defined gas transfer parameterisation, identifies that biological surfactants in the North Atlantic could suppress individual textlessspan classCombining double low line"inline-formula"textgreaterN2Otextless/spantextgreater sea-air gas fluxes by up to 13 %. The fourth and final case study illustrates how a dissipation-based gas transfer parameterisation can be implemented and used. The updated version of the toolbox (version 3) and all documentation is now freely available.
BibTeX:
@article{Holding2019,
  author = {Holding, Thomas and Ashton, Ian G. and Shutler, Jamie D. and Land, Peter E. and Nightingale, Philip D. and Rees, Andrew P. and Brown, Ian and Piolle, Jean Francois and Kock, Annette and Bange, Hermann W. and Woolf, David K. and Goddijn-Murphy, Lonneke and Pereira, Ryan and Paul, Frederic and Girard-Ardhuin, Fanny and Chapron, Bertrand and Rehder, Gregor and Ardhuin, Fabrice and Donlon, Craig J.},
  title = {The fluxengine air-sea gas flux toolbox: Simplified interface and extensions for in situ analyses and multiple sparingly soluble gases},
  journal = {Ocean Science},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {15},
  number = {6},
  pages = {1707--1728},
  doi = {10.5194/os-15-1707-2019}
}
Horemans JA, Arriga N and Ceulemans R (2019), "Greenhouse gas budget of a poplar bioenergy plantation in Belgium: CO2 uptake outweighs CH4 and N2O emissions", GCB Bioenergy., oct, 2019. Vol. 11(12), pp. 1435-1443. Wiley.
Abstract: Biomass from short-rotation coppice (SRC) of woody perennials is being increasingly used as a bioenergy source to replace fossil fuels, but accurate assessments of the long-term greenhouse gas (GHG) balance of SRC are lacking. To evaluate its mitigation potential, we monitored the GHG balance of a poplar (Populus) SRC in Flanders, Belgium, over 7 years comprising three rotations (i.e., two 2 year rotations and one 3 year rotation). In the beginning—that is, during the establishment year and during each year immediately following coppicing—the SRC plantation was a net source of GHGs. Later on—that is, during each second or third year after coppicing—the site shifted to a net sink. From the sixth year onward, there was a net cumulative GHG uptake reaching −35.8 Mg CO2 eq/ha during the seventh year. Over the three rotations, the total CO2 uptake was −51.2 Mg CO2/ha, while the emissions of CH4 and N2O amounted to 8.9 and 6.5 Mg CO2 eq/ha, respectively. As the site was non-fertilized, non-irrigated, and only occasionally flooded, CO2 fluxes dominated the GHG budget. Soil disturbance after land conversion and after coppicing were the main drivers for CO2 losses. One single N2O pulse shortly after SRC establishment contributed significantly to the N2O release. The results prove the potential of SRC biomass plantations to reduce GHG emissions and demonstrate that, for the poplar plantation under study, the high CO2 uptake outweighs the emissions of non-CO2 greenhouse gases.
BibTeX:
@article{Horemans2019,
  author = {Horemans, Joanna A. and Arriga, Nicola and Ceulemans, Reinhart},
  title = {Greenhouse gas budget of a poplar bioenergy plantation in Belgium: CO2 uptake outweighs CH4 and N2O emissions},
  journal = {GCB Bioenergy},
  publisher = {Wiley},
  year = {2019},
  volume = {11},
  number = {12},
  pages = {1435--1443},
  doi = {10.1111/gcbb.12648}
}
van der Horst SVJ, Pitman AJ, De Kauwe MG, Ukkola A, Abramowitz G and Isaac P (2019), "How representative are FLUXNET measurements of surface fluxes during temperature extremes?", Biogeosciences., apr, 2019. Vol. 16(8), pp. 1829-1844.
BibTeX:
@article{Horst2019,
  author = {van der Horst, Sophie V. J. and Pitman, Andrew J. and De Kauwe, Martin G. and Ukkola, Anna and Abramowitz, Gab and Isaac, Peter},
  title = {How representative are FLUXNET measurements of surface fluxes during temperature extremes?},
  journal = {Biogeosciences},
  year = {2019},
  volume = {16},
  number = {8},
  pages = {1829--1844},
  url = {https://www.biogeosciences.net/16/1829/2019/},
  doi = {10.5194/bg-16-1829-2019}
}
Huang M, Piao S, Ciais P, Peñuelas J, Wang X, Keenan TF, Peng S, Berry JA, Wang K, Mao J, Alkama R, Cescatti A, Cuntz M, De Deurwaerder H, Gao M, He Y, Liu Y, Luo Y, Myneni RB, Niu S, Shi X, Yuan W, Verbeeck H, Wang T, Wu J and Janssens IA (2019), "Air temperature optima of vegetation productivity across global biomes", Nature Ecology and Evolution., mar, 2019. Vol. 3(5), pp. 772-779. Springer Science and Business Media LLC.
Abstract: The global distribution of the optimum air temperature for ecosystem-level gross primary productivity (Topteco) is poorly understood, despite its importance for ecosystem carbon uptake under future warming. We provide empirical evidence for the existence of such an optimum, using measurements of in situ eddy covariance and satellite-derived proxies, and report its global distribution. Topteco is consistently lower than the physiological optimum temperature of leaf-level photosynthetic capacity, which typically exceeds 30 °C. The global average Topteco is estimated to be 23 ± 6 °C, with warmer regions having higher Topteco values than colder regions. In tropical forests in particular, Topteco is close to growing-season air temperature and is projected to fall below it under all scenarios of future climate, suggesting a limited safe operating space for these ecosystems under future warming.
BibTeX:
@article{Huang2019,
  author = {Huang, Mengtian and Piao, Shilong and Ciais, Philippe and Peñuelas, Josep and Wang, Xuhui and Keenan, Trevor F. and Peng, Shushi and Berry, Joseph A. and Wang, Kai and Mao, Jiafu and Alkama, Ramdane and Cescatti, Alessandro and Cuntz, Matthias and De Deurwaerder, Hannes and Gao, Mengdi and He, Yue and Liu, Yongwen and Luo, Yiqi and Myneni, Ranga B. and Niu, Shuli and Shi, Xiaoying and Yuan, Wenping and Verbeeck, Hans and Wang, Tao and Wu, Jin and Janssens, Ivan A.},
  title = {Air temperature optima of vegetation productivity across global biomes},
  journal = {Nature Ecology and Evolution},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {3},
  number = {5},
  pages = {772--779},
  doi = {10.1038/s41559-019-0838-x}
}
Huang X, Xiao J and Ma M (2019), "Evaluating the Performance of Satellite-Derived Vegetation Indices for Estimating Gross Primary Productivity Using FLUXNET Observations across the Globe", Remote Sensing., aug, 2019. Vol. 11(15), pp. 1823.
Abstract: Satellite-derived vegetation indices (VIs) have been widely used to approximate or estimate gross primary productivity (GPP). However, it remains unclear how the VI-GPP relationship varies with indices, biomes, timescales, and the bidirectional reflectance distribution function (BRDF) effect. We examined the relationship between VIs and GPP for 121 FLUXNET sites across the globe and assessed how the VI-GPP relationship varied among a variety of biomes at both monthly and annual timescales. We used three widely-used VIs: normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), and 2-band EVI (EVI2) as well as a new VI - NIRV and used surface reflectance both with and without BRDF correction from the moderate resolution imaging spectroradiometer (MODIS) to calculate these indices. The resulting traditional (NDVI, EVI, EVI2, and NIRV) and BRDF-corrected (NDVIBRDF, EVIBRDF, EVI2BRDF, and NIRV, BRDF) VIs were used to examine the VI-GPP relationship. At the monthly scale, all VIs were moderate or strong predictors of GPP, and the BRDF correction improved their performance. EVI2BRDF and NIRV, BRDF had similar performance in capturing the variations in tower GPP as did the MODIS GPP product. The VIs explained lower variance in tower GPP at the annual scale than at the monthly scale. The BRDF-correction of surface reflectance did not improve the VI-GPP relationship at the annual scale. The VIs had similar capability in capturing the interannual variability in tower GPP as MODIS GPP. VIs were influenced by temperature and water stresses and were more sensitive to temperature stress than to water stress. VIs in combination with environmental factors could improve the prediction of GPP than VIs alone. Our findings can help us better understand how the VI-GPP relationship varies among indices, biomes, and timescales and how the BRDF effect influences the VI-GPP relationship.
BibTeX:
@article{Huang2019a,
  author = {Huang, Xiaojuan and Xiao, Jingfeng and Ma, Mingguo},
  title = {Evaluating the Performance of Satellite-Derived Vegetation Indices for Estimating Gross Primary Productivity Using FLUXNET Observations across the Globe},
  journal = {Remote Sensing},
  year = {2019},
  volume = {11},
  number = {15},
  pages = {1823},
  url = {https://www.mdpi.com/2072-4292/11/15/1823},
  doi = {10.3390/rs11151823}
}
Hurdebise Q, Aubinet M, Heinesch B and Vincke C (2019), "Increasing temperatures over an 18-year period shortens growing season length in a beech (Fagus sylvatica L.)-dominated forest", Annals of Forest Science., jul, 2019. Vol. 76(3) Springer Science and Business Media LLC.
Abstract: Key message: Using long-term measurements in a mature beech (Fagus sylvatica L.)-dominated forest located in east Belgium, this paper showed that spring and autumn temperature increases during the last two decades led to an earlier end and a shortening of the growing season. These phenological shifts impact negatively but not significantly the forest annual net ecosystem productivity. Context: The mechanisms controlling temperate forest phenology are not fully understood nor are the impacts of climate change and the consequences for forest productivity. Aims: The aim of this paper is to contribute to the understanding of how temperate forest phenology and net ecosystem productivity (NEP) interplay and respond to temperature and its evolution. Methods: Indicators of leaf phenology and productivity dynamics at the start and the end of the growing season, as well as combinations of these indicators (length of the growing season), were derived from a long-term (1997–2014) dataset of eddy covariance and light transmission measurements taken over a mature beech-dominated temperate forest. Results: The start and the end of the growing season were correlated to spring (and autumn, for the end) temperatures. Despite no trends in annual average temperatures being detected during the observation period, April and November temperatures significantly increased. As a result, an earlier but slower start and an earlier end, inducing a shorter length of the growing season, were observed over the studied period. The first shift positively impacts the mixed forest NEP but is mainly related to the presence of conifers in the subplot. The earlier end of the growing season, more related to beech phenology, negatively impacts the forest NEP. Overall, these two effects partially compensate each other, leading to a non-significant impact on NEP. Conclusion: Increasing temperatures over the 18-year studied period shortened the growing season length, without affecting significantly the mixed forest NEP. However, as beeches are only affected by the earlier end of the growing season, this suggests a phenologically driven beech productivity reduction in the forest.
BibTeX:
@article{Hurdebise2019,
  author = {Hurdebise, Quentin and Aubinet, Marc and Heinesch, Bernard and Vincke, Caroline},
  title = {Increasing temperatures over an 18-year period shortens growing season length in a beech (Fagus sylvatica L.)-dominated forest},
  journal = {Annals of Forest Science},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {76},
  number = {3},
  doi = {10.1007/s13595-019-0861-8}
}
Ivakhov VM, Paramonova NN, Privalov VI, Zinchenko AV, Loskutova MA, Makshtas AP, Kustov VY, Laurila T, Aurela M and Asmi E (2019), "Atmospheric Concentration of Carbon Dioxide at Tiksi and Cape Baranov Stations in 2010–2017", Russian Meteorology and Hydrology., apr, 2019. Vol. 44(4), pp. 291-299. Allerton Press.
Abstract: The study presents the results of continuous measurements of carbon dioxide concentration in the atmospheric surface layer at Tiksi and Cape Baranov Arctic stations over the period of August 2010–May 2017 and over the whole 2016, respectively. The amplitude of diurnal variations in the CO2 concentration in Tiksi from June to September is 1.1 ± 1.3, 2.4 ± 2.0, 4.1 ± 2.3, and 2.0 ± 2.4 ppm. Diurnal variations in CO2 at Cape Baranov station are absent. The observed seasonal variations in the CO2 concentration are compared with the data of the MBL empirical model for the marine atmospheric boundary layer of the Arctic region. In 2016, the difference between the observed and model concentrations at Tiksi and Cape Baranov stations amounted to 1.7 and 0.5 ppm, respectively, in winter and −3.0 and −1.9 ppm, respectively, in summer. It is shown that wildfires in Siberia caused a long synchronous increase in the CO2 concentration by 20 ppm in Tiksi and by 15 ppm at Cape Baranov station.
BibTeX:
@article{Ivakhov2019,
  author = {Ivakhov, V. M. and Paramonova, N. N. and Privalov, V. I. and Zinchenko, A. V. and Loskutova, M. A. and Makshtas, A. P. and Kustov, V. Y. and Laurila, T. and Aurela, M. and Asmi, E.},
  title = {Atmospheric Concentration of Carbon Dioxide at Tiksi and Cape Baranov Stations in 2010–2017},
  journal = {Russian Meteorology and Hydrology},
  publisher = {Allerton Press},
  year = {2019},
  volume = {44},
  number = {4},
  pages = {291--299},
  doi = {10.3103/S1068373919040095}
}
Jakovljević T, Marchetto A, Lovreškov L, Potočić N, Seletković I, Indir K, Jelić G, Butorac L, Zgrablić Ž, De Marco A, Simioni G, Ognjenović M and Jurinjak Tušek A (2019), "Assessment of Atmospheric Deposition and Vitality Indicators in Mediterranean Forest Ecosystems", Sustainability., nov, 2019. Vol. 11(23), pp. 6805. MDPI AG.
Abstract: Considering the fragility of the Mediterranean environment, there is an increasing need to improve the knowledge of this forest environment. The aim of this study was to examine the effects of air pollution on the forest ecosystem's condition by analyzing tree vitality. The study area was chosen to represent the most important and the most common species in Mediterranean forest ecosystems of the Eastern Adriatic coast. Quercus pubescens, Quercus ilex, Pinus halepensis, and Pinus nigra plots were equipped with rain collectors and dendrometer bands. Sampling, measurements, and analyses of atmospheric deposition, foliar nutrient, defoliation, and growth were all carried out. Results showed that actual N deposition loads were the lowest in Aleppo pine forest and the highest in holm oak forests. This, however, did not have an effect on the concentrations of N in foliage. Most elements' concentrations were in the plausible range. No relevant differences in mean defoliation between the plots were observed. The plots with a lower percentage of basal area increment (BAI%) were found to have lower defoliation. The research was conducted to bridge the gap in the knowledge of air pollutants and vitality indicators in different forest types. These findings are a valuable contribution to the sustainable forest management of Mediterranean forest.
BibTeX:
@article{Jakovljevic2019,
  author = {Jakovljević, Tamara and Marchetto, Aldo and Lovreškov, Lucija and Potočić, Nenad and Seletković, Ivan and Indir, Krunoslav and Jelić, Goran and Butorac, Lukrecija and Zgrablić, Željko and De Marco, Alessandra and Simioni, Guillaume and Ognjenović, Mladen and Jurinjak Tušek, Ana},
  title = {Assessment of Atmospheric Deposition and Vitality Indicators in Mediterranean Forest Ecosystems},
  journal = {Sustainability},
  publisher = {MDPI AG},
  year = {2019},
  volume = {11},
  number = {23},
  pages = {6805},
  doi = {10.3390/su11236805}
}
Järvi L, Havu M, Ward HC, Bellucco V, McFadden JP, Toivonen T, Heikinheimo V, Kolari P, Riikonen A and Grimmond CSB (2019), "Spatial Modeling of Local-Scale Biogenic and Anthropogenic Carbon Dioxide Emissions in Helsinki", Journal of Geophysical Research: Atmospheres., aug, 2019. Vol. 124(15), pp. 8363-8384. American Geophysical Union (AGU).
Abstract: There is a growing need to simulate the effect of urban planning on both local climate and greenhouse gas emissions. Here, a new urban surface carbon dioxide (CO2) flux module for the Surface Urban Energy and Water Balance Scheme is described and evaluated using eddy covariance observations at two sites in Helsinki in 2012. The spatial variability and magnitude of local-scale anthropogenic and biogenic CO2 flux components at high spatial (250 m × 250 m) and temporal (hourly) resolution are examined by combining high-resolution (down to 2 m) airborne lidar-derived land use data and mobility data to account for people's movement. Urban effects are included in the biogenic components parameterized using urban eddy covariance and chamber observations. Surface Urban Energy and Water Balance Scheme reproduces the seasonal and diurnal variability of the CO2 flux well. Annual totals deviate 3% from observations in the city center and 2% in a suburban location. In the latter, traffic is the dominant CO2 source but summertime vegetation partly offsets traffic-related emissions. In the city center, emissions from traffic and human metabolism dominate and the vegetation effect is minor due to the low proportion of vegetation surface cover (22%). Within central Helsinki, human metabolism accounts for 39% of the net local-scale emissions and together with road traffic is to a large extent responsible for the spatial variability of the emissions. Annually, the biogenic emissions and sinks are in near balance and thus the effect of vegetation on the carbon balance is small in this high-latitude city.
BibTeX:
@article{Jaervi2019,
  author = {Järvi, Leena and Havu, Minttu and Ward, Helen C. and Bellucco, Veronica and McFadden, Joseph P. and Toivonen, Tuuli and Heikinheimo, Vuokko and Kolari, Pasi and Riikonen, Anu and Grimmond, C. Sue B.},
  title = {Spatial Modeling of Local-Scale Biogenic and Anthropogenic Carbon Dioxide Emissions in Helsinki},
  journal = {Journal of Geophysical Research: Atmospheres},
  publisher = {American Geophysical Union (AGU)},
  year = {2019},
  volume = {124},
  number = {15},
  pages = {8363--8384},
  doi = {10.1029/2018JD029576}
}
Jauhiainen J, Alm J, Bjarnadottir B, Callesen I, Christiansen JR, Clarke N, Dalsgaard L, He H, Jordan S, Kazanavičiute V, Klemedtsson L, Lauren A, Lazdins A, Lehtonen A, Lohila A, Lupikis A, Mander Ü, Minkkinen K, Kasimir Å, Olsson M, Ojanen P, Óskarsson H, Sigurdsson BD, Søgaard G, Soosaar K, Vesterdal L and Laiho R (2019), "Reviews and syntheses: Greenhouse gas exchange data from drained organic forest soils-A review of current approaches and recommendations for future research", Biogeosciences., dec, 2019. Vol. 16(23), pp. 4687-4703. Copernicus GmbH.
Abstract: Drained organic forest soils in boreal and temperate climate zones are believed to be significant sources of the greenhouse gases (GHGs) carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), but the annual fluxes are still highly uncertain. Drained organic soils exemplify systems where many studies are still carried out with relatively small resources, several methodologies and manually operated systems, which further involve different options for the detailed design of the measurement and data analysis protocols for deriving the annual flux. It would be beneficial to set certain guidelines for how to measure and report the data, so that data from individual studies could also be used in synthesis work based on data collation and modelling. Such synthesis work is necessary for deciphering general patterns and trends related to, e.g., site types, climate, and management, and the development of corresponding emission factors, i.e. estimates of the net annual soil GHG emission and removal, which can be used in GHG inventories. Development of specific emission factors also sets prerequisites for the background or environmental data to be reported in individual studies. We argue that wide applicability greatly increases the value of individual studies. An overall objective of this paper is to support future monitoring campaigns in obtaining high-value data.We analysed peer-reviewed public cations presenting CO2, CH4 and N2O flux data for drained organic forest soils in boreal and temperate climate zones, focusing on data that have been used, or have the potential to be used, for estimating net annual soil GHG emissions and removals. We evaluated the methods used in data collection and identified major gaps in background or environmental data. Based on these, we formulated recommendations for future research.
BibTeX:
@article{Jauhiainen2019,
  author = {Jauhiainen, Jyrki and Alm, Jukka and Bjarnadottir, Brynhildur and Callesen, Ingeborg and Christiansen, Jesper R. and Clarke, Nicholas and Dalsgaard, Lise and He, Hongxing and Jordan, Sabine and Kazanavičiute, Vaiva and Klemedtsson, Leif and Lauren, Ari and Lazdins, Andis and Lehtonen, Aleksi and Lohila, Annalea and Lupikis, Ainars and Mander, Ülo and Minkkinen, Kari and Kasimir, Åsa and Olsson, Mats and Ojanen, Paavo and Óskarsson, Hlynur and Sigurdsson, Bjarni D. and Søgaard, Gunnhild and Soosaar, Kaido and Vesterdal, Lars and Laiho, Raija},
  title = {Reviews and syntheses: Greenhouse gas exchange data from drained organic forest soils-A review of current approaches and recommendations for future research},
  journal = {Biogeosciences},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {16},
  number = {23},
  pages = {4687--4703},
  doi = {10.5194/bg-16-4687-2019}
}
Jiang LQ, Carter BR, Feely RA, Lauvset SK and Olsen A (2019), "Surface ocean pH and buffer capacity: past, present and future", Scientific Reports., dec, 2019. Vol. 9(1) Springer Science and Business Media LLC.
Abstract: The ocean's chemistry is changing due to the uptake of anthropogenic carbon dioxide (CO2). This phenomenon, commonly referred to as “Ocean Acidification”, is endangering coral reefs and the broader marine ecosystems. In this study, we combine a recent observational seawater CO2 data product, i.e., the 6th version of the Surface Ocean CO2 Atlas (1991–2018, ˜23 million observations), with temporal trends at individual locations of the global ocean from a robust Earth System Model to provide a high-resolution regionally varying view of global surface ocean pH and the Revelle Factor. The climatology extends from the pre-Industrial era (1750 C.E.) to the end of this century under historical atmospheric CO2 concentrations (pre-2005) and the Representative Concentrations Pathways (post-2005) of the Intergovernmental Panel on Climate Change (IPCC)'s 5th Assessment Report. By linking the modeled pH trends to the observed modern pH distribution, the climatology benefits from recent improvements in both model design and observational data coverage, and is likely to provide improved regional OA trajectories than the model output could alone, therefore, will help guide the regional OA adaptation strategies. We show that air-sea CO2 disequilibrium is the dominant mode of spatial variability for surface pH, and discuss why pH and calcium carbonate mineral saturation states, two important metrics for OA, show contrasting spatial variability.
BibTeX:
@article{Jiang2019,
  author = {Jiang, Li Qing and Carter, Brendan R. and Feely, Richard A. and Lauvset, Siv K. and Olsen, Are},
  title = {Surface ocean pH and buffer capacity: past, present and future},
  journal = {Scientific Reports},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {9},
  number = {1},
  doi = {10.1038/s41598-019-55039-4}
}
Jiang P, Liu H, Piao S, Ciais P, Wu X, Yin Y and Wang H (2019), "Enhanced growth after extreme wetness compensates for post-drought carbon loss in dry forests", Nature Communications., jan, 2019. Vol. 10(1) Springer Science and Business Media LLC.
Abstract: While many studies have reported that drought events have substantial negative legacy effects on forest growth, it remains unclear whether wetness events conversely have positive growth legacy effects. Here, we report pervasive and substantial growth enhancement after extreme wetness by examining tree radial growth at 1929 forest sites, satellite-derived vegetation greenness, and land surface model simulations. Enhanced growth after extreme wetness lasts for 1 to 5 years and compensates for 93 ± 8% of the growth deficit after extreme drought across global water-limited regions. Remarkable wetness-enhanced growths are observed in dry forests and gymnosperms, whereas the enhanced growths after extreme wetness are much smaller in wet forests and angiosperms. Limited or no enhanced growths are simulated by the land surface models after extreme wetness. These findings provide new evidence for improving climate-vegetation models to include the legacy effects of both drought and wet climate extremes.
BibTeX:
@article{Jiang2019a,
  author = {Jiang, Peng and Liu, Hongyan and Piao, Shilong and Ciais, Philippe and Wu, Xiuchen and Yin, Yi and Wang, Hongya},
  title = {Enhanced growth after extreme wetness compensates for post-drought carbon loss in dry forests},
  journal = {Nature Communications},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {10},
  number = {1},
  doi = {10.1038/s41467-018-08229-z}
}
Jung M, Koirala S, Weber U, Ichii K, Gans F, Camps-Valls G, Papale D, Schwalm C, Tramontana G and Reichstein M (2019), "The FLUXCOM ensemble of global land-atmosphere energy fluxes", Scientific Data., dec, 2019. Vol. 6(1), pp. 74.
BibTeX:
@article{Jung2019,
  author = {Jung, Martin and Koirala, Sujan and Weber, Ulrich and Ichii, Kazuhito and Gans, Fabian and Camps-Valls, Gustau and Papale, Dario and Schwalm, Christopher and Tramontana, Gianluca and Reichstein, Markus},
  title = {The FLUXCOM ensemble of global land-atmosphere energy fluxes},
  journal = {Scientific Data},
  year = {2019},
  volume = {6},
  number = {1},
  pages = {74},
  url = {http://www.nature.com/articles/s41597-019-0076-8},
  doi = {10.1038/s41597-019-0076-8}
}
Juráň S, Šigut L, Holub P, Fares S, Klem K, Grace J and Urban O (2019), "Ozone flux and ozone deposition in a mountain spruce forest are modulated by sky conditions", Science of the Total Environment., jul, 2019. Vol. 672, pp. 296-304. Elsevier BV.
Abstract: In order to understand the main driving factors of ozone (O 3 ) deposition we tested the hypothesis that sky conditions (cloudy, partly cloudy, and clear sky) modulate O 3 flux in forest ecosystems via stomatal regulation. The hypothesis is based on the fact that complex microclimate conditions under cloudy sky usually stimulate stomatal conductance. O 3 fluxes were inferred from a concentration gradient in a mountainous Norway spruce forest in the Czech Republic (Central Europe) for years 2012–2016 and measured directly by eddy-covariance during the summer of 2017. Daily and seasonal O 3 depositions were calculated separately for days with cloudy, partly cloudy, and clear sky conditions. The data show unequivocally that more O 3 is taken up under cloudy and partially cloudy skies. Moreover, we found significant interactive effects of sky conditions and season on O 3 flux. Though there are other mechanisms and pathways involved in the transport of O 3 to the plant-soil system, the highest O 3 deposition was associated to the highest stomatal conductance during partly cloudy and cloudy sky conditions in all seasons, while lower O 3 ecosystem fluxes were observed under clear sky conditions despite the highest O 3 concentrations at this time. These findings suggest that forests growing at sites where conditions are predominantly cloudy are expected to deposit higher extent of O 3 than less-cloudy forests being thus more threatened by phytotoxic O 3 .
BibTeX:
@article{Juran2019,
  author = {Juráň, Stanislav and Šigut, Ladislav and Holub, Petr and Fares, Silvano and Klem, Karel and Grace, John and Urban, Otmar},
  title = {Ozone flux and ozone deposition in a mountain spruce forest are modulated by sky conditions},
  journal = {Science of the Total Environment},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {672},
  pages = {296--304},
  doi = {10.1016/j.scitotenv.2019.03.491}
}
Kadavý J, Adamec Z, Uherková B, Kneifl M, Knott R, Kučera A, Friedl M, Dařenová E, Skládanka J and Drápela K (2019), "Growth response of sessile oak and European hornbeam to traditional coppice-with-standards management", Forests., jun, 2019. Vol. 10(6), pp. 515. MDPI AG.
Abstract: Research Highlights: The influence of litter raking and livestock grazing on the development of juvenile sessile oak and European hornbeam sprouts as well as on sessile oak standards were studied. Such experiments are very rare, especially in central Europe where these activities have been prohibited for several decades. Little is known on how these ancient management activities affect tree growth. Background and Objectives: Traditional management practices in coppice forests such as grazing and litter raking have been abandoned, but have recently been studied as to whether these practices can substantially contribute to an increase in the species diversity of coppices. The important question is, however, how these practices influence the growth of coppice-with-standards. Therefore, this study focused on the effect of grazing, litter raking, and their combination on both sprouts and adult trees in a coppice-with-standards system one year after harvest. Materials and Methods: The experiment was carried out in the area of the Training Forest Enterprise Masaryk Forest Křtiny, Czech Republic, in a forest stand dominated by sessile oak and European hornbeam. We analyzed 132 oak polycormons, 132 hornbeam polycormons, and 163 oak standards. Results: The number of sprouts per stump was affected by the stump size and management practice: (A) coppice-with-standards, litter raking, and sheep grazing; (B) coppice-with-standards and sheep grazing; (C) coppice-with-standards and litter raking; and (D) coppice-with-standards), but not by tree species. The number of the sprouts as well as their height increased with the stump size. In contrast, grazing resulted in a smaller height of the sprouts while thinner sprouts were found under a combination of grazing and raking. When comparing the species, the oak sprouts were higher and thicker when compared to the hornbeam sprouts. The increment of standards increased after stand harvest. This, however, was not the result of grazing or raking, but the response to the reduction of tree number and thus of competition between neighboring trees. Conclusions: The results showed that there were rather negative impacts from the implemented traditional management practices on the growth of sprouts. This may lead to the question of whether ecological diversity resulting from the traditional practices may prevail their negative effect on the growth of the coppices.
BibTeX:
@article{Kadavy2019,
  author = {Kadavý, Jan and Adamec, Zdeněk and Uherková, Barbora and Kneifl, Michal and Knott, Robert and Kučera, Aleš and Friedl, Michal and Dařenová, Eva and Skládanka, Jiří and Drápela, Karel},
  title = {Growth response of sessile oak and European hornbeam to traditional coppice-with-standards management},
  journal = {Forests},
  publisher = {MDPI AG},
  year = {2019},
  volume = {10},
  number = {6},
  pages = {515},
  doi = {10.3390/f10060515}
}
Keenan TF, Migliavacca M, Papale D, Baldocchi D, Reichstein M, Torn M and Wutzler T (2019), "Widespread inhibition of daytime ecosystem respiration", Nature Ecology and Evolution., feb, 2019. Vol. 3(3), pp. 407-415.
Abstract: The global land surface absorbs about a third of anthropogenic emissions each year, due to the difference between two key processes: ecosystem photosynthesis and respiration. Despite the importance of these two processes, it is not possible to measure either at the ecosystem scale during the daytime. Eddy-covariance measurements are widely used as the closest ‘quasi-direct' ecosystem-scale observation from which to estimate ecosystem photosynthesis and respiration. Recent research, however, suggests that current estimates may be biased by up to 25%, due to a previously unaccounted for process: the inhibition of leaf respiration in the light. Yet the extent of inhibition remains debated, and implications for estimates of ecosystem-scale respiration and photosynthesis remain unquantified. Here, we quantify an apparent inhibition of daytime ecosystem respiration across the global FLUXNET eddy-covariance network and identify a pervasive influence that varies by season and ecosystem type. We develop partitioning methods that can detect an apparent ecosystem-scale inhibition of daytime respiration and find that diurnal patterns of ecosystem respiration might be markedly different than previously thought. The results call for the re-evaluation of global terrestrial carbon cycle models and also suggest that current global estimates of photosynthesis and respiration may be biased, some on the order of magnitude of anthropogenic fossil fuel emissions.
BibTeX:
@article{Keenan2019,
  author = {Keenan, Trevor F. and Migliavacca, Mirco and Papale, Dario and Baldocchi, Dennis and Reichstein, Markus and Torn, Margaret and Wutzler, Thomas},
  title = {Widespread inhibition of daytime ecosystem respiration},
  journal = {Nature Ecology and Evolution},
  year = {2019},
  volume = {3},
  number = {3},
  pages = {407--415},
  url = {http://www.nature.com/articles/s41559-019-0809-2},
  doi = {10.1038/s41559-019-0809-2}
}
Kitidis V, Shutler JD, Ashton I, Warren M, Brown I, Findlay H, Hartman SE, Sanders R, Humphreys M, Kivimäe C, Greenwood N, Hull T, Pearce D, McGrath T, Stewart BM, Walsham P, McGovern E, Bozec Y, Gac JP, van Heuven SM, Hoppema M, Schuster U, Johannessen T, Omar A, Lauvset SK, Skjelvan I, Olsen A, Steinhoff T, Körtzinger A, Becker M, Lefevre N, Diverrès D, Gkritzalis T, Cattrijsse A, Petersen W, Voynova YG, Chapron B, Grouazel A, Land PE, Sharples J and Nightingale PD (2019), "Winter weather controls net influx of atmospheric CO2 on the north-west European shelf", Scientific Reports., dec, 2019. Vol. 9(1) Springer Science and Business Media LLC.
Abstract: Shelf seas play an important role in the global carbon cycle, absorbing atmospheric carbon dioxide (CO2) and exporting carbon (C) to the open ocean and sediments. The magnitude of these processes is poorly constrained, because observations are typically interpolated over multiple years. Here, we used 298500 observations of CO2 fugacity (fCO2) from a single year (2015), to estimate the net influx of atmospheric CO2 as 26.2 ± 4.7 Tg C yr−1 over the open NW European shelf. CO2 influx from the atmosphere was dominated by influx during winter as a consequence of high winds, despite a smaller, thermally-driven, air-sea fCO2 gradient compared to the larger, biologically-driven summer gradient. In order to understand this climate regulation service, we constructed a carbon-budget supplemented by data from the literature, where the NW European shelf is treated as a box with carbon entering and leaving the box. This budget showed that net C-burial was a small sink of 1.3 ± 3.1 Tg C yr−1, while CO2 efflux from estuaries to the atmosphere, removed the majority of river C-inputs. In contrast, the input from the Baltic Sea likely contributes to net export via the continental shelf pump and advection (34.4 ± 6.0 Tg C yr−1).
BibTeX:
@article{Kitidis2019,
  author = {Kitidis, Vassilis and Shutler, Jamie D. and Ashton, Ian and Warren, Mark and Brown, Ian and Findlay, Helen and Hartman, Sue E. and Sanders, Richard and Humphreys, Matthew and Kivimäe, Caroline and Greenwood, Naomi and Hull, Tom and Pearce, David and McGrath, Triona and Stewart, Brian M. and Walsham, Pamela and McGovern, Evin and Bozec, Yann and Gac, Jean Philippe and van Heuven, Steven M.A.C. and Hoppema, Mario and Schuster, Ute and Johannessen, Truls and Omar, Abdirahman and Lauvset, Siv K. and Skjelvan, Ingunn and Olsen, Are and Steinhoff, Tobias and Körtzinger, Arne and Becker, Meike and Lefevre, Nathalie and Diverrès, Denis and Gkritzalis, Thanos and Cattrijsse, André and Petersen, Wilhelm and Voynova, Yoana G. and Chapron, Bertrand and Grouazel, Antoine and Land, Peter E. and Sharples, Jonathan and Nightingale, Philip D.},
  title = {Winter weather controls net influx of atmospheric CO2 on the north-west European shelf},
  journal = {Scientific Reports},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {9},
  number = {1},
  doi = {10.1038/s41598-019-56363-5}
}
Kiuru P, Ojala A, Mammarella I, Heiskanen J, Erkkilä KM, Miettinen H, Vesala T and Huttula T (2019), "Applicability and consequences of the integration of alternative models for CO2 transfer velocity into a process-based lake model", Biogeosciences., sep, 2019. Vol. 16(17), pp. 3297-3317. Copernicus GmbH.
Abstract: Freshwater lakes are important in carbon cycling, especially in the boreal zone where many lakes are supersaturated with the greenhouse gas carbon dioxide (CO2) and emit it to the atmosphere, thus ventilating carbon originally fixed by the terrestrial system. The exchange of CO2 between water and the atmosphere is commonly estimated using simple wind-based parameterizations or models of gas transfer velocity (k). More complex surface renewal models, however, have been shown to yield more correct estimates of k in comparison with direct CO2 flux measurements. We incorporated four gas exchange models with different complexity into a vertical process-based physico-biochemical lake model, MyLake C, and assessed the performance and applicability of the alternative lake model versions to simulate air-water CO2 fluxes over a small boreal lake. None of the incorporated gas exchange models significantly outperformed the other models in the simulations in comparison to the measured near-surface CO2 concentrations or respective air-water CO2 fluxes calculated directly with the gas exchange models using measurement data as input. The use of more complex gas exchange models in the simulation, on the contrary, led to difficulties in obtaining a sufficient gain of CO2 in the water column and thus resulted in lower CO2 fluxes and water column CO2 concentrations compared to the respective measurement-based values. The inclusion of sophisticated and more correct models for air-water CO2 exchange in process-based lake models is crucial in efforts to properly assess lacustrine carbon budgets through model simulations in both single lakes and on a larger scale. However, finding higher estimates for both the internal and external sources of inorganic carbon in boreal lakes is important if improved knowledge of the magnitude of CO2 evasion from lakes is included in future studies on lake carbon budgets.
BibTeX:
@article{Kiuru2019,
  author = {Kiuru, Petri and Ojala, Anne and Mammarella, Ivan and Heiskanen, Jouni and Erkkilä, Kukka Maaria and Miettinen, Heli and Vesala, Timo and Huttula, Timo},
  title = {Applicability and consequences of the integration of alternative models for CO2 transfer velocity into a process-based lake model},
  journal = {Biogeosciences},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {16},
  number = {17},
  pages = {3297--3317},
  doi = {10.5194/bg-16-3297-2019}
}
Klosterhalfen A, Graf A, Brüggemann N, Drüe C, Esser O, González-Dugo MP, Heinemann G, Jacobs CM, Mauder M, Moene AF, Ney P, Pütz T, Rebmann C, Rodríguez MR, Scanlon TM, Schmidt M, Steinbrecher R, Thomas CK, Valler V, Zeeman MJ and Vereecken H (2019), "Source partitioning of H2O and CO2 fluxes based on high-frequency eddy covariance data: A comparison between study sites", Biogeosciences., mar, 2019. Vol. 16(6), pp. 1111-1132. Copernicus GmbH.
Abstract: For an assessment of the roles of soil and vegetation in the climate system, a further understanding of the flux components of H2O and CO2 (e.g., transpiration, soil respiration) and their interaction with physical conditions and physiological functioning of plants and ecosystems is necessary. To obtain magnitudes of these flux components, we applied source partitioning approaches after Scanlon and Kustas (2010; SK10) and after Thomas et al. (2008; TH08) to high-frequency eddy covariance measurements of 12 study sites covering different ecosystems (croplands, grasslands, and forests) in different climatic regions. Both partitioning methods are based on higher-order statistics of the H2O and CO2 fluctuations, but proceed differently to estimate transpiration, evaporation, net primary production, and soil respiration. We compared and evaluated the partitioning results obtained with SK10 and TH08, including slight modifications of both approaches. Further, we analyzed the interrelations among the performance of the partitioning methods, turbulence characteristics, and site characteristics (such as plant cover type, canopy height, canopy density, and measurement height). We were able to identify characteristics of a data set that are prerequisites for adequate performance of the partitioning methods. SK10 had the tendency to overestimate and TH08 to underestimate soil flux components. For both methods, the partitioning of CO2 fluxes was less robust than for H2O fluxes. Results derived with SK10 showed relatively large dependencies on estimated water use efficiency (WUE) at the leaf level, which is a required input. Measurements of outgoing longwave radiation used for the estimation of foliage temperature (used in WUE) could slightly increase the quality of the partitioning results. A modification of the TH08 approach, by applying a cluster analysis for the conditional sampling of respiration-evaporation events, performed satisfactorily, but did not result in significant advantages compared to the original method versions developed by Thomas et al. (2008). The performance of each partitioning approach was dependent on meteorological conditions, plant development, canopy height, canopy density, and measurement height. Foremost, the performance of SK10 correlated page1112 negatively with the ratio between measurement height and canopy height. The performance of TH08 was more dependent on canopy height and leaf area index. In general, all site characteristics that increase dissimilarities between scalars appeared to enhance partitioning performance for SK10 and TH08.
BibTeX:
@article{Klosterhalfen2019a,
  author = {Klosterhalfen, Anne and Graf, Alexander and Brüggemann, Nicolas and Drüe, Clemens and Esser, Odilia and González-Dugo, María P. and Heinemann, Günther and Jacobs, Cor M.J. and Mauder, Matthias and Moene, Arnold F. and Ney, Patrizia and Pütz, Thomas and Rebmann, Corinna and Rodríguez, Mario Ramos and Scanlon, Todd M. and Schmidt, Marius and Steinbrecher, Rainer and Thomas, Christoph K. and Valler, Veronika and Zeeman, Matthias J. and Vereecken, Harry},
  title = {Source partitioning of H2O and CO2 fluxes based on high-frequency eddy covariance data: A comparison between study sites},
  journal = {Biogeosciences},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {16},
  number = {6},
  pages = {1111--1132},
  doi = {10.5194/bg-16-1111-2019}
}
Klosterhalfen A, Moene AF, Schmidt M, Scanlon TM, Vereecken H and Graf A (2019), "Sensitivity analysis of a source partitioning method for H2O and CO2 fluxes based on high frequency eddy covariance data: Findings from field data and large eddy simulations", Agricultural and Forest Meteorology., feb, 2019. Vol. 265, pp. 152-170. Elsevier BV.
Abstract: Scanlon and Sahu (2008) and Scanlon and Kustas (2010) proposed a source partitioning method (SK10 in the following) to estimate contributions of transpiration, evaporation, photosynthesis, and respiration to H2O and CO2 fluxes obtained by the eddy covariance method. High frequency eddy covariance raw data time series are needed, and the source partitioning is estimated based on separate application of the flux-variance similarity theory to stomatal and non-stomatal components of the regarded fluxes, as well as on additional assumptions on leaf-level water use efficiency (WUE). We applied SK10 to data from two test sites (forest and cropland) and analyzed partitioning results depending on various ways to estimate WUE from available data. Also, we conducted large eddy simulations (LES), simulating the turbulent transport of H2O and CO2 for contrasting vertical distributions of the canopy sinks/sources, as well as for varying relative magnitudes of soil sources and canopy sinks/sources. SK10 was applied to the synthetic high frequency data generated by LES and the effects of canopy type, measurement height, given sink-source-distributions, and input of varying WUEs were tested regarding the partitioning performance. SK10 requires that the correlation coefficient between stomatal and non-stomatal scalar fluctuations is determined by the ratio of the transfer efficiencies of these scalar components, an assumption (transfer assumption in the following) that could be tested with the generated LES data. The partitioning results of the field sites yielded satisfactory flux fractions, when fair-weather conditions (no precipitation) and a high productive state of the vegetation were present. Further, partitioning performance with regard to soil fluxes increased with crop maturity. Results also showed relatively large dependencies on WUE, where the partitioning factors (median) changed by around -57% and +36%. Measurements of outgoing longwave radiation used for the estimation of foliage temperature and WUE could slightly increase the plausibility of the partitioning results in comparison to soil respiration measurements by decreasing the partitioning factor by up to 42%. The LES-based analysis revealed that for a satisfying performance of SK10, a certain degree of decorrelation of the H2O and CO2 fluctuations (here, |ρq'c'| textless 0.975) was needed. This decorrelation is enhanced by a clear separation between soil sources and canopy sinks/sources, and for observations within the roughness sublayer. The expected dependence of the partitioning results on the WUE input could be observed. However, due to violation of the abovementioned transfer assumption, the known true input WUE did not yield the known true input partitioning. This could only be achieved after introducing correction factors for the transfer assumption, which were known however only in the special case of the LES experiments.
BibTeX:
@article{Klosterhalfen2019,
  author = {Klosterhalfen, A. and Moene, A. F. and Schmidt, M. and Scanlon, T. M. and Vereecken, H. and Graf, A.},
  title = {Sensitivity analysis of a source partitioning method for H2O and CO2 fluxes based on high frequency eddy covariance data: Findings from field data and large eddy simulations},
  journal = {Agricultural and Forest Meteorology},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {265},
  pages = {152--170},
  doi = {10.1016/j.agrformet.2018.11.003}
}
Knox SH, Jackson RB, Poulter B, McNicol G, Fluet-Chouinard E, Zhang Z, Hugelius G, Bousquet P, Canadell JG, Saunois M, Papale D, Chu H, Keenan TF, Baldocchi D, Torn MS, Mammarella I, Trotta C, Aurela M, Bohrer G, Campbell DI, Cescatti A, Chamberlain S, Chen J, Chen W, Dengel S, Desai AR, Euskirchen E, Friborg T, Gasbarra D, Goded I, Goeckede M, Heimann M, Helbig M, Hirano T, Hollinger DY, Iwata H, Kang M, Klatt J, Krauss KW, Kutzbach L, Lohila A, Mitra B, Morin TH, Nilsson MB, Niu S, Noormets A, Oechel WC, Peichl M, Peltola O, Reba ML, Richardson AD, Runkle BR, Ryu Y, Sachs T, Schäfer KV, Schmid HP, Shurpali N, Sonnentag O, Tang AC, Ueyama M, Vargas R, Vesala T, Ward EJ, Windham-Myers L, Wohlfahrt G and Zona D (2019), "FluXNET-CH4 synthesis activity objectives, observations, and future directions", Bulletin of the American Meteorological Society., dec, 2019. Vol. 100(12), pp. 2607-2632.
Abstract: We describe a new coordination activity and initial results for a global synthesis of eddy covariance CH4 flux measurements.
BibTeX:
@article{Knox2019,
  author = {Knox, Sara H. and Jackson, Robert B. and Poulter, Benjamin and McNicol, Gavin and Fluet-Chouinard, Etienne and Zhang, Zhen and Hugelius, Gustaf and Bousquet, Philippe and Canadell, Josep G. and Saunois, Marielle and Papale, Dario and Chu, Housen and Keenan, Trevor F. and Baldocchi, Dennis and Torn, Margaret S. and Mammarella, Ivan and Trotta, Carlo and Aurela, Mika and Bohrer, Gil and Campbell, David I. and Cescatti, Alessandro and Chamberlain, Samuel and Chen, Jiquan and Chen, Weinan and Dengel, Sigrid and Desai, Ankur R. and Euskirchen, Eugenie and Friborg, Thomas and Gasbarra, Daniele and Goded, Ignacio and Goeckede, Mathias and Heimann, Martin and Helbig, Manuel and Hirano, Takashi and Hollinger, David Y. and Iwata, Hiroki and Kang, Minseok and Klatt, Janina and Krauss, Ken W. and Kutzbach, Lars and Lohila, Annalea and Mitra, Bhaskar and Morin, Timothy H. and Nilsson, Mats B. and Niu, Shuli and Noormets, Asko and Oechel, Walter C. and Peichl, Matthias and Peltola, Olli and Reba, Michele L. and Richardson, Andrew D. and Runkle, Benjamin R.K. and Ryu, Youngryel and Sachs, Torsten and Schäfer, Karina V.R. and Schmid, Hans Peter and Shurpali, Narasinha and Sonnentag, Oliver and Tang, Angela C.I. and Ueyama, Masahito and Vargas, Rodrigo and Vesala, Timo and Ward, Eric J. and Windham-Myers, Lisamarie and Wohlfahrt, Georg and Zona, Donatella},
  title = {FluXNET-CH4 synthesis activity objectives, observations, and future directions},
  journal = {Bulletin of the American Meteorological Society},
  year = {2019},
  volume = {100},
  number = {12},
  pages = {2607--2632},
  url = {http://journals.ametsoc.org/doi/10.1175/BAMS-D-18-0268.1},
  doi = {10.1175/BAMS-D-18-0268.1}
}
Kohonen K-M, Kolari P, Kooijmans LM, Chen H, Seibt U, Sun W and Mammarella I (2019), "Towards standardized processing of eddy covariance flux measurements of carbonyl sulfide", Atmospheric Measurement Techniques Discussions., oct, 2019. , pp. 1-30. Copernicus GmbH.
Abstract: Carbonyl sulfide (COS) flux measurements with the eddy covariance (EC) technique are growing in popularity with the recent development in using COS to estimate gross photosynthesis at the ecosystem scale. Flux data intercomparison would benefit from standardized protocols for COS flux data processing. In this study, we analyze how various data processing steps affect the final flux and provide a method for gap-filling COS fluxes. Different methods for determining the lag time between COS mixing ratio and the vertical wind velocity (w) resulted in a maximum of 12 % difference in the cumulative COS flux. Due to limited COS measurement precision, small COS fluxes (below approximately 3 pmol m−2 s−1) could not be detected when the lag time was determined from maximizing the covariance between COS and w. We recommend using a combination of COS and carbon dioxide (CO2) lag times in determining the COS flux, depending on the flux magnitude compared to the detection limit of each averaging period. Different high frequency spectral corrections had a maximum effect of 10 % on COS flux calculations and different detrending methods only 1.2 %. Relative total uncertainty was more than five times higher for low COS fluxes (absolute flux lower than 3 pmol m−2 s−1) than for low CO2 fluxes (lower than 1.5 μmol m−2 s−1), indicating a low signal-to-noise ratio of COS fluxes. Due to similarities in ecosystem COS and CO2 exchange, and the low signal-to-noise ratio of COS fluxes that is similar to methane, we recommend a combination of CO2 and methane flux processing protocols for COS EC fluxes. [ABSTRACT FROM AUTHOR]
BibTeX:
@article{Kohonen2019,
  author = {Kohonen, Kukka-Maaria and Kolari, Pasi and Kooijmans, Linda M. and Chen, Huilin and Seibt, Ulli and Sun, Wu and Mammarella, Ivan},
  title = {Towards standardized processing of eddy covariance flux measurements of carbonyl sulfide},
  journal = {Atmospheric Measurement Techniques Discussions},
  publisher = {Copernicus GmbH},
  year = {2019},
  pages = {1--30},
  doi = {10.5194/amt-2019-313}
}
Kondo M, Patra PK, Sitch S, Friedlingstein P, Poulter B, Chevallier F, Ciais P, Canadell JG, Bastos A, Lauerwald R, Calle L, Ichii K, Anthoni P, Arneth A, Haverd V, Jain AK, Kato E, Kautz M, Law RM, Lienert S, Lombardozzi D, Maki T, Nakamura T, Peylin P, Rödenbeck C, Zhuravlev R, Saeki T, Tian H, Zhu D and Ziehn T (2019), "State of the science in reconciling top-down and bottom-up approaches for terrestrial CO2 budget", Global Change Biology., mar, 2019. Vol. 26(3), pp. 1068-1084. Wiley.
Abstract: Robust estimates of CO2 budget, CO2 exchanged between the atmosphere and terrestrial biosphere, are necessary to better understand the role of the terrestrial biosphere in mitigating anthropogenic CO2 emissions. Over the past decade, this field of research has advanced through understanding of the differences and similarities of two fundamentally different approaches: “top-down” atmospheric inversions and “bottom-up” biosphere models. Since the first studies were undertaken, these approaches have shown an increasing level of agreement, but disagreements in some regions still persist, in part because they do not estimate the same quantity of atmosphere–biosphere CO2 exchange. Here, we conducted a thorough comparison of CO2 budgets at multiple scales and from multiple methods to assess the current state of the science in estimating CO2 budgets. Our set of atmospheric inversions and biosphere models, which were adjusted for a consistent flux definition, showed a high level of agreement for global and hemispheric CO2 budgets in the 2000s. Regionally, improved agreement in CO2 budgets was notable for North America and Southeast Asia. However, large gaps between the two methods remained in East Asia and South America. In other regions, Europe, boreal Asia, Africa, South Asia, and Oceania, it was difficult to determine whether those regions act as a net sink or source because of the large spread in estimates from atmospheric inversions. These results highlight two research directions to improve the robustness of CO2 budgets: (a) to increase representation of processes in biosphere models that could contribute to fill the budget gaps, such as forest regrowth and forest degradation; and (b) to reduce sink–source compensation between regions (dipoles) in atmospheric inversion so that their estimates become more comparable. Advancements on both research areas will increase the level of agreement between the top-down and bottom-up approaches and yield more robust knowledge of regional CO2 budgets.
BibTeX:
@article{Kondo2019,
  author = {Kondo, Masayuki and Patra, Prabir K. and Sitch, Stephen and Friedlingstein, Pierre and Poulter, Benjamin and Chevallier, Frederic and Ciais, Philippe and Canadell, Josep G. and Bastos, Ana and Lauerwald, Ronny and Calle, Leonardo and Ichii, Kazuhito and Anthoni, Peter and Arneth, Almut and Haverd, Vanessa and Jain, Atul K. and Kato, Etsushi and Kautz, Markus and Law, Rachel M. and Lienert, Sebastian and Lombardozzi, Danica and Maki, Takashi and Nakamura, Takashi and Peylin, Philippe and Rödenbeck, Christian and Zhuravlev, Ruslan and Saeki, Tazu and Tian, Hanqin and Zhu, Dan and Ziehn, Tilo},
  title = {State of the science in reconciling top-down and bottom-up approaches for terrestrial CO2 budget},
  journal = {Global Change Biology},
  publisher = {Wiley},
  year = {2019},
  volume = {26},
  number = {3},
  pages = {1068--1084},
  doi = {10.1111/gcb.14917}
}
Kooijmans LM, Sun W, Aalto J, Erkkilä KM, Maseyk K, Seibt U, Vesala T, Mammarella I and Chen H (2019), "Influences of light and humidity on carbonyl sulfide-based estimates of photosynthesis", Proceedings of the National Academy of Sciences of the United States of America., jan, 2019. Vol. 116(7), pp. 2470-2475. Proceedings of the National Academy of Sciences.
Abstract: Understanding climate controls on gross primary productivity (GPP) is crucial for accurate projections of the future land carbon cycle. Major uncertainties exist due to the challenge in separating GPP and respiration from observations of the carbon dioxide (CO 2 ) flux. Carbonyl sulfide (COS) has a dominant vegetative sink, and plant COS uptake is used to infer GPP through the leaf relative uptake (LRU) ratio of COS to CO 2 fluxes. However, little is known about variations of LRU under changing environmental conditions and in different phenological stages. We present COS and CO 2 fluxes and LRU of Scots pine branches measured in a boreal forest in Finland during the spring recovery and summer. We find that the diurnal dynamics of COS uptake is mainly controlled by stomatal conductance, but the leaf internal conductance could significantly limit the COS uptake during the daytime and early in the season. LRU varies with light due to the differential light responses of COS and CO 2 uptake, and with vapor pressure deficit (VPD) in the peak growing season, indicating a humidity-induced stomatal control. Our COS-based GPP estimates show that it is essential to incorporate the variability of LRU with environmental variables for accurate estimation of GPP on ecosystem, regional, and global scales.
BibTeX:
@article{Kooijmans2019,
  author = {Kooijmans, Linda M.J. and Sun, Wu and Aalto, Juho and Erkkilä, Kukka Maaria and Maseyk, Kadmiel and Seibt, Ulrike and Vesala, Timo and Mammarella, Ivan and Chen, Huilin},
  title = {Influences of light and humidity on carbonyl sulfide-based estimates of photosynthesis},
  journal = {Proceedings of the National Academy of Sciences of the United States of America},
  publisher = {Proceedings of the National Academy of Sciences},
  year = {2019},
  volume = {116},
  number = {7},
  pages = {2470--2475},
  doi = {10.1073/pnas.1807600116}
}
Korkiakoski M, Tuovinen JP, Penttilä T, Sarkkola S, Ojanen P, Minkkinen K, Rainne J, Laurila T and Lohila A (2019), "Greenhouse gas and energy fluxes in a boreal peatland forest after clear-cutting", Biogeosciences., sep, 2019. Vol. 16(19), pp. 3703-3723. Copernicus GmbH.
Abstract: The most common forest management method in Fennoscandia is rotation forestry, including clear-cutting and forest regeneration. In clear-cutting, stem wood is removed and the logging residues are either removed or left on site. Clear-cutting changes the microclimate and vegetation structure at the site, both of which affect the site's carbon balance. Peat soils with poor aeration and high carbon densities are especially prone to such changes, and significant changes in greenhouse gas exchange can be expected. We measured carbon dioxide (CO2) and energy fluxes with the eddy covariance method for 2 years (April 2016-March 2018) after clear-cutting a drained peatland forest. We observed a significant rise (23 cm) in the water table level and a large CO2 source (first year: 3086 ± 148 g CO2 m-2 yr-1; second year: 2072 ± 124 g CO2 m-2 yr-1). These large CO2 emissions resulted from the very low gross primary production (GPP) following the removal of photosynthesizing trees and the decline of ground vegetation, unable to compensate for the decomposition of logging residues and peat. During the second summer (June-August) after the clear-cutting, GPP had already increased by 96 % and total ecosystem respiration decreased by 14 % from the previous summer. The mean daytime ratio of sensible to latent heat flux decreased after harvesting from 2.6 in May 2016 to 1.0 in August 2016, and in 2017 it varied mostly within 0.6-1.0. In April-September, the mean daytime sensible heat flux was 33 % lower and latent heat flux 40 % higher in 2017, probably due to the recovery of ground vegetation that increased evapotranspiration and albedo of the site. In addition to CO2 and energy fluxes, we measured methane (CH4) and nitrous oxide (N2O) fluxes with manual chambers. After the clear-cutting, the site turned from a small CH4 sink into a small source and from N2O neutral to a significant N2O source. Compared to the large CO2 emissions, the 100-year global warming potential (GWP100) of the CH4 emissions was negligible. Also, the GWP100 due to increased N2O emissions was less than 10 % of that of the CO2 emission change.
BibTeX:
@article{Korkiakoski2019,
  author = {Korkiakoski, Mika and Tuovinen, Juha Pekka and Penttilä, Timo and Sarkkola, Sakari and Ojanen, Paavo and Minkkinen, Kari and Rainne, Juuso and Laurila, Tuomas and Lohila, Annalea},
  title = {Greenhouse gas and energy fluxes in a boreal peatland forest after clear-cutting},
  journal = {Biogeosciences},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {16},
  number = {19},
  pages = {3703--3723},
  doi = {10.5194/bg-16-3703-2019}
}
Kosonen Z, Schnyder E, Hiltbrunner E, Thimonier A, Schmitt M, Seitler E and Thöni L (2019), "Current atmospheric nitrogen deposition still exceeds critical loads for sensitive, semi-natural ecosystems in Switzerland", Atmospheric Environment., aug, 2019. Vol. 211, pp. 214-225. Elsevier BV.
Abstract: Increased atmospheric nitrogen (N) deposition is driving nutrient imbalances, soil acidification, biodiversity losses and the long-term reduction in stability of sensitive ecosystems which previously had limited N. In this study, we analysed the concentrations of seven different N compounds in precipitation and in the air at 34 sites across Switzerland. We calculated the N deposition by precipitation (bulk deposition) and applied the inferential method to derive dry deposition (gases, aerosols) from air concentrations. We then quantified the total inorganic N deposition by adding together the bulk and dry deposition. Finally, the total inorganic N input into the sensitive ecosystems of the 34 sites was compared to the critical loads of these ecosystems. N deposition by precipitation was the main contributor to the total N load in 16 out of 34 sites, especially into open ecosystems such as alpine/subalpine grassland, mountain hay meadows, and raised bogs. Dry deposition of ammonia (NH3) was the second most important pathway, in particular for forests close to agricultural activities, due to high NH3 concentrations and the higher deposition velocity. The N deposition exceeded the lower limit of the Critical Load of Nitrogen (CLN) range at most sites, and at many sites even surpassed the upper limit of the CLN range. No, or minor, exceedances of the critical loads for N were found only at remote sites at higher elevation in the Central Alps. Annual inorganic N deposition between 2000 and 2017 revealed a significant decline in oxidised N compounds at four of five sites (−1.6–1.8% per year), but reduced compounds only decreased at two sites (−1% and −1.4% per year) and even increased at one site (+1.2% per year), despite adopted abatement strategies for agricultural practices. This emphasises that most sensitive ecosystems in Switzerland continue to be exposed to excessive N loads through atmospheric deposition, with detrimental consequences for the biodiversity and stability of these ecosystems.
BibTeX:
@article{Kosonen2019,
  author = {Kosonen, Zaida and Schnyder, Elvira and Hiltbrunner, Erika and Thimonier, Anne and Schmitt, Maria and Seitler, Eva and Thöni, Lotti},
  title = {Current atmospheric nitrogen deposition still exceeds critical loads for sensitive, semi-natural ecosystems in Switzerland},
  journal = {Atmospheric Environment},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {211},
  pages = {214--225},
  doi = {10.1016/j.atmosenv.2019.05.005}
}
Kozii N, Haahti K, Tor-ngern P, Chi J, Hasselquist EM, Laudon H, Launiainen S, Oren R, Peichl M, Wallerman J and Hasselquist N (2019), "Partitioning the forest water balance within a boreal catchment using sapflux, eddy covariance and process-based model", Hydrology and Earth System Sciences Discussions., oct, 2019. , pp. 1-50. Copernicus GmbH.
Abstract: Predicting the binding mode of flexible polypeptides to proteins is an important task that falls outside the domain of applicability of most small molecule and protein−protein docking tools. Here, we test the small molecule flexible ligand docking program Glide on a set of 19 non-α-helical peptides and systematically improve pose prediction accuracy by enhancing Glide sampling for flexible polypeptides. In addition, scoring of the poses was improved by post-processing with physics-based implicit solvent MM- GBSA calculations. Using the best RMSD among the top 10 scoring poses as a metric, the success rate (RMSD ≤ 2.0 Å for the interface backbone atoms) increased from 21% with default Glide SP settings to 58% with the enhanced peptide sampling and scoring protocol in the case of redocking to the native protein structure. This approaches the accuracy of the recently developed Rosetta FlexPepDock method (63% success for these 19 peptides) while being over 100 times faster. Cross-docking was performed for a subset of cases where an unbound receptor structure was available, and in that case, 40% of peptides were docked successfully. We analyze the results and find that the optimized polypeptide protocol is most accurate for extended peptides of limited size and number of formal charges, defining a domain of applicability for this approach.
BibTeX:
@article{Kozii2019,
  author = {Kozii, Natalia and Haahti, Kersti and Tor-ngern, Pantana and Chi, Jinshu and Hasselquist, Eliza Maher and Laudon, Hjalmar and Launiainen, Samuli and Oren, Ram and Peichl, Matthias and Wallerman, Jörgen and Hasselquist, Niles},
  title = {Partitioning the forest water balance within a boreal catchment using sapflux, eddy covariance and process-based model},
  journal = {Hydrology and Earth System Sciences Discussions},
  publisher = {Copernicus GmbH},
  year = {2019},
  pages = {1--50},
  doi = {10.5194/hess-2019-541}
}
Krupková L, Havránková K, Krejza J, Sedlák P and Marek MV (2019), "Impact of water scarcity on spruce and beech forests", Journal of Forestry Research. Vol. 30(3), pp. 899-909.
Abstract: One of the greatest threats posed by ongoing climate change may be regarded the drought caused by changes in precipitation distribution. The aim of presented study was to characterize reactions to dry conditions and conditions without drought stress on gross primary production (GPP) and net ecosystem production (NEP) of spruce and beech forests, as these two species dominate within the European continent. Daily courses of GPP and NEP of these two species were evaluated in relation to an expected decrease in CO2 uptake during dry days. The occurrence of CO2 uptake hysteresis in daily production was also investigated. Our study was performed at Bílý Kříž (spruce) and Štítná (beech) mountain forest sites during 2010–2012 period. We applied eddy covariance technique for the estimation of carbon fluxes, vapor pressure deficit and precipitation characteristics together with the SoilClim model for the determination of drought conditions, and the inverse of the Penman–Monteith equation to compute canopy conductance. Significant differences were found in response to reduced water supply for both species. Spruce reacts by closing its stomata before noon and maintaining a reduced photosynthetic activity for the rest of the day, while beech keeps its stomata open as long as possible and slightly reduces photosynthetic activity evenly throughout the entire day. In the spruce forest, we found substantial hysteresis in the light response curve of GPP. In the beech forest, the shape of this curve was different: evening values exceeded morning values.
BibTeX:
@article{Krupkova2019,
  author = {Krupková, Lenka and Havránková, Kateřina and Krejza, Jan and Sedlák, Pavel and Marek, Michal V.},
  title = {Impact of water scarcity on spruce and beech forests},
  journal = {Journal of Forestry Research},
  year = {2019},
  volume = {30},
  number = {3},
  pages = {899--909},
  doi = {10.1007/s11676-018-0642-5}
}
Kulmala L, Pumpanen J, Kolari P, Dengel S, Berninger F, Köster K, Matkala L, Vanhatalo A, Vesala T and Bäck J (2019), "Inter- and intra-annual dynamics of photosynthesis differ between forest floor vegetation and tree canopy in a subarctic Scots pine stand", Agricultural and Forest Meteorology., jun, 2019. Vol. 271, pp. 1-11. Elsevier BV.
Abstract: We studied the inter- and intra-annual dynamics of the photosynthesis of forest floor vegetation and tree canopy in a subarctic Scots pine stand at the northern timberline in Finland. We tackled the issue using three different approaches: 1) measuring carbon dioxide exchange above and below canopy with the eddy covariance technique, 2) modelling the photosynthesis of the tree canopy based on shoot chamber measurements, and 3) upscaling the forest floor photosynthesis using biomass estimates and available information on the annual cycle of photosynthetic capacity of those species. The studied ecosystem was generally a weak sink of carbon but the sink strength showed notable year-to-year variation. Total ecosystem respiration and photosynthesis indicated a clear temperature limitation for the carbon exchange. However, the increase in photosynthetic production was steeper than the increase in respiration with temperature, indicating that warm temperatures increase the sink strength and do not stimulate the total ecosystem respiration as much in the 4-year window studied. The interannual variation in the photosynthetic production of the forest stand mainly resulted from the forest floor vegetation, whereas the photosynthesis of the tree canopy seemed to be more stable from year to year. Tree canopy photosynthesis increased earlier in the spring, whereas that of the forest floor increased after snowmelt, highlighting that models for photosynthesis in the northern area should also include snow cover in order to accurately estimate the seasonal dynamics of photosynthesis in these forests.
BibTeX:
@article{Kulmala2019,
  author = {Kulmala, Liisa and Pumpanen, Jukka and Kolari, Pasi and Dengel, Sigrid and Berninger, Frank and Köster, Kajar and Matkala, Laura and Vanhatalo, Anni and Vesala, Timo and Bäck, Jaana},
  title = {Inter- and intra-annual dynamics of photosynthesis differ between forest floor vegetation and tree canopy in a subarctic Scots pine stand},
  journal = {Agricultural and Forest Meteorology},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {271},
  pages = {1--11},
  doi = {10.1016/j.agrformet.2019.02.029}
}
Lagergren F, Jönsson AM, Linderson H and Lindroth A (2019), "Time shift between net and gross CO2 uptake and growth derived from tree rings in pine and spruce", Trees - Structure and Function., jun, 2019. Vol. 33(3), pp. 765-776.
Abstract: Key message: A 6–9 month backward time shift of the carbon uptake gave the highest correlation between annual biomass increment and carbon uptake in this old even aged forest. Abstract: Plants' carbon uptake and allocation to different biomass compartments is an important process for both wood production and climate mitigation. Measurements of the net ecosystem carbon dioxide exchange between ecosystems and the atmosphere provide insights into the processes of photosynthesis, respiration and accumulation of carbon over time, and the increase in woody biomass can be assessed by allometric functions based on stem diameter measurements. The fraction of carbon allocated to radial stem growth varies over time, and a lag between carbon uptake and growth can be expected. The dynamics of non-structural carbohydrates and autotrophic and heterotrophic respiration are key mechanisms for understanding this lag effect. In this study, a 9-year record of carbon flux and tree-ring data from Norunda, Sweden was used to investigate the relationship between net and gross carbon uptake and carbon allocated to growth. The flux data were aggregated to monthly sums. When full 12-month periods of accumulated carbon exchange were successively shifted backwards in time, the highest correlation was found with a 6–9 month shift, showing that a large part of the previous growing season was important for explaining the biomass increment of the following year.
BibTeX:
@article{Lagergren2019,
  author = {Lagergren, Fredrik and Jönsson, Anna Maria and Linderson, Hans and Lindroth, Anders},
  title = {Time shift between net and gross CO2 uptake and growth derived from tree rings in pine and spruce},
  journal = {Trees - Structure and Function},
  year = {2019},
  volume = {33},
  number = {3},
  pages = {765--776},
  url = {http://link.springer.com/10.1007/s00468-019-01814-9},
  doi = {10.1007/s00468-019-01814-9}
}
Langvall O and Ottosson Löfvenius M (2019), "Long-term standardized forest phenology in Sweden: a climate change indicator", International Journal of Biometeorology., oct, 2019.
Abstract: Because climate change alters patterns of vegetative growth, long-term phenological measurements and observations can provide important data for analyzing its impact. Phenological assessments are usually made as records of calendar dates when specific phase changes occur. Such assessments have benefits and are used in Citizen Science monitoring. However, these kinds of data often have low statistical precision when describing gradual changes. Frequent monitoring of the phenological traits of forest trees and berries as they undergo gradual change is needed to acquire good temporal resolution of transitions relative to other factors, such as susceptibility to frosts, insects, and fungi, and the use of berries as a food resource. Intensive weekly monitoring of the growth of apical and branch buds and the elongation of shoots and leaves on four tree species, and the abundance of flowers and berries of bilberry and lingonberry, has been performed in Sweden since 2006. Here, we present quantitative methods for interpolating such data, which detail the gradual changes between assessments in order to describe average rates of development and amount of interannual variation. Our analysis has shown the active growth period of trees to differ with latitude. We also observed a change in the timing of the maximum numbers of ripening berries and their successive decline. Data from tree phenology assessments can be used to recommend best forestry practice and to model tree growth, while berry data can be used to estimate when food resources for animals are most available.
BibTeX:
@article{Langvall2019,
  author = {Langvall, Ola and Ottosson Löfvenius, Mikaell},
  title = {Long-term standardized forest phenology in Sweden: a climate change indicator},
  journal = {International Journal of Biometeorology},
  year = {2019},
  url = {http://link.springer.com/10.1007/s00484-019-01817-8},
  doi = {10.1007/s00484-019-01817-8}
}
Lebehot AD, Halloran PR, Watson AJ, McNeall D, Ford DA, Landschützer P, Lauvset SK and Schuster U (2019), "Reconciling Observation and Model Trends in North Atlantic Surface CO2", Global Biogeochemical Cycles., oct, 2019. Vol. 33(10), pp. 1204-1222. American Geophysical Union (AGU).
Abstract: The North Atlantic Ocean is a region of intense uptake of atmospheric CO2. To assess how this CO2 sink has evolved over recent decades, various approaches have been used to estimate basin-wide uptake from the irregularly sampled in situ CO2 observations. Until now, the lack of robust uncertainties associated with observation-based gap-filling methods required to produce these estimates has limited the capacity to validate climate model simulated surface ocean CO2 concentrations. After robustly quantifying basin-wide and annually varying interpolation uncertainties using both observational and model data, we show that the North Atlantic surface ocean fugacity of CO2 (fCO2−ocean) increased at a significantly slower rate than that simulated by the latest generation of Earth System Models during the period 1992–2014. We further show, with initialized model simulations, that the inability of these models to capture the observed trend in surface fCO2−ocean is primarily due to biases in the models' ocean biogeochemistry. Our results imply that current projections may underestimate the contribution of the North Atlantic to mitigating increasing future atmospheric CO2 concentrations.
BibTeX:
@article{Lebehot2019,
  author = {Lebehot, Alice D. and Halloran, Paul R. and Watson, Andrew J. and McNeall, Doug and Ford, David A. and Landschützer, Peter and Lauvset, Siv K. and Schuster, Ute},
  title = {Reconciling Observation and Model Trends in North Atlantic Surface CO2},
  journal = {Global Biogeochemical Cycles},
  publisher = {American Geophysical Union (AGU)},
  year = {2019},
  volume = {33},
  number = {10},
  pages = {1204--1222},
  doi = {10.1029/2019GB006186}
}
Lefèvre N, Veleda D, Tyaquiçã P, Perruche C, Diverrès D and Ibánhez JSP (2019), "Basin-Scale Estimate of the Sea-Air CO2 Flux During the 2010 Warm Event in the Tropical North Atlantic", Journal of Geophysical Research: Biogeosciences., apr, 2019. Vol. 124(4), pp. 973-986. American Geophysical Union (AGU).
Abstract: Following the anomalous warming event occurring in the tropical North Atlantic in 2010, higher than usual surface fugacity of CO2 (fCO2) was observed. To evaluate the spatial extent of these anomalies and their drivers, and to quantify the sea-air CO2 flux at basin scale, the Mercator-Ocean model is used from 2006 to 2014 within the region 0–30°N, 70–15°W. Model outputs are generally in accordance with underway sea surface temperature, sea surface salinity, and surface fCO2 recorded by two merchant ships. The anomalous warming of 2010 is well reproduced by the model and is the main driver of fCO2 anomalies. The first coupled Empirical Orthogonal Function mode, between sea surface temperature and fCO2, captures more than 70% of the total variance and is characterized by a basin-scale warming associated to positive fCO2 anomalies. The corresponding principal components are correlated to the Tropical North Atlantic Index and identify 2010 as the year with the highest positive anomaly over 2006–2014. Exceptions to this general pattern are located near the African coast, where the weakening of the coastal upwelling causes negative inorganic carbon anomalies, and close to the Amazon River plume, where fCO2 anomalies are primarily associated with sea surface salinity anomalies. Although the fCO2 anomalies of 2010 appear mostly in spring, they affect the annual CO2 budget and lead to an increased CO2 outgassing twice as large (46.2 Tg C per year) as the mean annual flux over the 2006–2014 period (23.3 Tg C per year).
BibTeX:
@article{Lefevre2019,
  author = {Lefèvre, Nathalie and Veleda, Doris and Tyaquiçã, Pedro and Perruche, Coralie and Diverrès, Denis and Ibánhez, J. Severino P.},
  title = {Basin-Scale Estimate of the Sea-Air CO2 Flux During the 2010 Warm Event in the Tropical North Atlantic},
  journal = {Journal of Geophysical Research: Biogeosciences},
  publisher = {American Geophysical Union (AGU)},
  year = {2019},
  volume = {124},
  number = {4},
  pages = {973--986},
  doi = {10.1029/2018JG004840}
}
Leufen LH and Schädler G (2019), "Calculating the turbulent fluxes in the atmospheric surface layer with neural networks", Geoscientific Model Development., may, 2019. Vol. 12(5), pp. 2033-2047.
Abstract: The turbulent fluxes of momentum, heat and water vapour link the Earth's surface with the atmosphere. Therefore, the correct modelling of the flux interactions between these two systems with very different timescales is vital for climate and weather forecast models. Conventionally, these fluxes are modelled using Monin-Obukhov similarity theory (MOST) with stability functions derived from a small number of field experiments. This results in a range of formulations of these functions and thus also in differences in the flux calculations; furthermore, the underlying equations are non-linear and have to be solved iteratively at each time step of the model. In this study, we tried a different and more flexible approach, namely using an artificial neural network (ANN) to calculate the scaling quantities uand(used to parameterise the fluxes), thereby avoiding function fitting and iteration. The network was trained and validated with multi-year data sets from seven grassland, forest and wetland sites worldwide using the Broyden-Fletcher-Goldfarb-Shanno (BFGS) quasi-Newton backpropagation algorithm and six-fold cross validation. Extensive sensitivity tests showed that an ANN with six input variables and one hidden layer gave results comparable to (and in some cases even slightly better than) the standard method; moreover, this ANN performed considerably better than a multivariate linear regression model. Similar satisfying results were obtained when the ANN routine was implemented in a one-dimensional stand-alone land surface model (LSM), paving the way for implementation in three-dimensional climate models. In the case of the one-dimensional LSM, no CPU time was saved when using the ANN version, as the small time step of the standard version required only one iteration in most cases. This may be different in models with longer time steps, e.g. global climate models.
BibTeX:
@article{Leufen2019,
  author = {Leufen, Lukas Hubert and Schädler, Gerd},
  title = {Calculating the turbulent fluxes in the atmospheric surface layer with neural networks},
  journal = {Geoscientific Model Development},
  year = {2019},
  volume = {12},
  number = {5},
  pages = {2033--2047},
  url = {https://www.geosci-model-dev.net/12/2033/2019/},
  doi = {10.5194/gmd-12-2033-2019}
}
Li S, Yuan W, Ciais P, Viovy N, Ito A, Jia B and Zhu D (2019), "Benchmark estimates for aboveground litterfall data derived from ecosystem models", Environmental Research Letters., jul, 2019. Vol. 14(8), pp. 84020. IOP Publishing.
Abstract: Litter production is a fundamental ecosystem process, which plays an important role in regulating terrestrial carbon and nitrogen cycles. However, there are substantial differences in the litter production simulations among ecosystem models, and a global benchmarking evaluation to measure the performance of these models is still lacking. In this study, we generated a global dataset of aboveground litterfall production (i.e. cLitter), a benchmark as the defined reference to test model performance, by combining systematic measurements taken from a substantial number of surveys (1079 sites) with a machine learning technique (i.e. random forest, RF). Our study demonstrated that the RF model is an effective tool for upscaling local litterfall production observations to the global scale. On average, the model predicted 23.15 Pg C yr-1 of aboveground litterfall production. Our results revealed substantial differences in the aboveground litterfall production simulations among the five investigated ecosystem models. Compared to the reference data at the global scale, most of models could reproduce the spatial patterns of aboveground litterfall production, but the magnitude of simulations differed substantially from the reference data. Overall, ORCHIDEE-MICT performed the best among the five investigated ecosystem models.
BibTeX:
@article{Li2019a,
  author = {Li, Shihua and Yuan, Wenping and Ciais, Philippe and Viovy, Nicolas and Ito, Akihiko and Jia, Bingrui and Zhu, Dan},
  title = {Benchmark estimates for aboveground litterfall data derived from ecosystem models},
  journal = {Environmental Research Letters},
  publisher = {IOP Publishing},
  year = {2019},
  volume = {14},
  number = {8},
  pages = {84020},
  doi = {10.1088/1748-9326/ab2ee4}
}
Li X and Xiao J (2019), "Mapping photosynthesis solely from solar-induced chlorophyll fluorescence: A global, fine-resolution dataset of gross primary production derived from OCO-2", Remote Sensing., oct, 2019. Vol. 11(21), pp. 2563.
Abstract: Accurately quantifying gross primary production (GPP) globally is critical for assessing plant productivity, carbon balance, and carbon-climate feedbacks, while current GPP estimates exhibit substantial uncertainty. Solar-induced chlorophyll fluorescence (SIF) observed by the Orbiting Carbon Observatory-2 (OCO-2) has offered unprecedented opportunities for monitoring land photosynthesis, while its sparse coverage remains a bottleneck for mapping finer-resolution GPP globally. Here, we used the global, OCO-2-based SIF product (GOSIF) and linear relationships between SIF and GPP to map GPP globally at a 0.05° spatial resolution and 8-day time step for the period from 2000 to 2017. To account for the uncertainty of GPP estimates resulting from the SIF-GPP relationship, we used a total of eight SIF-GPP relationships with different forms (universal and biome-specific, with and without intercept) at both site and grid cell levels to estimate GPP. Our results showed that all of the eight SIF-GPP relationships performed well in estimating GPP globally. The ensemble mean 8-day GPP was generally highly correlated with flux tower GPP for 91 eddy covariance flux sites across the globe (R2 = 0.74, Root Mean Square Error = 1.92 g C m-2 d-1). Our fine-resolution GPP estimates showed reasonable spatial and seasonal variations across the globe and fully captured both seasonal cycles and spatial patterns present in our coarse-resolution (1°) GPP estimates based on coarse-resolution SIF data directly aggregated from discrete OCO-2 soundings. SIF-GPP relationships with different forms could lead to significant differences in annual GPP particularly in the tropics. Our ensemble global annual GPP estimate (135.5 ± 8.8 Pg C yr-1) is between the median estimate of non-process based methods and the median estimate of process-based models. Our GPP estimates showed interannual variability in many regions and exhibited increasing trends in many parts of the globe particularly in the Northern Hemisphere. With the availability of high-quality, gridded SIF observations from space (e.g., TROPOMI, FLEX), our novel approach does not rely on any other input data (e.g., climate data, soil properties) and therefore can map GPP solely based on satellite SIF observations and potentially lead to more accurate GPP estimates at regional to global scales. The use of a universal SIF-GPP relationship versus biome-specific relationships can also avoid the uncertainty associated with land cover maps. Our novel, independent GPP product (GOSIF GPP), freely available at our data repository, will be valuable for studying photosynthesis, carbon cycle, agricultural production, and ecosystem responses to climate change and disturbances, informing ecosystem management, and benchmarking terrestrial biosphere and Earth system models.
BibTeX:
@article{Li2019,
  author = {Li, Xing and Xiao, Jingfeng},
  title = {Mapping photosynthesis solely from solar-induced chlorophyll fluorescence: A global, fine-resolution dataset of gross primary production derived from OCO-2},
  journal = {Remote Sensing},
  year = {2019},
  volume = {11},
  number = {21},
  pages = {2563},
  url = {https://www.mdpi.com/2072-4292/11/21/2563},
  doi = {10.3390/rs11212563}
}
Lian J, Bréon FM, Broquet G, Scott Zaccheo T, Dobler J, Ramonet M, Staufer J, Santaren D, Xueref-Remy I and Ciais P (2019), "Analysis of temporal and spatial variability of atmospheric CO2 concentration within Paris from the GreenLITE™ laser imaging experiment", Atmospheric Chemistry and Physics., nov, 2019. Vol. 19(22), pp. 13809-13825. Copernicus GmbH.
Abstract: In 2015, the Greenhouse gas Laser Imaging Tomography Experiment (GreenLITE™) measurement system was deployed for a long-duration experiment in the center of Paris, France. The system measures near-surface atmospheric CO2 concentrations integrated along 30 horizontal chords ranging in length from 2.3 to 5.2 km and covering an area of 25 km2 over the complex urban environment. In this study, we use this observing system together with six conventional in situ point measurements and the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) and two urban canopy schemes (Urban Canopy Model-UCM; Building Effect Parameterization-BEP) at a horizontal resolution of 1 km to analyze the temporal and spatial variations in CO2 concentrations within the city of Paris and its vicinity for the 1-year period spanning December 2015 to November 2016. Such an analysis aims at supporting the development of CO2 atmospheric inversion systems at the city scale. Results show that both urban canopy schemes in the WRF-Chem model are capable of reproducing the seasonal cycle and most of the synoptic variations in the atmospheric CO2 point measurements over the suburban areas as well as the general corresponding spatial differences in CO2 concentration that span the urban area. However, within the city, there are larger discrepancies between the observations and the model results with very distinct features during winter and summer. During winter, the GreenLITE™ measurements clearly demonstrate that one urban canopy scheme (BEP) provides a much better description of temporal variations and horizontal differences in CO2 concentrations than the other (UCM) does. During summer, much larger CO2 horizontal differences are indicated by the GreenLITE™ system than both the in situ measurements and the model results, with systematic east-west variations.
BibTeX:
@article{Lian2019,
  author = {Lian, Jinghui and Bréon, François Marie and Broquet, Grégoire and Scott Zaccheo, T. and Dobler, Jeremy and Ramonet, Michel and Staufer, Johannes and Santaren, Diego and Xueref-Remy, Irène and Ciais, Philippe},
  title = {Analysis of temporal and spatial variability of atmospheric CO2 concentration within Paris from the GreenLITE™ laser imaging experiment},
  journal = {Atmospheric Chemistry and Physics},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {19},
  number = {22},
  pages = {13809--13825},
  doi = {10.5194/acp-19-13809-2019}
}
Lin M, Malyshev S, Shevliakova E, Paulot F, Horowitz LW, Fares S, Mikkelsen TN and Zhang L (2019), "Sensitivity of Ozone Dry Deposition to Ecosystem-Atmosphere Interactions: A Critical Appraisal of Observations and Simulations", Global Biogeochemical Cycles., oct, 2019. Vol. 33(10), pp. 1264-1288. American Geophysical Union (AGU).
Abstract: The response of ozone (O3) dry deposition to ecosystem-atmosphere interactions is poorly understood but is central to determining the potential for extreme pollution events under current and future climate conditions. Using observations and an interactive dry deposition scheme within two dynamic vegetation land models (Geophysical Fluid Dynamics Laboratory LM3.0/LM4.0) driven by observation-based meteorological forcings over 1948–2014, we investigate the factors controlling seasonal and interannual variability (IAV) in O3 deposition velocities (Vd,O3). Stomatal activity in this scheme is determined mechanistically, depending on phenology, soil moisture, vapor pressure deficit, and CO2 concentration. Soil moisture plays a key role in modulating the observed and simulated Vd,O3 seasonal changes over evergreen forests in Mediterranean Europe, South Asia, and the Amazon. Analysis of multiyear observations at forest sites in Europe and North America reveals drought stress to reduce Vd,O3 by ˜50%. Both LM3.0 and LM4.0 capture the observed Vd,O3 decreases due to drought; however, IAV is weaker by a factor of 2 in LM3.0 coupled to atmospheric models, particularly in regions with large precipitation biases. IAV in summertime Vd,O3 to forests, driven primarily by the stomatal pathway, is largest (15–35%) in semiarid regions of western Europe, eastern North America, and northeastern China. Monthly mean Vd,O3 for the highest year is 2 to 4 times that of the lowest, with significant implications for surface O3 variability and extreme events. Using Vd,O3 from LM4.0 in an atmospheric chemistry model improves the simulation of surface O3 abundance and spatial variability (reduces mean biases by ˜10 ppb) relative to the widely used Wesely scheme.
BibTeX:
@article{Lin2019,
  author = {Lin, Meiyun and Malyshev, Sergey and Shevliakova, Elena and Paulot, Fabien and Horowitz, Larry W. and Fares, Silvano and Mikkelsen, Teis N. and Zhang, Leiming},
  title = {Sensitivity of Ozone Dry Deposition to Ecosystem-Atmosphere Interactions: A Critical Appraisal of Observations and Simulations},
  journal = {Global Biogeochemical Cycles},
  publisher = {American Geophysical Union (AGU)},
  year = {2019},
  volume = {33},
  number = {10},
  pages = {1264--1288},
  doi = {10.1029/2018GB006157}
}
Liu Y, Piao S, Gasser T, Ciais P, Yang H, Wang H, Keenan TF, Huang M, Wan S, Song J, Wang K, Janssens IA, Peñuelas J, Huntingford C, Wang X, Altaf Arain M, Fang Y, Fisher JB, Huang M, Huntzinger DN, Ito A, Jain AK, Mao J, Michalak AM, Peng C, Poulter B, Schwalm C, Shi X, Tian H, Wei Y, Zeng N, Zhu Q and Wang T (2019), "Field-experiment constraints on the enhancement of the terrestrial carbon sink by CO2 fertilization", Nature Geoscience., sep, 2019. Vol. 12(10), pp. 809-814. Springer Science and Business Media LLC.
Abstract: Clarifying how increased atmospheric CO2 concentration (eCO2) contributes to accelerated land carbon sequestration remains important since this process is the largest negative feedback in the coupled carbon–climate system. Here, we constrain the sensitivity of the terrestrial carbon sink to eCO2 over the temperate Northern Hemisphere for the past five decades, using 12 terrestrial ecosystem models and data from seven CO2 enrichment experiments. This constraint uses the heuristic finding that the northern temperate carbon sink sensitivity to eCO2 is linearly related to the site-scale sensitivity across the models. The emerging data-constrained eCO2 sensitivity is 0.64 ± 0.28 PgC yr−1 per hundred ppm of eCO2. Extrapolating worldwide, this northern temperate sensitivity projects the global terrestrial carbon sink to increase by 3.5 ± 1.9 PgC yr−1 for an increase in CO2 of 100 ppm. This value suggests that CO2 fertilization alone explains most of the observed increase in global land carbon sink since the 1960s. More CO2 enrichment experiments, particularly in boreal, arctic and tropical ecosystems, are required to explain further the responsible processes.
BibTeX:
@article{Liu2019,
  author = {Liu, Yongwen and Piao, Shilong and Gasser, Thomas and Ciais, Philippe and Yang, Hui and Wang, Han and Keenan, Trevor F. and Huang, Mengtian and Wan, Shiqiang and Song, Jian and Wang, Kai and Janssens, Ivan A. and Peñuelas, Josep and Huntingford, Chris and Wang, Xuhui and Altaf Arain, Muhammad and Fang, Yuanyuan and Fisher, Joshua B. and Huang, Maoyi and Huntzinger, Deborah N. and Ito, Akihiko and Jain, Atul K. and Mao, Jiafu and Michalak, Anna M. and Peng, Changhui and Poulter, Benjamin and Schwalm, Christopher and Shi, Xiaoying and Tian, Hanqin and Wei, Yaxing and Zeng, Ning and Zhu, Qiuan and Wang, Tao},
  title = {Field-experiment constraints on the enhancement of the terrestrial carbon sink by CO2 fertilization},
  journal = {Nature Geoscience},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {12},
  number = {10},
  pages = {809--814},
  doi = {10.1038/s41561-019-0436-1}
}
Lognoul M, Debacq A, De Ligne A, Dumont B, Manise T, Bodson B, Heinesch B and Aubinet M (2019), "N 2 O flux short-term response to temperature and topsoil disturbance in a fertilized crop: An eddy covariance campaign", Agricultural and Forest Meteorology., jun, 2019. Vol. 271, pp. 193-206. Elsevier BV.
Abstract: Using the eddy covariance technique, half-hourly N 2 O fluxes were measured over a sugar beet crop (ICOS Station, Lonzée, BE) from fertilization to harvest. Several parameters of the data quality control tests were adapted to suit the characteristics of N 2 O. No u* filtering threshold could be seen for N 2 O fluxes; therefore, it was determined based on CO 2 data. The uncertainty of N 2 O fluxes was assessed for several aspects of data treatment (total random uncertainty, spectral correction, u* filtering, gap-filling), which were combined to determine the uncertainty of the N 2 O budget. Between fertilization and harvest, the crop emitted 1.83 (± 0.21) kg N 2 O-N ha −1 corresponding to 1.2% of N supplies. Flux variability was characterized by three episodes of high emissions across the experiment, interspersed with lower background fluxes. These peak events were driven by soil moisture and temperature, dependent on the time-scale. Soil water content at 5 cm was identified as the single trigger for N 2 O emission peaks given sufficient N availability, while intraday oscillations were positively correlated to the variations in surface temperature rather than deeper soil temperatures. For the first time, an inhibiting and short-term effect of topsoil disturbance (seed-bed preparation) on N 2 O fluxes was recorded, which interrupted the peak that followed fertilization, and delayed the start of the next high emission episode. This observation, along with the synchronicity found between surface temperature and diel oscillations of N 2 O fluxes, supports the hypothesis of a N 2 O-producing microbial community located in the topmost soil layer. Given that a third of the overall N 2 O emissions during the measurement campaign occurred between fertilization and seed-bed preparation, further investigation into the timing of farming operations as mitigation strategies is needed. The contribution of N 2 O emissions to the net greenhouse gas balance (which comprises CO 2 and N 2 O fluxes) was estimated at between 20 and 66%. Our results stress the importance of including nitrous oxide when measuring gas exchanges in fertilized crops, and to do so at high temporal resolution for improved estimates.
BibTeX:
@article{Lognoul2019,
  author = {Lognoul, M. and Debacq, A. and De Ligne, A. and Dumont, B. and Manise, T. and Bodson, B. and Heinesch, B. and Aubinet, M.},
  title = {N 2 O flux short-term response to temperature and topsoil disturbance in a fertilized crop: An eddy covariance campaign},
  journal = {Agricultural and Forest Meteorology},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {271},
  pages = {193--206},
  doi = {10.1016/j.agrformet.2019.02.033}
}
Lupon A, Denfeld BA, Laudon H, Leach J, Karlsson J and Sponseller RA (2019), "Groundwater inflows control patterns and sources of greenhouse gas emissions from streams", Limnology and Oceanography., jul, 2019. Vol. 64(4), pp. 1545-1557.
Abstract: Headwater streams can be important sources of carbon dioxide (CO2) and methane (CH4) to the atmosphere. However, the influence of groundwater–stream connectivity on the patterns and sources of carbon (C) gas evasion is still poorly understood. We explored these connections in the boreal landscape through a detailed study of a 1.4 km lake outlet stream that is hydrologically fed by multiple topographically driven groundwater input zones. We measured stream and groundwater dissolved organic C (DOC), CO2, and CH4 concentrations every 50 m biweekly during the ice-free period and estimated in-stream C gas production through a mass balance model and independent estimates of aquatic metabolism. The spatial pattern of C gas concentrations was consistent over time, with peaks of both CH4 and CO2 concentrations occurring after each groundwater input zone. Moreover, lateral C gas inputs from riparian soils were the major source of CO2 and CH4 to the stream. DOC mineralization and CH4 oxidation within the stream accounted for 17–51% of stream CO2 emissions, and this contribution was the greatest during relatively higher flows. Overall, our results illustrate how the nature and arrangement of groundwater flowpaths can organize patterns of stream C concentrations, transformations, and emissions by acting as a direct source of gases and by supplying organic substrates that fuel aquatic metabolism. Hence, refined assessments of how catchment structure influences the timing and magnitude of groundwater–stream connections are crucial for mechanistically understanding and scaling C evasion rates from headwaters.
BibTeX:
@article{Lupon2019,
  author = {Lupon, Anna and Denfeld, Blaize A. and Laudon, Hjalmar and Leach, Jason and Karlsson, Jan and Sponseller, Ryan A.},
  title = {Groundwater inflows control patterns and sources of greenhouse gas emissions from streams},
  journal = {Limnology and Oceanography},
  year = {2019},
  volume = {64},
  number = {4},
  pages = {1545--1557},
  url = {http://doi.wiley.com/10.1002/lno.11134},
  doi = {10.1002/lno.11134}
}
Macovei VA, Torres-Valdés S, Hartman SE, Schuster U, Moore CM, Brown PJ, Hydes DJ and Sanders RJ (2019), "Temporal Variability in the Nutrient Biogeochemistry of the Surface North Atlantic: 15 Years of Ship of Opportunity Data", Global Biogeochemical Cycles., dec, 2019. Vol. 33(12), pp. 1674-1692. American Geophysical Union (AGU).
Abstract: Ocean biological processes play an important role in the global carbon cycle via the production of organic matter and its subsequent export. Often, this flux is assumed to be in steady state; however, it is dependent on nutrients introduced to surface waters via multiple mechanisms, some of which are likely to exhibit both intra-annual and interannual variability leading to comparable variability in ocean carbon uptake. Here we test this variability using surface (5 m) inorganic nutrient concentrations from voluntary observing ships and satellite-derived estimates of chlorophyll and net primary production. At lower latitudes, the seasonality is small, and the monthly averages of nitrate:phosphate are lower than the canonical 16:1 Redfield ratio, implying nitrogen limitation, a situation confirmed via a series of nutrient limitation experiments conducted between Bermuda and Puerto Rico. The nutrient seasonal cycle is more pronounced at higher latitudes, with clear interannual variability. Over a large area of the midlatitude North Atlantic, the winters of 2009/2010 and 2010/2011 had nitrate values more than 1μmol L−1 higher than the 2002–2017 average, suggesting that during this period, the system may have shifted to phosphorus limitation. This nitrate increase meant that, in the region between 31° and 39° N, new production calculated from nitrate uptake was 20.5g C m−2 in 2010, more than four times higher than the median value of the whole observing period. Overall, we suggest that substantial variability in nutrient concentrations and biological carbon uptake occurs in the North Atlantic with interannual variability apparent over a number of different time scales.
BibTeX:
@article{Macovei2019,
  author = {Macovei, V. A. and Torres-Valdés, S. and Hartman, S. E. and Schuster, U. and Moore, C. M. and Brown, P. J. and Hydes, D. J. and Sanders, R. J.},
  title = {Temporal Variability in the Nutrient Biogeochemistry of the Surface North Atlantic: 15 Years of Ship of Opportunity Data},
  journal = {Global Biogeochemical Cycles},
  publisher = {American Geophysical Union (AGU)},
  year = {2019},
  volume = {33},
  number = {12},
  pages = {1674--1692},
  doi = {10.1029/2018GB006132}
}
Mäkelä J, Knauer J, Aurela M, Black A, Heimann M, Kobayashi H, Lohila A, Mammarella I, Margolis H, Markkanen T, Susiluoto J, Thum T, Viskari T, Zaehle S and Aalto T (2019), "Parameter calibration and stomatal conductance formulation comparison for boreal forests with adaptive population importance sampler in the land surface model JSBACH", Geoscientific Model Development., sep, 2019. Vol. 12(9), pp. 4075-4098. Copernicus GmbH.
Abstract: We calibrated the JSBACH model with six different stomatal conductance formulations using measurements from 10 FLUXNET coniferous evergreen sites in the boreal zone. The parameter posterior distributions were generated by the adaptive population importance sampler (APIS); then the optimal values were estimated by a simple stochastic optimisation algorithm. The model was constrained with in situ observations of evapotranspiration (ET) and gross primary production (GPP). We identified the key parameters in the calibration process. These parameters control the soil moisture stress function and the overall rate of carbon fixation. The JSBACH model was also modified to use a delayed effect of temperature for photosynthetic activity in spring. This modification enabled the model to correctly reproduce the springtime increase in GPP for all conifer sites used in this study. Overall, the calibration and model modifications improved the coefficient of determination and the model bias for GPP with all stomatal conductance formulations. However, only the coefficient of determination was clearly improved for ET. The optimisation resulted in best performance by the Bethy, Ball-Berry, and the Friend and Kiang stomatal conductance models. We also optimised the model during a drought event at a Finnish Scots pine forest site. This optimisation improved the model behaviour but resulted in significant changes to the parameter values except for the unified stomatal optimisation model (USO). Interestingly, the USO demonstrated the best performance during this event.
BibTeX:
@article{Maekelae2019,
  author = {Mäkelä, Jarmo and Knauer, Jürgen and Aurela, Mika and Black, Andrew and Heimann, Martin and Kobayashi, Hideki and Lohila, Annalea and Mammarella, Ivan and Margolis, Hank and Markkanen, Tiina and Susiluoto, Jouni and Thum, Tea and Viskari, Toni and Zaehle, Sönke and Aalto, Tuula},
  title = {Parameter calibration and stomatal conductance formulation comparison for boreal forests with adaptive population importance sampler in the land surface model JSBACH},
  journal = {Geoscientific Model Development},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {12},
  number = {9},
  pages = {4075--4098},
  doi = {10.5194/gmd-12-4075-2019}
}
Mäki M, Aaltonen H, Heinonsalo J, Hellén H, Pumpanen J and Bäck J (2019), "Boreal forest soil is a significant and diverse source of volatile organic compounds", Plant and Soil., may, 2019. Vol. 441(1-2), pp. 89-110. Springer Science and Business Media LLC.
Abstract: Aims: Vegetation emissions of volatile organic compounds (VOCs) are intensively studied world-wide, because oxidation products of VOCs contribute to atmospheric processes. The overall aim of this study was to identify and quantify the VOCs that originate from boreal podzolized forest soil at different depths, in addition to studying the association of VOC concentrations with VOC and CO2 fluxes from the boreal forest floor. Methods: This is the first published study that measures belowground VOC concentrations at different depths in a podzol soil combined with simultaneous flux measurements from the boreal forest floor. The VOC concentrations were determined by sampling VOCs from air inside soil layers using the gas collectors and adsorbent tubes. Forest floor VOC fluxes were determined using a dynamic enclosure technique. All the VOC samples were analysed using a thermal desorption-gas chromatograph-mass spectrometer. Results: More than 50 VOCs, dominated by monoterpenes and sesquiterpenes, were detected in the air space in the soil during two measurement campaigns. The O-horizon was a significant monoterpene source, because it contained fresh isoprenoid-rich litter. Belowground monoterpene concentrations were largely decoupled from forest floor monoterpene fluxes; thus, it seems that production processes and storages of VOCs partly differ from those VOCs that are simultaneously released from the forest floor. Both fluxes and concentrations of the monoterpenes and sesquiterpenes correlated with the CO2 fluxes in autumn, indicating that VOC release was driven by microbial activity. Conclusions: This is the first study where below-ground VOC concentrations were quantified in situ, and for this reason, this study provides valuable insights to the VOC sources present in soils.
BibTeX:
@article{Maeki2019,
  author = {Mäki, Mari and Aaltonen, Hermanni and Heinonsalo, Jussi and Hellén, Heidi and Pumpanen, Jukka and Bäck, Jaana},
  title = {Boreal forest soil is a significant and diverse source of volatile organic compounds},
  journal = {Plant and Soil},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {441},
  number = {1-2},
  pages = {89--110},
  doi = {10.1007/s11104-019-04092-z}
}
Männistö E, Korrensalo A, Alekseychik P, Mammarella I, Peltola O, Vesala T and Tuittila ES (2019), "Multi-year methane ebullition measurements from water and bare peat surfaces of a patterned boreal bog", Biogeosciences., jun, 2019. Vol. 16(11), pp. 2409-2421. Copernicus GmbH.
Abstract: We measured methane ebullition from a patterned boreal bog situated in the Siikaneva wetland complex in southern Finland. Measurements were conducted on water (W) and bare peat surfaces (BP) in three growing seasons (2014-2016) using floating gas traps. The volume of the trapped gas was measured weekly, and methane and carbon dioxide (CO2) concentrations of bubbles were analysed from fresh bubble samples that were collected separately. We applied a mixed-effect model to quantify the effect of the environmental controlling factors on the ebullition. Ebullition was higher from W than from BP, and more bubbles were released from open water (OW) than from the water's edge (EW). On average, ebullition rate was the highest in the wettest year (2016) and ranged between 0 and 253 mgm-2 d-1 with a median of 2 mg m-2 d-1, 0 and 147 mgm-2 d-1 with a median of 3 mgm-2 d-1, and 0 and 186 mgm-2 d-1 with a median of 28 mgm-2 d-1 in 2014, 2015, and 2016, respectively. Ebullition increased together with increasing peat temperature, weekly air temperature sum and atmospheric pressure, and decreasing water table (WT). Methane concentration in the bubbles released from W was 15-20 times higher than the CO2 concentration, and from BP it was 10 times higher. The proportion of ebullition fluxes upscaled to ecosystem level for the peak season was 2 %-8% and 2 %-5% of the total flux measured with eddy covariance technique and with chambers and gas traps, respectively. Thus, the contribution of methane ebullition from wet non-vegetated surfaces of the bog to the total ecosystemscale methane emission appeared to be small.
BibTeX:
@article{Maennistoe2019,
  author = {Männistö, Elisa and Korrensalo, Aino and Alekseychik, Pavel and Mammarella, Ivan and Peltola, Olli and Vesala, Timo and Tuittila, Eeva Stiina},
  title = {Multi-year methane ebullition measurements from water and bare peat surfaces of a patterned boreal bog},
  journal = {Biogeosciences},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {16},
  number = {11},
  pages = {2409--2421},
  doi = {10.5194/bg-16-2409-2019}
}
Martinez MA, Woodcroft BJ, Ignacio Espinoza JC, Zayed AA, Singleton CM, Boyd JA, Li YF, Purvine S, Maughan H, Hodgkins SB, Anderson D, Sederholm M, Temperton B, Bolduc B, Saleska SR, Tyson GW and Rich VI (2019), "Discovery and ecogenomic context of a global Caldiserica-related phylum active in thawing permafrost, Candidatus Cryosericota phylum nov., Ca. Cryosericia class nov., Ca. Cryosericales ord. nov., Ca. Cryosericaceae fam. nov., comprising the four species Cryosericum septentrionale gen. nov. sp. nov., Ca. C. hinesii sp. nov., Ca. C. odellii sp. nov., Ca. C. terrychapinii sp. nov.", Systematic and Applied Microbiology., jan, 2019. Vol. 42(1), pp. 54-66. Elsevier BV.
Abstract: The phylum Caldiserica was identified from the hot spring 16S rRNA gene lineage ‘OP5' and named for the sole isolate Caldisericum exile, a hot spring sulfur-reducing chemoheterotroph. Here we characterize 7 Caldiserica metagenome-assembled genomes (MAGs) from a thawing permafrost site in Stordalen Mire, Arctic Sweden. By 16S rRNA and marker gene phylogenies, and average nucleotide and amino acid identities, these Stordalen Mire Caldiserica (SMC) MAGs form part of a divergent clade from C. exile. Genome and meta-transcriptome and proteome analyses suggest that unlike Caldisericum, the SMCs (i) are carbohydrate- and possibly amino acid fermenters that can use labile plant compounds and peptides, and (ii) encode adaptations to low temperature. The SMC clade rose to community dominance within permafrost, with a peak metagenome-based relative abundance of ∼60%. It was also physiologically active in the upper seasonally-thawed soil. Beyond Stordalen Mire, analysis of 16S rRNA gene surveys indicated a global distribution of this clade, predominantly in anaerobic, carbon-rich and cold environments. These findings establish the SMCs as four novel phenotypically and ecologically distinct species within a single novel genus, distinct from C. exile clade at the phylum level. The SMCs are thus part of a novel cold-habitat phylum for an understudied, globally-distributed superphylum encompassing the Caldiserica. We propose the names Candidatus Cryosericota phylum nov., Ca. Cryosericia class nov., Ca. Cryosericales ord. nov., Ca. Cryosericaceae fam. nov., Ca. Cryosericum gen. nov., Ca. Cryosericum septentrionale sp. nov., Ca. C. hinesii sp. nov., Ca. C. odellii sp. nov., and Ca. C. terrychapinii sp. nov.
BibTeX:
@article{Martinez2019,
  author = {Martinez, Miguel A. and Woodcroft, Ben J. and Ignacio Espinoza, Julio C. and Zayed, Ahmed A. and Singleton, Caitlin M. and Boyd, Joel A. and Li, Yueh Fen and Purvine, Samuel and Maughan, Heather and Hodgkins, Suzanne B. and Anderson, Darya and Sederholm, Maya and Temperton, Ben and Bolduc, Benjamin and Saleska, Scott R. and Tyson, Gene W. and Rich, Virginia I.},
  title = {Discovery and ecogenomic context of a global Caldiserica-related phylum active in thawing permafrost, Candidatus Cryosericota phylum nov., Ca. Cryosericia class nov., Ca. Cryosericales ord. nov., Ca. Cryosericaceae fam. nov., comprising the four species Cryosericum septentrionale gen. nov. sp. nov., Ca. C. hinesii sp. nov., Ca. C. odellii sp. nov., Ca. C. terrychapinii sp. nov.},
  journal = {Systematic and Applied Microbiology},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {42},
  number = {1},
  pages = {54--66},
  doi = {10.1016/j.syapm.2018.12.003}
}
McGloin R, Šigut L, Fischer M, Foltýnová L, Chawla S, Trnka M, Pavelka M and Marek MV (2019), "Available Energy Partitioning During Drought at Two Norway Spruce Forests and a European Beech Forest in Central Europe", Journal of Geophysical Research: Atmospheres., apr, 2019. Vol. 124(7), pp. 3726-3742. American Geophysical Union (AGU).
Abstract: Partitioning of the available energy at the Earth's surface into the latent heat (LE) and sensible heat (H) fluxes has important climatological, hydrological, and physiological implications. With the prediction of more frequent droughts in central Europe in the near future, there is a particular need to understand variability in available energy partitioning under drought stress conditions at forest ecosystems that are common in the region, such as Norway spruce and European beech. Using eddy covariance measurements from two Norway spruce sites with contrasting wet and dry climates and one European beech site in the Czech Republic, it was found that the proportion of energy partitioned into H was greater at the spruce sites than at the beech site in all conditions during the growing season. The difference between the mean midday (09:00–15:00) β values for low stress conditions and drought stress conditions was much smaller at the European beech site (β = 1.04 vs. 1.11) than at the wet (β = 1.52 vs. 2.50) and dry Norway spruce (β = 1.80 vs. 2.70) sites, indicating that β was not as sensitive to drought stress at the European beech site as at the Norway spruce sites. The high β values and enhancement of drought conditions through positive feedback processes at Norway spruce stands mean that the potential substitution of Norway spruce monocultures with mixed broadleaf-coniferous stands in central Europe will likely lessen the severity of droughts and heat waves in the region.
BibTeX:
@article{McGloin2019,
  author = {McGloin, Ryan and Šigut, Ladislav and Fischer, Milan and Foltýnová, Lenka and Chawla, Shilpi and Trnka, Miroslav and Pavelka, Marian and Marek, Michal V.},
  title = {Available Energy Partitioning During Drought at Two Norway Spruce Forests and a European Beech Forest in Central Europe},
  journal = {Journal of Geophysical Research: Atmospheres},
  publisher = {American Geophysical Union (AGU)},
  year = {2019},
  volume = {124},
  number = {7},
  pages = {3726--3742},
  doi = {10.1029/2018JD029490}
}
Monteil G, Broquet G, Scholze M, Lang M, Karstens U, Gerbig C, Koch F-T, Smith N, Thompson R, White E, Meesters A, Ciais P, Ganesan A, Manning A, Mischurow M, Peters W, Peylin P, Tarniewicz J, Rigby M, Rödenbeck C, Vermeulen A and Walton E (2019), "The regional EUROpean atmospheric transport inversion COMparison, EUROCOM: first results on European wide terrestrial carbon fluxes for the period 2006–2015", Atmospheric Chemistry and Physics Discussions., dec, 2019. , pp. 1-40. Copernicus GmbH.
Abstract: Atmospheric inversions have been used for the past two decades to derive large scale constraints on the sources and sinks of CO 2 into the atmosphere. The development of high density in-situ surface observation networks, such as ICOS in Europe, enables in theory inversions at a resolution close to the country scale in Europe. This has led to the development of many regional inversion systems capable of assimilating these high-resolution data, in Europe and elsewhere. The EURO-COM project (EUROpean atmospheric transport inversion COMparison) is a collaboration between seven European research 5 institutes, which aims at producing a collective assessment of the net carbon flux between the terrestrial ecosystems and the atmosphere in Europe for the period 2006-2015. It aims in particular at investigating the capacity of the inversions to deliver consistent flux estimates from the country scale up to the continental scale. The project participants were provided with a common database of in-situ observed CO 2 concentrations (including the observation sites that are now part of the ICOS network), and were tasked with providing their best estimate of the net terrestrial 10 carbon flux for that period, and for a large domain covering the entire European Union. The inversion systems differ by the transport model, the inversion approach and the choice of observation and prior constraints, enabling us to widely explore the space of uncertainties. This paper describes the intercomparison protocol and the participating systems, and it presents the first results from a reference set of inversions, at the continental scale and in four large regions. At the continental scale, the regional inversions 15 1 https://doi. support the assumption that European ecosystems are a relatively small sink (-0.21±0.2 PgC/year). We find that the convergence of the regional inversions at this scale is not better than that obtained in state-of-the-art global inversions. However, more robust results are obtained for sub-regions within Europe, and in these areas with dense observational coverage, the objective of delivering robust country scale flux estimates appears achievable in the near future.
BibTeX:
@article{Monteil2019,
  author = {Monteil, Guillaume and Broquet, Grégoire and Scholze, Marko and Lang, Matthew and Karstens, Ute and Gerbig, Christof and Koch, Frank-Thomas and Smith, Naomi and Thompson, Rona and White, Emily and Meesters, Antoon and Ciais, Philippe and Ganesan, Anita and Manning, Alistair and Mischurow, Michael and Peters, Wouter and Peylin, Philippe and Tarniewicz, Jerôme and Rigby, Matt and Rödenbeck, Christian and Vermeulen, Alex and Walton, Evie},
  title = {The regional EUROpean atmospheric transport inversion COMparison, EUROCOM: first results on European wide terrestrial carbon fluxes for the period 2006–2015},
  journal = {Atmospheric Chemistry and Physics Discussions},
  publisher = {Copernicus GmbH},
  year = {2019},
  pages = {1--40},
  doi = {10.5194/acp-2019-1008}
}
Morel X, Decharme B, Delire C, Krinner G, Lund M, Hansen BU and Mastepanov M (2019), "A New Process-Based Soil Methane Scheme: Evaluation Over Arctic Field Sites With the ISBA Land Surface Model", Journal of Advances in Modeling Earth Systems., jan, 2019. Vol. 11(1), pp. 293-326. American Geophysical Union (AGU).
Abstract: Permafrost soils and arctic wetlands methane emissions represent an important challenge for modeling the future climate. Here we present a process-based model designed to correctly represent the main thermal, hydrological, and biogeochemical processes related to these emissions for general land surface modeling. We propose a new multilayer soil carbon and gas module within the Interaction Soil-Biosphere-Atmosphere (ISBA) land-surface model (LSM). This module represents carbon pools, vertical carbon dynamics, and both oxic and anoxic organic matter decomposition. It also represents the soil gas processes for CH 4 , CO 2 , and O 2 through the soil column. We base CH 4 production and oxydation on an O 2 control instead of the classical water table level strata approach used in state-of-the-art soil CH 4 models. We propose a new parametrization of CH 4 oxydation using recent field experiments and use an explicit O 2 limitation for soil carbon decomposition. Soil gas transport is computed explicitly, using a revisited formulation of plant-mediated transport, a new representation of gas bulk diffusivity in porous media closer to experimental observations, and an innovative advection term for ebullition. We evaluate this advanced model on three climatically distinct sites : two in Greenland (Nuuk and Zackenberg) and one in Siberia (Chokurdakh). The model realistically reproduces methane and carbon dioxide emissions from both permafrosted and nonpermafrosted sites. The evolution and vertical characteristics of the underground processes leading to these fluxes are consistent with current knowledge. Results also show that physics is the main driver of methane fluxes, and the main source of variability appears to be the water table depth.
BibTeX:
@article{Morel2019,
  author = {Morel, X. and Decharme, B. and Delire, C. and Krinner, G. and Lund, M. and Hansen, B. U. and Mastepanov, M.},
  title = {A New Process-Based Soil Methane Scheme: Evaluation Over Arctic Field Sites With the ISBA Land Surface Model},
  journal = {Journal of Advances in Modeling Earth Systems},
  publisher = {American Geophysical Union (AGU)},
  year = {2019},
  volume = {11},
  number = {1},
  pages = {293--326},
  doi = {10.1029/2018MS001329}
}
Nangini C, Peregon A, Ciais P, Weddige U, Vogel F, Wang J, Bréon FM, Bachra S, Wang Y, Gurney K, Yamagata Y, Appleby K, Telahoun S, Canadell JG, Grübler A, Dhakal S and Creutzig F (2019), "A global dataset of co2 emissions and ancillary data related to emissions for 343 cities", Scientific Data., jan, 2019. Vol. 6(1) Springer Science and Business Media LLC.
Abstract: We present a global dataset of anthropogenic carbon dioxide (CO2) emissions for 343 cities. The dataset builds upon data from CDP (187 cities, few in developing countries), the Bonn Center for Local Climate Action and Reporting (73 cities, mainly in developing countries), and data collected by Peking University (83 cities in China). The CDP data being self-reported by cities, we applied quality control procedures, documented the type of emissions and reporting method used, and made a correction to separate CO2 emissions from those of other greenhouse gases. Further, a set of ancillary data that have a direct or potentially indirect impact on CO2 emissions were collected from other datasets (e.g. socio-economic and traffic indices) or calculated (climate indices, urban area expansion), then combined with the emission data. We applied several quality controls and validation comparisons with independent datasets. The dataset presented here is not intended to be comprehensive or a representative sample of cities in general, as the choice of cities is based on self-reporting not a designed sampling procedure.
BibTeX:
@article{Nangini2019,
  author = {Nangini, Cathy and Peregon, Anna and Ciais, Philippe and Weddige, Ulf and Vogel, Felix and Wang, Jun and Bréon, François Marie and Bachra, Simeran and Wang, Yilong and Gurney, Kevin and Yamagata, Yoshiki and Appleby, Kyra and Telahoun, Sara and Canadell, Josep G. and Grübler, Arnulf and Dhakal, Shobhakar and Creutzig, Felix},
  title = {A global dataset of co2 emissions and ancillary data related to emissions for 343 cities},
  journal = {Scientific Data},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {6},
  number = {1},
  doi = {10.1038/sdata.2018.280}
}
Natali SM, Watts JD, Rogers BM, Potter S, Ludwig SM, Selbmann AK, Sullivan PF, Abbott BW, Arndt KA, Birch L, Björkman MP, Bloom AA, Celis G, Christensen TR, Christiansen CT, Commane R, Cooper EJ, Crill P, Czimczik C, Davydov S, Du J, Egan JE, Elberling B, Euskirchen ES, Friborg T, Genet H, Göckede M, Goodrich JP, Grogan P, Helbig M, Jafarov EE, Jastrow JD, Kalhori AA, Kim Y, Kimball JS, Kutzbach L, Lara MJ, Larsen KS, Lee BY, Liu Z, Loranty MM, Lund M, Lupascu M, Madani N, Malhotra A, Matamala R, McFarland J, McGuire AD, Michelsen A, Minions C, Oechel WC, Olefeldt D, Parmentier FJW, Pirk N, Poulter B, Quinton W, Rezanezhad F, Risk D, Sachs T, Schaefer K, Schmidt NM, Schuur EA, Semenchuk PR, Shaver G, Sonnentag O, Starr G, Treat CC, Waldrop MP, Wang Y, Welker J, Wille C, Xu X, Zhang Z, Zhuang Q and Zona D (2019), "Large loss of CO2 in winter observed across the northern permafrost region", Nature Climate Change., oct, 2019. Vol. 9(11), pp. 852-857. Springer Science and Business Media LLC.
Abstract: Recent warming in the Arctic, which has been amplified during the winter1–3, greatly enhances microbial decomposition of soil organic matter and subsequent release of carbon dioxide (CO2)4. However, the amount of CO2 released in winter is not known and has not been well represented by ecosystem models or empirically based estimates5,6. Here we synthesize regional in situ observations of CO2 flux from Arctic and boreal soils to assess current and future winter carbon losses from the northern permafrost domain. We estimate a contemporary loss of 1,662 TgC per year from the permafrost region during the winter season (October–April). This loss is greater than the average growing season carbon uptake for this region estimated from process models (−1,032 TgC per year). Extending model predictions to warmer conditions up to 2100 indicates that winter CO2 emissions will increase 17% under a moderate mitigation scenario—Representative Concentration Pathway 4.5—and 41% under business-as-usual emissions scenario—Representative Concentration Pathway 8.5. Our results provide a baseline for winter CO2 emissions from northern terrestrial regions and indicate that enhanced soil CO2 loss due to winter warming may offset growing season carbon uptake under future climatic conditions.
BibTeX:
@article{Natali2019,
  author = {Natali, Susan M. and Watts, Jennifer D. and Rogers, Brendan M. and Potter, Stefano and Ludwig, Sarah M. and Selbmann, Anne Katrin and Sullivan, Patrick F. and Abbott, Benjamin W. and Arndt, Kyle A. and Birch, Leah and Björkman, Mats P. and Bloom, A. Anthony and Celis, Gerardo and Christensen, Torben R. and Christiansen, Casper T. and Commane, Roisin and Cooper, Elisabeth J. and Crill, Patrick and Czimczik, Claudia and Davydov, Sergey and Du, Jinyang and Egan, Jocelyn E. and Elberling, Bo and Euskirchen, Eugenie S. and Friborg, Thomas and Genet, Hélène and Göckede, Mathias and Goodrich, Jordan P. and Grogan, Paul and Helbig, Manuel and Jafarov, Elchin E. and Jastrow, Julie D. and Kalhori, Aram A.M. and Kim, Yongwon and Kimball, John S. and Kutzbach, Lars and Lara, Mark J. and Larsen, Klaus S. and Lee, Bang Yong and Liu, Zhihua and Loranty, Michael M. and Lund, Magnus and Lupascu, Massimo and Madani, Nima and Malhotra, Avni and Matamala, Roser and McFarland, Jack and McGuire, A. David and Michelsen, Anders and Minions, Christina and Oechel, Walter C. and Olefeldt, David and Parmentier, Frans Jan W. and Pirk, Norbert and Poulter, Ben and Quinton, William and Rezanezhad, Fereidoun and Risk, David and Sachs, Torsten and Schaefer, Kevin and Schmidt, Niels M. and Schuur, Edward A.G. and Semenchuk, Philipp R. and Shaver, Gaius and Sonnentag, Oliver and Starr, Gregory and Treat, Claire C. and Waldrop, Mark P. and Wang, Yihui and Welker, Jeffrey and Wille, Christian and Xu, Xiaofeng and Zhang, Zhen and Zhuang, Qianlai and Zona, Donatella},
  title = {Large loss of CO2 in winter observed across the northern permafrost region},
  journal = {Nature Climate Change},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {9},
  number = {11},
  pages = {852--857},
  doi = {10.1038/s41558-019-0592-8}
}
Ney P, Graf A, Bogena H, Diekkrüger B, Drüe C, Esser O, Heinemann G, Klosterhalfen A, Pick K, Pütz T, Schmidt M, Valler V and Vereecken H (2019), "CO2 fluxes before and after partial deforestation of a Central European spruce forest", Agricultural and Forest Meteorology., aug, 2019. Vol. 274, pp. 61-74. Elsevier BV.
Abstract: A seven year CO2-flux dataset measured in a 70 year old spruce monoculture is presented, of which 22% was deforested three years after the start of the measurements to accelerate regeneration towards natural deciduous vegetation. An eddy covariance (EC) system, mounted on top of a tower within the spruce forest, continuously sampled fluxes of momentum, sensible heat, latent heat and CO2. After clear-cutting, a second EC station with an identical set of instruments was installed inside the deforested area. In total, we examined an EC dataset including three years before (forest) and four years after partial deforestation (forest and deforested). Full time series and annual carbon budgets of the net ecosystem exchange (NEE) and its components gross primary production (GPP) and total ecosystem respiration (Reco) were calculated for both EC sites. Soil respiration was measured with manual chambers on average every month after the deforestation at 75 measurement points in the forest and deforested area. Annual sums of NEE measured above the forest indicated a strong carbon sink of -660 (-535) g C m-2 y-1 with small interannual variability ±78 (72) g C m-2 y-1 (values in brackets including correction for self-heating of the open-path gas analyzer). In the first year after partial deforestation, regrowth on the clearcut consisted mainly of grasses, with beginning of the second year shrubs and young trees became increasingly important. The regrowth of vegetation is reflected in the annual sums of NEE, which decreased from a carbon source of 521 (548) g C m-2 y-1 towards 82 (236) g C m-2 y-1 over the past four years, due to an increase in the magnitude of GPP from 385 (447) to 892 (1036) g C m-2 y-1.
BibTeX:
@article{Ney2019,
  author = {Ney, Patrizia and Graf, Alexander and Bogena, Heye and Diekkrüger, Bernd and Drüe, Clemens and Esser, Odilia and Heinemann, Günther and Klosterhalfen, Anne and Pick, Katharina and Pütz, Thomas and Schmidt, Marius and Valler, Veronika and Vereecken, Harry},
  title = {CO2 fluxes before and after partial deforestation of a Central European spruce forest},
  journal = {Agricultural and Forest Meteorology},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {274},
  pages = {61--74},
  doi = {10.1016/j.agrformet.2019.04.009}
}
Nijp JJ, Metselaar K, Limpens J, Bartholomeus HM, Nilsson MB, Berendse F and van der Zee SE (2019), "High-resolution peat volume change in a northern peatland: Spatial variability, main drivers, and impact on ecohydrology", Ecohydrology., aug, 2019. Vol. 12(6) Wiley.
Abstract: The depth of the groundwater table below the surface and its spatiotemporal variability are major controls on all major biogeophysical processes in northern peatlands, including ecohydrology, carbon balance, and greenhouse gas exchange. In these ecosystems, water table fluctuations are buffered by compression and expansion of peat. Controls on peat volume change and its spatial variability, however, remain elusive, hampering accurate assessment of climate change impact on functioning of peatlands. We therefore (1) analysed patterning of seasonal surface elevation change at high spatial resolution (0.5 m); (2) assessed its relationship with vegetation, geohydrology, and position within the peatland; and (3) quantified the consequences for peatland surface topography and ecohydrology. Changes in surface elevation were monitored using digital close-range photogrammetry along a transect in a northern peatland from after snowmelt up to midgrowing season (May–July). Surface elevation change was substantial and varied spatially from −0.062 to +0.012 m over the measurement period. Spatial patterns of peat volume change were correlated up to 40.8 m. Spatial variation of peat volume change was mainly controlled by changes in water table, and to a lesser extent to vegetation, with peat volume change magnitude increasing from lawn ' hollow ' flark. Our observations suggest that patchiness and vertical variability of peatland surface topography are a function of the groundwater table. In dry conditions, the variability of surface elevation increases and more localized groundwater flows may develop. Consequently, spatially variable peat volume change may enhance peatland water retention and thereby sustain carbon uptake during drought.
BibTeX:
@article{Nijp2019,
  author = {Nijp, Jelmer J. and Metselaar, Klaas and Limpens, Juul and Bartholomeus, Harm M. and Nilsson, Mats B. and Berendse, Frank and van der Zee, Sjoerd E.A.T.M.},
  title = {High-resolution peat volume change in a northern peatland: Spatial variability, main drivers, and impact on ecohydrology},
  journal = {Ecohydrology},
  publisher = {Wiley},
  year = {2019},
  volume = {12},
  number = {6},
  doi = {10.1002/eco.2114}
}
Nilsson E, Rutgersson A, Dingwell A, Björkqvist JV, Pettersson H, Axell L, Nyberg J and Strömstedt E (2019), "Characterization of wave energy potential for the Baltic Sea with focus on the Swedish exclusive economic zone", Energies., feb, 2019. Vol. 12(5), pp. 793.
Abstract: In this study, a third-generation wave model is used to examine the wave power resource for the Baltic Sea region at an unprecedented one-kilometer-scale resolution for the years 1998 to 2013. Special focus is given to the evaluation and description of wave field characteristics for the Swedish Exclusive Economic Zone (SEEZ). It is carried out to provide a more detailed assessment of the potential of waves as a renewable energy resource for the region. The wave energy potential is largely controlled by the distance from the coast and the fetch associated with the prevailing dominant wave direction. The ice cover is also shown to significantly influence the wave power resource, especially in the most northern basins of the SEEZ. For the areas in focus here, the potential annual average wave energy flux reaches 45 MWh/m/year in the two sub-basins with the highest wave energies, but local variations are up to 65 MWh/m/year. The assessment provides the basis for a further detailed identification of potential sites for wave energy converters. An outlook is given for additional aspects studied within a broad multi-disciplinary project to assess the conditions for offshore wave energy conversion within the SEEZ.
BibTeX:
@article{Nilsson2019,
  author = {Nilsson, Erik and Rutgersson, Anna and Dingwell, Adam and Björkqvist, Jan Victor and Pettersson, Heidi and Axell, Lars and Nyberg, Johan and Strömstedt, Erland},
  title = {Characterization of wave energy potential for the Baltic Sea with focus on the Swedish exclusive economic zone},
  journal = {Energies},
  year = {2019},
  volume = {12},
  number = {5},
  pages = {793},
  url = {http://www.mdpi.com/1996-1073/12/5/793},
  doi = {10.3390/en12050793}
}
Nisbet EG, Manning MR, Dlugokencky EJ, Fisher RE, Lowry D, Michel SE, Myhre CL, Platt SM, Allen G, Bousquet P, Brownlow R, Cain M, France JL, Hermansen O, Hossaini R, Jones AE, Levin I, Manning AC, Myhre G, Pyle JA, Vaughn BH, Warwick NJ and White JW (2019), "Very Strong Atmospheric Methane Growth in the 4 Years 2014–2017: Implications for the Paris Agreement", Global Biogeochemical Cycles., mar, 2019. Vol. 33(3), pp. 318-342. American Geophysical Union (AGU).
Abstract: Atmospheric methane grew very rapidly in 2014 (12.7 ± 0.5 ppb/year), 2015 (10.1 ± 0.7 ppb/year), 2016 (7.0 ± 0.7 ppb/year), and 2017 (7.7 ± 0.7 ppb/year), at rates not observed since the 1980s. The increase in the methane burden began in 2007, with the mean global mole fraction in remote surface background air rising from about 1,775 ppb in 2006 to 1,850 ppb in 2017. Simultaneously the 13C/12C isotopic ratio (expressed as δ13CCH4) has shifted, has shifted, now trending negative for more than a decade. The causes of methane's recent mole fraction increase are therefore either a change in the relative proportions (and totals) of emissions from biogenic and thermogenic and pyrogenic sources, especially in the tropics and subtropics, or a decline in the atmospheric sink of methane, or both. Unfortunately, with limited measurement data sets, it is not currently possible to be more definitive. The climate warming impact of the observed methane increase over the past decade, if continued at textgreater5 ppb/year in the coming decades, is sufficient to challenge the Paris Agreement, which requires sharp cuts in the atmospheric methane burden. However, anthropogenic methane emissions are relatively very large and thus offer attractive targets for rapid reduction, which are essential if the Paris Agreement aims are to be attained.
BibTeX:
@article{Nisbet2019,
  author = {Nisbet, E. G. and Manning, M. R. and Dlugokencky, E. J. and Fisher, R. E. and Lowry, D. and Michel, S. E. and Myhre, C. Lund and Platt, S. M. and Allen, G. and Bousquet, P. and Brownlow, R. and Cain, M. and France, J. L. and Hermansen, O. and Hossaini, R. and Jones, A. E. and Levin, I. and Manning, A. C. and Myhre, G. and Pyle, J. A. and Vaughn, B. H. and Warwick, N. J. and White, J. W.C.},
  title = {Very Strong Atmospheric Methane Growth in the 4 Years 2014–2017: Implications for the Paris Agreement},
  journal = {Global Biogeochemical Cycles},
  publisher = {American Geophysical Union (AGU)},
  year = {2019},
  volume = {33},
  number = {3},
  pages = {318--342},
  doi = {10.1029/2018GB006009}
}
Omar AM, Thomas H, Olsen A, Becker M, Skjelvan I and Reverdin G (2019), "Trends of Ocean Acidification and pCO2 in the Northern North Sea, 2003–2015", Journal of Geophysical Research: Biogeosciences., oct, 2019. Vol. 124(10), pp. 3088-3103. American Geophysical Union (AGU).
Abstract: For continental shelf regions, the long-term trend in sea surface carbon dioxide (CO2) partial pressure (pCO2) and rates of ocean acidification are not accurately known. Here, we investigate the decadal trend of observed wintertime pCO2 as well as computed wintertime pH and aragonite saturation state (Ωar) in the northern North Sea, using the first decade long monthly underway data from a voluntary observing ship covering the period 2004–2015. We also evaluate how seawater CO2 chemistry, in response to physical and biological processes, drives variations in the above parameters on seasonal and interannual timescales. In the northern North Sea, pCO2, pH, and Ωar are subject to strong seasonal variations with mean wintertime values of 375 ± 11 μatm, 8.17 ± 0.01, and 1.96 ± 0.05. Dissolved inorganic carbon is found to be the primary driver of both seasonal and interannual changes while total alkalinity and sea surface temperature have secondary effects that reduce the changes produced by dissolved inorganic carbon. Average interannual variations during winter are around 3%, 0.1%, and 2% for pCO2, pH, and Ωar, respectively and slightly larger in the eastern part of the study area (Skagerrak region) than in the western part (North Atlantic Water region). Statistically significant long-term trends were found only in the North Atlantic Water region with mean annual rates of 2.39 ± 0.58 μatm/year, −0.0024 ± 0.001 year-1, and −0.010 ± 0.003 year-1 for pCO2, pH, and Ωar, respectively. The drivers of the observed trends as well as reasons for the lack of statistically significant trends in the Skagerrak region are discussed.
BibTeX:
@article{Omar2019,
  author = {Omar, A. M. and Thomas, H. and Olsen, A. and Becker, M. and Skjelvan, I. and Reverdin, G.},
  title = {Trends of Ocean Acidification and pCO2 in the Northern North Sea, 2003–2015},
  journal = {Journal of Geophysical Research: Biogeosciences},
  publisher = {American Geophysical Union (AGU)},
  year = {2019},
  volume = {124},
  number = {10},
  pages = {3088--3103},
  doi = {10.1029/2018JG004992}
}
Palacz A, Telszewski M, Rehder G and Bittig H (2019), "Training the Next Generation of Marine Biogeochemists", Eos., nov, 2019. Vol. 100 American Geophysical Union (AGU).
Abstract: Early-career scientists came together recently to learn to use a suite of ocean biogeochemical sensors, with the goal of closing the knowledge gap between ocean technology and potential end users.
BibTeX:
@article{Palacz2019,
  author = {Palacz, Artur and Telszewski, Maciej and Rehder, Gregor and Bittig, Henry},
  title = {Training the Next Generation of Marine Biogeochemists},
  journal = {Eos},
  publisher = {American Geophysical Union (AGU)},
  year = {2019},
  volume = {100},
  doi = {10.1029/2019eo136334}
}
Pandey S, Houweling S, Krol M, Aben I, Nechita‐Banda N, Thoning K, Röckmann T, Yin Y, Segers A and Dlugokencky EJ (2019), "Influence of Atmospheric Transport on Estimates of Variability in the Global Methane Burden", Geophysical Research Letters., feb, 2019. Vol. 46(4), pp. 2302-2311.
BibTeX:
@article{Pandey2019,
  author = {Pandey, Sudhanshu and Houweling, Sander and Krol, Maarten and Aben, Ilse and Nechita‐Banda, Narcisa and Thoning, Kirk and Röckmann, Thomas and Yin, Yi and Segers, Arjo and Dlugokencky, Edward J.},
  title = {Influence of Atmospheric Transport on Estimates of Variability in the Global Methane Burden},
  journal = {Geophysical Research Letters},
  year = {2019},
  volume = {46},
  number = {4},
  pages = {2302--2311},
  url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2018GL081092},
  doi = {10.1029/2018GL081092}
}
Peaucelle M, Bacour C, Ciais P, Vuichard N, Kuppel S, Peñuelas J, Belelli Marchesini L, Blanken PD, Buchmann N, Chen J, Delpierre N, Desai AR, Dufrene E, Gianelle D, Gimeno-Colera C, Gruening C, Helfter C, Hörtnagl L, Ibrom A, Joffre R, Kato T, Kolb TE, Law B, Lindroth A, Mammarella I, Merbold L, Minerbi S, Montagnani L, Šigut L, Sutton M, Varlagin A, Vesala T, Wohlfahrt G, Wolf S, Yakir D and Viovy N (2019), "Covariations between plant functional traits emerge from constraining parameterization of a terrestrial biosphere model", Global Ecology and Biogeography., jun, 2019. Vol. 28(9), pp. 1351-1365. Wiley.
Abstract: Aim: The mechanisms of plant trait adaptation and acclimation are still poorly understood and, consequently, lack a consistent representation in terrestrial biosphere models (TBMs). Despite the increasing availability of geo-referenced trait observations, current databases are still insufficient to cover all vegetation types and environmental conditions. In parallel, the growing number of continuous eddy-covariance observations of energy and CO2 fluxes has enabled modellers to optimize TBMs with these data. Past attempts to optimize TBM parameters mostly focused on model performance, overlooking the ecological properties of ecosystems. The aim of this study was to assess the ecological consistency of optimized trait-related parameters while improving the model performances for gross primary productivity (GPP) at sites. Location: Worldwide. Time period: 1992–2012. Major taxa studied: Trees and C3 grasses. Methods: We optimized parameters of the ORCHIDEE model against 371 site-years of GPP estimates from the FLUXNET network, and we looked at global covariation among parameters and with climate. Results: The optimized parameter values were shown to be consistent with leaf-scale traits, in particular, with well-known trade-offs observed at the leaf level, echoing the leaf economic spectrum theory. Results showed a marked sensitivity of trait-related parameters to local bioclimatic variables and reproduced the observed relationships between traits and climate. Main conclusions: Our approach validates some biological processes implemented in the model and enables us to study ecological properties of vegetation at the canopy level, in addition to some traits that are difficult to observe experimentally. This study stresses the need for: (a) implementing explicit trade-offs and acclimation processes in TBMs; (b) improving the representation of processes to avoid model-specific parameterization; and (c) performing systematic measurements of traits at FLUXNET sites in order to gather information on plant ecophysiology and plant diversity, together with micro-meteorological conditions.
BibTeX:
@article{Peaucelle2019,
  author = {Peaucelle, Marc and Bacour, Cédric and Ciais, Philippe and Vuichard, Nicolas and Kuppel, Sylvain and Peñuelas, Josep and Belelli Marchesini, Luca and Blanken, Peter D. and Buchmann, Nina and Chen, Jiquan and Delpierre, Nicolas and Desai, Ankur R. and Dufrene, Eric and Gianelle, Damiano and Gimeno-Colera, Cristina and Gruening, Carsten and Helfter, Carole and Hörtnagl, Lukas and Ibrom, Andreas and Joffre, Richard and Kato, Tomomichi and Kolb, Thomas E. and Law, Beverly and Lindroth, Anders and Mammarella, Ivan and Merbold, Lutz and Minerbi, Stefano and Montagnani, Leonardo and Šigut, Ladislav and Sutton, Mark and Varlagin, Andrej and Vesala, Timo and Wohlfahrt, Georg and Wolf, Sebastian and Yakir, Dan and Viovy, Nicolas},
  editor = {Lenoir, Jonathan},
  title = {Covariations between plant functional traits emerge from constraining parameterization of a terrestrial biosphere model},
  journal = {Global Ecology and Biogeography},
  publisher = {Wiley},
  year = {2019},
  volume = {28},
  number = {9},
  pages = {1351--1365},
  doi = {10.1111/geb.12937}
}
Peaucelle M, Ciais P, Maignan F, Nicolas M, Cecchini S and Viovy N (2019), "Representing explicit budburst and senescence processes for evergreen conifers in global models", Agricultural and Forest Meteorology., mar, 2019. Vol. 266-267, pp. 97-108. Elsevier BV.
Abstract: Global ecosystem models lack an explicit representation of budburst and senescence for evergreen conifers despite their primordial role in the carbon cycle. In this study we evaluated eight different budburst models, combining forcing, chilling and photoperiod, for their ability to describe spring budburst, and one model of needle senescence for temperate evergreen coniferous forests. The models' parameters were optimized against field observations from a national forest monitoring network in France. The best fitting budburst model was determined according to a new metrics which accounts for both temporal and spatial variabilities of budburst events across sites. The best model could reproduce observed budburst dates both at the site scale (±5 days) and at regional scale (±12 days). We also showed that the budburst models parameterized at site scale lose some predictive capability when applied at coarser spatial resolution, e.g., in grid-based simulations. The selected budburst model was then coupled to a senescence function defined from needle survivorship observations in order to describe the full phenology cycle of coniferous forests. Implemented in the process-driven ecosystem model ORCHIDEE, this new conifer phenology module represented accurately the intra and inter-annual dynamics of leaf area index at both the local and regional scales when compared against MODIS remote sensing observations. A sensitivity analysis showed only a small impact of the new budburst model on the timing of the seasonal cycle of photosynthesis (GPP). Yet, due to the faster renewal of needles compared to the standard version of ORCHIDEE, we simulated an increase in the GPP by on average 15% over France, while the simulated needle turnover was doubled. Compared to 1970–2000, projections indicated an advancement of the budburst date of 10.3 ± 2.8 and 12.3 ± 4.1 days in average over the period 2060–2100 with the best forcing and chilling-forcing models respectively. Our study suggests that including an explicit simulation of needle budburst and senescence for evergreen conifers in global terrestrial ecosystem models may significantly impact future projections of carbon budgets.
BibTeX:
@article{Peaucelle2019b,
  author = {Peaucelle, Marc and Ciais, Philippe and Maignan, Fabienne and Nicolas, Manuel and Cecchini, Sébastien and Viovy, Nicolas},
  title = {Representing explicit budburst and senescence processes for evergreen conifers in global models},
  journal = {Agricultural and Forest Meteorology},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {266-267},
  pages = {97--108},
  doi = {10.1016/j.agrformet.2018.12.008}
}
Peaucelle M, Janssens IA, Stocker BD, Descals Ferrando A, Fu YH, Molowny-Horas R, Ciais P and Peñuelas J (2019), "Spatial variance of spring phenology in temperate deciduous forests is constrained by background climatic conditions", Nature Communications., nov, 2019. Vol. 10(1) Springer Science and Business Media LLC.
Abstract: Leaf unfolding in temperate forests is driven by spring temperature, but little is known about the spatial variance of that temperature dependency. Here we use in situ leaf unfolding observations for eight deciduous tree species to show that the two factors that control chilling (number of cold days) and heat requirement (growing degree days at leaf unfolding, GDDreq) only explain 30% of the spatial variance of leaf unfolding. Radiation and aridity differences among sites together explain 10% of the spatial variance of leaf unfolding date, and 40% of the variation in GDDreq. Radiation intensity is positively correlated with GDDreq and aridity is negatively correlated with GDDreq spatial variance. These results suggest that leaf unfolding of temperate deciduous trees is adapted to local mean climate, including water and light availability, through altered sensitivity to spring temperature. Such adaptation of heat requirement to background climate would imply that models using constant temperature response are inherently inaccurate at local scale.
BibTeX:
@article{Peaucelle2019c,
  author = {Peaucelle, Marc and Janssens, Ivan A. and Stocker, Benjamin D. and Descals Ferrando, Adrià and Fu, Yongshuo H. and Molowny-Horas, Roberto and Ciais, Philippe and Peñuelas, Josep},
  title = {Spatial variance of spring phenology in temperate deciduous forests is constrained by background climatic conditions},
  journal = {Nature Communications},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {10},
  number = {1},
  doi = {10.1038/s41467-019-13365-1}
}
Peltola O, Vesala T, Gao Y, Räty O, Alekseychik P, Aurela M, Chojnicki B, Desai AR, Dolman AJ, Euskirchen ES, Friborg T, Göckede M, Helbig M, Humphreys E, Jackson RB, Jocher G, Joos F, Klatt J, Knox SH, Kowalska N, Kutzbach L, Lienert S, Lohila A, Mammarella I, Nadeau DF, Nilsson MB, Oechel WC, Peichl M, Pypker T, Quinton W, Rinne J, Sachs T, Samson M, Schmid HP, Sonnentag O, Wille C, Zona D and Aalto T (2019), "Monthly gridded data product of northern wetland methane emissions based on upscaling eddy covariance observations", Earth System Science Data., aug, 2019. Vol. 11(3), pp. 1263-1289.
Abstract: Natural wetlands constitute the largest and most uncertain source of methane (CH4) to the atmosphere and a large fraction of them are found in the northern latitudes. These emissions are typically estimated using process ("bottom-up") or inversion ("top-down") models. However, estimates from these two types of models are not independent of each other since the top-down estimates usually rely on the a priori estimation of these emissions obtained with process models. Hence, independent spatially explicit validation data are needed. Here we utilize a random forest (RF) machine-learning technique to upscale CH4 eddy covariance flux measurements from 25 sites to estimate CH4 wetland emissions from the northern latitudes (north of 45° N). Eddy covariance data from 2005 to 2016 are used for model development. The model is then used to predict emissions during 2013 and 2014. The predictive performance of the RF model is evaluated using a leave-one-site-out cross-validation scheme. The performance (Nash-Sutcliffe model efficiency D 0:47) is comparable to previous studies upscaling net ecosystem exchange of carbon dioxide and studies comparing process model output against site-level CH4 emission data. The global distribution of wetlands is one major source of uncertainty for upscaling CH4. Thus, three wetland distribution maps are utilized in the upscaling. Depending on the wetland distribution map, the annual emissions for the northern wetlands yield 32 (22.3-41.2, 95 % confidence interval calculated from a RF model ensemble), 31 (21.4-39.9) or 38 (25.9-49.5) Tg(CH4) yr-1. To further evaluate the uncertainties of the upscaled CH4 flux data products we also compared them against output from two process models (LPX-Bern and WetCHARTs), and methodological issues related to CH4 flux upscaling are discussed. The monthly upscaled CH4 flux data products are available at https://doi.org/10.5281/zenodo.2560163 (Peltola et al., 2019).
BibTeX:
@article{Peltola2019,
  author = {Peltola, Olli and Vesala, Timo and Gao, Yao and Räty, Olle and Alekseychik, Pavel and Aurela, Mika and Chojnicki, Bogdan and Desai, Ankur R. and Dolman, Albertus J. and Euskirchen, Eugenie S. and Friborg, Thomas and Göckede, Mathias and Helbig, Manuel and Humphreys, Elyn and Jackson, Robert B. and Jocher, Georg and Joos, Fortunat and Klatt, Janina and Knox, Sara H. and Kowalska, Natalia and Kutzbach, Lars and Lienert, Sebastian and Lohila, Annalea and Mammarella, Ivan and Nadeau, Daniel F. and Nilsson, Mats B. and Oechel, Walter C. and Peichl, Matthias and Pypker, Thomas and Quinton, William and Rinne, Janne and Sachs, Torsten and Samson, Mateusz and Schmid, Hans Peter and Sonnentag, Oliver and Wille, Christian and Zona, Donatella and Aalto, Tuula},
  title = {Monthly gridded data product of northern wetland methane emissions based on upscaling eddy covariance observations},
  journal = {Earth System Science Data},
  year = {2019},
  volume = {11},
  number = {3},
  pages = {1263--1289},
  url = {https://www.earth-syst-sci-data.net/11/1263/2019/},
  doi = {10.5194/essd-11-1263-2019}
}
Petzold A, Asmi A, Vermeulen A, Pappalardo G, Bailo D, Schaap D, Glaves HM, Bundke U and Zhao Z (2019), "ENVRI-FAIR - Interoperable Environmental FAIR Data and Services for Society, Innovation and Research", In 2019 15th International Conference on eScience (eScience)., sep, 2019. , pp. 277-280. IEEE.
BibTeX:
@inproceedings{Petzold2019,
  author = {Petzold, Andreas and Asmi, Ari and Vermeulen, Alex and Pappalardo, Gelsomina and Bailo, Daniele and Schaap, Dick and Glaves, Helen M. and Bundke, Ulrich and Zhao, Zhiming},
  title = {ENVRI-FAIR - Interoperable Environmental FAIR Data and Services for Society, Innovation and Research},
  booktitle = {2019 15th International Conference on eScience (eScience)},
  publisher = {IEEE},
  year = {2019},
  pages = {277--280},
  url = {https://ieeexplore.ieee.org/document/9041704/},
  doi = {10.1109/eScience.2019.00038}
}
Pierrot D, Steinhoff T and Oceanographic A (2019), "Installation of Autonomous Underway pCO2 Instruments onboard Ships of Opportunity".
BibTeX:
@misc{Pierrot2019,
  author = {Pierrot, D and Steinhoff, T and Oceanographic, Atlantic},
  title = {Installation of Autonomous Underway pCO2 Instruments onboard Ships of Opportunity},
  booktitle = {NOAA Technical Report},
  publisher = {Atlantic Oceanographic and Meteorological Laboratory},
  year = {2019},
  volume = {OAR-AOML-5},
  number = {April},
  pages = {31},
  doi = {10.25923/ffz6-0x48}
}
Pisso I, Sollum E, Grythe H, Kristiansen NI, Cassiani M, Eckhardt S, Arnold D, Morton D, Thompson RL, Groot Zwaaftink CD, Evangeliou N, Sodemann H, Haimberger L, Henne S, Brunner D, Burkhart JF, Fouilloux A, Brioude J, Philipp A, Seibert P and Stohl A (2019), "The Lagrangian particle dispersion model FLEXPART version 10.4", Geoscientific Model Development., dec, 2019. Vol. 12(12), pp. 4955-4997.
Abstract: The Lagrangian particle dispersion model FLEXPART in its original version in the mid-1990s was designed for calculating the long-range and mesoscale dispersion of hazardous substances from point sources, such as those released after an accident in a nuclear power plant. Over the past decades, the model has evolved into a comprehensive tool for multi-scale atmospheric transport modeling and analysis and has attracted a global user community. Its application fields have been extended to a large range of atmospheric gases and aerosols, e.g., greenhouse gases, short-lived climate forcers like black carbon and volcanic ash, and it has also been used to study the atmospheric branch of the water cycle. Given suitable meteorological input data, it can be used for scales from dozens of meters to global. In particular, inverse modeling based on source-receptor relationships from FLEXPART has become widely used. In this paper, we present FLEXPART version 10.4, which works with meteorological input data from the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) and data from the United States National Centers of Environmental Prediction (NCEP) Global Forecast System (GFS). Since the last publication of a detailed FLEXPART description (version 6.2), the model has been improved in different aspects such as performance, physicochemical parameterizations, input/output formats, and available preprocessing and post-processing software. The model code has also been parallelized using the Message Passing Interface (MPI). We demonstrate that the model scales well up to using 256 processors, with a parallel efficiency greater than 75 % for up to 64 processes on multiple nodes in runs with very large numbers of particles. The deviation from 100 % efficiency is almost entirely due to the remaining nonparallelized parts of the code, suggesting large potential for further speedup. A new turbulence scheme for the convective boundary layer has been developed that considers the skewness in the vertical velocity distribution (updrafts and downdrafts) and vertical gradients in air density. FLEXPART is the only model available considering both effects, making it highly accurate for small-scale applications, e.g., to quantify dispersion in the vicinity of a point source. The wettextlessspan idCombining double low line"page4956"/textgreater deposition scheme for aerosols has been completely rewritten and a new, more detailed gravitational settling parameterization for aerosols has also been implemented. FLEXPART has had the option of running backward in time from atmospheric concentrations at receptor locations for many years, but this has now been extended to also work for deposition values and may become useful, for instance, for the interpretation of ice core measurements. To our knowledge, to date FLEXPART is the only model with that capability. Furthermore, the temporal variation and temperature dependence of chemical reactions with the OH radical have been included, allowing for more accurate simulations for species with intermediate lifetimes against the reaction with OH, such as ethane. Finally, user settings can now be specified in a more flexible namelist format, and output files can be produced in NetCDF format instead of FLEXPART's customary binary format. In this paper, we describe these new developments. Moreover, we present some tools for the preparation of the meteorological input data and for processing FLEXPART output data, and we briefly report on alternative FLEXPART versions.
BibTeX:
@article{Pisso2019,
  author = {Pisso, Ignacio and Sollum, Espen and Grythe, Henrik and Kristiansen, Nina I. and Cassiani, Massimo and Eckhardt, Sabine and Arnold, Delia and Morton, Don and Thompson, Rona L. and Groot Zwaaftink, Christine D. and Evangeliou, Nikolaos and Sodemann, Harald and Haimberger, Leopold and Henne, Stephan and Brunner, Dominik and Burkhart, John F. and Fouilloux, Anne and Brioude, Jerome and Philipp, Anne and Seibert, Petra and Stohl, Andreas},
  title = {The Lagrangian particle dispersion model FLEXPART version 10.4},
  journal = {Geoscientific Model Development},
  year = {2019},
  volume = {12},
  number = {12},
  pages = {4955--4997},
  url = {https://www.geosci-model-dev.net/12/4955/2019/},
  doi = {10.5194/gmd-12-4955-2019}
}
Proietti C, Anav A, Vitale M, Fares S, Fornasier MF, Screpanti A, Salvati L, Paoletti E, Sicard P and De Marco A (2019), "A new wetness index to evaluate the soil water availability influence on gross primary production of european forests", Climate., mar, 2019. Vol. 7(3), pp. 42. MDPI AG.
Abstract: Rising temperature, drought and more-frequent extreme climatic events have been predicted for the next decades in many regions around the globe. In this framework, soil water availability plays a pivotal role in affecting vegetation productivity, especially in arid or semi-arid environments. However, direct measurements of soil moisture are scarce, and modeling estimations are still subject to biases. Further investigation on the effect of soil moisture on plant productivity is required. This study aims at analyzing spatio-temporal variations of a modified temperature vegetation wetness index (mTVWI), a proxy of soil moisture, and evaluating its effect on gross primary production (GPP) in forests. The study was carried out in Europe on 19 representative tree species during the 2000-2010 time period. Results outline a north-south gradient of mTVWI with minimum values (low soil water availability) in Southern Europe and maximum values (high soil water availability) in Northeastern Europe. A low soil water availability negatively affected GPP from 20 to 80%, as a function of site location, tree species, and weather conditions. Such a wetness index improves our understanding of water stress impacts, which is crucial for predicting the response of forest carbon cycling to drought and aridity.
BibTeX:
@article{Proietti2019,
  author = {Proietti, Chiara and Anav, Alessandro and Vitale, Marcello and Fares, Silvano and Fornasier, Maria Francesca and Screpanti, Augusto and Salvati, Luca and Paoletti, Elena and Sicard, Pierre and De Marco, Alessandra},
  title = {A new wetness index to evaluate the soil water availability influence on gross primary production of european forests},
  journal = {Climate},
  publisher = {MDPI AG},
  year = {2019},
  volume = {7},
  number = {3},
  pages = {42},
  doi = {10.3390/cli7030042}
}
Puche N, Senapati N, Flechard CR, Klumpp K, Kirschbaum MU and Chabbi A (2019), "Modeling carbon and water fluxes of managed grasslands: Comparing flux variability and net carbon budgets between grazed and mowed systems", Agronomy., apr, 2019. Vol. 9(4), pp. 183. MDPI AG.
Abstract: The CenW ecosystem model simulates carbon, water, and nitrogen cycles following ecophysiological processes and management practices on a daily basis. We tested and evaluated the model using five years eddy covariance measurements from two adjacent but differently managed grasslands in France. The data were used to independently parameterize CenW for the two grassland sites. Very good agreements, i.e., high model efficiencies and correlations, between observed and modeled fluxes were achieved. We showed that the CenW model captured day‐to‐day, seasonal, and interannual variability observed in measured CO2 and water fluxes. We also showed that following typical management practices (i.e., mowing and grazing), carbon gain was severely curtailed through a sharp and severe reduction in photosynthesizing biomass. We also identified large model/data discrepancies for carbon fluxes during grazing events caused by the noncapture by the eddy covariance system of large respiratory losses of C from dairy cows when they were present in the paddocks. The missing component of grazing animal respiration in the net carbon budget of the grazed grassland can be quantitatively important and can turn sites from being C sinks to being neutral or C sources. It means that extra care is needed in the processing of eddy covariance data from grazed pastures to correctly calculate their annual CO2 balances and carbon budgets.
BibTeX:
@article{Puche2019,
  author = {Puche, Nicolas and Senapati, Nimai and Flechard, Christophe R. and Klumpp, Katia and Kirschbaum, Miko U.F. and Chabbi, Abad},
  title = {Modeling carbon and water fluxes of managed grasslands: Comparing flux variability and net carbon budgets between grazed and mowed systems},
  journal = {Agronomy},
  publisher = {MDPI AG},
  year = {2019},
  volume = {9},
  number = {4},
  pages = {183},
  doi = {10.3390/agronomy9040183}
}
Räsänen A, Aurela M, Juutinen S, Kumpula T, Lohila A, Penttilä T and Virtanen T (2019), "Detecting northern peatland vegetation patterns at ultra-high spatial resolution", Remote Sensing in Ecology and Conservation., dec, 2019. Wiley.
Abstract: Within northern peatlands, landscape elements such as vegetation and topography are spatially heterogenic from ultra-high (centimeter level) to coarse scale. In addition to within-site spatial heterogeneity, there is evident between-site heterogeneity, but there is a lack of studies assessing whether different combinations of remotely sensed features and mapping approaches are needed in different types of landscapes. We evaluated the value of different mapping methods and remote sensing datasets and analyzed the kinds of differences present in vegetation patterns and their mappability between three northern boreal peatland landscapes in northern Finland. We utilized field-inventoried vegetation plots together with spectral, textural, topography and vegetation height remote sensing data from 0.02- to 3-m pixel size. Remote sensing data included true-color unmanned aerial vehicle images, aerial images with four spectral bands, aerial lidar data and multiple PlanetScope satellite images. We used random forest regressions for tracking plant functional type (PFT) coverage, non-metric multidimensional scaling ordination axes and fuzzy k-medoid plant community clusters. PFT regressions had variable performance for different study sites (R2 −0.03 to 0.69). Spatial patterns of some spectrally or structurally distinctive PFTs could be predicted relatively well. The first ordination axis represented wetness gradient and was well predicted using remotely sensed data (R2 0.64 to 0.82), but the other three axes had a less straightforward explanation and lower mapping performance (R2 −0.09 to 0.53). Plant community clusters were predicted most accurately in the sites with clear string-flark topography but less accurately in the flatter site (R2 0.16–0.82). The most important remote sensing features differed between dependent variables and study sites: different topographic, spectral and textural features; and coarse-scale and fine-scale datasets were the most important in different tasks. We suggest that multiple different mapping approaches should be tested and several remote sensing datasets used when maps of vegetation are produced.
BibTeX:
@article{Raesaenen2019,
  author = {Räsänen, Aleksi and Aurela, Mika and Juutinen, Sari and Kumpula, Timo and Lohila, Annalea and Penttilä, Timo and Virtanen, Tarmo},
  editor = {Horning, Ned and Zhang, Jian},
  title = {Detecting northern peatland vegetation patterns at ultra-high spatial resolution},
  journal = {Remote Sensing in Ecology and Conservation},
  publisher = {Wiley},
  year = {2019},
  doi = {10.1002/rse2.140}
}
Räsänen A, Juutinen S, Aurela M and Virtanen T (2019), "Predicting aboveground biomass in Arctic landscapes using very high spatial resolution satellite imagery and field sampling", International Journal of Remote Sensing., nov, 2019. Vol. 40(3), pp. 1175-1199. Informa UK Limited.
Abstract: Remote sensing based biomass estimates in Arctic areas are usually produced using coarse spatial resolution satellite imagery, which is incapable of capturing the fragmented nature of tundra vegetation communities. We mapped aboveground biomass using field sampling and very high spatial resolution (VHSR) satellite images (QuickBird, WorldView-2 and WorldView-3) in four different Arctic tundra or peatland sites with low vegetation located in Russia, Canada, and Finland. We compared site-specific and cross-site empirical regressions. First, we classified species into plant functional types and estimated biomass using easy, non-destructive field measurements (cover, height). Second, we used the cover/height-based biomass as the response variable and used combinations of single bands and vegetation indices in predicting total biomass. We found that plant functional type biomass could be predicted reasonably well in most cases using cover and height as the explanatory variables (adjusted R 2 0.21–0.92), and there was considerable variation in the model fit when the total biomass was predicted with satellite spectra (adjusted R 2 0.33–0.75). There were dissimilarities between cross-site and site-specific regression estimates in satellite spectra based regressions suggesting that the same regression should be used only in areas with similar kinds of vegetation. We discuss the considerable variation in biomass and plant functional type composition within and between different Arctic landscapes and how well this variation can be reproduced using VHSR satellite images. Overall, the usage of VHSR images creates new possibilities but to utilize them to full potential requires similarly more detailed in-situ data related to biomass inventories and other ecosystem change studies and modelling.
BibTeX:
@article{Raesaenen2019a,
  author = {Räsänen, Aleksi and Juutinen, Sari and Aurela, Mika and Virtanen, Tarmo},
  title = {Predicting aboveground biomass in Arctic landscapes using very high spatial resolution satellite imagery and field sampling},
  journal = {International Journal of Remote Sensing},
  publisher = {Informa UK Limited},
  year = {2019},
  volume = {40},
  number = {3},
  pages = {1175--1199},
  doi = {10.1080/01431161.2018.1524176}
}
Räsänen A, Juutinen S, Tuittila ES, Aurela M and Virtanen T (2019), "Comparing ultra-high spatial resolution remote-sensing methods in mapping peatland vegetation", Journal of Vegetation Science., jul, 2019. Vol. 30(5), pp. 1016-1026. Wiley.
Abstract: Questions: How to map floristic variation in a patterned fen in an ecologically meaningfully way? Can plant communities be delineated with species data generalized into plant functional types? What are the benefits and drawbacks of the two selected remote-sensing approaches in mapping vegetation patterns, namely: (a) regression models of floristically defined fuzzy plant community clusters and (b) classification of predefined habitat types that combine vegetation and land cover information?. Location: Treeless 0.4 km2 mesotrophic string–flark fen in Kaamanen, northern Finland. Methods: We delineated plant community clusters with fuzzy c-means clustering based on two different inventories of plant species and functional type distribution. We used multiple optical remote-sensing data sets, digital elevation models and vegetation height models derived from drone, aerial and satellite platforms from ultra-high to very high spatial resolution (0.05–3 m) in an object-based approach. We mapped spatial patterns for fuzzy and crisp plant community clusters using boosted regression trees, and fuzzy and crisp habitat types using supervised random forest classification. Results: Clusters delineated with species-specific data or plant functional type data produced comparable results. However, species-specific data for graminoids and mosses improved the accuracy of clustering in the case of flarks and string margins. Mapping accuracy was higher for habitat types (overall accuracy 0.72) than for fuzzy plant community clusters (R2 values between 0.27 and 0.67). Conclusions: For ecologically meaningful mapping of a patterned fen vegetation, plant functional types provide enough information. However, if the aim is to capture floristic variation in vegetation as realistically as possible, species-specific data should be used. Maps of plant community clusters and habitat types complement each other. While fuzzy plant communities appear to be floristically most accurate, crisp habitat types are easiest to interpret and apply to different landscape and biogeochemical cycle analyses and modeling.
BibTeX:
@article{Raesaenen2019b,
  author = {Räsänen, Aleksi and Juutinen, Sari and Tuittila, Eeva Stiina and Aurela, Mika and Virtanen, Tarmo},
  editor = {Rocchini, Duccio},
  title = {Comparing ultra-high spatial resolution remote-sensing methods in mapping peatland vegetation},
  journal = {Journal of Vegetation Science},
  publisher = {Wiley},
  year = {2019},
  volume = {30},
  number = {5},
  pages = {1016--1026},
  doi = {10.1111/jvs.12769}
}
Réjou-Méchain M, Barbier N, Couteron P, Ploton P, Vincent G, Herold M, Mermoz S, Saatchi S, Chave J, de Boissieu F, Féret JB, Takoudjou SM and Pélissier R (2019), "Upscaling Forest Biomass from Field to Satellite Measurements: Sources of Errors and Ways to Reduce Them", Surveys in Geophysics., may, 2019. Vol. 40(4), pp. 881-911. Springer Science and Business Media LLC.
Abstract: Forest biomass monitoring is at the core of the research agenda due to the critical importance of forest dynamics in the carbon cycle. However, forest biomass is never directly measured; thus, upscaling it from trees to stand or larger scales (e.g., countries, regions) relies on a series of statistical models that may propagate large errors. Here, we review the main steps usually adopted in forest aboveground biomass mapping, highlighting the major challenges and perspectives. We show that there is room for improvement along the scaling-up chain from field data collection to satellite-based large-scale mapping, which should lead to the adoption of effective practices to better control the propagation of errors. We specifically illustrate how the increasing use of emerging technologies to collect massive amounts of high-quality data may significantly improve the accuracy of forest carbon maps. Furthermore, we discuss how sources of spatially structured biases that directly propagate into remote sensing models need to be better identified and accounted for when extrapolating forest carbon estimates, e.g., through a stratification design. We finally discuss the increasing realism of 3D simulated stands, which, through radiative transfer modelling, may contribute to a better understanding of remote sensing signals and open avenues for the direct calibration of large-scale products, thereby circumventing several current difficulties.
BibTeX:
@article{RejouMechain2019,
  author = {Réjou-Méchain, Maxime and Barbier, Nicolas and Couteron, Pierre and Ploton, Pierre and Vincent, Grégoire and Herold, Martin and Mermoz, Stéphane and Saatchi, Sassan and Chave, Jérôme and de Boissieu, Florian and Féret, Jean Baptiste and Takoudjou, Stéphane Momo and Pélissier, Raphaël},
  title = {Upscaling Forest Biomass from Field to Satellite Measurements: Sources of Errors and Ways to Reduce Them},
  journal = {Surveys in Geophysics},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {40},
  number = {4},
  pages = {881--911},
  doi = {10.1007/s10712-019-09532-0}
}
Riihimäki H, Luoto M and Heiskanen J (2019), "Estimating fractional cover of tundra vegetation at multiple scales using unmanned aerial systems and optical satellite data", Remote Sensing of Environment., apr, 2019. Vol. 224, pp. 119-132.
Abstract: Fractional cover of green vegetation (FCover) is a key variable when observing Arctic vegetation under a changing climate. Vegetation changes over large areas are traditionally monitored by linking plot-scale measurements to satellite data. However, integrating field and satellite data is not straightforward. Typically, the satellite data are at a much coarser scale in comparison to field measurements. Here, we studied how Unmanned Aerial Systems (UASs) can be used to bridge this gap. We covered three 250 m × 250 m sites in Fennoscandian tundra with varying productivity and FCover, ranging from barren vegetation to shrub tundra. The UAS sites were then used to train satellite data-based FCover models. First, we created a binary vegetation classification (absent, present) by using UAS-derived RGB-orthomosaics and logistic regression. Secondly, we used the classification to calculate FCover to Planet CubeSat (3 m), Sentinel-2A MSI (10 m, 20 m), and Landsat 8 OLI (30 m) grids, and examined how well FCover is explained by various spectral vegetation indices (VI) derived from satellite data. The overall classification accuracies for the UAS sites were ≥90%. The UAS-FCover were strongly related to the tested VIs (D 2 89% at best). The explained deviance was generally higher for coarser resolution data, indicating that the effect of data resolution should be taken into account when comparing results from different sensors. VIs based on red-edge (at 740 nm, 783 nm), or near-infrared and shortwave infrared (SWIR) had the highest performance. We recommend wider inspection of red-edge and SWIR bands for future Arctic vegetation research. Our results demonstrate that UASs can be used for observing FCover at multiple scales. Individual UAS sites can serve as focus areas, which provide information at the finest resolution (e.g. individual plants), whereas a sample of several UAS sites can be used to train satellite data and examine vegetation over larger extents.
BibTeX:
@article{Riihimaeki2019,
  author = {Riihimäki, Henri and Luoto, Miska and Heiskanen, Janne},
  title = {Estimating fractional cover of tundra vegetation at multiple scales using unmanned aerial systems and optical satellite data},
  journal = {Remote Sensing of Environment},
  year = {2019},
  volume = {224},
  pages = {119--132},
  url = {https://linkinghub.elsevier.com/retrieve/pii/S0034425719300367},
  doi = {10.1016/j.rse.2019.01.030}
}
Rineau F, Malina R, Beenaerts N, Arnauts N, Bardgett RD, Berg MP, Boerema A, Bruckers L, Clerinx J, Davin EL, De Boeck HJ, De Dobbelaer T, Dondini M, De Laender F, Ellers J, Franken O, Gilbert L, Gudmundsson L, Janssens IA, Johnson D, Lizin S, Longdoz B, Meire P, Meremans D, Milbau A, Moretti M, Nijs I, Nobel A, Pop IS, Puetz T, Reyns W, Roy J, Schuetz J, Seneviratne SI, Smith P, Solmi F, Staes J, Thiery W, Thijs S, Vanderkelen I, Van Landuyt W, Verbruggen E, Witters N, Zscheischler J and Vangronsveld J (2019), "Towards more predictive and interdisciplinary climate change ecosystem experiments", Nature Climate Change., oct, 2019. Vol. 9(11), pp. 809-816. Springer Science and Business Media LLC.
Abstract: Despite great advances, experiments concerning the response of ecosystems to climate change still face considerable challenges, including the high complexity of climate change in terms of environmental variables, constraints in the number and amplitude of climate treatment levels, and the limited scope of responses and interactions covered. Drawing on the expertise of researchers from a variety of disciplines, this Perspective outlines how computational and technological advances can help in designing experiments that can contribute to overcoming these challenges, and also outlines a first application of such an experimental design.
BibTeX:
@article{Rineau2019,
  author = {Rineau, Francois and Malina, Robert and Beenaerts, Natalie and Arnauts, Natascha and Bardgett, Richard D. and Berg, Matty P. and Boerema, Annelies and Bruckers, Liesbeth and Clerinx, Jan and Davin, Edouard L. and De Boeck, Hans J. and De Dobbelaer, Tom and Dondini, Marta and De Laender, Frederik and Ellers, Jacintha and Franken, Oscar and Gilbert, Lucy and Gudmundsson, Lukas and Janssens, Ivan A. and Johnson, David and Lizin, Sebastien and Longdoz, Bernard and Meire, Patrick and Meremans, Dominique and Milbau, Ann and Moretti, Michele and Nijs, Ivan and Nobel, Anne and Pop, Iuliu Sorin and Puetz, Thomas and Reyns, Wouter and Roy, Jacques and Schuetz, Jochen and Seneviratne, Sonia I. and Smith, Pete and Solmi, Francesca and Staes, Jan and Thiery, Wim and Thijs, Sofie and Vanderkelen, Inne and Van Landuyt, Wouter and Verbruggen, Erik and Witters, Nele and Zscheischler, Jakob and Vangronsveld, Jaco},
  title = {Towards more predictive and interdisciplinary climate change ecosystem experiments},
  journal = {Nature Climate Change},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {9},
  number = {11},
  pages = {809--816},
  doi = {10.1038/s41558-019-0609-3}
}
Rosíková J, Darenova E, Kučera A, Volařík D and Vranová V (2019), "Effect of different dolomitic limestone dosages on soil respiration in a mid-altitudinal Norway spruce stand", IForest., aug, 2019. Vol. 12(4), pp. 357-365. Italian Society of Sivilculture and Forest Ecology (SISEF).
Abstract: The study focuses on the effect of chemical amelioration of dolomitic limestone (doses of 0, 2, 3, 4, 6, 9 and 26 t ha-1) on soil respiration in a Norway spruce monoculture in mid-altitudinal elevation during one-year period after application. Firstly, the soil respiration was measured in situ as monthly CO2 efflux from the soil surface horizon in the period May to October 2016. Secondly, basal respiration, microbial biomass carbon and metabolic quotient of the organic H and organo-mineral A horizons were assessed under laboratory conditions within one year after the treatment. Soil CO2 efflux increased by 3 to 31% and by 29 to 98% for the ameliorant of 2 and 26 t ha-1, respectively, compared to the unlimed control treatment. The CO2 efflux was significantly driven by external conditions such as soil moisture and temperature, especially in the last seasonal months. Basal respiration of the H horizon increased up to a dose of 9 t ha-1 but decreased at 26 t ha-1. In the A horizon, microbial activity increased in all the limed variants compared to the non-limed variant. A similar trend was observed in microbial carbon and the metabolic quotient of the soil. Our results prove that the ameliorant doses commonly used in the forestry sector (3-4 t ha-1) substantially increase the soil microbial activity during (soil CO2 efflux) and after (laboratory data) the first year after application. This results in the accelerated mineralization of soil organic material and subsequent loss from the forest ecosystem.
BibTeX:
@article{Rosikova2019,
  author = {Rosíková, Jana and Darenova, Eva and Kučera, Aleš and Volařík, Daniel and Vranová, Valerie},
  title = {Effect of different dolomitic limestone dosages on soil respiration in a mid-altitudinal Norway spruce stand},
  journal = {IForest},
  publisher = {Italian Society of Sivilculture and Forest Ecology (SISEF)},
  year = {2019},
  volume = {12},
  number = {4},
  pages = {357--365},
  doi = {10.3832/ifor2894-012}
}
Šálek M and Szabó-Takács B (2019), "Comparison of SAFNWC/MSG satellite cloud type with Vaisala CL51 ceilometer-detected cloud base layer using the sky condition algorithm and Vaisala BL-View software", Atmosphere., jun, 2019. Vol. 10(6), pp. 316. MDPI AG.
Abstract: Ceilometer detection can be used to determine cloud type based on cloud layer height. Satellite observations provide images of clouds' physical properties. During the summer and winter of 2017, Satellite Application Facility on support to Nowcasting/Very Short-Range Forecasting Meteosat Second Generation (SAFNWC/MSG) cloud type was compared to cloud base layers based upon a sky condition algorithm of Vaisala CL51 ceilometer and the BL-View applied range-variant smoothing backscatter profile at the National Atmospheric Observatory in Košetice, Czech Republic. This study investigated whether the larger measurement range of CL51 improved high cloud base detection and the effect of the range-variant smoothing on cloud base detection. The comparison utilized a multi-category contingency table wherein hit rate, false alarm ratio, frequency of bias, and proportion correct were evaluated. The accuracy of low-level and high cloud type detection by satellite was almost identical in both seasons compared to that using the sky condition algorithm. The occurrence of satellite high cloud detection was greatest when the ceilometer detected high cloud base above low and/or medium cloud base. The hit rate of high cloud detection increased significantly when the BL-View-produced cloud base layer was applied as a reference. We conclude that BL-View produces more accurate high cloud base detection.
BibTeX:
@article{Salek2019,
  author = {Šálek, Milan and Szabó-Takács, Beáta},
  title = {Comparison of SAFNWC/MSG satellite cloud type with Vaisala CL51 ceilometer-detected cloud base layer using the sky condition algorithm and Vaisala BL-View software},
  journal = {Atmosphere},
  publisher = {MDPI AG},
  year = {2019},
  volume = {10},
  number = {6},
  pages = {316},
  doi = {10.3390/atmos10060316}
}
Schepaschenko D, Chave J, Phillips OL, Lewis SL, Davies SJ, Réjou-Méchain M, Sist P, Scipal K, Perger C, Herault B, Labrière N, Hofhansl F, Affum-Baffoe K, Aleinikov A, Alonso A, Amani C, Araujo-Murakami A, Armston J, Arroyo L, Ascarrunz N, Azevedo C, Baker T, Bałazy R, Bedeau C, Berry N, Bilous AM, Bilous SY, Bissiengou P, Blanc L, Bobkova KS, Braslavskaya T, Brienen R, Burslem DF, Condit R, Cuni-Sanchez A, Danilina D, Del Castillo Torres D, Derroire G, Descroix L, Sotta ED, D'Oliveira MV, Dresel C, Erwin T, Evdokimenko MD, Falck J, Feldpausch TR, Foli EG, Foster R, Fritz S, Garcia-Abril AD, Gornov A, Gornova M, Gothard-Bassébé E, Gourlet-Fleury S, Guedes M, Hamer KC, Susanty FH, Higuchi N, Coronado EN, Hubau W, Hubbell S, Ilstedt U, Ivanov VV, Kanashiro M, Karlsson A, Karminov VN, Killeen T, Koffi JCK, Konovalova M, Kraxner F, Krejza J, Krisnawati H, Krivobokov LV, Kuznetsov MA, Lakyda I, Lakyda PI, Licona JC, Lucas RM, Lukina N, Lussetti D, Malhi Y, Manzanera JA, Marimon B, Junior BHM, Martinez RV, Martynenko OV, Matsala M, Matyashuk RK, Mazzei L, Memiaghe H, Mendoza C, Mendoza AM, Moroziuk OV, Mukhortova L, Musa S, Nazimova DI, Okuda T, Oliveira LC, Ontikov PV, Osipov AF, Pietsch S, Playfair M, Poulsen J, Radchenko VG, Rodney K, Rozak AH, Ruschel A, Rutishauser E, See L, Shchepashchenko M, Shevchenko N, Shvidenko A, Silveira M, Singh J, Sonké B, Souza C, Stereʼnczak K, Stonozhenko L, Sullivan MJ, Szatniewska J, Taedoumg H, Ter Steege H, Tikhonova E, Toledo M, Trefilova OV, Valbuena R, Gamarra LV, Vasiliev S, Vedrova EF, Verhovets SV, Vidal E, Vladimirova NA, Vleminckx J, Vos VA, Vozmitel FK, Wanek W, West TA, Woell H, Woods JT, Wortel V, Yamada T, Nur Hajar ZS and Zo-Bi IC (2019), "The Forest Observation System, building a global reference dataset for remote sensing of forest biomass", Scientific data., oct, 2019. Vol. 6(1), pp. 198. Springer Science and Business Media LLC.
Abstract: Forest biomass is an essential indicator for monitoring the Earth's ecosystems and climate. It is a critical input to greenhouse gas accounting, estimation of carbon losses and forest degradation, assessment of renewable energy potential, and for developing climate change mitigation policies such as REDD+, among others. Wall-to-wall mapping of aboveground biomass (AGB) is now possible with satellite remote sensing (RS). However, RS methods require extant, up-to-date, reliable, representative and comparable in situ data for calibration and validation. Here, we present the Forest Observation System (FOS) initiative, an international cooperation to establish and maintain a global in situ forest biomass database. AGB and canopy height estimates with their associated uncertainties are derived at a 0.25 ha scale from field measurements made in permanent research plots across the world's forests. All plot estimates are geolocated and have a size that allows for direct comparison with many RS measurements. The FOS offers the potential to improve the accuracy of RS-based biomass products while developing new synergies between the RS and ground-based ecosystem research communities.
BibTeX:
@article{Schepaschenko2019,
  author = {Schepaschenko, Dmitry and Chave, Jérôme and Phillips, Oliver L. and Lewis, Simon L. and Davies, Stuart J. and Réjou-Méchain, Maxime and Sist, Plinio and Scipal, Klaus and Perger, Christoph and Herault, Bruno and Labrière, Nicolas and Hofhansl, Florian and Affum-Baffoe, Kofi and Aleinikov, Alexei and Alonso, Alfonso and Amani, Christian and Araujo-Murakami, Alejandro and Armston, John and Arroyo, Luzmila and Ascarrunz, Nataly and Azevedo, Celso and Baker, Timothy and Bałazy, Radomir and Bedeau, Caroline and Berry, Nicholas and Bilous, Andrii M. and Bilous, Svitlana Yu and Bissiengou, Pulchérie and Blanc, Lilian and Bobkova, Kapitolina S. and Braslavskaya, Tatyana and Brienen, Roel and Burslem, David F.R.P. and Condit, Richard and Cuni-Sanchez, Aida and Danilina, Dilshad and Del Castillo Torres, Dennis and Derroire, Géraldine and Descroix, Laurent and Sotta, Eleneide Doff and D'Oliveira, Marcus V.N. and Dresel, Christopher and Erwin, Terry and Evdokimenko, Mikhail D. and Falck, Jan and Feldpausch, Ted R. and Foli, Ernest G. and Foster, Robin and Fritz, Steffen and Garcia-Abril, Antonio Damian and Gornov, Aleksey and Gornova, Maria and Gothard-Bassébé, Ernest and Gourlet-Fleury, Sylvie and Guedes, Marcelino and Hamer, Keith C. and Susanty, Farida Herry and Higuchi, Niro and Coronado, Eurídice N.Honorio and Hubau, Wannes and Hubbell, Stephen and Ilstedt, Ulrik and Ivanov, Viktor V. and Kanashiro, Milton and Karlsson, Anders and Karminov, Viktor N. and Killeen, Timothy and Koffi, Jean Claude Konan and Konovalova, Maria and Kraxner, Florian and Krejza, Jan and Krisnawati, Haruni and Krivobokov, Leonid V. and Kuznetsov, Mikhail A. and Lakyda, Ivan and Lakyda, Petro I. and Licona, Juan Carlos and Lucas, Richard M. and Lukina, Natalia and Lussetti, Daniel and Malhi, Yadvinder and Manzanera, José Antonio and Marimon, Beatriz and Junior, Ben Hur Marimon and Martinez, Rodolfo Vasquez and Martynenko, Olga V. and Matsala, Maksym and Matyashuk, Raisa K. and Mazzei, Lucas and Memiaghe, Hervé and Mendoza, Casimiro and Mendoza, Abel Monteagudo and Moroziuk, Olga V. and Mukhortova, Liudmila and Musa, Samsudin and Nazimova, Dina I. and Okuda, Toshinori and Oliveira, Luis Claudio and Ontikov, Petr V. and Osipov, Andrey F. and Pietsch, Stephan and Playfair, Maureen and Poulsen, John and Radchenko, Vladimir G. and Rodney, Kenneth and Rozak, Andes H. and Ruschel, Ademir and Rutishauser, Ervan and See, Linda and Shchepashchenko, Maria and Shevchenko, Nikolay and Shvidenko, Anatoly and Silveira, Marcos and Singh, James and Sonké, Bonaventure and Souza, Cintia and Stereʼnczak, Krzysztof and Stonozhenko, Leonid and Sullivan, Martin J.P. and Szatniewska, Justyna and Taedoumg, Hermann and Ter Steege, Hans and Tikhonova, Elena and Toledo, Marisol and Trefilova, Olga V. and Valbuena, Ruben and Gamarra, Luis Valenzuela and Vasiliev, Sergey and Vedrova, Estella F. and Verhovets, Sergey V. and Vidal, Edson and Vladimirova, Nadezhda A. and Vleminckx, Jason and Vos, Vincent A. and Vozmitel, Foma K. and Wanek, Wolfgang and West, Thales A.P. and Woell, Hannsjorg and Woods, John T. and Wortel, Verginia and Yamada, Toshihiro and Nur Hajar, Zamah Shari and Zo-Bi, Irié Casimir},
  title = {The Forest Observation System, building a global reference dataset for remote sensing of forest biomass},
  journal = {Scientific data},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {6},
  number = {1},
  pages = {198},
  doi = {10.1038/s41597-019-0196-1}
}
Silva BJ, Gaspar FL, Tyaquiçã P, Lefèvre N and Flores Montes MJ (2019), "Carbon chemistry variability around a tropical archipelago", Marine and Freshwater Research. Vol. 70(6), pp. 767-780. CSIRO Publishing.
Abstract: Oceanic islands affect the surrounding oceanic circulation by producing upwelling or vortices, resulting in the rising of a richer and colder subsurface water mass. This process increases primary production and can change some biogeochemical processes, such as carbon chemistry and the biological pump. The aim of this study was to describe the vertical variability of carbon chemistry around Fernando de Noronha Archipelago (FNA) and to verify how the island mass effect (IME) can affect carbon distribution. Two transects on opposite sides of the FNA were established according to the direction of the central South Equatorial Current, and samples were collected in July 2010, September 2012 and July 2014 from the surface down to a depth of 500 m. The results showed strong stratification, with an uplift of the thermohaline structure, which resulted in an increase of chlorophyll- A concentration downstream of the island during the 2010 and 2014 cruises. Carbon chemistry parameters were strongly correlated with temperature, salinity and dissolved oxygen along the water column and did not change between sides of the island in the periods studied. We conclude that the IME did not significantly affect carbon chemistry, which was more correlated with thermohaline gradient.
BibTeX:
@article{Silva2019,
  author = {Silva, Brenno J. and Gaspar, Felipe L. and Tyaquiçã, Pedro and Lefèvre, Nathalie and Flores Montes, Manuel J.},
  title = {Carbon chemistry variability around a tropical archipelago},
  journal = {Marine and Freshwater Research},
  publisher = {CSIRO Publishing},
  year = {2019},
  volume = {70},
  number = {6},
  pages = {767--780},
  doi = {10.1071/MF18011}
}
Sofie Lansø A, Luke Smallman T, Heile Christensen J, Williams M, Pilegaard K, Sorensen LL and Geels C (2019), "Simulating the atmospheric CO2 concentration across the heterogeneous landscape of Denmark using a coupled atmosphere-biosphere mesoscale model system", Biogeosciences., apr, 2019. Vol. 16(7), pp. 1505-1524. Copernicus GmbH.
Abstract: Although coastal regions only amount to 7% of the global oceans, their contribution to the global oceanic air-sea CO2 exchange is proportionally larger, with fluxes in some estuaries being similar in magnitude to terrestrial surface fluxes of CO2. Across a heterogeneous surface consisting of a coastal marginal sea with estuarine properties and varied land mosaics, the surface fluxes of CO2 from both marine areas and terrestrial surfaces were investigated in this study together with their impact in atmospheric CO2 concentrations by the usage of a high-resolution modelling framework. The simulated terrestrial fluxes across the study region of Denmark experienced an east-west gradient corresponding to the distribution of the land cover classification, their biological activity and the urbanised areas. Annually, the Danish terrestrial surface had an uptake of approximately 7000 GgC yr1. While the marine fluxes from the North Sea and the Danish inner waters were smaller annually, with about 1800 and 1300 GgC yr1, their sizes are comparable to annual terrestrial fluxes from individual land cover classifications in the study region and hence are not negligible. The contribution of terrestrial surfaces fluxes was easily detectable in both simulated and measured concentrations of atmospheric CO2 at the only tall tower site in the study region. Although, the tower is positioned next to Roskilde Fjord, the local marine impact was not distinguishable in the simulated concentrations. But the regional impact from the Danish inner waters and the Baltic Sea increased the atmospheric concentration by up to 0.5 ppm during the winter months.
BibTeX:
@article{SofieLanso2019,
  author = {Sofie Lansø, Anne and Luke Smallman, Thomas and Heile Christensen, Jesper and Williams, Mathew and Pilegaard, Kim and Sorensen, Lise Lotte and Geels, Camilla},
  title = {Simulating the atmospheric CO2 concentration across the heterogeneous landscape of Denmark using a coupled atmosphere-biosphere mesoscale model system},
  journal = {Biogeosciences},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {16},
  number = {7},
  pages = {1505--1524},
  doi = {10.5194/bg-16-1505-2019}
}
Song J, Wan S, Piao S, Hui D, Hovenden MJ, Ciais P, Liu Y, Liu Y, Zhong M, Zheng M, Ma G, Zhou Z and Ru J (2019), "Elevated CO 2 does not stimulate carbon sink in a semi-arid grassland", Ecology Letters., jan, 2019. Vol. 22(3), pp. 458-468. Wiley.
Abstract: Elevated CO 2 is widely accepted to enhance terrestrial carbon sink, especially in arid and semi-arid regions. However, great uncertainties exist for the CO 2 fertilisation effects, particularly when its interactions with other global change factors are considered. A four-factor (CO 2 , temperature, precipitation and nitrogen) experiment revealed that elevated CO 2 did not affect either gross ecosystem productivity or ecosystem respiration, and consequently resulted in no changes of net ecosystem productivity in a semi-arid grassland despite whether temperature, precipitation and nitrogen were elevated or not. The observations could be primarily attributable to the offset of ecosystem carbon uptake by enhanced soil carbon release under CO 2 enrichment. Our findings indicate that arid and semi-arid ecosystems may not be sensitive to CO 2 enrichment as previously expected and highlight the urgent need to incorporate this mechanism into most IPCC carbon-cycle models for convincing projection of terrestrial carbon sink and its feedback to climate change.
BibTeX:
@article{Song2019,
  author = {Song, Jian and Wan, Shiqiang and Piao, Shilong and Hui, Dafeng and Hovenden, Mark J. and Ciais, Philippe and Liu, Yongwen and Liu, Yinzhan and Zhong, Mingxing and Zheng, Mengmei and Ma, Gaigai and Zhou, Zhenxing and Ru, Jingyi},
  editor = {Knops, Johannes},
  title = {Elevated CO 2 does not stimulate carbon sink in a semi-arid grassland},
  journal = {Ecology Letters},
  publisher = {Wiley},
  year = {2019},
  volume = {22},
  number = {3},
  pages = {458--468},
  doi = {10.1111/ele.13202}
}
Soussana JF, Lutfalla S, Ehrhardt F, Rosenstock T, Lamanna C, Havlík P, Richards M, Wollenberg E(L, Chotte JL, Torquebiau E, Ciais P, Smith P and Lal R (2019), "Matching policy and science: Rationale for the ‘4 per 1000 - soils for food security and climate' initiative", Soil and Tillage Research., may, 2019. Vol. 188, pp. 3-15. Elsevier BV.
Abstract: At the 21st session of the United Nations Framework Convention on Climate Change (UNFCCC, COP21), a voluntary action plan, the ‘4 per 1000 Initiative: Soils for Food Security and Climate' was proposed under the Agenda for Action. The Initiative underlines the role of soil organic matter (SOM) in addressing the three-fold challenge of food and nutritional security, adaptation to climate change and mitigation of human-induced greenhouse gases (GHGs) emissions. It sets an ambitious aspirational target of a 4 per 1000 (i.e. 0.4%) rate of annual increase in global soil organic carbon (SOC) stocks, with a focus on agricultural lands where farmers would ensure the carbon stewardship of soils, like they manage day-to-day multipurpose production systems in a changing environment. In this paper, the opportunities and challenges for the 4 per 1000 initiative are discussed. We show that the 4 per 1000 target, calculated relative to global top soil SOC stocks, is consistent with literature estimates of the technical potential for SOC sequestration, though the achievable potential is likely to be substantially lower given socio-economic constraints. We calculate that land-based negative emissions from additional SOC sequestration could significantly contribute to reducing the anthropogenic CO 2 equivalent emission gap identified from Nationally Determined Contributions pledged by countries to stabilize global warming levels below 2 °C or even 1.5 °C under the Paris agreement on climate. The 4 per 1000 target could be implemented by taking into account differentiated SOC stock baselines, reversing the current trend of huge soil CO 2 losses, e.g. from agriculture encroaching peatland soils. We further discuss the potential benefits of SOC stewardship for both degraded and healthy soils along contrasting spatial scales (field, farm, landscape and country) and temporal (year to century) horizons. Last, we present some of the implications relative to non-CO 2 GHGs emissions, water and nutrients use as well as co-benefits for crop yields and climate change adaptation. We underline the considerable challenges associated with the non-permanence of SOC stocks and show how the rates of adoption and the duration of improved soil management practices could alter the global impacts of practices under the 4 per 1000 initiative. We conclude that the 4 per 1000 initiative has potential to support multiple sustainable development goals (SDGs) of the 2030 Agenda. It can be regarded as no-regret since increasing SOC in agricultural soils will contribute to food security benefits that will enhance resilience to climate change. However, social, economic and environmental safeguards will be needed to ensure an equitable and sustainable implementation of the 4 per 1000 target.
BibTeX:
@article{Soussana2019,
  author = {Soussana, Jean François and Lutfalla, Suzanne and Ehrhardt, Fiona and Rosenstock, Todd and Lamanna, Christine and Havlík, Petr and Richards, Meryl and Wollenberg, Eva (Lini) and Chotte, Jean Luc and Torquebiau, Emmanuel and Ciais, Philippe and Smith, Pete and Lal, Rattan},
  title = {Matching policy and science: Rationale for the ‘4 per 1000 - soils for food security and climate' initiative},
  journal = {Soil and Tillage Research},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {188},
  pages = {3--15},
  doi = {10.1016/j.still.2017.12.002}
}
Spielmann FM, Wohlfahrt G, Hammerle A, Kitz F, Migliavacca M, Alberti G, Ibrom A, El-Madany TS, Gerdel K, Moreno G, Kolle O, Karl T, Peressotti A and Delle Vedove G (2019), "Gross Primary Productivity of Four European Ecosystems Constrained by Joint CO2 and COS Flux Measurements", Geophysical Research Letters., may, 2019. Vol. 46(10), pp. 5284-5293. American Geophysical Union (AGU).
Abstract: Gross primary productivity (GPP), the gross uptake of carbon dioxide (CO2) by plant photosynthesis, is the primary driver of the land carbon sink, which presently removes around one quarter of the anthropogenic CO2 emissions each year. GPP, however, cannot be measured directly and the resulting uncertainty undermines our ability to project the magnitude of the future land carbon sink. Carbonyl sulfide (COS) has been proposed as an independent proxy for GPP as it diffuses into leaves in a fashion very similar to CO2, but in contrast to the latter is generally not emitted. Here we use concurrent ecosystem-scale flux measurements of CO2 and COS at four European biomes for a joint constraint on CO2 flux partitioning. The resulting GPP estimates generally agree with classical approaches relying exclusively on CO2 fluxes but indicate a systematic underestimation under low light conditions, demonstrating the importance of using multiple approaches for constraining present-day GPP.
BibTeX:
@article{Spielmann2019,
  author = {Spielmann, F. M. and Wohlfahrt, G. and Hammerle, A. and Kitz, F. and Migliavacca, M. and Alberti, G. and Ibrom, A. and El-Madany, T. S. and Gerdel, K. and Moreno, G. and Kolle, O. and Karl, T. and Peressotti, A. and Delle Vedove, G.},
  title = {Gross Primary Productivity of Four European Ecosystems Constrained by Joint CO2 and COS Flux Measurements},
  journal = {Geophysical Research Letters},
  publisher = {American Geophysical Union (AGU)},
  year = {2019},
  volume = {46},
  number = {10},
  pages = {5284--5293},
  doi = {10.1029/2019GL082006}
}
Steinhoff T, Gkritzalis T, Lauvset SK, Jones S, Schuster U, Olsen A, Becker M, Bozzano R, Brunetti F, Cantoni C, Cardin V, Diverrès D, Fiedler B, Fransson A, Giani M, Hartman S, Hoppema M, Jeansson E, Johannessen T, Kitidis V, Körtzinger A, Landa C, Lefèvre N, Luchetta A, Naudts L, Nightingale PD, Omar AM, Pensieri S, Pfeil B, Castaño-Primo R, Rehder G, Rutgersson A, Sanders R, Schewe I, Siena G, Skjelvan I, Soltwedel T, van Heuven S and Watson A (2019), "Constraining the Oceanic Uptake and Fluxes of Greenhouse Gases by Building an Ocean Network of Certified Stations: The Ocean Component of the Integrated Carbon Observation System, ICOS-Oceans", Frontiers in Marine Science., sep, 2019. Vol. 6
Abstract: The European Research Infrastructure Consortium “Integrated Carbon Observation System” (ICOS) aims at delivering high quality greenhouse gas (GHG) observations and derived data products (e.g., regional GHG-flux maps) for constraining the GHG balance on a European level, on a sustained long-term basis. The marine domain (ICOS-Oceans) currently consists of 11 Ship of Opportunity lines (SOOP – Ship of Opportunity Program) and 10 Fixed Ocean Stations (FOSs) spread across European waters, including the North Atlantic and Arctic Oceans and the Barents, North, Baltic, and Mediterranean Seas. The stations operate in a harmonized and standardized way based on community-proven protocols and methods for ocean GHG observations, improving operational conformity as well as quality control and assurance of the data. This enables the network to focus on long term research into the marine carbon cycle and the anthropogenic carbon sink, while preparing the network to include other GHG fluxes. ICOS data are processed on a near real-time basis and will be published on the ICOS Carbon Portal (CP), allowing monthly estimates of CO2 air-sea exchange to be quantified for European waters. ICOS establishes transparent operational data management routines following the FAIR (Findable, Accessible, Interoperable, and Reusable) guiding principles allowing amongst others reproducibility, interoperability, and traceability. The ICOS-Oceans network is actively integrating with the atmospheric (e.g., improved atmospheric measurements onboard SOOP lines) and ecosystem (e.g., oceanic direct gas flux measurements) domains of ICOS, and utilizes techniques developed by the ICOS Central Facilities and the CP. There is a strong interaction with the international ocean carbon cycle community to enhance interoperability and harmonize data flow. The future vision of ICOS-Oceans includes ship-based ocean survey sections to obtain a three-dimensional understanding of marine carbon cycle processes and optimize the existing network design.
BibTeX:
@article{Steinhoff2019,
  author = {Steinhoff, Tobias and Gkritzalis, Thanos and Lauvset, Siv K. and Jones, Steve and Schuster, Ute and Olsen, Are and Becker, Meike and Bozzano, Roberto and Brunetti, Fabio and Cantoni, Carolina and Cardin, Vanessa and Diverrès, Denis and Fiedler, Björn and Fransson, Agneta and Giani, Michele and Hartman, Sue and Hoppema, Mario and Jeansson, Emil and Johannessen, Truls and Kitidis, Vassilis and Körtzinger, Arne and Landa, Camilla and Lefèvre, Nathalie and Luchetta, Anna and Naudts, Lieven and Nightingale, Philip D. and Omar, Abdirahman M. and Pensieri, Sara and Pfeil, Benjamin and Castaño-Primo, Rocío and Rehder, Gregor and Rutgersson, Anna and Sanders, Richard and Schewe, Ingo and Siena, Giuseppe and Skjelvan, Ingunn and Soltwedel, Thomas and van Heuven, Steven and Watson, Andrew},
  title = {Constraining the Oceanic Uptake and Fluxes of Greenhouse Gases by Building an Ocean Network of Certified Stations: The Ocean Component of the Integrated Carbon Observation System, ICOS-Oceans},
  journal = {Frontiers in Marine Science},
  year = {2019},
  volume = {6},
  url = {https://www.frontiersin.org/article/10.3389/fmars.2019.00544/full},
  doi = {10.3389/fmars.2019.00544}
}
Stella P, Loubet B, de Berranger C, Charrier X, Ceschia E, Gerosa G, Finco A, Lamaud E, Serça D, George C and Ciuraru R (2019), "Soil ozone deposition: Dependence of soil resistance to soil texture", Atmospheric Environment., feb, 2019. Vol. 199, pp. 202-209. Elsevier BV.
Abstract: Soil deposition is an essential pathway for tropospheric ozone (O3) removal, but its controlling factors remain unclear. Here, we explored the variability of soil O3 resistance in response to soil texture. To this aim, data of O3 deposition over bare soil obtained from micrometeorological measurements under contrasted meteorological conditions for five sites were used. The results obtained are twofold: (i) soil resistance (Rsoil) increased with soil surface relative humidity (RHsurf), but (ii) this relationship exhibited large site-by-site variability. Further analysis showed that the minimum soil resistance (corresponding to completely dry soil surface or RHsurf = 0%) and the increase of Rsoil with RHsurf are both linked to soil clay content. These results can be explained by (i) the soil surface available for O3 deposition at a microscopic scale which is a function of the soil specific surface area, and (ii) the capacity of a soil to adsorb water according to its clay content and therefore to reduce the surface active for O3 deposition. From these results, a new parameterization has been established to estimate Rsoil as a function of RHsurf and soil clay fraction.
BibTeX:
@article{Stella2019,
  author = {Stella, P. and Loubet, B. and de Berranger, C. and Charrier, X. and Ceschia, E. and Gerosa, G. and Finco, A. and Lamaud, E. and Serça, D. and George, C. and Ciuraru, R.},
  title = {Soil ozone deposition: Dependence of soil resistance to soil texture},
  journal = {Atmospheric Environment},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {199},
  pages = {202--209},
  doi = {10.1016/j.atmosenv.2018.11.036}
}
Stoy PC, El-Madany TS, Fisher JB, Gentine P, Gerken T, Good SP, Klosterhalfen A, Liu S, Miralles DG, Perez-Priego O, Rigden AJ, Skaggs TH, Wohlfahrt G, Anderson RG, Coenders-Gerrits AMJ, Jung M, Maes WH, Mammarella I, Mauder M, Migliavacca M, Nelson JA, Poyatos R, Reichstein M, Scott RL and Wolf S (2019), "Reviews and syntheses: Turning the challenges of partitioning ecosystem evaporation and transpiration into opportunities", Biogeosciences., oct, 2019. Vol. 16(19), pp. 3747-3775. Copernicus GmbH.
Abstract: Evaporation (E) and transpiration (T) respond differently to ongoing changes in climate, atmospheric composition, and land use. It is difficult to partition ecosystem-scale evapotranspiration (ET) measurements into E and T, which makes it difficult to validate satellite data and land surface models. Here, we review current progress in partitioning E and T and provide a prospectus for how to improve theory and observations going forward. Recent advancements in analytical techniques create new opportunities for partitioning E and T at the ecosystem scale, but their assumptions have yet to be fully tested. For example, many approaches to partition E and T rely on the notion that plant canopy conductance and ecosystem water use efficiency exhibit optimal responses to atmospheric vapor pressure deficit (D). We use observations from 240 eddy covariance flux towers to demonstrate that optimal ecosystem response to D is a reasonable assumption, in agreement with recent studies, but more analysis is necessary to determine the conditions for which this assumption holds. Another critical assumption for many partitioning approaches is that ET can be approximated as T during ideal transpiring conditions, which has been challenged by observational studies. We demonstrate that T can exceed 95 % of ET from certain ecosystems, but other ecosystems do not appear to reach this value, which suggests that this assumption is ecosystem-dependent with implications for partitioning. It is important to further improve approaches for partitioning E and T, yet few multi-method comparisons have been undertaken to date. Advances in our understanding of carbon-water coupling at the stomatal, leaf, and canopy level open new perspectives on how to quantify T via its strong coupling with photosynthesis. Photosynthesis can be constrained at the ecosystem and global scales with emerging data sources including solar-induced fluorescence, carbonyl sulfide flux measurements, thermography, and more. Such comparisons would improve our mechanistic understanding of ecosystem water fluxes and provide the observations necessary to validate remote sensing algorithms and land surface models to understand the changing global water cycle.
BibTeX:
@article{Stoy2019,
  author = {Stoy, Paul C. and El-Madany, Tarek S. and Fisher, Joshua B. and Gentine, Pierre and Gerken, Tobias and Good, Stephen P. and Klosterhalfen, Anne and Liu, Shuguang and Miralles, Diego G. and Perez-Priego, Oscar and Rigden, Angela J. and Skaggs, Todd H. and Wohlfahrt, Georg and Anderson, Ray G. and Coenders-Gerrits, A. Miriam J. and Jung, Martin and Maes, Wouter H. and Mammarella, Ivan and Mauder, Matthias and Migliavacca, Mirco and Nelson, Jacob A. and Poyatos, Rafael and Reichstein, Markus and Scott, Russell L. and Wolf, Sebastian},
  title = {Reviews and syntheses: Turning the challenges of partitioning ecosystem evaporation and transpiration into opportunities},
  journal = {Biogeosciences},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {16},
  number = {19},
  pages = {3747--3775},
  doi = {10.5194/bg-16-3747-2019}
}
Su Y, Liu L, Wu J, Chen X, Shang J, Ciais P, Zhou G, Lafortezza R, Wang Y, Yuan W, Wang Y, Zhang H, Huang G and Huang N (2019), "Quantifying the biophysical effects of forests on local air temperature using a novel three-layered land surface energy balance model", Environment International., nov, 2019. Vol. 132, pp. 105080. Elsevier BV.
Abstract: The well-documented energy balance dynamics within forest ecosystems are poorly implemented in studies of the biophysical effects of forests. This results in limitations to the accurate quantification of forest cooling/warming on local air temperature. Taking into consideration the forest air space, this study proposes a three-layered (canopy, forest air space and soil [CAS]) land surface energy balance model to simulate air temperature within forest spaces (Taf) and subsequently to evaluate its biophysical effects on forest cooling/warming, i.e., the air temperature gradient (∆Ta) between the Taf and air temperature of open spaces (Tao) (∆Ta = Taf − Tao). We test the model using field data for 23 sites across 10 cities worldwide; the model shows satisfactory performance with the test data. High-latitude forests show greater seasonal dynamics of ∆Ta, generating considerable cooling of local air temperatures in warm seasons but minimal cooling or even warming effects during cool seasons, while low-latitude tropical forests always exert cooling effects with less interannual variability. The interannual dynamics of ∆Ta are significantly related to the seasonality of solar geometry and canopy leaf phenology. The differences between forest canopy temperature (Tc) and Tao, which are the two most important terms attributed by the CAS model in impacting Taf, explain a large part of forest cooling and warming (May–July: R2 = 0.35; November–January: R2 = 0.51). The novel CAS model provides a feasible way to represent the energy balance within forest ecosystems and to assess its impacts on local air temperatures globally.
BibTeX:
@article{Su2019,
  author = {Su, Yongxian and Liu, Liyang and Wu, Jianping and Chen, Xiuzhi and Shang, Jiali and Ciais, Philippe and Zhou, Guoyi and Lafortezza, Raffaele and Wang, Yingping and Yuan, Wenping and Wang, Yilong and Zhang, Hongou and Huang, Guangqing and Huang, Ningsheng},
  title = {Quantifying the biophysical effects of forests on local air temperature using a novel three-layered land surface energy balance model},
  journal = {Environment International},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {132},
  pages = {105080},
  doi = {10.1016/j.envint.2019.105080}
}
Super I, Denier van der Gon HA, Dellaert SN and Peters W (2019), "Optimizing a dynamic fossil fuel CO2 emission model with CTDAS (v1.0) for an urban area using atmospheric observations of CO2, CO, NOx, and SO2", Geoscientific Model Development Discussions., nov, 2019. , pp. 1-38. Copernicus GmbH.
BibTeX:
@article{Super2019,
  author = {Super, Ingrid and Denier van der Gon, Hugo A. and Dellaert, Stijn N. and Peters, Wouter},
  title = {Optimizing a dynamic fossil fuel CO2 emission model with CTDAS (v1.0) for an urban area using atmospheric observations of CO2, CO, NOx, and SO2},
  journal = {Geoscientific Model Development Discussions},
  publisher = {Copernicus GmbH},
  year = {2019},
  pages = {1--38},
  doi = {10.5194/gmd-2019-283}
}
Svensson N, Bergström H, Rutgersson A and Sahlée E (2019), "Modification of the Baltic Sea wind field by land-sea interaction", Wind Energy., jun, 2019. Vol. 22(6), pp. 764-779.
Abstract: The wind and turbulence fields over a small, high-latitude sea are investigated. These fields are highly influenced by the proximity to the coast, which is never more than 200 km away. Simulations with the WRF model over the Baltic Sea are compared with a simplified, stationary wind model driven by the synoptic forcing. The difference between the models is therefore representative of the mesoscale influence. The results show that the largest wind-field modifications compared with a neutral atmosphere occur during spring and summer, with a mean monthly increase of up to approximately 1 ms−1 at typical hub heights and upper rotor area (120-170 m height) in the WRF model. The main reason for this is large-scale low-level jets caused by the land-sea temperature differences, likely increasing in strength due to inertial oscillations. These kind of events can be persistent for approximately 12 hours and cover almost the entire basin, causing wind speed and wind shear to increase considerably. The strongest effect is around 2000 to 2300 local time. Sea breezes and coastal low-level jets are of less importance, but while sea breezes are mostly detected near the coastline, other types of coastal jets can extend large distances off the coast. During autumn and winter, there are fewer low-level jet occurrences, but the wind profile cannot be explained by the classical theory of the one-dimensional model. This indicates that the coastal environment is complex and may be affected by advection from land surfaces to a large degree even when unstable conditions dominate.
BibTeX:
@article{Svensson2019,
  author = {Svensson, Nina and Bergström, Hans and Rutgersson, Anna and Sahlée, Erik},
  title = {Modification of the Baltic Sea wind field by land-sea interaction},
  journal = {Wind Energy},
  year = {2019},
  volume = {22},
  number = {6},
  pages = {764--779},
  url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/we.2320},
  doi = {10.1002/we.2320}
}
Tanhua T, Pouliquen S, Hausman J, O'Brien KM, Bricher P, de Bruin T, Buck JJ, Burger EF, Carval T, Casey KS, Diggs S, Giorgetti A, Glaves H, Harscoat V, Kinkade D, Muelbert JH, Novellino A, Pfeil BG, Pulsifer P, Van de Putte AP, Robinson E, Shaap D, Smirnov A, Smith N, Snowden DP, Spears T, Stall S, Tacoma M, Thijsse P, Tronstad S, Vandenberghe T, Wengren M, Wyborn L and Zhao Z (2019), "Ocean FAIR data services", Frontiers in Marine Science., aug, 2019. Vol. 6(JUL) Frontiers Media SA.
Abstract: Well-founded data management systems are of vital importance for ocean observing systems as they ensure that essential data are not only collected but also retained and made accessible for analysis and application by current and future users. Effective data management requires collaboration across activities including observations, metadata and data assembly, quality assurance and control (QA/QC), and data publication that enables local and interoperable discovery and access, and secure archiving that guarantees long-term preservation. To achieve this, data should be Findable, Accessible, Interoperable, and Reusable (FAIR). Here, we outline how these principles apply to ocean data, and illustrate them with a few examples. In recent decades, ocean data managers, in close collaboration with international organizations, have played an active role in the improvement of environmental data standardization, accessibility and interoperability through different projects, enhancing access to observation data at all stages of the data life cycle and fostering the development of integrated services targeted to research, regulatory and operational users. As ocean observing systems evolve and an increasing number of autonomous platforms and sensors are deployed, the volume and variety of data increases dramatically. For instance, there are more than 70 data catalogues that contain metadata records for the polar oceans, a situation that makes comprehensive data discovery beyond the capacity of most researchers. To better serve research, operational, and commercial users, more efficient turnaround of quality data in known formats and made available through web services is necessary. In particular, automation of data workflows will be critical to reduce friction throughout the data value chain. Adhering to the FAIR principles with free, timely and unrestricted access to ocean observation data is beneficial for the originators, has obvious benefits for users and is an essential foundation for the development of new services made possible with big data technologies.
BibTeX:
@article{Tanhua2019,
  author = {Tanhua, Toste and Pouliquen, Sylvie and Hausman, Jessica and O'Brien, Kevin M. and Bricher, Pip and de Bruin, Taco and Buck, Justin J. and Burger, Eugene F. and Carval, Thierry and Casey, Kenneth S. and Diggs, Steve and Giorgetti, Alessandra and Glaves, Helen and Harscoat, Valerie and Kinkade, Danie and Muelbert, Jose H. and Novellino, Antonio and Pfeil, Benjamin G. and Pulsifer, Peter and Van de Putte, Anton P. and Robinson, Erin and Shaap, Dick and Smirnov, Alexander and Smith, Neville and Snowden, Derrick P. and Spears, Tobias and Stall, Shelley and Tacoma, Marten and Thijsse, Peter and Tronstad, Stein and Vandenberghe, Thomas and Wengren, Micha and Wyborn, Lesley and Zhao, Zhiming},
  title = {Ocean FAIR data services},
  journal = {Frontiers in Marine Science},
  publisher = {Frontiers Media SA},
  year = {2019},
  volume = {6},
  number = {JUL},
  doi = {10.3389/fmars.2019.00440}
}
Tebaldini S, Ho Tong Minh D, Mariotti d'Alessandro M, Villard L, Le Toan T and Chave J (2019), "The Status of Technologies to Measure Forest Biomass and Structural Properties: State of the Art in SAR Tomography of Tropical Forests", Surveys in Geophysics., may, 2019. Vol. 40(4), pp. 779-801. Springer Science and Business Media LLC.
Abstract: Synthetic aperture radar (SAR) tomography (TomoSAR) is an emerging technology to image the 3D structure of the illuminated media. TomoSAR exploits the key feature of microwaves to penetrate into vegetation, snow, and ice, hence providing the possibility to see features that are hidden to optical and hyper-spectral systems. The research on the use of P-band waves, in particular, has been largely propelled since 2007 in experimental studies supporting the future spaceborne Mission BIOMASS, to be launched in 2022 with the aim of mapping forest aboveground biomass (AGB) accurately and globally. The results obtained in the frame of these studies demonstrated that TomoSAR can be used for accurate retrieval of geophysical variables such as forest height and terrain topography and, especially in the case of dense tropical forests, to provide a more direct link to AGB. This paper aims at providing the reader with a comprehensive understanding of TomoSAR and its application for remote sensing of forested areas, with special attention to the case of tropical forests. We will introduce the basic physical principles behind TomoSAR, present the most relevant experimental results of the last decade, and discuss the potentials of BIOMASS tomography.
BibTeX:
@article{Tebaldini2019,
  author = {Tebaldini, Stefano and Ho Tong Minh, Dinh and Mariotti d'Alessandro, Mauro and Villard, Ludovic and Le Toan, Thuy and Chave, Jerome},
  title = {The Status of Technologies to Measure Forest Biomass and Structural Properties: State of the Art in SAR Tomography of Tropical Forests},
  journal = {Surveys in Geophysics},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {40},
  number = {4},
  pages = {779--801},
  doi = {10.1007/s10712-019-09539-7}
}
Tian H, Yang J, Xu R, Lu C, Canadell JG, Davidson EA, Jackson RB, Arneth A, Chang J, Ciais P, Gerber S, Ito A, Joos F, Lienert S, Messina P, Olin S, Pan S, Peng C, Saikawa E, Thompson RL, Vuichard N, Winiwarter W, Zaehle S and Zhang B (2019), "Global soil nitrous oxide emissions since the preindustrial era estimated by an ensemble of terrestrial biosphere models: Magnitude, attribution, and uncertainty", Global Change Biology., dec, 2019. Vol. 25(2), pp. 640-659. Wiley.
Abstract: Our understanding and quantification of global soil nitrous oxide (N 2 O) emissions and the underlying processes remain largely uncertain. Here, we assessed the effects of multiple anthropogenic and natural factors, including nitrogen fertilizer (N) application, atmospheric N deposition, manure N application, land cover change, climate change, and rising atmospheric CO 2 concentration, on global soil N 2 O emissions for the period 1861–2016 using a standard simulation protocol with seven process-based terrestrial biosphere models. Results suggest global soil N 2 O emissions have increased from 6.3 ± 1.1 Tg N 2 O-N/year in the preindustrial period (the 1860s) to 10.0 ± 2.0 Tg N 2 O-N/year in the recent decade (2007–2016). Cropland soil emissions increased from 0.3 Tg N 2 O-N/year to 3.3 Tg N 2 O-N/year over the same period, accounting for 82% of the total increase. Regionally, China, South Asia, and Southeast Asia underwent rapid increases in cropland N 2 O emissions since the 1970s. However, US cropland N 2 O emissions had been relatively flat in magnitude since the 1980s, and EU cropland N 2 O emissions appear to have decreased by 14%. Soil N 2 O emissions from predominantly natural ecosystems accounted for 67% of the global soil emissions in the recent decade but showed only a relatively small increase of 0.7 ± 0.5 Tg N 2 O-N/year (11%) since the 1860s. In the recent decade, N fertilizer application, N deposition, manure N application, and climate change contributed 54%, 26%, 15%, and 24%, respectively, to the total increase. Rising atmospheric CO 2 concentration reduced soil N 2 O emissions by 10% through the enhanced plant N uptake, while land cover change played a minor role. Our estimation here does not account for indirect emissions from soils and the directed emissions from excreta of grazing livestock. To address uncertainties in estimating regional and global soil N 2 O emissions, this study recommends several critical strategies for improving the process-based simulations.
BibTeX:
@article{Tian2019,
  author = {Tian, Hanqin and Yang, Jia and Xu, Rongting and Lu, Chaoqun and Canadell, Josep G. and Davidson, Eric A. and Jackson, Robert B. and Arneth, Almut and Chang, Jinfeng and Ciais, Philippe and Gerber, Stefan and Ito, Akihiko and Joos, Fortunat and Lienert, Sebastian and Messina, Palmira and Olin, Stefan and Pan, Shufen and Peng, Changhui and Saikawa, Eri and Thompson, Rona L. and Vuichard, Nicolas and Winiwarter, Wilfried and Zaehle, Sönke and Zhang, Bowen},
  title = {Global soil nitrous oxide emissions since the preindustrial era estimated by an ensemble of terrestrial biosphere models: Magnitude, attribution, and uncertainty},
  journal = {Global Change Biology},
  publisher = {Wiley},
  year = {2019},
  volume = {25},
  number = {2},
  pages = {640--659},
  doi = {10.1111/gcb.14514}
}
Tiralla N, Panferov O, Kreilein H, Olchev A, Ali AA and Knohl A (2019), "Quantification of leaf emisivities of forest species: Effects on modeled energy and matter fluxes in forest ecosystems", Geography, Environment, Sustainability., jul, 2019. Vol. 12(2), pp. 245-258. Faculty of Geography Lomonosov Moscow State University.
Abstract: Climate change has distinct regional and local differences in its impacts on the land surface. One of the important parameters determining the climate change signal is the emissivity (ε) of the surface. In forest-climate interactions, the leaf surface emissivity plays a decisive role. The accurate determination of leaf emissivities is crucial for the appropriate interpretation of measured energy and matter fluxes between the forest and the atmosphere. In this study, we quantified the emissivity of the five broadleaf tree species Acer pseudoplatanus, Fagus sylvatica, Fraxinus excelsior, Populus simonii and Populus candicans. Measurements of leaf surface temperatures were conducted under laboratory conditions in a controlled-climate chamber within the temperature range of +8 °C and +32 °C. Based on these measurements, broadband leaf emissivities ε (ε for the spectral range of 8-14 µm) were calculated. Average ε8-14 µm was 0.958±0.002 for all species with very little variation among species. In a second step, the soil-vegetation-atmosphere transfer model ‘MixFor-SVAT' was applied to examine the effects of e changes on radiative, sensible and latent energy fluxes of the Hainich forest in Central Germany. Model experiments were driven by meteorological data measured at the Hainich site. The simulations were forced with the calculated ε value as well as with minimum and maximum values obtained from the literature. Significant effects of ε changes were detected. The strongest effect was identified for the sensible heat flux with a sensitivity of 20.7 % per 1 % ε change. Thus, the variability of ε should be considered in climate change studies.
BibTeX:
@article{Tiralla2019,
  author = {Tiralla, Nina and Panferov, Oleg and Kreilein, Heinrich and Olchev, Alexander and Ali, Ashehad A. and Knohl, Alexander},
  title = {Quantification of leaf emisivities of forest species: Effects on modeled energy and matter fluxes in forest ecosystems},
  journal = {Geography, Environment, Sustainability},
  publisher = {Faculty of Geography Lomonosov Moscow State University},
  year = {2019},
  volume = {12},
  number = {2},
  pages = {245--258},
  doi = {10.24057/2071-9388-2018-86}
}
Tsuruta A, Aalto T, Backman L, Krol MC, Peters W, Lienert S, Joos F, Miller PA, Zhang W, Laurila T, Hatakka J, Leskinen A, Lehtinen KE, Peltola O, Vesala T, Levula J, Dlugokencky E, Heimann M, Kozlova E, Aurela M, Lohila A, Kauhaniemi M and Gomez-Pelaez AJ (2019), "Methane budget estimates in Finland from the CarbonTracker Europe-CH4 data assimilation system", Tellus, Series B: Chemical and Physical Meteorology., jan, 2019. Vol. 71(1), pp. 1-20. Informa UK Limited.
Abstract: We estimated the CH4 budget in Finland for 2004–2014 using the CTE-CH4 data assimilation system with an extended atmospheric CH4 observation network of seven sites from Finland to surrounding regions (Hyytiälä, Kjølnes, Kumpula, Pallas, Puijo, Sodankylä, and Utö). The estimated average annual total emission for Finland is 0.6 ± 0.5 Tg CH4 yr−1. Sensitivity experiments show that the posterior biospheric emission estimates for Finland are between 0.3 and 0.9 Tg CH4 yr−1, which lies between the LPX-Bern-DYPTOP (0.2 Tg CH4 yr−1) and LPJG-WHyMe (2.2 Tg CH4 yr−1) process-based model estimates. For anthropogenic emissions, we found that the EDGAR v4.2 FT2010 inventory (0.4 Tg CH4 yr−1) is likely to overestimate emissions in southernmost Finland, but the extent of overestimation and possible relocation of emissions are difficult to derive from the current observation network. The posterior emission estimates were especially reliant on prior information in central Finland. However, based on analysis of posterior atmospheric CH4, we found that the anthropogenic emission distribution based on a national inventory is more reliable than the one based on EDGAR v4.2 FT2010. The contribution of total emissions in Finland to global total emissions is only about 0.13%, and the derived total emissions in Finland showed no trend during 2004–2014. The model using optimized emissions was able to reproduce observed atmospheric CH4 at the sites in Finland and surrounding regions fairly well (correlation textgreater0.75, bias (Formula presented.) ppb), supporting adequacy of the observations to be used in atmospheric inversion studies. In addition to global budget estimates, we found that CTE-CH4 is also applicable for regional budget estimates, where small scale (1º × 1º in this case) optimization is possible with a dense observation network.
BibTeX:
@article{Tsuruta2019,
  author = {Tsuruta, Aki and Aalto, Tuula and Backman, Leif and Krol, Maarten C. and Peters, Wouter and Lienert, Sebastian and Joos, Fortunat and Miller, Paul A. and Zhang, Wenxin and Laurila, Tuomas and Hatakka, Juha and Leskinen, Ari and Lehtinen, Kari E.J. and Peltola, Olli and Vesala, Timo and Levula, Janne and Dlugokencky, Ed and Heimann, Martin and Kozlova, Elena and Aurela, Mika and Lohila, Annalea and Kauhaniemi, Mari and Gomez-Pelaez, Angel J.},
  title = {Methane budget estimates in Finland from the CarbonTracker Europe-CH4 data assimilation system},
  journal = {Tellus, Series B: Chemical and Physical Meteorology},
  publisher = {Informa UK Limited},
  year = {2019},
  volume = {71},
  number = {1},
  pages = {1--20},
  doi = {10.1080/16000889.2018.1565030}
}
Tuovinen JP, Aurela M, Hatakka J, Räsänen A, Virtanen T, Mikola J, Ivakhov V, Kondratyev V and Laurila T (2019), "Interpreting eddy covariance data from heterogeneous Siberian tundra: Land-cover-specific methane fluxes and spatial representativeness", Biogeosciences., jan, 2019. Vol. 16(2), pp. 255-274. Copernicus GmbH.
Abstract: The non-uniform spatial integration, an inherent feature of the eddy covariance (EC) method, creates a challenge for flux data interpretation in a heterogeneous environment, where the contribution of different land cover types varies with flow conditions, potentially resulting in biased estimates in comparison to the areally averaged fluxes and land cover attributes. We modelled flux footprints and characterized the spatial scale of our EC measurements in Tiksi, a tundra site in northern Siberia. We used leaf area index (LAI) and land cover class (LCC) data, derived from very-high-spatial-resolution satellite imagery and field surveys, and quantified the sensor location bias. We found that methane (CH 4 ) fluxes varied strongly with wind direction (-0:09 to 0.59 μgCH 4 m -2 s -1 on average) during summer 2014, reflecting the distribution of different LCCs. Other environmental factors had only a minor effect on short-term flux variations but influenced the seasonal trend. Using footprint weights of grouped LCCs as explanatory variables for the measured CH 4 flux, we developed a multiple regression model to estimate LCC group-specific fluxes. This model showed that wet fen and graminoid tundra patches in locations with topography-enhanced wetness acted as strong sources (1.0 μgCH 4 m -2 s -1 during the peak emission period), while mineral soils were significant sinks (-0:13 μgCH 4 m -2 s -1 ). To assess the representativeness of measurements, we upscaled the LCC group-specific fluxes to different spatial scales. Despite the landscape heterogeneity and rather poor representativeness of EC data with respect to the areally averaged LAI and coverage of some LCCs, the mean flux was close to the CH 4 balance upscaled to an area of 6.3 km 2 , with a location bias of 14 %. We recommend that EC site descriptions in a heterogeneous environment should be complemented with footprint-weighted highresolution data on vegetation and other site characteristics.
BibTeX:
@article{Tuovinen2019,
  author = {Tuovinen, Juha Pekka and Aurela, Mika and Hatakka, Juha and Räsänen, Aleksi and Virtanen, Tarmo and Mikola, Juha and Ivakhov, Viktor and Kondratyev, Vladimir and Laurila, Tuomas},
  title = {Interpreting eddy covariance data from heterogeneous Siberian tundra: Land-cover-specific methane fluxes and spatial representativeness},
  journal = {Biogeosciences},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {16},
  number = {2},
  pages = {255--274},
  doi = {10.5194/bg-16-255-2019}
}
Vernet M, Geibert W, Hoppema M, Brown PJ, Haas C, Hellmer HH, Jokat W, Jullion L, Mazloff M, Bakker DC, Brearley JA, Croot P, Hattermann T, Hauck J, Hillenbrand CD, Hoppe CJ, Huhn O, Koch BP, Lechtenfeld OJ, Meredith MP, Naveira Garabato AC, Nöthig EM, Peeken I, Rutgers van der Loeff MM, Schmidtko S, Schröder M, Strass VH, Torres-Valdés S and Verdy A (2019), "The Weddell Gyre, Southern Ocean: Present Knowledge and Future Challenges", Reviews of Geophysics., jul, 2019. Vol. 57(3), pp. 623-708. American Geophysical Union (AGU).
Abstract: The Weddell Gyre (WG) is one of the main oceanographic features of the Southern Ocean south of the Antarctic Circumpolar Current which plays an influential role in global ocean circulation as well as gas exchange with the atmosphere. We review the state-of-the art knowledge concerning the WG from an interdisciplinary perspective, uncovering critical aspects needed to understand this system's role in shaping the future evolution of oceanic heat and carbon uptake over the next decades. The main limitations in our knowledge are related to the conditions in this extreme and remote environment, where the polar night, very low air temperatures, and presence of sea ice year-round hamper field and remotely sensed measurements. We highlight the importance of winter and under-ice conditions in the southern WG, the role that new technology will play to overcome present-day sampling limitations, the importance of the WG connectivity to the low-latitude oceans and atmosphere, and the expected intensification of the WG circulation as the westerly winds intensify. Greater international cooperation is needed to define key sampling locations that can be visited by any research vessel in the region. Existing transects sampled since the 1980s along the Prime Meridian and along an East-West section at ˜62°S should be maintained with regularity to provide answers to the relevant questions. This approach will provide long-term data to determine trends and will improve representation of processes for regional, Antarctic-wide, and global modeling efforts—thereby enhancing predictions of the WG in global ocean circulation and climate.
BibTeX:
@article{Vernet2019,
  author = {Vernet, M. and Geibert, W. and Hoppema, M. and Brown, P. J. and Haas, C. and Hellmer, H. H. and Jokat, W. and Jullion, L. and Mazloff, M. and Bakker, D. C.E. and Brearley, J. A. and Croot, P. and Hattermann, T. and Hauck, J. and Hillenbrand, C. D. and Hoppe, C. J.M. and Huhn, O. and Koch, B. P. and Lechtenfeld, O. J. and Meredith, M. P. and Naveira Garabato, A. C. and Nöthig, E. M. and Peeken, I. and Rutgers van der Loeff, M. M. and Schmidtko, S. and Schröder, M. and Strass, V. H. and Torres-Valdés, S. and Verdy, A.},
  title = {The Weddell Gyre, Southern Ocean: Present Knowledge and Future Challenges},
  journal = {Reviews of Geophysics},
  publisher = {American Geophysical Union (AGU)},
  year = {2019},
  volume = {57},
  number = {3},
  pages = {623--708},
  doi = {10.1029/2018RG000604}
}
Vincent-Barbaroux C, Berveiller D, Lelarge-Trouverie C, Maia R, Máguas C, Pereira J, Chaves MM and Damesin C (2019), "Carbon-use strategies in stem radial growth of two oak species, one Temperate deciduous and one Mediterranean evergreen: what can be inferred from seasonal variations in the δ13C of the current year ring?", Tree physiology., may, 2019. Vol. 39(8), pp. 1329-1341. Oxford University Press (OUP).
Abstract: Tree ring synthesis is a key process in wood production; however, little is known of the origin and fate of the carbon involved. We used natural 13C abundance to investigate the carbon-use process for the ring development in a temperate deciduous (Quercus petraea (Matt.) Liebl.) and a Mediterranean evergreen (Quercus ilex L.) oak. The sapwood carbon reserves, phloem sucrose contents, stem respired CO2 efflux and their respective carbon isotope compositions (δ13C) were recorded over 1 year, in the native area of each species. The seasonal δ13C variation of the current year ring was determined in the total ring throughout the seasons, as well as in slices from the fully mature ring after the growth season (intra-ring pattern). Although the budburst dates of the two oaks were similar, the growth of Quercus ilex began 50 days later. Both species exhibited growth cessation during the hot and dry summer but only Q. ilex resumed in the autumn. In the deciduous oak, xylem starch storage showed clear variations during the radial growth. The intra-ring δ13C variations of the two species exhibited similar ranges, but contrasting patterns, with an early increase for Q. petraea. Comparison between δ13C of starch and total ring suggested that Q. petraea (but not Q. ilex) builds its rings using reserves during the first month of growth. Shifts in ring and soluble sugars δ13C suggested an interspecific difference in either the phloem unloading or the use of fresh assimilate inside the ring. A decrease in ring δ13C for both oaks between the end of the radial growth and the winter is attributed to a lignification of ring cell walls after stem increment. This study highlighted the differences in carbon-use during ring growth for evergreen and deciduous oaks, as well as the benefits of exploring the process using natural 13C abundance.
BibTeX:
@article{VincentBarbaroux2019,
  author = {Vincent-Barbaroux, Cécile and Berveiller, Daniel and Lelarge-Trouverie, Caroline and Maia, Rodrigo and Máguas, Cristina and Pereira, João and Chaves, Manuela M. and Damesin, Claire},
  title = {Carbon-use strategies in stem radial growth of two oak species, one Temperate deciduous and one Mediterranean evergreen: what can be inferred from seasonal variations in the δ13C of the current year ring?},
  journal = {Tree physiology},
  publisher = {Oxford University Press (OUP)},
  year = {2019},
  volume = {39},
  number = {8},
  pages = {1329--1341},
  doi = {10.1093/treephys/tpz043}
}
Vitale D, Bilancia M and Papale D (2019), "A multiple imputation strategy for eddy covariance data", Journal of Environmental Informatics., jul, 2019. Vol. 34(2), pp. 68-87. International Society for Environmental Information Science (ISEIS).
Abstract: Half-hourly time series of net ecosystem exchange (NEE) of CO2, latent heat flux (LE) and sensible heat flux (H) measured through the micro-meteorological eddy covariance (EC) technique are noisy and show a high percentage of missing data. By using EC measurements that are part of the FLUXNET2015 dataset, we evaluate the performance of a multiple imputation (MI) strategy based on an efficient computational strategy introduced in Honaker and King (2010), combining the classic Expectation-Maximization (EM) algorithm with a bootstrap approach, in order to take draws from a suitable approximation of posterior distribution of model parameters. Armed with these instruments, we are able to introduce three new multiple imputation models, characterized by an increasing level of complexity, and built on top of multivariate normality assumption: 1) MLR, which imputes EC missing values using a static multiple linear regression of observed values of suitable input variables; 2) ADL, which enriches with dynamic properties the static specification of MLR, by considering an autoregressive distributed lag specification; 3) PADL, which adds further complexity by embedding the ADL model in a panel-data perspective. Under several artificial gap scenarios, we show that PADL has a better ability in modeling the complex dynamics of ecosystem fluxes and reconstructing missing data points, thus providing unbiased imputations and preserving the original sampling distribution. The added flexibility arising from the time series cross section structure of PADL warrants improved performances, outperforming those of other imputation methods, as well as of the marginal distribution sampling algorithm (MDS), a widely used gap-filling approach introduced by Reichstein et al. (2005), especially in the case of nighttime flux data. It is expected that the strategy proposed in this paper will become useful in creating multiple imputations for a variety of EC datasets, providing valid inferences for a broad range of scientific estimands (such as annual budgets).
BibTeX:
@article{Vitale2019,
  author = {Vitale, D. and Bilancia, M. and Papale, D.},
  title = {A multiple imputation strategy for eddy covariance data},
  journal = {Journal of Environmental Informatics},
  publisher = {International Society for Environmental Information Science (ISEIS)},
  year = {2019},
  volume = {34},
  number = {2},
  pages = {68--87},
  doi = {10.3808/jei.201800391}
}
Vitale D, Bilancia M and Papale D (2019), "Modelling random uncertainty of eddy covariance flux measurements", Stochastic Environmental Research and Risk Assessment., mar, 2019. Vol. 33(3), pp. 725-746. Springer Science and Business Media LLC.
Abstract: The eddy-covariance (EC) technique is considered the most direct and reliable method to calculate flux exchanges of the main greenhouse gases over natural ecosystems and agricultural fields. The resulting measurements are extremely important to characterize ecosystem exchanges of carbon, water, energy and other trace gases, and are widely used to validate or constrain parameter of land surface models via data assimilation techniques. For this purpose, the availability of both complete half-hourly flux time series and its associated uncertainty is mandatory. However, uncertainty estimation for EC data is challenging because the standard procedures based on repeated sampling are not suitable for this kind of measurements, and the presence of missing data makes it difficult to build any sensible time series model with time-varying second-order moments that can provide estimates of total random uncertainty. To overcome such limitations, this paper describes a new method in the context of the strategy based on the model residual approach proposed by Richardson et al. (Agric For Meteorol 148(1): 38–50, 2008). The proposed approach consists in (1) estimating the conditional mean process as representative of the true signal underlying observed data and (2) estimating the conditional variance process as representative of the total random uncertainty affecting EC data. The conditional mean process is estimated through the multiple imputation algorithm recently proposed by Vitale et al. (J Environ Inform https://doi.org/10.3808/jei.201800391, 2018). The conditional variance process is estimated through the stochastic volatility model introduced by Beltratti and Morana (Econ Notes 30(2): 205–234, 2001). This strategy is applied to ten sites that are part of FLUXNET2015 dataset, selected in such a way to cover various ecosystem types under different climatic regimes around the world. The estimated uncertainty is compared with estimates by other well-established methods, and it is demonstrated that the scaling relationship between uncertainty and flux magnitude is preserved. Additionally, the proposed strategy allows obtaining a complete half-hourly time series of uncertainty estimates, which are expected to be useful for many users of EC flux data.
BibTeX:
@article{Vitale2019a,
  author = {Vitale, Domenico and Bilancia, Massimo and Papale, Dario},
  title = {Modelling random uncertainty of eddy covariance flux measurements},
  journal = {Stochastic Environmental Research and Risk Assessment},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {33},
  number = {3},
  pages = {725--746},
  doi = {10.1007/s00477-019-01664-4}
}
Vogel FR, Frey M, Staufer J, Hase F, Broquet G, Xueref-Remy I, Chevallier F, Ciais P, Sha MK, Chelin P, Jeseck P, Janssen C, Té Y, Groß J, Blumenstock T, Tu Q and Orphal J (2019), "XCO2 in an emission hot-spot region: The COCCON Paris campaign 2015", Atmospheric Chemistry and Physics., mar, 2019. Vol. 19(5), pp. 3271-3285. Copernicus GmbH.
Abstract: Providing timely information on urban greenhouse gas (GHG) emissions and their trends to stakeholders relies on reliable measurements of atmospheric concentrations and the understanding of how local emissions and atmospheric transport influence these observations. Portable Fourier transform infrared (FTIR) spectrometers were deployed at five stations in the Paris metropolitan area to provide column-averaged concentrations of CO2 (XCO2) during a field campaign in spring of 2015, as part of the Collaborative Carbon Column Observing Network (COCCON). Here, we describe and analyze the variations of XCO2 observed at different sites and how they changed over time. We find that observations upwind and downwind of the city centre differ significantly in their XCO2 concentrations, while the overall variability of the daily cycle is similar, i.e. increasing during night-time with a strong decrease (typically 2-3 ppm) during the afternoon. An atmospheric transport model framework (CHIMERECAMS) was used to simulate XCO2 and predict the same behaviour seen in the observations, which supports key findings, e.g. that even in a densely populated region like Paris (over 12 million people), biospheric uptake of CO2 can be of major influence on daily XCO2 variations. Despite a general offset between modelled and observed XCO2, the model correctly predicts the impact of the meteorological parameters (e.g. wind direction and speed) on the concentration gradients between different stations. When analyzing local gradients of XCO2 for upwind and downwind station pairs, those local gradients are found to be less sensitive to changes in XCO2 boundary conditions and biogenic fluxes within the domain and we find the model-data agreement further improves. Our modelling framework indicates that the local XCO2 gradient between the stations is dominated by the fossil fuel CO2 signal of the Paris metropolitan area. This furtherhighlights the potential usefulness of XCO2 observations to help optimize future urban GHG emission estimates.
BibTeX:
@article{Vogel2019,
  author = {Vogel, Felix R. and Frey, Matthias and Staufer, Johannes and Hase, Frank and Broquet, Grégoire and Xueref-Remy, Irène and Chevallier, Frédéric and Ciais, Philippe and Sha, Mahesh Kumar and Chelin, Pascale and Jeseck, Pascal and Janssen, Christof and Té, Yao and Groß, Jochen and Blumenstock, Thomas and Tu, Qiansi and Orphal, Johannes},
  title = {XCO2 in an emission hot-spot region: The COCCON Paris campaign 2015},
  journal = {Atmospheric Chemistry and Physics},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {19},
  number = {5},
  pages = {3271--3285},
  doi = {10.5194/acp-19-3271-2019}
}
Voigt C, Marushchak ME, Mastepanov M, Lamprecht RE, Christensen TR, Dorodnikov M, Jackowicz-Korczyʼnski M, Lindgren A, Lohila A, Nykänen H, Oinonen M, Oksanen T, Palonen V, Treat CC, Martikainen PJ and Biasi C (2019), "Ecosystem carbon response of an Arctic peatland to simulated permafrost thaw", Global Change Biology., feb, 2019. Vol. 25(5), pp. 1746-1764. Wiley.
Abstract: Permafrost peatlands are biogeochemical hot spots in the Arctic as they store vast amounts of carbon. Permafrost thaw could release part of these long-term immobile carbon stocks as the greenhouse gases (GHGs) carbon dioxide (CO 2 ) and methane (CH 4 ) to the atmosphere, but how much, at which time-span and as which gaseous carbon species is still highly uncertain. Here we assess the effect of permafrost thaw on GHG dynamics under different moisture and vegetation scenarios in a permafrost peatland. A novel experimental approach using intact plant–soil systems (mesocosms) allowed us to simulate permafrost thaw under near-natural conditions. We monitored GHG flux dynamics via high-resolution flow-through gas measurements, combined with detailed monitoring of soil GHG concentration dynamics, yielding insights into GHG production and consumption potential of individual soil layers. Thawing the upper 10–15 cm of permafrost under dry conditions increased CO 2 emissions to the atmosphere (without vegetation: 0.74 ± 0.49 vs. 0.84 ± 0.60 g CO 2 –C m −2 day −1 ; with vegetation: 1.20 ± 0.50 vs. 1.32 ± 0.60 g CO 2 –C m −2 day −1 , mean ± SD, pre- and post-thaw, respectively). Radiocarbon dating ( 14 C) of respired CO 2 , supported by an independent curve-fitting approach, showed a clear contribution (9%–27%) of old carbon to this enhanced post-thaw CO 2 flux. Elevated concentrations of CO 2 , CH 4 , and dissolved organic carbon at depth indicated not just pulse emissions during the thawing process, but sustained decomposition and GHG production from thawed permafrost. Oxidation of CH 4 in the peat column, however, prevented CH 4 release to the atmosphere. Importantly, we show here that, under dry conditions, peatlands strengthen the permafrost–carbon feedback by adding to the atmospheric CO 2 burden post-thaw. However, as long as the water table remains low, our results reveal a strong CH 4 sink capacity in these types of Arctic ecosystems pre- and post-thaw, with the potential to compensate part of the permafrost CO 2 losses over longer timescales.
BibTeX:
@article{Voigt2019,
  author = {Voigt, Carolina and Marushchak, Maija E. and Mastepanov, Mikhail and Lamprecht, Richard E. and Christensen, Torben R. and Dorodnikov, Maxim and Jackowicz-Korczyʼnski, Marcin and Lindgren, Amelie and Lohila, Annalea and Nykänen, Hannu and Oinonen, Markku and Oksanen, Timo and Palonen, Vesa and Treat, Claire C. and Martikainen, Pertti J. and Biasi, Christina},
  title = {Ecosystem carbon response of an Arctic peatland to simulated permafrost thaw},
  journal = {Global Change Biology},
  publisher = {Wiley},
  year = {2019},
  volume = {25},
  number = {5},
  pages = {1746--1764},
  doi = {10.1111/gcb.14574}
}
Wang S, Garcia M, Bauer-Gottwein P, Jakobsen J, Zarco-Tejada PJ, Bandini F, Paz VS and Ibrom A (2019), "High spatial resolution monitoring land surface energy, water and CO2 fluxes from an Unmanned Aerial System", Remote Sensing of Environment., aug, 2019. Vol. 229, pp. 14-31. Elsevier BV.
Abstract: High spatial resolution maps of land surface energy, water and CO2 fluxes, e.g. evapotranspiration (ET)and gross primary productivity (GPP), are important for agricultural monitoring, ecosystem and water resources management. However, it is not clear which is the optimal (e.g. coarsest possible)spatial resolution to capture those fluxes accurately. Unmanned Aerial Systems (UAS)can address this by collecting very high spatial resolution (textless1 m, VHR)imagery. The objective of this study is to model ET and GPP dynamics using VHR optical and thermal imagery and quantify the influence of the spatial heterogeneity in the flux simulations and validations. The study was conducted at a deciduous willow bioenergy eddy covariance (EC)flux site in Denmark. Flight campaigns were conducted during the growing seasons of 2016 and 2017 with a hexacopter equipped with RGB, multispectral and thermal infrared cameras. A ‘top-down' modeling approach consisting of the Priestley–Taylor Jet Propulsion Laboratory model and a light use efficiency model sharing the same canopy biophysical constraints was used to estimate ET and GPP. Model outputs were benchmarked by EC flux observations with the source weighted footprint. Our results indicate that our model can well estimate the instantaneous net radiation, ET, GPP, evaporative fraction, light use efficiency and water use efficiency with root-mean-square deviations (RMSD)of 31.6 Wtextperiodcenteredm−2, 41.2 Wtextperiodcenteredm−2, 3.12 μmoltextperiodcenteredCtextperiodcenteredm−2textperiodcentereds−1, 0.08, 0.16 gtextperiodcenteredCtextperiodcenteredMJ−1 and 0.35 gtextperiodcenteredCtextperiodcenteredkg−1, respectively. Further, it is found that using a footprint model to sample different areas of VHR imagery can be a tool to provide better diurnal estimates to benchmark with EC data. Moreover, these VHR maps (0.3 m)allowed us to quantify metrics of spatial heterogeneity by using semivariogram analysis and by aggregating model inputs into different spatial resolutions. For instance, we find that in this site, the aggregation of simulated GPP using the source weighted mean of the EC footprint was about 30% lower in RMSD than using the arithmetic mean of the footprint. This demonstrates the accuracy of the modeled VHR spatial patterns. Nevertheless, we also find that imagery resolution consistent with the canopy size (around 1.5 m in our study)is sufficient to capture the spatial heterogeneity of the fluxes as transpiration and canopy assimilation of CO2 are processes regulated at the tree crown level. Our results highlight the importance of considering the land surface heterogeneity for flux modeling and the source contribution within the EC footprint for model benchmarking at appropriate spatial resolutions.
BibTeX:
@article{Wang2019,
  author = {Wang, Sheng and Garcia, Monica and Bauer-Gottwein, Peter and Jakobsen, Jakob and Zarco-Tejada, Pablo J. and Bandini, Filippo and Paz, Verónica Sobejano and Ibrom, Andreas},
  title = {High spatial resolution monitoring land surface energy, water and CO2 fluxes from an Unmanned Aerial System},
  journal = {Remote Sensing of Environment},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {229},
  pages = {14--31},
  doi = {10.1016/j.rse.2019.03.040}
}
Wang Y, Ciais P, Broquet G, Bréon FM, Oda T, Lespinas F, Meijer Y, Loescher A, Janssens-Maenhout G, Zheng B, Xu H, Tao S, Gurney KR, Roest G, Santaren D and Su Y (2019), "A global map of emission clumps for future monitoring of fossil fuel CO2 emissions from space", Earth System Science Data., may, 2019. Vol. 11(2), pp. 687-703. Copernicus GmbH.
Abstract: A large fraction of fossil fuel CO 2 emissions emanate from "hotspots", such as cities (where direct CO 2 emissions related to fossil fuel combustion in transport, residential, commercial sectors, etc., excluding emissions from electricity-producing power plants, occur), isolated power plants, and manufacturing facilities, which cover a small fraction of the land surface. The coverage of all high-emitting cities and point sources across the globe by bottom-up inventories is far from complete, and for most of those covered, the uncertainties in CO 2 emission estimates in bottom-up inventories are too large to allow continuous and rigorous assessment of emission changes (Gurney et al., 2019). Space-borne imagery of atmospheric CO 2 has the potential to provide independent estimates of CO 2 emissions from hotspots. But first, what a hotspot is needs to be defined for the purpose of satellite observations. The proposed space-borne imagers with global coverage planned for the coming decade have a pixel size on the order of a few square kilometers and a XCO 2 accuracy and precision of textless 1 ppm for individual measurements of vertically integrated columns of dry-air mole fractions of CO 2 (XCO 2 ). This resolution and precision is insufficient to provide a cartography of emissions for each individual pixel. Rather, the integrated emission of diffuse emitting areas and intense point sources is sought. In this study, we characterize area and point fossil fuel CO 2 emitting sources which generate coherent XCO 2 plumes that may be observed from space. We characterize these emitting sources around the globe and they are referred to as "emission clumps" hereafter. An algorithm is proposed to identify emission clumps worldwide, based on the ODIAC global high-resolution 1 km fossil fuel emission data product. The clump algorithm selects the major urban areas from a GIS (geographic information system) file and two emission thresholds. The selected urban areas and a high emission threshold are used to identify clump cores such as inner city areas or large power plants. A low threshold and a random walker (RW) scheme are then used to aggregate all grid cells contiguous to cores in order to define a single clump. With our definition of the thresholds, which are appropriate for a space imagery with 0.5 ppm precision for a single XCO 2 measurement, a total of 11 314 individual clumps, with 5088 area clumps, and 6226 point-source clumps (power plants) are identified. These clumps contribute 72% of the global fossil fuel CO 2 emissions according to the ODIAC inventory. The emission clumps is a new tool for comparing fossil fuel CO 2 emissions from different inventories and objectively identifying emitting areas that have a potential to be detected by future global satellite imagery of XCO 2 . The emission clump data product is distributed from https://doi.org/10.6084/m9.figshare.7217726.v1.
BibTeX:
@article{Wang2019a,
  author = {Wang, Yilong and Ciais, Philippe and Broquet, Grégoire and Bréon, François Marie and Oda, Tomohiro and Lespinas, Franck and Meijer, Yasjka and Loescher, Armin and Janssens-Maenhout, Greet and Zheng, Bo and Xu, Haoran and Tao, Shu and Gurney, Kevin R. and Roest, Geoffrey and Santaren, Diego and Su, Yongxian},
  title = {A global map of emission clumps for future monitoring of fossil fuel CO2 emissions from space},
  journal = {Earth System Science Data},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {11},
  number = {2},
  pages = {687--703},
  doi = {10.5194/essd-11-687-2019}
}
Wanninkhof R, Pickers PA, Omar AM, Sutton A, Murata A, Olsen A, Stephens BB, Tilbrook B, Munro D, Pierrot D, Rehder G, Santana-Casiano JM, Müller JD, Trinanes J, Tedesco K, O'Brien K, Currie K, Barbero L, Telszewski M, Hoppema M, Ishii M, González-Dávila M, Bates NR, Metzl N, Suntharalingam P, Feely RA, ichiro Nakaoka S, Lauvset SK, Takahashi T, Steinhoff T and Schuster U (2019), "A surface ocean CO2 reference network, SOCONET and associated marine boundary layer CO2 measurements", Frontiers in Marine Science., jul, 2019. Vol. 6(JUL) Frontiers Media SA.
Abstract: The Surface Ocean CO2 NETwork (SOCONET) and atmospheric Marine Boundary Layer (MBL) CO2 measurements from ships and buoys focus on the operational aspects of measurements of CO2 in both the ocean surface and atmospheric MBLs. The goal is to provide accurate pCO2 data to within 2 micro atmosphere (μatm) for surface ocean and 0.2 parts per million (ppm) for MBL measurements following rigorous best practices, calibration and intercomparison procedures. Platforms and data will be tracked in near real-time and final quality-controlled data will be provided to the community within a year. The network, involving partners worldwide, will aid in production of important products such as maps of monthly resolved surface ocean CO2 and air-sea CO2 flux measurements. These products and other derivatives using surface ocean and MBL CO2 data, such as surface ocean pH maps and MBL CO2 maps, will be of high value for policy assessments and socio-economic decisions regarding the role of the ocean in sequestering anthropogenic CO2 and how this uptake is impacting ocean health by ocean acidification. SOCONET has an open ocean emphasis but will work with regional (coastal) networks. It will liaise with intergovernmental science organizations such as Global Atmosphere Watch (GAW), and the joint committee for and ocean and marine meteorology (JCOMM). Here we describe the details of this emerging network and its proposed operations and practices.
BibTeX:
@article{Wanninkhof2019,
  author = {Wanninkhof, Rik and Pickers, Penelope A. and Omar, Abdirahman M. and Sutton, Adrienne and Murata, Akihiko and Olsen, Are and Stephens, Britton B. and Tilbrook, Bronte and Munro, David and Pierrot, Denis and Rehder, Gregor and Santana-Casiano, J. Magdalena and Müller, Jens D. and Trinanes, Joaquin and Tedesco, Kathy and O'Brien, Kevin and Currie, Kim and Barbero, Leticia and Telszewski, Maciej and Hoppema, Mario and Ishii, Masao and González-Dávila, Melchor and Bates, Nicholas R. and Metzl, Nicolas and Suntharalingam, Parvadha and Feely, Richard A. and ichiro Nakaoka, Shin and Lauvset, Siv K. and Takahashi, Taro and Steinhoff, Tobias and Schuster, Ute},
  title = {A surface ocean CO2 reference network, SOCONET and associated marine boundary layer CO2 measurements},
  journal = {Frontiers in Marine Science},
  publisher = {Frontiers Media SA},
  year = {2019},
  volume = {6},
  number = {JUL},
  doi = {10.3389/fmars.2019.00400}
}
White ED, Rigby M, Lunt MF, Luke Smallman T, Comyn-Platt E, Manning AJ, Ganesan AL, O'Doherty S, Stavert AR, Stanley K, Williams M, Levy P, Ramonet M, Forster GL, Manning AC and Palmer PI (2019), "Quantifying the UK's carbon dioxide flux: An atmospheric inverse modelling approach using a regional measurement network", Atmospheric Chemistry and Physics., apr, 2019. Vol. 19(7), pp. 4345-4365. Copernicus GmbH.
Abstract: We present a method to derive atmosphericobservation-based estimates of carbon dioxide (CO2) fluxes at the national scale, demonstrated using data from a network of surface tall-tower sites across the UK and Ireland over the period 2013-2014. The inversion is carried out using simulations from a Lagrangian chemical transport model and an innovative hierarchical Bayesian Markov chain Monte Carlo (MCMC) framework, which addresses some of the traditional problems faced by inverse modelling studies, such as subjectivity in the specification of model and prior uncertainties. Biospheric fluxes related to gross primary productivity and terrestrial ecosystem respiration are solved separately in the inversion and then combined a posteriori to determine net ecosystem exchange of CO2. Two different models, Data Assimilation Linked Ecosystem Carbon (DALEC) and Joint UK Land Environment Simulator (JULES), provide prior estimates for these fluxes. We carry out separate inversions to assess the impact of these different priors on the posterior flux estimates and evaluate the differences between the prior and posterior estimates in terms of missing model components. The Numerical Atmospheric dispersion Modelling Environment (NAME) is used to relate fluxes to the measurements taken across the regional network. Posterior CO2 estimates from the two inversions agree within estimated uncertainties, despite large differences in the prior fluxes from the different models. With our method, averaging results from 2013 and 2014, we find a total annual net biospheric flux for the UK of 8±79 TgCO2 yr-1 (DALEC prior) and 64±85 TgCO2 yr-1 (JULES prior), where negative values represent an uptake of CO2. These biospheric CO2 estimates show that annual UK biospheric sources and sinks are roughly in balance. These annual mean estimates consistently indicate a greater net release of CO2 than the prior estimates, which show much more pronounced uptake in summer months.
BibTeX:
@article{White2019,
  author = {White, Emily D. and Rigby, Matthew and Lunt, Mark F. and Luke Smallman, T. and Comyn-Platt, Edward and Manning, Alistair J. and Ganesan, Anita L. and O'Doherty, Simon and Stavert, Ann R. and Stanley, Kieran and Williams, Mathew and Levy, Peter and Ramonet, Michel and Forster, Grant L. and Manning, Andrew C. and Palmer, Paul I.},
  title = {Quantifying the UK's carbon dioxide flux: An atmospheric inverse modelling approach using a regional measurement network},
  journal = {Atmospheric Chemistry and Physics},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {19},
  number = {7},
  pages = {4345--4365},
  doi = {10.5194/acp-19-4345-2019}
}
Xia J, Yuan W, Lienert S, Joos F, Ciais P, Viovy N, ping Wang Y, Wang X, Zhang H, Chen Y and Tian X (2019), "Global Patterns in Net Primary Production Allocation Regulated by Environmental Conditions and Forest Stand Age: A Model-Data Comparison", Journal of Geophysical Research: Biogeosciences., jul, 2019. Vol. 124(7), pp. 2039-2059. American Geophysical Union (AGU).
Abstract: The allocation of net primary production (NPP) to different plant structures, such as leaves, wood, and fine roots, plays an important role in the terrestrial carbon cycle. However, the biogeographical patterns of NPP allocation are not well understood. We constructed a global database of forest NPP to investigate the observed spatial patterns of forest NPP allocation, as influenced by environmental drivers and forest stand age. We then examined whether dynamic global vegetation models (DGVMs) could capture these allocation patterns. The NPP allocation response to variations in temperature or precipitation was often opposite in leaves and fine roots, a finding consistent with the functional balance theory for allocation. The observed allocation to fine roots decreased with increasing temperature and precipitation. The observed allocation to wood and leaves decreased with forest stand age. The simulated allocation with five DGVMs was compared with the observations. The five models captured the spatial gradient of lower allocation to fine roots with increasing temperature and precipitation but did not capture coincident gradients in allocation to wood and leaves. None of the five models adequately represented the changes in allocation with forest stand age. Specifically, the models did not reproduce the decrease in allocation to wood and leaves and the increase in allocation to fine roots with increasing forest stand age. An accurate simulation of NPP allocation requires more realistic representation of multiple processes that are closely related to allocation. The NPP allocation database can be used to develop DGVMs.
BibTeX:
@article{Xia2019,
  author = {Xia, Jiangzhou and Yuan, Wenping and Lienert, Sebastian and Joos, Fortunat and Ciais, Philippe and Viovy, Nicolas and ping Wang, Ying and Wang, Xufeng and Zhang, Haicheng and Chen, Yang and Tian, Xiangjun},
  title = {Global Patterns in Net Primary Production Allocation Regulated by Environmental Conditions and Forest Stand Age: A Model-Data Comparison},
  journal = {Journal of Geophysical Research: Biogeosciences},
  publisher = {American Geophysical Union (AGU)},
  year = {2019},
  volume = {124},
  number = {7},
  pages = {2039--2059},
  doi = {10.1029/2018JG004777}
}
Xu X, Du H, Fan W, Hu J, Mao F and Dong H (2019), "Long-term trend in vegetation gross primary production, phenology and their relationships inferred from the FLUXNET data", Journal of Environmental Management., sep, 2019. Vol. 246, pp. 605-616.
BibTeX:
@article{Xu2019,
  author = {Xu, Xiaojun and Du, Huaqiang and Fan, Weiliang and Hu, Junguo and Mao, Fangjie and Dong, Hao},
  title = {Long-term trend in vegetation gross primary production, phenology and their relationships inferred from the FLUXNET data},
  journal = {Journal of Environmental Management},
  year = {2019},
  volume = {246},
  pages = {605--616},
  url = {https://linkinghub.elsevier.com/retrieve/pii/S0301479719308242},
  doi = {10.1016/j.jenvman.2019.06.023}
}
Yuan W, Zheng Y, Piao S, Ciais P, Lombardozzi D, Wang Y, Ryu Y, Chen G, Dong W, Hu Z, Jain AK, Jiang C, Kato E, Li S, Lienert S, Liu S, Nabel JE, Qin Z, Quine T, Sitch S, Smith WK, Wang F, Wu C, Xiao Z and Yang S (2019), "Increased atmospheric vapor pressure deficit reduces global vegetation growth", Science Advances., aug, 2019. Vol. 5(8), pp. eaax1396. American Association for the Advancement of Science (AAAS).
Abstract: Atmospheric vapor pressure deficit (VPD) is a critical variable in determining plant photosynthesis. Synthesis of four global climate datasets reveals a sharp increase of VPD after the late 1990s. In response, the vegetation greening trend indicated by a satellite-derived vegetation index (GIMMS3g), which was evident before the late 1990s, was subsequently stalled or reversed. Terrestrial gross primary production derived from two satellite-based models (revised EC-LUE and MODIS) exhibits persistent and widespread decreases after the late 1990s due to increased VPD, which offset the positive CO2 fertilization effect. Six Earth system models have consistently projected continuous increases of VPD throughout the current century. Our results highlight that the impacts of VPD on vegetation growth should be adequately considered to assess ecosystem responses to future climate conditions.
BibTeX:
@article{Yuan2019,
  author = {Yuan, Wenping and Zheng, Yi and Piao, Shilong and Ciais, Philippe and Lombardozzi, Danica and Wang, Yingping and Ryu, Youngryel and Chen, Guixing and Dong, Wenjie and Hu, Zhongming and Jain, Atul K. and Jiang, Chongya and Kato, Etsushi and Li, Shihua and Lienert, Sebastian and Liu, Shuguang and Nabel, Julia E.M.S. and Qin, Zhangcai and Quine, Timothy and Sitch, Stephen and Smith, William K. and Wang, Fan and Wu, Chaoyang and Xiao, Zhiqiang and Yang, Song},
  title = {Increased atmospheric vapor pressure deficit reduces global vegetation growth},
  journal = {Science Advances},
  publisher = {American Association for the Advancement of Science (AAAS)},
  year = {2019},
  volume = {5},
  number = {8},
  pages = {eaax1396},
  doi = {10.1126/sciadv.aax1396}
}
Zeeman MJ, Shupe H, Baessler C and Ruehr NK (2019), "Productivity and vegetation structure of three differently managed temperate grasslands", Agriculture, Ecosystems and Environment., feb, 2019. Vol. 270-271, pp. 129-148. Elsevier BV.
Abstract: An improved regional assessment of the productivity of grasslands depends on comprehensive knowledge of the interactions between climatic drivers, vegetation properties and human activity. Managed grasslands in Europe display highly dynamic responses, which contribute to the challenge in making representative model simulations. Therefore, we investigated the relationships between vegetation state changes and productivity of meadow grasslands by comparing three study sites in Southern Germany (DE-Fen, DE-RbW, DE-Gwg), which are characterised by different management intensities and elevations. Weekly observations of vegetation height, leaf area, above-ground biomass and plant functional types were compared to estimates of the gross ecosystem productivity (GEP) determined from atmospheric surface exchange of carbon dioxide. We found that the cumulative GEP of these grasslands correlated positively with management intensity and negatively with elevation at the seasonal scale. The differences in above-ground vegetation properties among the three sites were most pronounced during spring and contributed to significant differences in annual carbon (200%) and nitrogen (4%) biomass yields. Nevertheless, when periods between harvests were considered individually, the relationship between GEP and above-ground biomass, leaf area and vegetation height appeared to follow unified patterns for all sites. In addition, our study highlights a substantial potential for systematic error based on the techniques used to quantify vegetation properties and a mitigating approach was evaluated that includes continuous automated observations of vegetation height. These outcomes can serve as a reference for modelling studies on the seasonal allocation of carbon and vegetation properties in managed humid temperate grassland systems.
BibTeX:
@article{Zeeman2019,
  author = {Zeeman, Matthias J. and Shupe, Heather and Baessler, Cornelia and Ruehr, Nadine K.},
  title = {Productivity and vegetation structure of three differently managed temperate grasslands},
  journal = {Agriculture, Ecosystems and Environment},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {270-271},
  pages = {129--148},
  doi = {10.1016/j.agee.2018.10.003}
}
Zellweger C, Steinbrecher R, Laurent O, Lee H, Kim S, Emmenegger L, Steinbacher M and Buchmann B (2019), "Recent advances in measurement techniques for atmospheric carbon monoxide and nitrous oxide observations", Atmospheric Measurement Techniques., nov, 2019. Vol. 12(11), pp. 5863-5878. Copernicus GmbH.
Abstract: Carbon monoxide (CO) and nitrous oxide (textlessspan classCombining double low line inline-formula N2O/span) are two key parameters in the observation of the atmosphere, relevant to air quality and climate change, respectively. For CO, various analytical techniques have been in use over the last few decades. In contrast, span classCombining double low line inline-formula N2O/span was mainly measured using gas chromatography (GC) with an electron capture detector (ECD). In recent years, new spectroscopic methods have become available which are suitable for both CO and span classCombining double low line inline-formula N2O/span. These include infrared (IR) spectroscopic techniques such as cavity ring-down spectroscopy (CRDS), off-axis integrated cavity output spectroscopy (OA-ICOS) and Fourier transform infrared spectroscopy (FTIR). Corresponding instruments became recently commercially available and are increasingly used at atmospheric monitoring stations. We analysed results obtained through performance audits conducted within the framework of the Global Atmosphere Watch (GAW) quality management system of the World Meteorology Organization (WMO). These results reveal that current spectroscopic measurement techniques have clear advantages with respect to data quality objectives compared to more traditional methods for measuring CO and span classCombining double low line inline-formula N2O/span. Further, they allow for a smooth continuation of historic CO and span classCombining double low line inline-formula N2O/span time series. However, special care is required concerning potential water vapour interference on the CO amount fraction reported by near-IR CRDS instruments. This is reflected in the results of parallel measurement campaigns, which clearly indicate that drying the sample air leads to an improved accuracy of CO measurements with such near-IR CRDS instruments.
BibTeX:
@article{Zellweger2019,
  author = {Zellweger, Christoph and Steinbrecher, Rainer and Laurent, Olivier and Lee, Haeyoung and Kim, Sumin and Emmenegger, Lukas and Steinbacher, Martin and Buchmann, Brigitte},
  title = {Recent advances in measurement techniques for atmospheric carbon monoxide and nitrous oxide observations},
  journal = {Atmospheric Measurement Techniques},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {12},
  number = {11},
  pages = {5863--5878},
  doi = {10.5194/amt-12-5863-2019}
}
Zhang W, Jansson PE, Sigsgaard C, McConnell A, Jammet MM, Westergaard-Nielsen A, Lund M, Friborg T, Michelsen A and Elberling B (2019), "Model-data fusion to assess year-round CO2 fluxes for an arctic heath ecosystem in West Greenland (69°N)", Agricultural and Forest Meteorology., jul, 2019. Vol. 272-273, pp. 176-186. Elsevier BV.
Abstract: Quantifying net CO2 exchange (NEE)of arctic terrestrial ecosystems in response to changes in climatic and environmental conditions is central to understanding ecosystem functioning and assessing potential feedbacks of the carbon cycle to future climate changes. However, annual CO2 budgets for arctic tundra are rare due to the difficulties of performing measurements during non-growing seasons. It is still unclear to what extent arctic tundra ecosystems currently act as a CO2 source, sink or are in balance. This study presents year-round eddy-covariance (EC)measurements of CO2 fluxes for an arctic heath ecosystem on Disko Island, West Greenland (69 °N)over five years. Based on a fusion of year-round EC-derived CO2 fluxes, soil temperature and moisture, the process-oriented model (CoupModel)has been constrained to quantify an annual budget and characterize seasonal patterns of CO2 fluxes. The results show that total photosynthesis corresponds to -202 ± 20 g C m−2 yr-1 with ecosystem respiration of 167 ± 28 g C m-2 yr-1, resulting in NEE of -35 ± 15 g C m-2 yr-1. The respiration loss is mainly described as decomposition of near-surface litter. A year with an anomalously deep snowpack shows a threefold increase in the rate of ecosystem respiration compared to other years. Due to the high CO2 emissions during that winter, the annual budget results in a marked reduction in the CO2 sink. The seasonal patterns of photosynthesis and soil respiration were described using response functions of the forcing atmosphere and soil conditions. Snow depth, topography-related soil moisture, and growing season warmth are identified as important environmental characteristics which most influence seasonal rates of gas exchange.
BibTeX:
@article{Zhang2019,
  author = {Zhang, Wenxin and Jansson, Per Erik and Sigsgaard, Charlotte and McConnell, Alistair and Jammet, Mathilde Manon and Westergaard-Nielsen, Andreas and Lund, Magnus and Friborg, Thomas and Michelsen, Anders and Elberling, Bo},
  title = {Model-data fusion to assess year-round CO2 fluxes for an arctic heath ecosystem in West Greenland (69°N)},
  journal = {Agricultural and Forest Meteorology},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {272-273},
  pages = {176--186},
  doi = {10.1016/j.agrformet.2019.02.021}
}
Zhang Y, Goll D, Bastos A, Balkanski Y, Boucher O, Cescatti A, Collier M, Gasser T, Ghattas J, Li L, Piao S, Viovy N, Zhu D and Ciais P (2019), "Increased Global Land Carbon Sink Due to Aerosol-Induced Cooling", Global Biogeochemical Cycles., mar, 2019. Vol. 33(3), pp. 439-457. American Geophysical Union (AGU).
Abstract: Anthropogenic aerosols have contributed to historical climate change through their interactions with radiation and clouds. In turn, climate change due to aerosols has impacted the C cycle. Here we use a set of offline simulations made with the Organising Carbon and Hydrology In Dynamic Ecosystems (ORCHIDEE) land surface model driven by bias-corrected climate fields from simulations of three Coupled Model Intercomparison Project Phase 5 (CMIP5) Earth system models (ESMs; IPSL-CM5A-LR, CSIRO-Mk3.6.0, and GISS-E2-R) to quantify the climate-related impacts of aerosols on land carbon fluxes during 1860–2005. We found that climate change from anthropogenic aerosols (CCAA) globally cooled the climate, and increased land carbon storage, or cumulative net biome production (NBP), by 11.6–41.8 PgC between 1860 and 2005. The increase in NBP from CCAA mainly occurs in the tropics and northern midlatitudes, primarily due to aerosol-induced cooling. At high latitudes, cooling caused stronger decrease in gross primary production (GPP) than in total ecosystem respiration (TER), leading to lower NBP. At midlatitudes, cooling-induced decrease in TER is stronger than that of GPP, resulting in NBP increase. At low latitudes, NBP was also enhanced due to the cooling-induced GPP increase, but precipitation decline from CCAA may negate the effect of temperature. The three ESMs show large divergence in low-latitude CCAA precipitation response to aerosols, which results in considerable uncertainties in regional estimations of CCAA effects on carbon fluxes. Our results suggest that better understanding and simulation of how anthropogenic aerosols affect precipitation in ESMs is required for a more accurate attribution of aerosol effects on the terrestrial carbon cycle.
BibTeX:
@article{Zhang2019a,
  author = {Zhang, Yuan and Goll, Daniel and Bastos, Ana and Balkanski, Yves and Boucher, Olivier and Cescatti, Alessandro and Collier, Mark and Gasser, Thomas and Ghattas, Josefine and Li, Laurent and Piao, Shilong and Viovy, Nicolas and Zhu, Dan and Ciais, Philippe},
  title = {Increased Global Land Carbon Sink Due to Aerosol-Induced Cooling},
  journal = {Global Biogeochemical Cycles},
  publisher = {American Geophysical Union (AGU)},
  year = {2019},
  volume = {33},
  number = {3},
  pages = {439--457},
  doi = {10.1029/2018GB006051}
}
Zheng B, Chevallier F, Yin Y, Ciais P, Fortems-Cheiney A, Deeter MN, Parker RJ, Wang Y, Worden HM and Zhao Y (2019), "Global atmospheric carbon monoxide budget 2000-2017 inferred from multi-species atmospheric inversions", Earth System Science Data., sep, 2019. Vol. 11(3), pp. 1411-1436. Copernicus GmbH.
Abstract: Atmospheric carbon monoxide (CO) concentrations have been decreasing since 2000, as observed by both satellite-and ground-based instruments, but global bottom-up emission inventories estimate increasing anthropogenic CO emissions concurrently. In this study, we use a multi-species atmospheric Bayesian inversion approach to attribute satellite-observed atmospheric CO variations to its sources and sinks in order to achieve a full closure of the global CO budget during 2000-2017. Our observation constraints include satellite retrievals of the total column mole fraction of CO, formaldehyde (HCHO), and methane (CH4) that are all major components of the atmospheric CO cycle. Three inversions (i.e., 2000-2017, 2005-2017, and 2010-2017) are performed to use the observation data to the maximum extent possible as they become available and assess the consistency of inversion results to the assimilation of more trace gas species. We identify a declining trend in the global CO budget since 2000 (three inversions are broadly consistent during overlapping periods), driven by reduced anthropogenic emissions in the US and Europe (both likely from the transport sector), and in China (likely from industry and residential sectors), as well as by reduced biomass burning emissions globally, especially in equatorial Africa (associated with reduced burned areas). We show that the trends and drivers of the inversionbased CO budget are not affected by the inter-annual variation assumed for prior CO fluxes. All three inversions contradict the global bottom-up inventories in the world's top two emitters: for the sign of anthropogenic emission trends in China (e.g., here-0:8 ± 0:5 % yr-1 since 2000, while the prior gives 1:3 ± 0:4 % yr-1) and for the rate of anthropogenic emission increase in South Asia (e.g., here 1:0 ± 0:6 % yr-1 since 2000, smaller than 3:5 ± 0:4 % yr-1 in the prior inventory). The posterior model CO concentrations and trends agree well with independent ground-based observations and correct the prior model bias. The comparison of the three inversions with different observation constraints further suggests that the most complete constrained inversion that assimilates CO, HCHO, and CH4 has a good representation of the global CO budget, and therefore matches best with independent observations, while the inversion only assimilating CO tends to underestimate both the decrease in anthropogenic CO emissions and the increase in the CO chemical production. The global CO budget data from all three inversions in this study can be accessed from https://doi.org/10.6084/m9.figshare.c.4454453.v1 (Zheng et al., 2019).
BibTeX:
@article{Zheng2019,
  author = {Zheng, Bo and Chevallier, Frederic and Yin, Yi and Ciais, Philippe and Fortems-Cheiney, Audrey and Deeter, Merritt N. and Parker, Robert J. and Wang, Yilong and Worden, Helen M. and Zhao, Yuanhong},
  title = {Global atmospheric carbon monoxide budget 2000-2017 inferred from multi-species atmospheric inversions},
  journal = {Earth System Science Data},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {11},
  number = {3},
  pages = {1411--1436},
  doi = {10.5194/essd-11-1411-2019}
}
Zhou M, Langerock B, Sha MK, Kumps N, Hermans C, Petri C, Warneke T, Chen H, Metzger JM, Kivi R, Heikkinen P, Ramonet M and De Mazière M (2019), "Retrieval of atmospheric CH4 vertical information from ground-based FTS near-infrared spectra", Atmospheric Measurement Techniques., nov, 2019. Vol. 12(11), pp. 6125-6141. Copernicus GmbH.
Abstract: The Total Carbon Column Observing Network (TCCON) column-averaged dry air mole fraction of CH4 (XCH4) measurements have been widely used to validate satellite observations and to estimate model simulations. The GGG2014 code is the standard TCCON retrieval software used in performing a profile scaling retrieval. In order to obtain several vertical pieces of information in addition to the total column, in this study, the SFIT4 retrieval code is applied to retrieve the CH4 mole fraction vertical profile from the Fourier transform spectrometer (FTS) spectrum at six sites (Ny-Ålesund, Sodankylä, Bialystok, Bremen, Orléans and St Denis) during the time period of 2016-2017. The retrieval strategy of the CH4 profile retrieval from groundbased FTS near-infrared (NIR) spectra using the SFIT4 code (SFIT4NIR) is investigated. The degree of freedom for signal (DOFS) of the SFIT4NIR retrieval is about 2.4, with two distinct pieces of information in the troposphere and in the stratosphere. The averaging kernel and error budget of the SFIT4NIR retrieval are presented. The data accuracy and precision of the SFIT4NIR retrievals, including the total column and two partial columns (in the troposphere and stratosphere), are estimated by TCCON standard retrievals, ground-based in situ measurements, Atmospheric Chemistry Experiment - Fourier Transform Spectrometer (ACE-FTS) satellite observations, TCCON proxy data and AirCore and aircraft measurements. By comparison against TCCON standard retrievals, it is found that the retrieval uncertainty of SFIT4NIR XCH4 is similar to that of TCCON standard retrievals with systematic uncertainty within 0.35 % and random uncertainty of about 0.5 %. The tropospheric and stratospheric XCH4 from SFIT4NIR retrievals are assessed by comparison with AirCore and aircraft measurements, and there is a 1.0 ± 0.3 % overestimation in the SFIT4NIR tropospheric XCH4 and a 4.0 ± 2.0 % underestimation in the SFIT4NIR stratospheric XCH4, which are within the systematic uncertainties of SFIT4NIR-retrieved partial columns in the troposphere and stratosphere respectively.
BibTeX:
@article{Zhou2019,
  author = {Zhou, Minqiang and Langerock, Bavo and Sha, Mahesh Kumar and Kumps, Nicolas and Hermans, Christian and Petri, Christof and Warneke, Thorsten and Chen, Huilin and Metzger, Jean Marc and Kivi, Rigel and Heikkinen, Pauli and Ramonet, Michel and De Mazière, Martine},
  title = {Retrieval of atmospheric CH4 vertical information from ground-based FTS near-infrared spectra},
  journal = {Atmospheric Measurement Techniques},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {12},
  number = {11},
  pages = {6125--6141},
  doi = {10.5194/amt-12-6125-2019}
}
Zhou M, Langerock B, Vigouroux C, Kumar Sha M, Hermans C, Metzger JM, Chen H, Ramonet M, Kivi R, Heikkinen P, Smale D, Pollard DF, Jones N, Velazco VA, García OE, Schneider M, Palm M, Warneke T and De Mazière M (2019), "TCCON and NDACC XCO measurements: Difference, discussion and application", Atmospheric Measurement Techniques., nov, 2019. Vol. 12(11), pp. 5979-5995. Copernicus GmbH.
Abstract: Column-averaged dry-air mole fraction of CO (XCO) measurements are obtained from two ground-based Fourier transform infrared (FTIR) spectrometer networks: the Total Carbon Column Observing Network (TCCON) and the Network for the Detection of Atmospheric Composition Change (NDACC). In this study, the differences between the TCCON and NDACC XCO measurements are investigated and discussed based on six NDACC-TCCON sites using data over the period 2007-2017. A direct comparison shows that the NDACC XCO measurements are about 5.5 % larger than the TCCON data at Ny-Ålesund, Bremen, and Izaña (Northern Hemisphere), and the absolute bias between the NDACC and TCCON data is within 2 % at Saint-Denis, Wollongong and Lauder (Southern Hemisphere). The hemispheric dependence of the bias is mainly attributed to their smoothing errors. The systematic smoothing error of the TCCON XCO data varies in the range between 0.2 % (Bremen) and 7.9 % (Lauder), and the random smoothing error varies in the range between 2.0 % and 3.6 %. The systematic smoothing error of NDACC data is between 0.1 % and 0.8 %, and the random smoothing error of NDACC data is about 0.3 %. For TCCON data, the smoothing error is significant because it is higher than the reported uncertainty, particularly at Southern Hemisphere sites. To reduce the influence from the a priori profiles and different vertical sensitivities, the scaled NDACC a priori profiles are used as the common a priori profiles for comparing TCCON and NDACC retrievals. As a result, the biases between TCCON and NDACC XCO measurements become more consistent (5.6 %-8.5 %) with a mean value of 6.8 % at these sites. To determine the sources of the remaining bias, regular AirCore measurements at Orléans and Sodankylä are compared to co-located TCCON measurements. It is found that TCCON XCO measurements are 6.1 ± 1.6 % and 8.0 ± 3.2 % smaller than the AirCore measurements at Orléans and Sodankylä, respectively, indicating that the scaling factor of TCCON XCO data should be around 1.0000 instead of 1.0672. Further investigations should be carried out in the TCCON community to determine the correct scaling factor to be applied to the TCCON XCO data. This paper also demonstrates that the smoothing error must be taken into account when comparing FTIR XCO data, and especially TCCON XCO data, with model or satellite data.
BibTeX:
@article{Zhou2019a,
  author = {Zhou, Minqiang and Langerock, Bavo and Vigouroux, Corinne and Kumar Sha, Mahesh and Hermans, Christian and Metzger, Jean Marc and Chen, Huilin and Ramonet, Michel and Kivi, Rigel and Heikkinen, Pauli and Smale, Dan and Pollard, David F. and Jones, Nicholas and Velazco, Voltaire A. and García, Omaira E. and Schneider, Matthias and Palm, Mathias and Warneke, Thorsten and De Mazière, Martine},
  title = {TCCON and NDACC XCO measurements: Difference, discussion and application},
  journal = {Atmospheric Measurement Techniques},
  publisher = {Copernicus GmbH},
  year = {2019},
  volume = {12},
  number = {11},
  pages = {5979--5995},
  doi = {10.5194/amt-12-5979-2019}
}
Zhu P, Zhuang Q, Welp L, Ciais P, Heimann M, Peng B, Li W, Bernacchi C, Roedenbeck C and Keenan TF (2019), "Recent warming has resulted in smaller gains in net carbon uptake in northern high latitudes", Journal of Climate., sep, 2019. Vol. 32(18), pp. 5849-5863. American Meteorological Society.
Abstract: Carbon balance of terrestrial ecosystems in the northern high latitudes (NHL) is sensitive to climate change. It remains uncertain whether current regional carbon uptake capacity can be sustained under future warming. Here the atmospheric CO2 drawdown rate (CDR) between 1974 and 2014, defined as the CO2 decrease in ppm over the number of days in spring or summer, is estimated using atmospheric CO2 observations at Barrow (now known as Utqiaġvik), Alaska. We found that the sensitivity of CDR to interannual seasonal air temperature anomalies has trended toward less carbon uptake for a given amount of warming over this period. Changes in interannual temperature sensitivity of CDR suggest that relatively warm springs now result in less of a carbon uptake enhancement. Similarly, relatively warm summers now result in greater carbon release. These results generally agree with the sensitivity of net carbon exchange (NCE) estimated by atmospheric CO2 inversion. When NCE was aggregated over North America (NA) and Eurasia (EA), separately, the temperature sensitivity of NCE in NA has changed more than in EA. To explore potential mechanisms of this signal, we also examine trends in interannual variability of other climate variables (soil temperature and precipitation), satellite-derived gross primary production (GPP), and Trends in Net Land–Atmosphere Carbon Exchanges (TRENDY) model ensemble results. Our analysis suggests that the weakened spring sensitivity of CDR may be related to the slowdown in seasonal soil thawing rate, while the summer sensitivity change may be caused by the temporally coincident decrease in temperature sensitivity of photosynthesis. This study suggests that the current NHL carbon sink may become unsustainable as temperatures warm further. We also found that current carbon cycle models do not represent the decrease in temperature sensitivity of net carbon flux. We argue that current carbon–climate models misrepresent important aspect of the carbon–climate feedback and bias the estimation of warming influence on NHL carbon balance.
BibTeX:
@article{Zhu2019,
  author = {Zhu, Peng and Zhuang, Qianlai and Welp, Lisa and Ciais, Philippe and Heimann, Martin and Peng, Bin and Li, Wenyu and Bernacchi, Carl and Roedenbeck, Christian and Keenan, Trevor F.},
  title = {Recent warming has resulted in smaller gains in net carbon uptake in northern high latitudes},
  journal = {Journal of Climate},
  publisher = {American Meteorological Society},
  year = {2019},
  volume = {32},
  number = {18},
  pages = {5849--5863},
  doi = {10.1175/JCLI-D-18-0653.1}
}
Ziegler C, Coste S, Stahl C, Delzon S, Levionnois S, Cazal J, Cochard H, Esquivel-Muelbert A, Goret JY, Heuret P, Jaouen G, Santiago LS and Bonal D (2019), "Large hydraulic safety margins protect Neotropical canopy rainforest tree species against hydraulic failure during drought", Annals of Forest Science., dec, 2019. Vol. 76(4) Springer Science and Business Media LLC.
Abstract: Key message: Abundant Neotropical canopy-tree species are more resistant to drought-induced branch embolism than what is currently admitted. Large hydraulic safety margins protect them from hydraulic failure under actual drought conditions. Context: Xylem vulnerability to embolism, which is associated to survival under extreme drought conditions, is being increasingly studied in the tropics, but data on the risk of hydraulic failure for lowland Neotropical rainforest canopy-tree species, thought to be highly vulnerable, are lacking. Aims: The purpose of this study was to gain more knowledge on species drought-resistance characteristics in branches and leaves and the risk of hydraulic failure of abundant rainforest canopy-tree species during the dry season. Methods: We first assessed the range of branch xylem vulnerability to embolism using the flow-centrifuge technique on 1-m-long sun-exposed branches and evaluated hydraulic safety margins with leaf turgor loss point and midday water potential during normal- and severe-intensity dry seasons for a large set of Amazonian rainforest canopy-tree species. Results: Tree species exhibited a broad range of embolism resistance, with the pressure threshold inducing 50% loss of branch hydraulic conductivity varying from − 1.86 to − 7.63 MPa. Conversely, we found low variability in leaf turgor loss point and dry season midday leaf water potential, and mostly large, positive hydraulic safety margins. Conclusions: Rainforest canopy-tree species growing under elevated mean annual precipitation can have high resistance to embolism and are more resistant than what was previously thought. Thanks to early leaf turgor loss and high embolism resistance, most species have a low risk of hydraulic failure and are well able to withstand normal and even severe dry seasons.
BibTeX:
@article{Ziegler2019,
  author = {Ziegler, Camille and Coste, Sabrina and Stahl, Clément and Delzon, Sylvain and Levionnois, Sébastien and Cazal, Jocelyn and Cochard, Hervé and Esquivel-Muelbert, Adriane and Goret, Jean Yves and Heuret, Patrick and Jaouen, Gaëlle and Santiago, Louis S. and Bonal, Damien},
  title = {Large hydraulic safety margins protect Neotropical canopy rainforest tree species against hydraulic failure during drought},
  journal = {Annals of Forest Science},
  publisher = {Springer Science and Business Media LLC},
  year = {2019},
  volume = {76},
  number = {4},
  doi = {10.1007/s13595-019-0905-0}
}
Ziembliʼnska K, Urbaniak M, Dukat P and Olejnik J (2019), "Measurements of co2 fluxes at non-ideal eddy covariance sites", Journal of Visualized Experiments., jun, 2019. Vol. 2019(148) MyJove Corporation.
Abstract: This protocol is an example of utilizing the eddy covariance (EC) technique to investigate spatially and temporally averaged net CO2 fluxes (net ecosystem production, NEP), in non-typical ecosystems, on a currently reforested windthrow area in Poland. After a tornado event, a relatively narrow “corridor” was created within surviving forest stands, which complicates such kind of experiments. The application of other measuring techniques, such as the chamber method, is even more difficult under these circumstances, because especially at the beginning, fallen trees and in general great heterogeneity of the site provide a challenging platform to perform flux measurements and then to properly upscale obtained results. In comparison with standard EC measurements carried out in untouched forests, the case of windthrow areas requires special consideration when it comes to the site location and data analysis in order to ensure their representativeness. Therefore, here we present a protocol of real-time, continuous CO2 flux measurements at a dynamically changing, non-ideal EC site, which includes (1) site location and instrumentation setup, (2) flux computation, (3) rigorous data filtering and quality control, and (4) gap filling and net fluxes partitioning into CO2 respiration and absorption. The main advantage of the described methodology is that it provides a detailed description of the experimental setup and measurement performance from scratch, which can be applied to other spatially limited ecosystems. It can also be viewed as a list of recommendations on how to deal with unconventional site operation, providing a description for non-specialists. Obtained quality-checked, gap filled, half-hour values of net CO2, as well as absorption and respiration fluxes, can be finally aggregated into daily, monthly, seasonal or annual totals.
BibTeX:
@article{Ziemblinska2019,
  author = {Ziembliʼnska, Klaudia and Urbaniak, Marek and Dukat, Paulina and Olejnik, Janusz},
  title = {Measurements of co2 fluxes at non-ideal eddy covariance sites},
  journal = {Journal of Visualized Experiments},
  publisher = {MyJove Corporation},
  year = {2019},
  volume = {2019},
  number = {148},
  doi = {10.3791/59525}
}
Zöll U, Lucas-Moffat AM, Wintjen P, Schrader F, Beudert B and Brümmer C (2019), "Is the biosphere-atmosphere exchange of total reactive nitrogen above forest driven by the same factors as carbon dioxide? An analysis using artificial neural networks", Atmospheric Environment., jun, 2019. Vol. 206, pp. 108-118. Elsevier BV.
Abstract: Phase and amplitude of ecosystem-atmosphere fluxes of reactive nitrogen compounds are poorly understood due to a lack of suitable observation methods. Understanding the biophysical controls of the surface nitrogen exchange is essential for the parameterization of process-based and chemical transport models that can be used for the determination of regional or national nitrogen budgets. In this study, we investigated similarities in time series of net total reactive nitrogen (ΣNr) and carbon dioxide (CO2) fluxes above forest with regard to their variability and driving factors. We found corresponding shapes of the mean diurnal summertime patterns of ΣNr and CO2. While ecosystem respiration leads to a net CO2 release at night, ΣNr was on average deposited throughout the entire observation period. Using artificial neural network analysis, global radiation (Rg) was identified to be the main control for both ΣNr and CO2. While the concentration of ΣNr substantially improved the coefficient of determination for ΣNr fluxes when used as a secondary driver, only minor improvements of 2–3% were found for CO2 fluxes when using for example temperature or vapour pressure deficit (VPD) as secondary driver. Considering two dominant drivers, 41 and 66% of the variability in ΣNr and CO2 fluxes, respectively, could be explained. Further data stratification for ΣNr revealed that higher concentrations, higher temperature, and higher VPD as well as dry leaf surfaces tend to favour higher deposition of ΣNr, whereas lower concentrations, lower temperature, and lower VPD as well as wet leaf surfaces mainly correspond to situations when less ΣNr was deposited or even emitted. Our results support the understanding of biosphere-atmosphere interactions, their driving factors, and establish a link between ΣNr and CO2 exchange, which may be beneficial for future developments in state-of-the-art exchange modelling.
BibTeX:
@article{Zoell2019,
  author = {Zöll, Undine and Lucas-Moffat, Antje M. and Wintjen, Pascal and Schrader, Frederik and Beudert, Burkhard and Brümmer, Christian},
  title = {Is the biosphere-atmosphere exchange of total reactive nitrogen above forest driven by the same factors as carbon dioxide? An analysis using artificial neural networks},
  journal = {Atmospheric Environment},
  publisher = {Elsevier BV},
  year = {2019},
  volume = {206},
  pages = {108--118},
  doi = {10.1016/j.atmosenv.2019.02.042}
}
Achat DL, Martel S, Picart D, Moisy C, Augusto L, Bakker MR and Loustau D (2018), "Modelling the nutrient cost of biomass harvesting under different silvicultural and climate scenarios in production forests", Forest Ecology and Management., dec, 2018. Vol. 429, pp. 642-653. Elsevier BV.
Abstract: Intensifying the use of forest biomass to produce fuelwood, through the removal of harvest residues or reductions in rotation length, increases nutrient outputs and can ultimately lead to reduced soil fertility. We developed a modelling approach for the evaluation of different forest management options under future climate scenarios. This approach allows management systems to be evaluated in terms of their nutrient costs by quantifying several variables: nutrient outputs (N, P, K, Ca and Mg) resulting from harvesting, ecosystem N and P balances, and changes in organic C, N and P stocks in the soil. In addition, we calculated a “nutrient cost index” (in kg-harvested-biomass g-exported-nutrients−1). As part of this study, we looked at the effects of harvesting branches, foliage and stumps in addition to tree stems, as well as the effects of changing rotation length in Pinus pinaster, Pseudotsuga menziesii and Fagus sylvatica forest stands, under contrasting Representative Concentration Pathway climate scenarios (RCPs). Comparably to previous studies, our simulations showed that removing harvest residues and, to a lesser extent, reducing rotation length have high nutrient costs. Climate was also found to have an impact, mainly caused by larger amounts of standing tree biomass, and therefore larger biomass harvests and increased nutrient outputs in the scenario which involved elevated atmospheric CO2. Using contrasting forest management systems and climates, we showed that our modelling approach can be used to guide forest managers in their choice of future silvicultural practices (rotation length, conventional stem-only harvest versus intensive harvest, thinning regime) based on future climate scenarios. Finally, our approach can be used to determine, more accurately than simple allometric relationships, the amounts of nutrients that would need to be applied in order to compensate for losses.
BibTeX:
@article{Achat2018,
  author = {Achat, David L. and Martel, Simon and Picart, Delphine and Moisy, Christophe and Augusto, Laurent and Bakker, Mark R. and Loustau, Denis},
  title = {Modelling the nutrient cost of biomass harvesting under different silvicultural and climate scenarios in production forests},
  journal = {Forest Ecology and Management},
  publisher = {Elsevier BV},
  year = {2018},
  volume = {429},
  pages = {642--653},
  doi = {10.1016/j.foreco.2018.06.047}
}
Acosta M, Darenova E, Krupková L and Pavelka M (2018), "Seasonal and inter-annual variability of soil CO2 efflux in a Norway spruce forest over an eight-year study", Agricultural and Forest Meteorology., jun, 2018. Vol. 256-257, pp. 93-103. Elsevier BV.
Abstract: Automated soil CO2 efflux chamber measurements were carried out over a period of eight years in a young Norway spruce forest in the northeast region of the Czech Republic to determine seasonal and inter-annual variables affecting this flux. The data obtained was summarized and analysed with the aims of estimating long-term carbon losses from the soil and comparing selected models to determine the model best describing soil CO2 efflux. Our results show that seasonal variation in soil CO2 efflux was driven mainly by soil temperature, while inter-annual variation showed the closest relationship with precipitation. The total amount of carbon released from the soil into the atmosphere per season varied from 6.4 to 11.2 tC ha−1 over the eight-year record. One of the variables used in the CO2 efflux models, beside environmental variables, was day of year (DOY). Incorporating this variable into models improved the estimation of soil CO2 efflux dynamics. Therefore, we assume that models incorporating DOY could be used effectively to gap-fill measured soil chamber data. These models could also be appropriate for filling longer gaps on a scale from days to weeks, because DOY, as a single parameter, covers up to 80% of variability in the data. This study also demonstrated the different levels of correlation between investigated climate variables and soil CO2 efflux at seasonal and inter-annual time scales. This highlights the importance of different environmental variables in interpreting long-term soil CO2 efflux data and also modelling the complexity of the processes connected with soil CO2 efflux in Norway spruce forest.
BibTeX:
@article{Acosta2018,
  author = {Acosta, Manuel and Darenova, Eva and Krupková, Lenka and Pavelka, Marian},
  title = {Seasonal and inter-annual variability of soil CO2 efflux in a Norway spruce forest over an eight-year study},
  journal = {Agricultural and Forest Meteorology},
  publisher = {Elsevier BV},
  year = {2018},
  volume = {256-257},
  pages = {93--103},
  doi = {10.1016/j.agrformet.2018.03.005}
}
Aguilos M, Hérault B, Burban B, Wagner F and Bonal D (2018), "What drives long-term variations in carbon flux and balance in a tropical rainforest in French Guiana?", Agricultural and Forest Meteorology. Vol. 253-254, pp. 114-123. Elsevier BV.
Abstract: A thorough understanding of how tropical forests respond to climate is important to improve ecosystem process models and to reduce uncertainties in current and future global carbon balance calculations. The Amazon rainforest, a major contributor to the global carbon cycle, is subject to strong intra- and interannual variations in climate conditions. Understanding their effect on carbon fluxes between the ecosystem and the atmosphere and on the resulting carbon balance is still incomplete. We examined the long-term (over a 12-year period; 2004–2015) variations in gross primary productivity (GPP), ecosystem respiration (RE) and net ecosystem exchange (NEE) in a tropical rainforest in French Guiana and identified key climatic drivers influencing the changes. The study period was characterized by strong differences in climatic conditions among years, particularly differences in the intensity of the dry and wet seasons, as well as differences in annual carbon fluxes and balance. Annual average GPP varied from 3384.9 g C m−2 yr‒1 (95% CI [3320.7, 3445.9]) to 4061.2 g C m−2 yr‒1 (95% CI [3980.1, 4145.0]). RE varied even more than GPP, with a difference of 933.1 C m−2 yr‒1 between the minimum (3020.6 g C m−2 yr‒1; 95% CI [2889.4, 3051.3]) and maximum (3953.7 g C m−2 yr‒1; 95% CI [3887.6, 4019.6]) values. Although NEE showed large interannual variability (nine-fold), from ‒65.6 g C m−2 yr‒1 (95% CI [‒4.4, ‒126.0]) to ‒590.5 g C m−2 yr‒1 (95% CI [‒532.3, ‒651.6]), the forest remained a carbon sink over the 12-year period. A combination of global radiation (Rg), relative extractable water (REW) and soil temperature (Ts) explained 51% of the daily variations for GPP, 30% for RE and 39% for NEE. Global radiation was always the best predictor of these variations, but soil water content and temperature did also influence carbon fluxes and balance. Seasonally, Rg was the major controlling factor for GPP, RE and NEE during the wet season. During the dry season, variations in carbon fluxes and balance were poorly explained by climate factors. Yet, REW was the key driver of variations in NEE during the dry season. This study highlights that, over the long-term, carbon fluxes and balance in such tropical rainforest ecosystems are largely controlled by both radiation and water limitation. Even though variations in Rg have a greater impact on these fluxes, water limitation during seasonal droughts is enough to reduce ecosystem productivity, respiration and carbon uptake. The reduced precipitation expected in tropical rainforest areas under future climatic conditions will therefore strongly influence carbon fluxes and carbon uptake. This study also highlights the importance for land surface or dynamic global vegetation models to consider the main drivers of carbon fluxes and balance separately for dry and wet seasons.
BibTeX:
@article{Aguilos2018,
  author = {Aguilos, Maricar and Hérault, Bruno and Burban, Benoit and Wagner, Fabien and Bonal, Damien},
  title = {What drives long-term variations in carbon flux and balance in a tropical rainforest in French Guiana?},
  journal = {Agricultural and Forest Meteorology},
  publisher = {Elsevier BV},
  year = {2018},
  volume = {253-254},
  pages = {114--123},
  doi = {10.1016/j.agrformet.2018.02.009}
}
Aguilos M, Stahl C, Burban B, Hérault B, Courtois E, Coste S, Wagner F, Ziegler C, Takagi K and Bonal D (2018), "Interannual and seasonal variations in ecosystem transpiration and water use efficiency in a tropical rainforest", Forests., dec, 2018. Vol. 10(1), pp. 14. MDPI AG.
Abstract: Warmer and drier climates over Amazonia have been predicted for the next century with expected changes in regional water and carbon cycles. We examined the impact of interannual and seasonal variations in climate conditions on ecosystem-level evapotranspiration (ET) and water use efficiency (WUE) to determine key climatic drivers and anticipate the response of these ecosystems to climate change. We used daily climate and eddyflux data recorded at the Guyaflux site in French Guiana from 2004 to 2014. ET and WUE exhibited weak interannual variability. The main climatic driver of ET and WUE was global radiation (Rg), but relative extractable water (REW) and soil temperature (Ts) did also contribute. At the seasonal scale, ET and WUE showed a modal pattern driven by Rg, with maximum values for ET in July and August and for WUE at the beginning of the year. By removing radiation effects during water depleted periods, we showed that soil water stress strongly reduced ET. In contrast, drought conditions enhanced radiation-normalized WUE in almost all the years, suggesting that the lack of soil water had a more severe effect on ecosystem evapotranspiration than on photosynthesis. Our results are of major concern for tropical ecosystem modeling because they suggest that under future climate conditions, tropical forest ecosystems will be able to simultaneously adjust CO 2 and H 2 O fluxes. Yet, for tropical forests under future conditions, the direction of change in WUE at the ecosystem scale is hard to predict, since the impact of radiation on WUE is counterbalanced by adjustments to soil water limitations. Developing mechanistic models that fully integrate the processes associated with CO 2 and H 2 O flux control should help researchers understand and simulate future functional adjustments in these ecosystems.
BibTeX:
@article{Aguilos2018a,
  author = {Aguilos, Maricar and Stahl, Clément and Burban, Benoit and Hérault, Bruno and Courtois, Elodie and Coste, Sabrina and Wagner, Fabien and Ziegler, Camille and Takagi, Kentaro and Bonal, Damien},
  title = {Interannual and seasonal variations in ecosystem transpiration and water use efficiency in a tropical rainforest},
  journal = {Forests},
  publisher = {MDPI AG},
  year = {2018},
  volume = {10},
  number = {1},
  pages = {14},
  doi = {10.3390/f10010014}
}
Alivernini A, Fares S, Ferrara C and Chianucci F (2018), "An objective image analysis method for estimation of canopy attributes from digital cover photography", Trees - Structure and Function., feb, 2018. Vol. 32(3), pp. 713-723. Springer Nature.
Abstract: Key message: A method was proposed to remove the subjectivity of gap size analyses approaches implemented by default in cover photography. The method yielded robust and replicable measurements of forest canopy attributes. Abstract: Digital cover photography (DCP) is an increasingly popular method to estimate canopy attributes of forest canopies. Compared with other canopy photographic methods, DCP is fast, simple, and less sensitive to image acquisition and processing. However, the image processing steps used by default in DCP have a large substantial subjective component, particularly regarding the separation of canopy gaps into large gaps and small gaps. In this study, we proposed an objective procedure to analyse DCP based on the statistical distribution of gaps occurring in any image. The new method was tested in 11 deciduous forest stands in central Italy, with different tree composition, stand density, and structure, which is representative of the natural variation of these forest types. Results indicated that the new method removed the subjectivity of manual and semi-automated gap size classifications performed so far in cover photography. A comparison with direct LAI measurements demonstrated that the new method outperformed the previous approaches and increased the precision of LAI estimates. Results have important implications in forestry, because the simplicity of the method allowed objective, reliable, and highly reproducible estimates of canopy attributes, which are largely suitable in forest monitoring, where measures are routinely repeated. In addition, the use of a restricted field of view enables implementation of this photographic method in many devices, including smartphones, downward-looking cameras, and unmanned aerial vehicles.
BibTeX:
@article{Alivernini2018,
  author = {Alivernini, Alessandro and Fares, Silvano and Ferrara, Carlotta and Chianucci, Francesco},
  title = {An objective image analysis method for estimation of canopy attributes from digital cover photography},
  journal = {Trees - Structure and Function},
  publisher = {Springer Nature},
  year = {2018},
  volume = {32},
  number = {3},
  pages = {713--723},
  doi = {10.1007/s00468-018-1666-3}
}
Al-Yaari A, Dayau S, Chipeaux C, Aluome C, Kruszewski A, Loustau D and Wigneron JP (2018), "The AQUI soil moisture network for satellite microwave remote sensing validation in South-Western France", Remote Sensing., nov, 2018. Vol. 10(11), pp. 1839. MDPI AG.
Abstract: Global soil moisture (SM) products are currently available thanks to microwave remote sensing techniques. Validation of these satellite-based SM products over different vegetation and climate conditions is a crucial step. INRA (National Institute of Agricultural Research) has set up the AQUI SM and soil temperature in situ network (composed of three main sites Bouron, Bilos, and Hermitage), over a flat area of dense pine forests, in South-Western France (the Bordeaux-Aquitaine region) to validate the Soil Moisture and Ocean salinity (SMOS) satellite SM products. SMOS was launched in 2009 by the European Space Agency (ESA). The aims of this study are to present the AQUI network and to evaluate the SMOS SM product (in the new SMOS-IC version) along with other microwave SM products such as the active ASCAT (Advanced Scatterometer) and the ESA combined (passive and active) CCI (Climate Change Initiative) SM retrievals. A first comparison, using Pearson correlation, Bias, RMSE (Root Mean Square Error), and Un biased RMSE (ubRMSE) scores, between the 0-5 cm AQUI network and ASCAT, CCI, and SMOS SM products was conducted. In general all the three products were able to reproduce the annual cycle of the AQUI in situ observations. CCI and ASCAT had best and similar correlations (R˜0.72) over the Bouron and Bilos sites. All had comparable correlations over the Hermitage sites with overall average values of 0.74, 0.68, and 0.69 for CCI, SMOS-IC, and ASCAT, respectively. Considering anomalies, correlation values decreased for all products with best ability to capture day to day variations obtained by ASCAT. CCI (followed by SMOS-IC) had the best ubRMSE values (mostly textless 0.04 m3/m3) over most of the stations. Although the region is highly impacted by radio frequency interferences, SMOS-IC followed correctly the in situ SM dynamics. All the three remotely-sensed SM products (except SMOS-IC over some stations) overestimated the AQUI in situ SM observations. These results demonstrate that the AQUI network is likely to be well-suited for satellite microwave remote sensing evaluations/validations.
BibTeX:
@article{AlYaari2018,
  author = {Al-Yaari, A. and Dayau, S. and Chipeaux, C. and Aluome, C. and Kruszewski, A. and Loustau, D. and Wigneron, J. P.},
  title = {The AQUI soil moisture network for satellite microwave remote sensing validation in South-Western France},
  journal = {Remote Sensing},
  publisher = {MDPI AG},
  year = {2018},
  volume = {10},
  number = {11},
  pages = {1839},
  doi = {10.3390/rs10111839}
}
Ameli AA and Craig JR (2018), "Semi-analytical 3D solution for assessing radial collector well pumping impacts on groundwater-surface water interaction", Hydrology Research., apr, 2018. Vol. 49(1), pp. 17-26. IWA Publishing.
Abstract: We present a new semi-analytical flow and transport model for the simulation of 3D steady-state flow and particle movement between groundwater, a surface water body and a radial collector well in geometrically complex unconfined aquifers. This precise and grid-free Series Solution-analytic element method approach handles the irregular configurations of radial wells more efficiently than grid-based methods. This method is then used to explore how pumping well location and river shape interact and together influence (1) transit time distribution (TTD) of captured water in a radial collector well and TTD of groundwater discharged into the river and (2) the percentage of well waters captured from different sources. Results show that meandering river shape plays a significant role in controlling the aforementioned metrics and that increasing the pumping rate has different consequences in different situations. This approach can also inform the design of water remediation and groundwater protection systems (e.g., river bank filtration and well head protection area).
BibTeX:
@article{Ameli2018,
  author = {Ameli, Ali A. and Craig, James R.},
  title = {Semi-analytical 3D solution for assessing radial collector well pumping impacts on groundwater-surface water interaction},
  journal = {Hydrology Research},
  publisher = {IWA Publishing},
  year = {2018},
  volume = {49},
  number = {1},
  pages = {17--26},
  doi = {10.2166/nh.2017.201}
}
Andersen T, Scheeren B, Peters W and Chen H (2018), "A UAV-based active AirCore system for measurements of greenhouse gases", Atmospheric Measurement Techniques. Vol. 11(5), pp. 2683-2699. Copernicus GmbH.
Abstract: We developed and field-tested an unmanned aerial vehicle (UAV)-based active AirCore for atmospheric mole fraction measurements of CO2, CH4, and CO. The system applies an alternative way of using the AirCore technique invented by NOAA. As opposed to the conventional concept of passively sampling air using the atmospheric pressure gradient during descent, the active AirCore collects atmospheric air samples using a pump to pull the air through the tube during flight, which opens up the possibility to spatially sample atmospheric air. The active AirCore system used for this study weighs ∼-1.1-kg. It consists of a ∼-50-m long stainless-steel tube, a small stainless-steel tube filled with magnesium perchlorate, a KNF micropump, and a 45-μm orifice working together to form a critical flow of dried atmospheric air through the active AirCore. A cavity ring-down spectrometer (CRDS) was used to analyze the air samples on site not more than 7-min after landing for mole fraction measurements of CO2, CH4, and CO. We flew the active AirCore system on a UAV near the atmospheric measurement station at Lutjewad, located in the northwest of the city of Groningen in the Netherlands. Five consecutive flights took place over a 5-h period on the same morning, from sunrise until noon. We validated the measurements of CO2 and CH4 from the active AirCore against those from the Lutjewad station at 60-m. The results show a good agreement between the measurements from the active AirCore and the atmospheric station (N-Combining double low line-146; R2CO2: 0.97 and R2CH4: 0.94; and mean differences: CO2: 0.18-ppm and CH4: 5.13-ppb). The vertical and horizontal resolution (for CH4) at typical UAV speeds of 1.5 and 2.5-m-s-1 were determined to be ±24.7 to 29.3 and ±41.2 to 48.9-m, respectively, depending on the storage time. The collapse of the nocturnal boundary layer and the buildup of the mixed layer were clearly observed with three consecutive vertical profile measurements in the early morning hours. Besides this, we furthermore detected a CH4 hotspot in the coastal wetlands from a horizontal flight north to the dike, which demonstrates the potential of this new active AirCore method to measure at locations where other techniques have no practical access.
BibTeX:
@article{Andersen2018,
  author = {Andersen, Truls and Scheeren, Bert and Peters, Wouter and Chen, Huilin},
  title = {A UAV-based active AirCore system for measurements of greenhouse gases},
  journal = {Atmospheric Measurement Techniques},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {11},
  number = {5},
  pages = {2683--2699},
  doi = {10.5194/amt-11-2683-2018}
}
Arrouays D, Saby NP, Boukir H, Jolivet C, Ratié C, Schrumpf M, Merbold L, Gielen B, Gogo S, Delpierre N, Vincent G, Klumpp K and Loustau D (2018), "Soil sampling and preparation for monitoring soil carbon", International Agrophysics., dec, 2018. Vol. 32(4), pp. 633-643.
Abstract: There is an urgent need for standardized monitoring of existing soil organic carbon stocks in order to accurately quantify potential negative or positive feedbacks with climate change on carbon fluxes. Given the uncertainty of flux measurements at the ecosystem scale, obtaining precise estimates of changes in soil organic carbon stocks is essential to provide an independent assessment of long-Term net ecosystem carbon exchange. Here we describe the standard procedure to monitor the soil organic carbon stocks within the footprint of an eddy covariance flux tower, as applied at ecosystem stations of the Integrated Carbon Observation System. The objectives are i) to ensure comparability between sites and to be able to draw general conclusions from the results obtained across many ecosystems and ii) to optimize the sampling design in order to be able to prove changes in time using a reduced number of samples. When sampling a given site at two periods, the objective is generally to assess if changes occurred in time. The changes that can be detected (i.e., demonstrated as statistically significant) depend on several parameters such as the number of samples, the spatial sampling design, and the inherent within-site soil variability. Depending on these parameters, one can define the 'minimum detectable change' which is the minimum value of changed that can be statistically proved. Using simulation studies, we address the trade-off between increasing the number of samples and getting lower minimum detectable changes of soil organic carbon stocks.
BibTeX:
@article{Arrouays2018,
  author = {Arrouays, Dominique and Saby, Nicolas P.A. and Boukir, Hakima and Jolivet, Claudy and Ratié, Céline and Schrumpf, Marion and Merbold, Lutz and Gielen, Bert and Gogo, Sébastien and Delpierre, Nicolas and Vincent, Gaëlle and Klumpp, Katja and Loustau, Denis},
  title = {Soil sampling and preparation for monitoring soil carbon},
  journal = {International Agrophysics},
  year = {2018},
  volume = {32},
  number = {4},
  pages = {633--643},
  url = {https://content.sciendo.com/view/journals/intag/32/4/article-p633.xml},
  doi = {10.1515/intag-2017-0047}
}
Arzoumanian E, Vogel FR, Bastos A, Gaynullin B, Laurent O, Ramonet M and Ciais P (2018), "Characterization of lower-cost medium precision atmospheric COtextlesssubtextgreater2textless/subtextgreater monitoring systems for urban areas using commercial NDIR sensors", Atmospheric Measurement Techniques Discussions. , pp. 1-22. Copernicus GmbH.
Abstract: textlessptextgreatertextlessstrongtextgreaterAbstract.textless/strongtextgreater COtextlesssubtextgreater2textless/subtextgreater emission estimates from urban areas can be obtained with a network of in-situ instruments measuring atmospheric COtextlesssubtextgreater2textless/subtextgreater combined with high-resolution (inverse) transport modeling. The distribution of COtextlesssubtextgreater2textless/subtextgreater emissions being highly heterogeneous in space and variable in time in urban areas, gradients of atmospheric COtextlesssubtextgreater2textless/subtextgreater need to be measured by numerous instruments placed at multiple locations around and possibly within these urban areas, which calls for the development of lower-cost medium precision sensors to allow a deployment at required densities. Medium precision is here set to be a random error (uncertainty) on hourly measurements of ±1 ppm or less, a precision requirement based on previous studies of network design in urban areas. Here we present tests of a HPP commercial NDIR sensors manufactured by Senseair AB performed in the laboratory and at actual field stations, the latter for COtextlesssubtextgreater2textless/subtextgreater concentration in the Paris area. The lower-cost medium precision sensors are shown to be sensitive to atmospheric pressure and temperature conditions. The sensors respond linearly to COtextlesssubtextgreater2textless/subtextgreater when measuring calibration tanks, but the regression slope between measured and true COtextlesssubtextgreater2textless/subtextgreater differs between individual sensors and changes with time. In addition to pressure and temperature variations, humidity impacts the measurement of COtextlesssubtextgreater2textless/subtextgreater, all causing systematic errors. In the field, an empirical calibration strategy is proposed based on parallel measurements with the lower-cost medium precision sensors and a high-precision instrument cavity ring-down instrument during 6 month. This empirical calibration method consists of using a multiple regression approach to create a model of the errors defined as the difference of COtextlesssubtextgreater2textless/subtextgreater measured by the lower-cost medium precision sensors relative to a calibrated high-precision instrument, based on predictors of air temperature, pressure and humidity. This error model shows good performances to explain the observed drifts of the lower-cost medium precision sensors on time scales of up to 1–2 months when trained against 1–2 weeks of high-precision instrument time series. Residual errors are contained within the ±1 ppm target, showing the feasibility to use networks of HPP instruments for urban COtextlesssubtextgreater2textless/subtextgreater networks, provided that they could be regularly calibrated against one anchor reference high-precision instrument.textless/ptextgreater
BibTeX:
@article{Arzoumanian2018,
  author = {Arzoumanian, Emmanuel and Vogel, Felix R. and Bastos, Ana and Gaynullin, Bakhram and Laurent, Olivier and Ramonet, Michel and Ciais, Philippe},
  title = {Characterization of lower-cost medium precision atmospheric COtextlesssubtextgreater2textless/subtextgreater monitoring systems for urban areas using commercial NDIR sensors},
  journal = {Atmospheric Measurement Techniques Discussions},
  publisher = {Copernicus GmbH},
  year = {2018},
  pages = {1--22},
  doi = {10.5194/amt-2018-329}
}
Assan S, Vogel FR, Gros V, Baudic A, Staufer J and Ciais P (2018), "Can we separate industrial CH4 emission sources from atmospheric observations? - A test case for carbon isotopes, PMF and enhanced APCA", Atmospheric Environment., aug, 2018. Vol. 187, pp. 317-327. Elsevier BV.
Abstract: A large factor contributing to the uncertainties associated with sector specific anthropogenic methane emissions is the lack of available methods and data to reliably discriminate the different production processes. In this study, a variety of source apportionment techniques were investigated and developed to improve CH4 apportionment for co-located CH4 sources. The goal was to distinguish emissions from different systems at a mid-stream natural gas (NG) site (compressor station). Continuous measurements of atmospheric CH4 and co-emitted volatile organic compounds (VOCs) were analysed using Principle Component Analysis (PCA) and Positive Matrix Factorisation (PMF) receptor models. After sensitivity studies, significant extensions were made to the classical PCA, (Monte Carlo Absolute PCA ‘MC-APCA' and Monte Carlo moving Absolute PCA ‘MC-mAPCA') to better suit this application. Results from the receptor models are compared and combined with isotopic analysis, examining both long and short-term temporal variations. This work determined MC-APCA and PMF to be the most appropriate techniques for the long-term analysis of dominant sources; according to MC-mAPCA, this was identified to be 77.5 ± 0.6% natural gas, while 66% of the remaining variability was associated with traffic-related proxies. Techniques such as the moving Miller-Tans method for isotopic source identification and MC-mAPCA gave an insight into the short-term variability of source composition. During most CH4 enhancement periods, δ13CH4 sources range from −40‰ to −45‰ while MC-mAPCA typically show methane to ethane ratios of 4%–8%, confirming the prevalence of NG emissions. Both techniques identified CH4 enhancements from intermittently contributing sources (in this case a ruminant source characterised by δ13CH4 -62 ± 3‰ and 0% C2H6:CH4), and differentiate small fluctuations in NG source composition. Overall, the best method to identify CH4 sources from atmospheric local measurements remains strongly dependant on the characteristics of said source. The campaign investigated here required sensitive analysis as it was predominantly single sourced, and focussed on the identification of two gas streams. In such a case, it was found that a combination of old and novel techniques provide the greatest information on the characteristics of CH4 sources and gives confidence in the results.
BibTeX:
@article{Assan2018,
  author = {Assan, Sabina and Vogel, F. R. and Gros, V. and Baudic, A. and Staufer, J. and Ciais, P.},
  title = {Can we separate industrial CH4 emission sources from atmospheric observations? - A test case for carbon isotopes, PMF and enhanced APCA},
  journal = {Atmospheric Environment},
  publisher = {Elsevier BV},
  year = {2018},
  volume = {187},
  pages = {317--327},
  doi = {10.1016/j.atmosenv.2018.05.004}
}
Bachy A, Aubinet M, Amelynck C, Schoon N, Bodson B, Moureaux C, Delaplace P, De Ligne A and Heinesch B (2018), "Methanol exchange dynamics between a temperate cropland soil and the atmosphere", Atmospheric Environment., mar, 2018. Vol. 176, pp. 229-239.
Abstract: Soil methanol (CH3OH) exchange is often considered as several orders of magnitude smaller than plant methanol exchange. However, for some ecosystems, it is significant in regard with plant exchange and worth thus better consideration. Our study sought to gain a better understanding of soil exchange. Methanol flux was measured at the ecosystem scale on a bare agricultural soil over two contrasted periods using the disjunct eddy covariance by mass scanning technique. A proton-transfer-reaction mass spectrometer was used for the methanol ambient mixing ratio measurements. Bi-directional exchange dynamics were observed. Methanol emission occurred under dry and warm conditions and correlated best with soil surface temperature, whereas methanol uptake occurred under wet and mild conditions and correlated well with the methanol ambient concentration. After having tested a physical adsorption-desorption model and by confronting our data with the literature, we propose that the exchange was ruled by both a physical adsorption/desorption mechanism and by a methanol source, which still needs to be identified. The soil emission decreased when the vegetation developed. The reasons for the decrease still need to be determined. Overall, the dynamics observed at our site were similar to those reported by other studies for both cropland and forest ecosystems. The mechanism proposed in our work can thus be possibly applied to other sites or ecosystems. In addition, the methanol exchange rate was in the upper range of the exchange rates reported by other soil studies, suggesting that cropland soils are more important methanol exchangers than those in other ecosystems and should therefore be further investigated.
BibTeX:
@article{Bachy2018,
  author = {Bachy, A. and Aubinet, M. and Amelynck, C. and Schoon, N. and Bodson, B. and Moureaux, C. and Delaplace, P. and De Ligne, A. and Heinesch, B.},
  title = {Methanol exchange dynamics between a temperate cropland soil and the atmosphere},
  journal = {Atmospheric Environment},
  year = {2018},
  volume = {176},
  pages = {229--239},
  url = {http://linkinghub.elsevier.com/retrieve/pii/S1352231017308579},
  doi = {10.1016/j.atmosenv.2017.12.016}
}
Ballantyne AP, Ciais P and Miller JB (2018), "Cautious Optimism and Incremental Goals Toward Stabilizing Atmospheric CO2", Earth's Future., dec, 2018. Vol. 6(12), pp. 1632-1637. American Geophysical Union (AGU).
Abstract: Fossil fuel emissions of CO2 to the atmosphere appear to have leveled off in recent years; however, atmospheric CO2 concentrations continue to rise. Our simple analysis shows that peaks in the growth rates of human population and fossil fuel emissions have been observed, but the growth rate of atmospheric CO2 has reached record levels and shows no indication of peaking. Before atmospheric CO2 concentrations can be stabilized at safe levels, a peak in the CO2 growth rate must be achieved.
BibTeX:
@article{Ballantyne2018,
  author = {Ballantyne, A. P. and Ciais, P. and Miller, J. B.},
  title = {Cautious Optimism and Incremental Goals Toward Stabilizing Atmospheric CO2},
  journal = {Earth's Future},
  publisher = {American Geophysical Union (AGU)},
  year = {2018},
  volume = {6},
  number = {12},
  pages = {1632--1637},
  doi = {10.1029/2018EF001012}
}
Balsamo G, Agusti-Panareda A, Albergel C, Arduini G, Beljaars A, Bidlot J, Bousserez N, Boussetta S, Brown A, Buizza R, Buontempo C, Chevallier F, Choulga M, Cloke H, Cronin MF, Dahoui M, Rosnay PD, Dirmeyer PA, Drusch M, Dutra E, Ek MB, Gentine P, Hewitt H, Keeley SP, Kerr Y, Kumar S, Lupu C, Mahfouf JF, McNorton J, Mecklenburg S, Mogensen K, Muñoz-Sabater J, Orth R, Rabier F, Reichle R, Ruston B, Pappenberger F, Sandu I, Seneviratne SI, Tietsche S, Trigo IF, Uijlenhoet R, Wedi N, Woolway RI and Zeng X (2018), "Satellite and in situ observations for advancing global earth surface modelling: A review", Remote Sensing., dec, 2018. Vol. 10(12), pp. 2038. MDPI AG.
Abstract: In this paper, we review the use of satellite-based remote sensing in combination with in situ data to inform Earth surface modelling. This involves verification and optimization methods that can handle both random and systematic errors and result in effective model improvement for both surface monitoring and prediction applications. The reasons for diverse remote sensing data and products include (i) their complementary areal and temporal coverage, (ii) their diverse and covariant information content, and (iii) their ability to complement in situ observations, which are often sparse and only locally representative. To improve our understanding of the complex behavior of the Earth system at the surface and sub-surface, we need large volumes of data from high-resolution modelling and remote sensing, since the Earth surface exhibits a high degree of heterogeneity and discontinuities in space and time. The spatial and temporal variability of the biosphere, hydrosphere, cryosphere and anthroposphere calls for an increased use of Earth observation (EO) data attaining volumes previously considered prohibitive. We review data availability and discuss recent examples where satellite remote sensing is used to infer observable surface quantities directly or indirectly, with particular emphasis on key parameters necessary for weather and climate prediction. Coordinated high-resolution remote-sensing and modelling/assimilation capabilities for the Earth surface are required to support an international application-focused effort.
BibTeX:
@article{Balsamo2018,
  author = {Balsamo, Gianpaolo and Agusti-Panareda, Anna and Albergel, Clement and Arduini, Gabriele and Beljaars, Anton and Bidlot, Jean and Bousserez, Nicolas and Boussetta, Souhail and Brown, Andy and Buizza, Roberto and Buontempo, Carlo and Chevallier, Frederic and Choulga, Margarita and Cloke, Hannah and Cronin, Meghan F. and Dahoui, Mohamed and Rosnay, Patricia De and Dirmeyer, Paul A. and Drusch, Matthias and Dutra, Emanuel and Ek, Michael B. and Gentine, Pierre and Hewitt, Helene and Keeley, Sarah P.E. and Kerr, Yann and Kumar, Sujay and Lupu, Cristina and Mahfouf, Jean Francois and McNorton, Joe and Mecklenburg, Susanne and Mogensen, Kristian and Muñoz-Sabater, Joaquín and Orth, Rene and Rabier, Florence and Reichle, Rolf and Ruston, Ben and Pappenberger, Florian and Sandu, Irina and Seneviratne, Sonia I. and Tietsche, Steffen and Trigo, Isabel F. and Uijlenhoet, Remko and Wedi, Nils and Woolway, R. Iestyn and Zeng, Xubin},
  title = {Satellite and in situ observations for advancing global earth surface modelling: A review},
  journal = {Remote Sensing},
  publisher = {MDPI AG},
  year = {2018},
  volume = {10},
  number = {12},
  pages = {2038},
  doi = {10.3390/rs10122038}
}
Barba J, Cueva A, Bahn M, Barron-Gafford GA, Bond-Lamberty B, Hanson PJ, Jaimes A, Kulmala L, Pumpanen J, Scott RL, Wohlfahrt G and Vargas R (2018), "Comparing ecosystem and soil respiration: Review and key challenges of tower-based and soil measurements", Agricultural and Forest Meteorology. Vol. 249, pp. 434-443.
Abstract: The net ecosystem exchange (NEE) is the difference between ecosystem CO2 assimilation and CO2 losses to the atmosphere. Ecosystem respiration (Reco), the efflux of CO2 from the ecosystem to the atmosphere, includes the soil-to-atmosphere carbon flux (i.e., soil respiration; Rsoil) and aboveground plant respiration. Therefore, Rsoil is a fraction of Reco and theoretically has to be smaller than Reco at daily, seasonal, and annual scales. However, several studies estimating Reco with the eddy covariance technique and measuring Rsoil within the footprint of the tower have reported higher Rsoil than Reco at different time scales. Here, we compare four different and contrasting ecosystems (from forest to grasslands, and from boreal to semiarid) to test if measurements of Reco are consistently higher than Rsoil. In general, both fluxes showed similar temporal patterns, but Reco was not consistently higher than Rsoil from daily to annual scales across sites. We identified several issues that apply for measuring NEE and measuring/upscaling Rsoil that could result in an underestimation of Reco and/or an overestimation of Rsoil. These issues are discussed based on (a) nighttime measurements of NEE, (b) Rsoil measurements, and (c) the interpretation of the functional relationships of these fluxes with temperature (i.e., Q10). We highlight that there is still a need for better integration of Rsoil with eddy covariance measurements to address challenges related to the spatial and temporal variability of Reco and Rsoil.
BibTeX:
@article{Barba2018,
  author = {Barba, Josep and Cueva, Alejandro and Bahn, Michael and Barron-Gafford, Greg A. and Bond-Lamberty, Benjamin and Hanson, Paul J. and Jaimes, Aline and Kulmala, Liisa and Pumpanen, Jukka and Scott, Russell L. and Wohlfahrt, Georg and Vargas, Rodrigo},
  title = {Comparing ecosystem and soil respiration: Review and key challenges of tower-based and soil measurements},
  journal = {Agricultural and Forest Meteorology},
  year = {2018},
  volume = {249},
  pages = {434--443},
  doi = {10.1016/j.agrformet.2017.10.028}
}
Barskov KV, Glazunov AV, Repina IA, Stepanenko VM, Lykossov VN and Mammarella I (2018), "On the Applicability of Similarity Theory for the Stable Atmospheric Boundary Layer over Complex Terrain", Izvestiya - Atmospheric and Ocean Physics., sep, 2018. Vol. 54(5), pp. 462-471. Pleiades Publishing Ltd.
Abstract: Micrometeorological measurements in the atmospheric boundary layer over a hilly forest terrain have been made on a meteorological tower at several levels from the forest canopy top to a height that exceeds the height of trees almost seven times. A semiempirical length scale depending on the local topography features and the underlying surface type has been proposed and calculated. This scale has been shown to allow the universal functions of the Monin–Obukhov similarity theory to be corrected for a stable atmospheric boundary layer over complex terrain without substantial modification when compared to the universal functions over a homogeneous surface with small roughness elements. This approach can be used to refine the methods for calculating turbulent momentum fluxes from profile measurements over spatially inhomogeneous landscapes.
BibTeX:
@article{Barskov2018,
  author = {Barskov, K. V. and Glazunov, A. V. and Repina, I. A. and Stepanenko, V. M. and Lykossov, V. N. and Mammarella, I.},
  title = {On the Applicability of Similarity Theory for the Stable Atmospheric Boundary Layer over Complex Terrain},
  journal = {Izvestiya - Atmospheric and Ocean Physics},
  publisher = {Pleiades Publishing Ltd},
  year = {2018},
  volume = {54},
  number = {5},
  pages = {462--471},
  doi = {10.1134/S0001433818050031}
}
Bastos A, Peregon A, Gani ÉA, Khudyaev S, Yue C, Li W, Gouveia CM and Ciais P (2018), "Influence of high-latitude warming and land-use changes in the early 20th century northern Eurasian CO2 sink", Environmental Research Letters., jun, 2018. Vol. 13(6), pp. 65014. IOP Publishing.
Abstract: While the global carbon budget (GCB) is relatively well constrained over the last decades of the 20th century [1], observations and reconstructions of atmospheric CO2 growth rate present large discrepancies during the earlier periods [2]. The large uncertainty in GCB has been attributed to the land biosphere, although it is not clear whether the gaps between observations and reconstructions are mainly because land-surface models (LSMs) underestimate inter-annual to decadal variability in natural ecosystems, or due to inaccuracies in land-use change reconstructions. As Eurasia encompasses about 15% of the terrestrial surface, 20% of the global soil organic carbon pool and constitutes a large CO2 sink, we evaluate the potential contribution of natural and human-driven processes to induce large anomalies in the biospheric CO2 fluxes in the early 20th century. We use an LSM specifically developed for high-latitudes, that correctly simulates Eurasian C-stocks and fluxes from observational records [3], in order to evaluate the sensitivity of the Eurasian sink to the strong high-latitude warming occurring between 1930 and 1950. We show that the LSM with improved high-latitude phenology, hydrology and soil processes, contrary to the group of LSMs in [2], is able to represent enhanced vegetation growth linked to boreal spring warming, consistent with tree-ring time-series [4]. By compiling a dataset of annual agricultural area in the Former Soviet Union that better reflects changes in cropland area linked with socio-economic fluctuations during the early 20th century, we show that land-abadonment during periods of crisis and war may result in reduced CO2 emissions from land-use change (44%-78% lower) detectable at decadal time-scales. Our study points to key processes that may need to be improved in LSMs and LUC datasets in order to better represent decadal variability in the land CO2 sink, and to better constrain the GCB during the pre-observational record.
BibTeX:
@article{Bastos2018,
  author = {Bastos, Ana and Peregon, Anna and Gani, Érico A. and Khudyaev, Sergey and Yue, Chao and Li, Wei and Gouveia, Célia M. and Ciais, Philippe},
  title = {Influence of high-latitude warming and land-use changes in the early 20th century northern Eurasian CO2 sink},
  journal = {Environmental Research Letters},
  publisher = {IOP Publishing},
  year = {2018},
  volume = {13},
  number = {6},
  pages = {65014},
  doi = {10.1088/1748-9326/aac4d3}
}
Basu S, Baker DF, Chevallier F, Patra PK, Liu J and Miller JB (2018), "The impact of transport model differences on CO2 surface flux estimates from OCO-2 retrievals of column average CO2", Atmospheric Chemistry and Physics. Vol. 18(10), pp. 7189-7215. Copernicus GmbH.
Abstract: We estimate the uncertainty of CO2 flux estimates in atmospheric inversions stemming from differences between different global transport models. Using a set of observing system simulation experiments (OSSEs), we estimate this uncertainty as represented by the spread between five different state-of-the-art global transport models (ACTM, LMDZ, GEOS-Chem, PCTM and TM5), for both traditional in situ CO2 inversions and inversions of XCO2 estimates from the Orbiting Carbon Observatory 2 (OCO-2). We find that, in the absence of relative biases between in situ CO2 and OCO-2 XCO2, OCO-2 estimates of terrestrial flux for TRANSCOM-scale land regions can be more robust to transport model differences than corresponding in situ CO2 inversions. This is due to a combination of the increased spatial coverage of OCO-2 samples and the total column nature of OCO-2 estimates. We separate the two effects by constructing hypothetical in situ networks with the coverage of OCO-2 but with only near-surface samples. We also find that the transport-driven uncertainty in fluxes is comparable between well-sampled northern temperate regions and poorly sampled tropical regions. Furthermore, we find that spatiotemporal differences in sampling, such as between OCO-2 land and ocean soundings, coupled with imperfect transport, can produce differences in flux estimates that are larger than flux uncertainties due to transport model differences. This highlights the need for sampling with as complete a spatial and temporal coverage as possible (e.g., using both land and ocean retrievals together for textlessspan styleCombining double low line"" classCombining double low line"text"textgreaterOCO-2textless/spantextgreater) to minimize the impact of selective sampling. Finally, our annual and monthly estimates of transport-driven uncertainties can be used to evaluate the robustness of conclusions drawn from real OCO-2 and in situ CO2 inversions.
BibTeX:
@article{Basu2018,
  author = {Basu, Sourish and Baker, David F. and Chevallier, Frédéric and Patra, Prabir K. and Liu, Junjie and Miller, John B.},
  title = {The impact of transport model differences on CO2 surface flux estimates from OCO-2 retrievals of column average CO2},
  journal = {Atmospheric Chemistry and Physics},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {18},
  number = {10},
  pages = {7189--7215},
  doi = {10.5194/acp-18-7189-2018}
}
Beaudoin N, Gallois N, Viennot P, Le Bas C, Puech T, Schott C, Buis S and Mary B (2018), "Evaluation of a spatialized agronomic model in predicting yield and N leaching at the scale of the Seine-Normandie Basin", Environmental Science and Pollution Research., sep, 2018. Vol. 25(24), pp. 23529-23558. Springer Nature.
Abstract: The EU directive has addressed ambitious targets concerning the quality of water bodies. Predicting water quality as affected by land use and management requires using dynamic agro-hydrogeological models. In this study, an agronomic model (STICS) and a hydrogeological model (MODCOU) have been associated in order to simulate nitrogen fluxes in the Seine-Normandie Basin, which is affected by nitrate pollution of groundwater due to intensive farming systems. This modeling platform was used to predict and understand the spatial and temporal evolution of water quality over the 1971–2013 period. A quality assurance protocol (Refsgaard et al. Environ Model Softw 20: 1201–1215, 2005) was used to qualify the reliability of STICS outputs. Four iterative runs of the model were carried out with improved parameterization of soils and crop management without any change in the model. Improving model inputs changed much more the spatial distribution of simulated N losses than their mean values. STICS slightly underestimated the crop yields compared to the observed values at the administrative district scale. The platform also slightly underestimated the nitrate concentration at the outlet level with a mean difference ranging from −1.4 to −9.2 mg NO3 L−1 according to the aquifer during the last decade. This outcome should help the stakeholders in decision-making to prevent nitrate pollution and provide new specifications for STICS development.
BibTeX:
@article{Beaudoin2018,
  author = {Beaudoin, N. and Gallois, N. and Viennot, P. and Le Bas, C. and Puech, T. and Schott, C. and Buis, S. and Mary, B.},
  title = {Evaluation of a spatialized agronomic model in predicting yield and N leaching at the scale of the Seine-Normandie Basin},
  journal = {Environmental Science and Pollution Research},
  publisher = {Springer Nature},
  year = {2018},
  volume = {25},
  number = {24},
  pages = {23529--23558},
  doi = {10.1007/s11356-016-7478-3}
}
Bergamaschi P, Karstens U, Manning AJ, Saunois M, Tsuruta A, Berchet A, Vermeulen AT, Arnold T, Janssens-Maenhout G, Hammer S, Levin I, Schmidt M, Ramonet M, Lopez M, Lavric J, Aalto T, Chen H, Feist DG, Gerbig C, Haszpra L, Hermansen O, Manca G, Moncrieff J, Meinhardt F, Necki J, Galkowski M, O'Doherty S, Paramonova N, Scheeren HA, Steinbacher M and Dlugokencky E (2018), "Inverse modelling of European CH4 emissions during 2006-2012 using different inverse models and reassessed atmospheric observations", Atmospheric Chemistry and Physics., jan, 2018. Vol. 18(2), pp. 901-920. Copernicus GmbH.
Abstract: We present inverse modelling (top down) estimates of European methane (CH4) emissions for 2006-2012 based on a new quality-controlled and harmonised in situ data set from 18 European atmospheric monitoring stations. We applied an ensemble of seven inverse models and performed four inversion experiments, investigating the impact of different sets of stations and the use of a priori information on emissions. The inverse models infer total CH4 emissions of 26.8 (20.2-29.7) Tg CH4 yr-1 (mean, 10th and 90th percentiles from all inversions) for the EU-28 for 2006-2012 from the four inversion experiments. For comparison, total anthropogenic CH4 emissions reported to UNFCCC (bottom up, based on statistical data and emissions factors) amount to only 21.3 Tg CH4 yr-1 (2006) to 18.8 Tg CH4 yr-1 (2012). A potential explanation for the higher range of top-down estimates compared to bottom-up inventories could be the contribution from natural sources, such as peatlands, wetlands, and wet soils. Based on seven different wetland inventories from the Wetland and Wetland CH4 Inter-comparison of Models Project (WETCHIMP), total wetland emissions of 4.3 (2.3-8.2) Tg CH4 yr-1 from the EU-28 are estimated. The hypothesis of significant natural emissions is supported by the finding that several inverse models yield significant seasonal cycles of derived CH4 emissions with maxima in summer, while anthropogenic CH4 emissions are assumed to have much lower seasonal variability. Taking into account the wetland emissions from the WETCHIMP ensemble, the top-down estimates are broadly consistent with the sum of anthropogenic and natural bottom-up inventories. However, the contribution of natural sources and their regional distribution remain rather uncertain. Furthermore, we investigate potential biases in the inverse models by comparison with regular aircraft profiles at four European sites and with vertical profiles obtained during the Infrastructure for Measurement of the European Carbon Cycle (IMECC) aircraft campaign. We present a novel approach to estimate the biases in the derived emissions, based on the comparison of simulated and measured enhancements of CH4 compared to the background, integrated over the entire boundary layer and over the lower troposphere. The estimated average regional biases range between -40 and 20 % at the aircraft profile sites in France, Hungary and Poland.
BibTeX:
@article{Bergamaschi2018,
  author = {Bergamaschi, Peter and Karstens, Ute and Manning, Alistair J. and Saunois, Marielle and Tsuruta, Aki and Berchet, Antoine and Vermeulen, Alexander T. and Arnold, Tim and Janssens-Maenhout, Greet and Hammer, Samuel and Levin, Ingeborg and Schmidt, Martina and Ramonet, Michel and Lopez, Morgan and Lavric, Jost and Aalto, Tuula and Chen, Huilin and Feist, Dietrich G. and Gerbig, Christoph and Haszpra, László and Hermansen, Ove and Manca, Giovanni and Moncrieff, John and Meinhardt, Frank and Necki, Jaroslaw and Galkowski, Michal and O'Doherty, Simon and Paramonova, Nina and Scheeren, Hubertus A. and Steinbacher, Martin and Dlugokencky, Ed},
  title = {Inverse modelling of European CH4 emissions during 2006-2012 using different inverse models and reassessed atmospheric observations},
  journal = {Atmospheric Chemistry and Physics},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {18},
  number = {2},
  pages = {901--920},
  doi = {10.5194/acp-18-901-2018}
}
Besnard S, Carvalhais N, Arain MA, Black A, De Bruin S, Buchmann N, Cescatti A, Chen J, Clevers JG, Desai AR, Gough CM, Havrankova K, Herold M, Hörtnagl L, Jung M, Knohl A, Kruijt B, Krupkova L, Law BE, Lindroth A, Noormets A, Roupsard O, Steinbrecher R, Varlagin A, Vincke C and Reichstein M (2018), "Quantifying the effect of forest age in annual net forest carbon balance", Environmental Research Letters., dec, 2018. Vol. 13(12), pp. 124018. IOP Publishing.
Abstract: Forests dominate carbon (C) exchanges between the terrestrial biosphere and the atmosphere on land. In the long term, the net carbon flux between forests and the atmosphere has been significantly impacted by changes in forest cover area and structure due to ecological disturbances and management activities. Current empirical approaches for estimating net ecosystem productivity (NEP) rarely consider forest age as a predictor, which represents variation in physiological processes that can respond differently to environmental drivers, and regrowth following disturbance. Here, we conduct an observational synthesis to empirically determine to what extent climate, soil properties, nitrogen deposition, forest age and management influence the spatial and interannual variability of forest NEP across 126 forest eddy-covariance flux sites worldwide. The empirical models explained up to 62% and 71% of spatio-temporal and across-site variability of annual NEP, respectively. An investigation of model structures revealed that forest age was a dominant factor of NEP spatio-temporal variability in both space and time at the global scale as compared to abiotic factors, such as nutrient availability, soil characteristics and climate. These findings emphasize the importance of forest age in quantifying spatio-temporal variation in NEP using empirical approaches.
BibTeX:
@article{Besnard2018,
  author = {Besnard, Simon and Carvalhais, Nuno and Arain, M. Altaf and Black, Andrew and De Bruin, Sytze and Buchmann, Nina and Cescatti, Alessandro and Chen, Jiquan and Clevers, Jan G.P.W. and Desai, Ankur R. and Gough, Christopher M. and Havrankova, Katerina and Herold, Martin and Hörtnagl, Lukas and Jung, Martin and Knohl, Alexander and Kruijt, Bart and Krupkova, Lenka and Law, Beverly E. and Lindroth, Anders and Noormets, Asko and Roupsard, Olivier and Steinbrecher, Rainer and Varlagin, Andrej and Vincke, Caroline and Reichstein, Markus},
  title = {Quantifying the effect of forest age in annual net forest carbon balance},
  journal = {Environmental Research Letters},
  publisher = {IOP Publishing},
  year = {2018},
  volume = {13},
  number = {12},
  pages = {124018},
  doi = {10.1088/1748-9326/aaeaeb}
}
Bogena H, Montzka C, Huisman J, Graf A, Schmidt M, Stockinger M, von Hebel C, Hendricks-Franssen H, van der Kruk J, Tappe W, Lücke A, Baatz R, Bol R, Groh J, Pütz T, Jakobi J, Kunkel R, Sorg J and Vereecken H (2018), "The TERENO-Rur Hydrological Observatory: A Multiscale Multi-Compartment Research Platform for the Advancement of Hydrological Science", Vadose Zone Journal. Vol. 17(1), pp. 180055. Soil Science Society of America.
Abstract: We provide an overview of the Rur hydrological observatory, which is the main observational platform of the TERENO (TERrestrial ENvironmental Observatories) Eifel/Lower Rhine Valley Observatory. The Rur catchment area exhibits distinct gradients in altitude, climate, land use, soil properties, and geology. The Eifel National Park is situated in the southern part of the Rur catchment and serves as a reference site for the hydrological observatory. We present information on general physical characteristics of the Rur catchment and describe the main features of the multi-scale and multi-compartment monitoring framework. In addition, we also present some examples of the ongoing interdisciplinary research that aims to advance the understanding of complex hydrological processes and interactions within the Rur catchment.
BibTeX:
@article{Bogena2018,
  author = {Bogena, H.R. and Montzka, C. and Huisman, J.A. and Graf, A. and Schmidt, M. and Stockinger, M. and von Hebel, C. and Hendricks-Franssen, H.J. and van der Kruk, J. and Tappe, W. and Lücke, A. and Baatz, R. and Bol, R. and Groh, J. and Pütz, T. and Jakobi, J. and Kunkel, R. and Sorg, J. and Vereecken, H.},
  title = {The TERENO-Rur Hydrological Observatory: A Multiscale Multi-Compartment Research Platform for the Advancement of Hydrological Science},
  journal = {Vadose Zone Journal},
  publisher = {Soil Science Society of America},
  year = {2018},
  volume = {17},
  number = {1},
  pages = {180055},
  doi = {10.2136/vzj2018.03.0055}
}
Brændholt A, Ibrom A, Larsen KS and Pilegaard K (2018), "Partitioning of ecosystem respiration in a beech forest", Agricultural and Forest Meteorology., apr, 2018. Vol. 252, pp. 88-98. Elsevier BV.
Abstract: Terrestrial ecosystem respiration (Reco) represents a major component of the global carbon cycle. It consists of many sub-components, such as aboveground plant respiration and belowground root and microbial respiration, each of which may respond differently to abiotic factors, and thus to global climate change. To correctly predict future carbon cycles in forest ecosystems, Reco must therefore be partitioned and understood for each of its various components. In this study we used the eddy covariance technique together with manual and automated closed-chambers to quantify the individual components of Reco in a temperate beech forest at diel, seasonal and annual time scales. Reco was measured by eddy covariance while respiration rates from soil, tree stems and isolated coarse tree roots were measured bi-hourly by an automated closed-chamber system. Soil respiration (Rsoil) was measured in intact plots, and heterotrophic Rsoil was measured in trenched plots. Tree stem (Rstem) and coarse root (Rroot) respiration were measured by custom made closed-chambers. We found that the contribution of Rstem to total Reco varied across the year, by only accounting for 6% of Reco during winter and 16% during the summer growing season. In contrast Rsoil was approximately half of Reco during winter (52%), spring (45%) and summer (49%), while the contribution increased to 79% during autumn. Based on observed fluxes in the trenched and intact soil plots, we found that autotrophic Rsoil accounted for 34% of Rsoil during summer, i.e. a relatively low fractional estimate compared to findings from other studies. It is likely that dead roots were still decomposing in the trenched soil plots thus causing overestimation of heterotrophic Rsoil. Diel Rstem and Rroot measurements showed a distinct pattern during summer with the highest respiration rates around 13:00-15:00 CET for Rstem, and the highest respiration seen from 9:00–15:00 for Rroot. In contrast, Rsoil showed the lowest respiration during daytime with no clear difference in the diel pattern between the intact and trenched soil plots. Finally, we calculated annual Rsoil for different transects, and found that annual Rsoil estimated from the previously used transect at the site was underestimated due to Rsoil of the transect not being representative for the spatial heterogeneity of Rsoil at the site. This highlights the importance of performing a sufficient number of chamber measurements at a site to adequately capture the spatial variation and estimate Rsoil correctly.
BibTeX:
@article{Brendholt2018,
  author = {Brændholt, Andreas and Ibrom, Andreas and Larsen, Klaus Steenberg and Pilegaard, Kim},
  title = {Partitioning of ecosystem respiration in a beech forest},
  journal = {Agricultural and Forest Meteorology},
  publisher = {Elsevier BV},
  year = {2018},
  volume = {252},
  pages = {88--98},
  doi = {10.1016/j.agrformet.2018.01.012}
}
Cameron D, Flechard C and Van Oijen M (2018), "Calibrating a process-based forest model with a rich observational dataset at 22 European forest sites", Biogeosciences Discussions., apr, 2018. , pp. 1-42.
Abstract: textlessptextgreatertextlessptextgreatertextlessstrongtextgreaterAbstract.textless/strongtextgreater In recent years model-data interaction has improved through use of probabilistic techniques to inform and reduce the uncertainty of model parameters, while also taking into account observational uncertainty. This study builds on previous work, through access to a richer representation of the plant-soil ecosystem at multiple European forest sites, than was previously available. Given this rich dataset, we asked which observational datasets were most effective in reducing uncertainty in model predictions and model-data differences. Also, since there is a lack of consensus about whether it is more beneficial to calibrate forest sites separately or together we revisited this question with a particular emphasis on which is most effective in reducing model-data differences and uncertainty. We performed single dataset Bayesian calibrations (BC) and compared the results with a calibration with all the observations included. We also compared calibrations where each pine forest site was calibrated separately with a calibration where all the pine sites were calibrated together. While measurements of plant and soil carbon stocks were more sparse, their inclusion in the BC were more important for reducing model-data differences and uncertainty in the above and belowground carbon pools than the greater numbers of carbon and water flux data. Our results suggest that use of calibration data representing just a few aspects of the ecosystem could be problematic, since improved model-data fits for the parts of the system represented by the data could be at the expense of other part of the system, where the model-data fit worsened. The single dataset calibrations helped to diagnose where there may be inconsistencies between different datasets or between the model and data or both. These inconsistencies hampered the reduction in model-data differences in the calibration with all the observations present. As expected, we found a strong relationship between the quantity of data included in the calibration and the uncertainty reduction after BC, finding the largest reduction in uncertainty when all the observations were included. For some ecosystem variables uncertainty reduced after calibration but model-data differences increased. This would suggest that there were deficiencies in the model or systematic errors in the data or both. These results advocate the use of calibration datasets which represent the rich diversity of the ecosystem under investigation but where model discrepancies and data systematic errors are explicitly represented in the BC. While separate calibrations at each forest site generally reduced model-data differences more than calibrating at all the sites together, parts of the ecosystem that were sparsely observed benefited more from the multi-site calibration. Multi-site calibration led to larger and more consistent reductions in uncertainty than separate calibrations at each site, especially for ecosystem variables with fewer observations. These results support the use of Bayesian hierarchical calibration which allows variation in model parameters between different sites while allowing information to be shared across sites for sparsely observed ecosystem variables.textless/ptextgreatertextless/ptextgreater
BibTeX:
@article{Cameron2018,
  author = {Cameron, David and Flechard, Christophe and Van Oijen, Marcel},
  title = {Calibrating a process-based forest model with a rich observational dataset at 22 European forest sites},
  journal = {Biogeosciences Discussions},
  year = {2018},
  pages = {1--42},
  url = {https://www.biogeosciences-discuss.net/bg-2018-156/},
  doi = {10.5194/bg-2018-156}
}
Campeau A, Bishop K, Nilsson MB, Klemedtsson L, Laudon H, Leith FI, Öquist M and Wallin MB (2018), "Stable Carbon Isotopes Reveal Soil-Stream DIC Linkages in Contrasting Headwater Catchments", Journal of Geophysical Research: Biogeosciences., jan, 2018. Vol. 123(1), pp. 149-167.
Abstract: Large CO2 evasion to the atmosphere occurs as dissolved inorganic carbon (DIC) is transported from soils to streams. While this physical process has been the focus of multiple studies, less is known about the underlying biogeochemical transformations that accompany this transfer of C from soils to streams. Here we used patterns in stream water and groundwater δ13C-DIC values within three headwater catchments with contrasting land cover to identify the sources and processes regulating DIC during its transport. We found that although considerable CO2 evasion occurs as DIC is transported from soils to streams, there were also other processes affecting the DIC pool. Methane production and mixing of C sources, associated with different types and spatial distribution of peat-rich areas within each catchment, had a significant influence on the δ13C-DIC values in both soils and streams. These processes represent an additional control on δ13C-DIC values and the catchment-scale cycling of DIC across different northern landscape types. The results from this study demonstrate that the transport of DIC from soils to streams results in more than just rapid CO2 evasion to the atmosphere but also represents a channel of C transformation, which questions some of our current conceptualizations of C cycling at the landscape scale.
BibTeX:
@article{Campeau2018,
  author = {Campeau, A. and Bishop, K. and Nilsson, M. B. and Klemedtsson, L. and Laudon, H. and Leith, F. I. and Öquist, M. and Wallin, M. B.},
  title = {Stable Carbon Isotopes Reveal Soil-Stream DIC Linkages in Contrasting Headwater Catchments},
  journal = {Journal of Geophysical Research: Biogeosciences},
  year = {2018},
  volume = {123},
  number = {1},
  pages = {149--167},
  url = {http://doi.wiley.com/10.1002/2017JG004083},
  doi = {10.1002/2017JG004083}
}
Carrara A, Kolari P, De Beeck MO, Arriga N, Berveiller D, Dengel S, Ibrom A, Merbold L, Rebmann C, Sabbatini S, Serrano-Ortíz P and Biraud SC (2018), "Radiation measurements at ICOS ecosystem stations", International Agrophysics., dec, 2018. Vol. 32(4), pp. 589-605.
Abstract: Solar radiation is a key driver of energy and carbon fluxes in natural ecosystems. Radiation measurements are essential for interpreting ecosystem scale greenhouse gases and energy fluxes as well as many other observations performed at ecosystem stations of the Integrated Carbon Observation System (ICOS). We describe and explain the relevance of the radiation variables that are monitored continuously at ICOS ecosystem stations and define recommendations to perform these measurements with consistent and comparable accuracy. The measurement methodology and instruments are described including detailed technical specifications. Guidelines for instrumental set up as well as for operation, maintenance and data collection are defined considering both ICOS scientific objectives and practical operational constraints. For measurements of short-wave (solar) and long wave (infrared) radiation components, requirements for the ICOS network are based on available well-defined state-of-The art standards (World Meteorological Organization, International Organization for Standardization). For photosynthetically active radiation measurements, some basic instrumental requirements are based on the performance of commercially available sensors. Since site specific conditions and practical constraints at individual ICOS ecosystem stations may hamper the applicability of standard requirements, we recommend that ICOS develops mid-Term coordinated actions to assess the effective level of uncertainties in radiation measurements at the network scale.
BibTeX:
@article{Carrara2018,
  author = {Carrara, Arnaud and Kolari, Pasi and De Beeck, Maarten Op and Arriga, Nicola and Berveiller, Daniel and Dengel, Sigrid and Ibrom, Andreas and Merbold, Lutz and Rebmann, Corinna and Sabbatini, Simone and Serrano-Ortíz, Penelope and Biraud, Sébastien C.},
  title = {Radiation measurements at ICOS ecosystem stations},
  journal = {International Agrophysics},
  year = {2018},
  volume = {32},
  number = {4},
  pages = {589--605},
  url = {https://content.sciendo.com/view/journals/intag/32/4/article-p589.xml},
  doi = {10.1515/intag-2017-0049}
}
Ciavatta S, Brewin RJ, Skákala J, Polimene L, de Mora L, Artioli Y and Allen JI (2018), "Assimilation of Ocean-Color Plankton Functional Types to Improve Marine Ecosystem Simulations", Journal of Geophysical Research: Oceans., feb, 2018. Vol. 123(2), pp. 834-854. American Geophysical Union (AGU).
Abstract: We assimilated phytoplankton functional types (PFTs) derived from ocean color into a marine ecosystem model, to improve the simulation of biogeochemical indicators and emerging properties in a shelf sea. Error-characterized chlorophyll concentrations of four PFTs (diatoms, dinoflagellates, nanoplankton, and picoplankton), as well as total chlorophyll for comparison, were assimilated into a physical-biogeochemical model of the North East Atlantic, applying a localized Ensemble Kalman filter. The reanalysis simulations spanned the years 1998–2003. The skill of the reference and reanalysis simulations in estimating ocean color and in situ biogeochemical data were compared by using robust statistics. The reanalysis outperformed both the reference and the assimilation of total chlorophyll in estimating the ocean-color PFTs (except nanoplankton), as well as the not-assimilated total chlorophyll, leading the model to simulate better the plankton community structure. Crucially, the reanalysis improved the estimates of not-assimilated in situ data of PFTs, as well as of phosphate and pCO2, impacting the simulation of the air-sea carbon flux. However, the reanalysis increased further the model overestimation of nitrate, in spite of increases in plankton nitrate uptake. The method proposed here is easily adaptable for use with other ecosystem models that simulate PFTs, for, e.g., reanalysis of carbon fluxes in the global ocean and for operational forecasts of biogeochemical indicators in shelf-sea ecosystems.
BibTeX:
@article{Ciavatta2018,
  author = {Ciavatta, S. and Brewin, R. J.W. and Skákala, J. and Polimene, L. and de Mora, L. and Artioli, Y. and Allen, J. I.},
  title = {Assimilation of Ocean-Color Plankton Functional Types to Improve Marine Ecosystem Simulations},
  journal = {Journal of Geophysical Research: Oceans},
  publisher = {American Geophysical Union (AGU)},
  year = {2018},
  volume = {123},
  number = {2},
  pages = {834--854},
  doi = {10.1002/2017JC013490}
}
Collalti A, Trotta C, Keenan TF, Ibrom A, Bond-Lamberty B, Grote R, Vicca S, Reyer CP, Migliavacca M, Veroustraete F, Anav A, Campioli M, Scoccimarro E, Šigut L, Grieco E, Cescatti A and Matteucci G (2018), "Thinning Can Reduce Losses in Carbon Use Efficiency and Carbon Stocks in Managed Forests Under Warmer Climate", Journal of Advances in Modeling Earth Systems. Vol. 10(10), pp. 2427-2452. American Geophysical Union (AGU).
Abstract: Forest carbon use efficiency (CUE, the ratio of net to gross primary productivity) represents the fraction of photosynthesis that is not used for plant respiration. Although important, it is often neglected in climate change impact analyses. Here we assess the potential impact of thinning on projected carbon cycle dynamics and implications for forest CUE and its components (i.e., gross and net primary productivity and plant respiration), as well as on forest biomass production. Using a detailed process-based forest ecosystem model forced by climate outputs of five Earth System Models under four representative climate scenarios, we investigate the sensitivity of the projected future changes in the autotrophic carbon budget of three representative European forests. We focus on changes in CUE and carbon stocks as a result of warming, rising atmospheric CO2 concentration, and forest thinning. Results show that autotrophic carbon sequestration decreases with forest development, and the decrease is faster with warming and in unthinned forests. This suggests that the combined impacts of climate change and changing CO2 concentrations lead the forests to grow faster, mature earlier, and also die younger. In addition, we show that under future climate conditions, forest thinning could mitigate the decrease in CUE, increase carbon allocation into more recalcitrant woody pools, and reduce physiological-climate-induced mortality risks. Altogether, our results show that thinning can improve the efficacy of forest-based mitigation strategies and should be carefully considered within a portfolio of mitigation options.
BibTeX:
@article{Collalti2018,
  author = {Collalti, Alessio and Trotta, Carlo and Keenan, Trevor F. and Ibrom, Andreas and Bond-Lamberty, Ben and Grote, Ruediger and Vicca, Sara and Reyer, Christopher P.O. and Migliavacca, Mirco and Veroustraete, Frank and Anav, Alessandro and Campioli, Matteo and Scoccimarro, Enrico and Šigut, Ladislav and Grieco, Elisa and Cescatti, Alessandro and Matteucci, Giorgio},
  title = {Thinning Can Reduce Losses in Carbon Use Efficiency and Carbon Stocks in Managed Forests Under Warmer Climate},
  journal = {Journal of Advances in Modeling Earth Systems},
  publisher = {American Geophysical Union (AGU)},
  year = {2018},
  volume = {10},
  number = {10},
  pages = {2427--2452},
  doi = {10.1029/2018MS001275}
}
Colomb, A., Conil, S., Delmotte, M., Heliasz, M., Hermannsen, O., Holst, J., … Yver-Kwok C (2018), "ICOS Atmospheric Greenhouse Gas Mole Fractions of CO2, CH4, CO, 14CO2 and Meteorological Observations 2016-2018, final quality controlled Level 2 data.".
BibTeX:
@misc{ColombA.ConilS.DelmotteM.HeliaszM.HermannsenO.HolstJ.dotsYverKwok2018,
  author = {Colomb, A., Conil, S., Delmotte, M., Heliasz, M., Hermannsen, O., Holst, J., … Yver-Kwok, C.},
  title = {ICOS Atmospheric Greenhouse Gas Mole Fractions of CO2, CH4, CO, 14CO2 and Meteorological Observations 2016-2018, final quality controlled Level 2 data.},
  booktitle = {Icos Eric},
  publisher = {ICOS ERIC},
  year = {2018},
  doi = {doi.org/10.18160/RHKC-VP22}
}
Conen F, Bukowiecki N, Gysel M, Steinbacher M, Fischer A and Reimann S (2018), "Low number concentration of ice nucleating particles in an aged smoke plume", Quarterly Journal of the Royal Meteorological Society., jul, 2018. Vol. 144(715), pp. 1991-1994. Wiley.
Abstract: Smoke from forest fires in the western part of North America reached the High Altitude Research Station Jungfraujoch, Switzerland, at the beginning of September 2017. Number concentration of ice nucleating particles (INPs) active at −15 °C or warmer decreased by about half during its passage. This is different to observations of enhanced INP concentrations in fresh plumes from forest fires. We hypothesise that INPs initially present in a smoke plume are lost or deactivated during long-range transport, while components of smoke capable of deactivating INPs originally present or mixed later into the plume continue to remain active across a longer distance.
BibTeX:
@article{Conen2018,
  author = {Conen, Franz and Bukowiecki, Nicolas and Gysel, Martin and Steinbacher, Martin and Fischer, Andrea and Reimann, Stefan},
  title = {Low number concentration of ice nucleating particles in an aged smoke plume},
  journal = {Quarterly Journal of the Royal Meteorological Society},
  publisher = {Wiley},
  year = {2018},
  volume = {144},
  number = {715},
  pages = {1991--1994},
  doi = {10.1002/qj.3312}
}
Darenova E, Acosta M, Pokorny R and Pavelka M (2018), "Variability in temperature dependence of stem CO 2 efflux from Norway spruce trees", Tree Physiology., feb, 2018. Vol. 38(9), pp. 1333-1344. Oxford University Press (OUP).
Abstract: This study presents results from continuous measurements of stem CO 2 efflux carried out for seven experimental seasons (from May to October) in a young Norway spruce forest. The objectives of the study were to determine variability in the response of stem CO 2 efflux to stem temperature over the season and to observe differences in the calculated relationship between stem temperature and CO 2 efflux based on full growing season data or on data divided into periods according to stem growth rate. Temperature sensitivity of stem CO 2 efflux (Q 10 ) calculated for the established periods ranged between 1.61 and 3.46 and varied over the season, with the lowest values occurring in July and August. Q 10 calculated using data from the full growing seasons ranged between 2.30 and 2.94 and was often significantly higher than Q 10 calculated for the individual periods. Temperature-normalized stem CO 2 efflux (R 10 ) determined using Q 10 from growing season data was overestimated when the temperature was below 10 °C and underestimated when the temperature was above 10 °C, compared with R 10 calculated using Q 10 established for the individual periods. The differences in daily mean R 10 calculated by these two approaches ranged between −0.9 and 0.2 μmol CO 2 m −2 s −1 . The results of this study confirm that long periods for determining the temperature dependence of stem CO 2 efflux encompass different statuses of the wood (especially in relation to stem growth). This may cause bias in models using this relationship for estimating stem CO 2 efflux as a function of temperature.
BibTeX:
@article{Darenova2018,
  author = {Darenova, Eva and Acosta, Manuel and Pokorny, Radek and Pavelka, Marian},
  editor = {Ryan, Michael},
  title = {Variability in temperature dependence of stem CO 2 efflux from Norway spruce trees},
  journal = {Tree Physiology},
  publisher = {Oxford University Press (OUP)},
  year = {2018},
  volume = {38},
  number = {9},
  pages = {1333--1344},
  doi = {10.1093/treephys/tpy006}
}
De Beeck MO, Gielen B, Merbold L, Ayres E, Serrano-Ortiz P, Acosta M, Pavelka M, Montagnani L, Nilsson M, Klemedtsson L, Vincke C, De Ligne A, Moureaux C, Maraʼnon-Jimenez S, Saunders M, Mereu S and Hörtnagl L (2018), "Soil-meteorological measurements at ICOS monitoring stations in terrestrial ecosystems", International Agrophysics., dec, 2018. Vol. 32(4), pp. 619-631.
Abstract: The Integrated Carbon Observation System is a pan-European research infrastructure providing standardized, long-Term observations of greenhouse gas concentrations and earth-Atmosphere greenhouse gas interactions. The terrestrial component of Integrated Carbon Observation System comprises a network of monitoring stations in terrestrial ecosystems where the principal activity is the measurement of ecosystem-Atmosphere fluxes of greenhouse gases and energy by means of the eddy covariance technique. At each station a large set of ancillary variables needed for the interpretation of observed fluxes and for process studies is additionally monitored. This set includes a subset of variables that describe the thermal and moisture conditions of the soil and which are here conveniently referred to as soil-meteorological variables: soil temperature, volumetric soil water content, water table depth, and soil heat flux density. This paper describes the standard methodology that has been developped for the monitoring of these variables at the ecosystem stations.
BibTeX:
@article{DeBeeck2018,
  author = {De Beeck, Maarten Op and Gielen, Bert and Merbold, Lutz and Ayres, Edward and Serrano-Ortiz, Penelope and Acosta, Manuel and Pavelka, Marian and Montagnani, Leonardo and Nilsson, Mats and Klemedtsson, Leif and Vincke, Caroline and De Ligne, Anne and Moureaux, Christine and Maraʼnon-Jimenez, Sara and Saunders, Matthew and Mereu, Simone and Hörtnagl, Lukas},
  title = {Soil-meteorological measurements at ICOS monitoring stations in terrestrial ecosystems},
  journal = {International Agrophysics},
  year = {2018},
  volume = {32},
  number = {4},
  pages = {619--631},
  url = {https://content.sciendo.com/view/journals/intag/32/4/article-p619.xml},
  doi = {10.1515/intag-2017-0041}
}
Denfeld BA, Klaus M, Laudon H, Sponseller RA and Karlsson J (2018), "Carbon Dioxide and Methane Dynamics in a Small Boreal Lake During Winter and Spring Melt Events", Journal of Geophysical Research: Biogeosciences., aug, 2018. Vol. 123(8), pp. 2527-2540. American Geophysical Union (AGU).
Abstract: In seasonally ice-covered lakes, carbon dioxide (CO2) and methane (CH4) emission at ice-off can account for a significant fraction of the annual budget. Yet knowledge of the mechanisms controlling below lake-ice carbon (C) dynamics and subsequent CO2 and CH4 emissions at ice-off is limited. To understand the control of below ice C dynamics, and C emissions in spring, we measured spatial variation in CO2, CH4, and dissolved inorganic and organic carbon from ice-on to ice-off, in a small boreal lake during a winter with sporadic melting events. Winter melt events were associated with decreased surface water DOC in the forest-dominated basin and increased surface water CH4 in the mire-dominated basin. At the whole-lake scale, CH4 accumulated below ice throughout the winter, whereas CO2 accumulation was greatest in early winter. Mass-balance estimates suggest that, in addition to the CO2 and CH4 accumulated during winter, external inputs of CO2 and CH4 and internal processing during ice-melt could represent significant sources of C gas emissions during ice-off. Moreover, internal processing of CO2 and CH4 worked in opposition, with production of CO2 and oxidation of CH4 dominating at ice-off. These findings have important implications for how small boreal lakes will respond to warmer winters in the future; increased winter melt events will likely increase external inputs below ice and thus alter the extent and timing of CO2 and CH4 emissions to the atmosphere at ice-off.
BibTeX:
@article{Denfeld2018,
  author = {Denfeld, B. A. and Klaus, M. and Laudon, H. and Sponseller, R. A. and Karlsson, J.},
  title = {Carbon Dioxide and Methane Dynamics in a Small Boreal Lake During Winter and Spring Melt Events},
  journal = {Journal of Geophysical Research: Biogeosciences},
  publisher = {American Geophysical Union (AGU)},
  year = {2018},
  volume = {123},
  number = {8},
  pages = {2527--2540},
  doi = {10.1029/2018JG004622}
}
Dengel S, Graf A, Grünwald T, Hehn M, Kolari P, Löfvenius MO, Merbold L, Nicolini G and Pavelka M (2018), "Standardized precipitation measurements within ICOS: Rain, snowfall and snow depth: A review", International Agrophysics., dec, 2018. Vol. 32(4), pp. 607-617.
Abstract: Precipitation is one of the most important abiotic variables related to plant growth. Using standardised measurements improves the comparability and quality of precipitation data as well as all other data within the Integrated Carbon Observation System network. Despite the spatial and temporal variation of some types of precipitation, a single point measurement satisfies the requirement as an ancillary variable for eddy covariance measurements. Here the term precipitation includes: rain, snowfall (liquid water equivalent) and snow depth, with the latter two being of interest only where occurring. Weighing gauges defined as Integrated Carbon Observation System standard with the capacity of continuously measuring liquid and solid precipitation are installed free-standing, away from obstacles obstructing rain or snowfall. In order to minimise wind-induced errors, gauges are shielded either naturally or artificially to reduce the adverse effect of wind speed on the measurements. Following standardised methods strengthens the compatibility and comparability of data with other standardised environmental observation networks while opening the possibility for synthesis studies of different precipitation measurement methodologies and types including a wide range of ecosystems and geolocations across Europe.
BibTeX:
@article{Dengel2018,
  author = {Dengel, Sigrid and Graf, Alexander and Grünwald, Thomas and Hehn, Markus and Kolari, Pasi and Löfvenius, Mikaell Ottosson and Merbold, Lutz and Nicolini, Giacomo and Pavelka, Marian},
  title = {Standardized precipitation measurements within ICOS: Rain, snowfall and snow depth: A review},
  journal = {International Agrophysics},
  year = {2018},
  volume = {32},
  number = {4},
  pages = {607--617},
  url = {https://content.sciendo.com/view/journals/intag/32/4/article-p607.xml},
  doi = {10.1515/intag-2017-0046}
}
Denvil-Sommer A, Gehlen M, Vrac M and Mejia C (2018), "FFNN-LSCE: A two-step neural network model for the reconstruction of surface ocean pCOtextlesssubtextgreater2textless/subtextgreater over the Global Ocean", Geoscientific Model Development Discussions., nov, 2018. , pp. 1-27. Copernicus GmbH.
Abstract: textlessptextgreatertextlessstrongtextgreaterAbstract.textless/strongtextgreater A new Feed-Forward Neural Network (FFNN) model is presented to reconstruct surface ocean partial pressure of carbon dioxide (pCOtextlesssubtextgreater2textless/subtextgreater) over the global ocean. The model consists of two steps: (1) reconstruction of pCOtextlesssubtextgreater2textless/subtextgreater climatology and (2) reconstruction of pCOtextlesssubtextgreater2textless/subtextgreater anomalies with respect to the climatology. For the first step, a gridded climatology was used as the target, along with sea surface salinity and temperature (SSS and SST), sea surface height (SSH), chlorophyll textlessitextgreateratextless/itextgreater (Chl), mixed layer depth (MLD), as well as latitude and longitude as predictors. For the second step, data from the Surface Ocean COtextlesssubtextgreater2textless/subtextgreater Atlas (SOCAT) provided the target. The same set of predictors was used during step 2 augmented by their anomalies. During each step, the FFNN model reconstructs the non-linear relations between pCOtextlesssubtextgreater2textless/subtextgreater and the ocean predictors. It provides monthly surface ocean pCOtextlesssubtextgreater2textless/subtextgreater distributions on a 1º x 1º grid for the period 2001–2016. Global ocean pCOtextlesssubtextgreater2textless/subtextgreater was reconstructed with a satisfying accuracy compared to independent observational data from SOCAT. However, errors are larger in regions with poor data coverage (e.g. Indian Ocean, Southern Ocean, subpolar Pacific). The model captured the strong interannual variability of surface ocean pCO2 with reasonable skills over the Equatorial Pacific associated with ENSO (El Niño Southern Oscillation). Our model was compared to three pCOtextlesssubtextgreater2textless/subtextgreater mapping methods that participated in the Surface Ocean pCOtextlesssubtextgreater2textless/subtextgreater Mapping intercomparison (SOCOM) initiative. We found a good agreement in seasonal and interannual variabilty between the models over the global ocean. However, important differences still exist at the regional scale, especially in the Southern hemisphere and in particular, the Southern Pacific and the Indian Ocean, as these regions suffer from poor data-coverage. Large regional uncertainties in reconstructed surface ocean pCOtextlesssubtextgreater2textless/subtextgreater and sea-air COtextlesssubtextgreater2textless/subtextgreater fluxes have a strong influence on global estimates of COtextlesssubtextgreater2textless/subtextgreater fluxes and trends.textless/ptextgreater
BibTeX:
@article{DenvilSommer2018,
  author = {Denvil-Sommer, Anna and Gehlen, Marion and Vrac, Mathieu and Mejia, Carlos},
  title = {FFNN-LSCE: A two-step neural network model for the reconstruction of surface ocean pCOtextlesssubtextgreater2textless/subtextgreater over the Global Ocean},
  journal = {Geoscientific Model Development Discussions},
  publisher = {Copernicus GmbH},
  year = {2018},
  pages = {1--27},
  doi = {10.5194/gmd-2018-247}
}
Digrado A, De La Motte LG, Bachy A, Mozaffar A, Schoon N, Bussotti F, Amelynck C, Dalcq AC, Fauconnier ML, Aubinet M, Heinesch B, Du Jardin P and Delaplace P (2018), "Decrease in the photosynthetic performance of temperate grassland species does not lead to a decline in the gross primary production of the ecosystem", Frontiers in Plant Science., feb, 2018. Vol. 9
Abstract: Plants, under stressful conditions, can proceed to photosynthetic adjustments in order to acclimatize and alleviate the detrimental impacts on the photosynthetic apparatus. However, it is currently unclear how adjustment of photosynthetic processes under environmental constraints by plants influences CO2 gas exchange at the ecosystem-scale. Over a 2-year period, photosynthetic performance of a temperate grassland ecosystemwas characterized by conducting frequent chlorophyll fluorescence (ChlF) measurements on three primary grassland species (Loliumperenne L., Taraxacum sp., and Trifolium repens L.). Ecosystem photosynthetic performance was estimated frommeasurements performed on the three dominant grassland species weighed based on their relative abundance. In addition, monitoring CO2 fluxes was performed by eddy covariance. The highest decrease in photosynthetic performance was detected in summer, when environmental constraints were combined. Dicot species (Taraxacum sp. and T. repens) presented the strongest capacity to up-regulate PSI and exhibited the highest electron transport efficiency under stressful environmental conditions compared with L. perenne. The decline in ecosystem photosynthetic performance did not lead to a reduction in gross primary productivity, likely because increased light energy was available under these conditions. The carbon amounts fixed at light saturation were not influenced by alterations in photosynthetic processes, suggesting photosynthesis was not impaired. Decreased photosynthetic performance was associated with high respiration flux, but both were influenced by temperature. Our study revealed variation in photosynthetic performance of a grassland ecosystem responded to environmental constraints, but alterations in photosynthetic processes appeared to exhibit a negligible influence on ecosystem CO2 fluxes.
BibTeX:
@article{Digrado2018,
  author = {Digrado, Anthony and De La Motte, Louis G. and Bachy, Aurélie and Mozaffar, Ahsan and Schoon, Niels and Bussotti, Filippo and Amelynck, Crist and Dalcq, Anne Catherine and Fauconnier, Marie Laure and Aubinet, Marc and Heinesch, Bernard and Du Jardin, Patrick and Delaplace, Pierre},
  title = {Decrease in the photosynthetic performance of temperate grassland species does not lead to a decline in the gross primary production of the ecosystem},
  journal = {Frontiers in Plant Science},
  year = {2018},
  volume = {9},
  url = {http://journal.frontiersin.org/article/10.3389/fpls.2018.00067/full},
  doi = {10.3389/fpls.2018.00067}
}
Du Toit A (2018), "Permafrost thawing and carbon metabolism", Nature Reviews Microbiology., jul, 2018. Vol. 16(9), pp. 519. Springer Nature.
Abstract: Three studies provide insights into the microbial lineages involved in carbon processing in thawing permafrost, the role of viruses in soil carbon cycling, and the pattern, extent and scientific implications of sampling bias in environmental field research across the Arctic.
BibTeX:
@article{DuToit2018,
  author = {Du Toit, Andrea},
  title = {Permafrost thawing and carbon metabolism},
  journal = {Nature Reviews Microbiology},
  publisher = {Springer Nature},
  year = {2018},
  volume = {16},
  number = {9},
  pages = {519},
  doi = {10.1038/s41579-018-0066-4}
}
Du E and de Vries W (2018), "Nitrogen-induced new net primary production and carbon sequestration in global forests", Environmental Pollution., nov, 2018. Vol. 242, pp. 1476-1487.
BibTeX:
@article{Du2018,
  author = {Du, Enzai and de Vries, Wim},
  title = {Nitrogen-induced new net primary production and carbon sequestration in global forests},
  journal = {Environmental Pollution},
  year = {2018},
  volume = {242},
  pages = {1476--1487},
  url = {https://linkinghub.elsevier.com/retrieve/pii/S0269749118325090},
  doi = {10.1016/j.envpol.2018.08.041}
}
Ducker JA, Holmes CD, Keenan TF, Fares S, Goldstein AH, Mammarella I, William Munger J and Schnell J (2018), "Synthetic ozone deposition and stomatal uptake at flux tower sites", Biogeosciences., sep, 2018. Vol. 15(17), pp. 5395-5413. Copernicus GmbH.
Abstract: We develop and evaluate a method to estimate O3 deposition and stomatal O3 uptake across networks of eddy covariance flux tower sites where O3 concentrations and O3 fluxes have not been measured. The method combines standard micrometeorological flux measurements, which constrain O3 deposition velocity and stomatal conductance, with a gridded dataset of observed surface O3 concentrations. Measurement errors are propagated through all calculations to quantify O3 flux uncertainties. We evaluate the method at three sites with O3 flux measurements: Harvard Forest, Blodgett Forest, and Hyytiälä Forest. The method reproduces 83% or more of the variability in daily stomatal uptake at these sites with modest mean bias (21% or less). At least 95% of daily average values agree with measurements within a factor of 2 and, according to the error analysis, the residual differences from measured O3 fluxes are consistent with the uncertainty in the underlying measurements. The product, called synthetic O3 flux or SynFlux, includes 43 FLUXNET sites in the United States and 60 sites in Europe, totaling 926 site years of data. This dataset, which is now public, dramatically expands the number and types of sites where O3 fluxes can be used for ecosystem impact studies and evaluation of air quality and climate models. Across these sites, the mean stomatal conductance and O3 deposition velocity is 0.03-1.0cms-1. The stomatal O3 flux during the growing season (typically April-September) is 0.5-11.0nmol O3m-2s-1 with a mean of 4.5nmol O3m-2s-1 and the largest fluxes generally occur where stomatal conductance is high, rather than where O3 concentrations are high. The conductance differences across sites can be explained by atmospheric humidity, soil moisture, vegetation type, irrigation, and land management. These stomatal fluxes suggest that ambient O3 degrades biomass production and CO2 sequestration by 20%-24% at crop sites, 6%-29% at deciduous broadleaf forests, and 4%-20% at evergreen needleleaf forests in the United States and Europe.
BibTeX:
@article{Ducker2018,
  author = {Ducker, Jason A. and Holmes, Christopher D. and Keenan, Trevor F. and Fares, Silvano and Goldstein, Allen H. and Mammarella, Ivan and William Munger, J. and Schnell, Jordan},
  title = {Synthetic ozone deposition and stomatal uptake at flux tower sites},
  journal = {Biogeosciences},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {15},
  number = {17},
  pages = {5395--5413},
  doi = {10.5194/bg-15-5395-2018}
}
Dušek J, Acosta M, Stellner S, Šigut L and Pavelka M (2018), "Consumption of atmospheric methane by soil in a lowland broadleaf mixed forest", Plant, Soil and Environment., aug, 2018. Vol. 64(8), pp. 400-406. Czech Academy of Agricultural Sciences.
Abstract: Soils of forest ecosystems can release or consume methane (CH4) depending on their specific hydrological regime. Our study reported the consumption of CH4 by soil in a lowland broadleaf mixed temperate forest in the Czech Republic (Central Europe). The motivation of our study was to determine the importance of CH4 fluxes in context of carbon dioxide (CO2) fluxes of a broadleaf mixed forest. CH4 and CO2 emissions from the soil were measured during the 2016 vegetation season on a long transect applying the chamber technique. The average daily consumption of atmospheric CH4 by the forest soil ranged from 0.83 to 1.15 mg CH4-C/m2/day. This consumption of CH4 during summer and autumn periods was not significantly affected by soil temperature and soil moisture. However, during spring period the consumption of CH4 was positively significantly affected by soil temperature and moisture. Estimated amount of carbon (CH4-C) consumed by the forest soil makes up a very small part of carbon (CO2-C) participated in the ecosystem carbon cycle.
BibTeX:
@article{Dusek2018,
  author = {Dušek, Jiří and Acosta, Manuel and Stellner, Stanislav and Šigut, Ladislav and Pavelka, Marian},
  title = {Consumption of atmospheric methane by soil in a lowland broadleaf mixed forest},
  journal = {Plant, Soil and Environment},
  publisher = {Czech Academy of Agricultural Sciences},
  year = {2018},
  volume = {64},
  number = {8},
  pages = {400--406},
  doi = {10.17221/183/2018-PSE}
}
Ehrhardt F, Soussana JF, Bellocchi G, Grace P, McAuliffe R, Recous S, Sándor R, Smith P, Snow V, de Antoni Migliorati M, Basso B, Bhatia A, Brilli L, Doltra J, Dorich CD, Doro L, Fitton N, Giacomini SJ, Grant B, Harrison MT, Jones SK, Kirschbaum MU, Klumpp K, Laville P, Léonard J, Liebig M, Lieffering M, Martin R, Massad RS, Meier E, Merbold L, Moore AD, Myrgiotis V, Newton P, Pattey E, Rolinski S, Sharp J, Smith WN, Wu L and Zhang Q (2018), "Assessing uncertainties in crop and pasture ensemble model simulations of productivity and N2O emissions", Global Change Biology., feb, 2018. Vol. 24(2), pp. e603-e616.
Abstract: Simulation models are extensively used to predict agricultural productivity and greenhouse gas emissions. However, the uncertainties of (reduced) model ensemble simulations have not been assessed systematically for variables affecting food security and climate change mitigation, within multi-species agricultural contexts. We report an international model comparison and benchmarking exercise, showing the potential of multi-model ensembles to predict productivity and nitrous oxide (N2O) emissions for wheat, maize, rice and temperate grasslands. Using a multi-stage modelling protocol, from blind simulations (stage 1) to partial (stages 2–4) and full calibration (stage 5), 24 process-based biogeochemical models were assessed individually or as an ensemble against long-term experimental data from four temperate grassland and five arable crop rotation sites spanning four continents. Comparisons were performed by reference to the experimental uncertainties of observed yields and N2O emissions. Results showed that across sites and crop/grassland types, 23%–40% of the uncalibrated individual models were within two standard deviations (SD) of observed yields, while 42 (rice) to 96% (grasslands) of the models were within 1 SD of observed N2O emissions. At stage 1, ensembles formed by the three lowest prediction model errors predicted both yields and N2O emissions within experimental uncertainties for 44% and 33% of the crop and grassland growth cycles, respectively. Partial model calibration (stages 2–4) markedly reduced prediction errors of the full model ensemble E-median for crop grain yields (from 36% at stage 1 down to 4% on average) and grassland productivity (from 44% to 27%) and to a lesser and more variable extent for N2O emissions. Yield-scaled N2O emissions (N2O emissions divided by crop yields) were ranked accurately by three-model ensembles across crop species and field sites. The potential of using process-based model ensembles to predict jointly productivity and N2O emissions at field scale is discussed.
BibTeX:
@article{Ehrhardt2018,
  author = {Ehrhardt, Fiona and Soussana, Jean François and Bellocchi, Gianni and Grace, Peter and McAuliffe, Russel and Recous, Sylvie and Sándor, Renáta and Smith, Pete and Snow, Val and de Antoni Migliorati, Massimiliano and Basso, Bruno and Bhatia, Arti and Brilli, Lorenzo and Doltra, Jordi and Dorich, Christopher D. and Doro, Luca and Fitton, Nuala and Giacomini, Sandro J. and Grant, Brian and Harrison, Matthew T. and Jones, Stephanie K. and Kirschbaum, Miko U.F. and Klumpp, Katja and Laville, Patricia and Léonard, Joël and Liebig, Mark and Lieffering, Mark and Martin, Raphaël and Massad, Raia S. and Meier, Elizabeth and Merbold, Lutz and Moore, Andrew D. and Myrgiotis, Vasileios and Newton, Paul and Pattey, Elizabeth and Rolinski, Susanne and Sharp, Joanna and Smith, Ward N. and Wu, Lianhai and Zhang, Qing},
  title = {Assessing uncertainties in crop and pasture ensemble model simulations of productivity and N2O emissions},
  journal = {Global Change Biology},
  year = {2018},
  volume = {24},
  number = {2},
  pages = {e603--e616},
  url = {http://doi.wiley.com/10.1111/gcb.13965},
  doi = {10.1111/gcb.13965}
}
Emerson JB, Roux S, Brum JR, Bolduc B, Woodcroft BJ, Jang HB, Singleton CM, Solden LM, Naas AE, Boyd JA, Hodgkins SB, Wilson RM, Trubl G, Li C, Frolking S, Pope PB, Wrighton KC, Crill PM, Chanton JP, Saleska SR, Tyson GW, Rich VI and Sullivan MB (2018), "Host-linked soil viral ecology along a permafrost thaw gradient", Nature Microbiology., jul, 2018. Vol. 3(8), pp. 870-880. Springer Nature.
Abstract: Climate change threatens to release abundant carbon that is sequestered at high latitudes, but the constraints on microbial metabolisms that mediate the release of methane and carbon dioxide are poorly understood 1–7 . The role of viruses, which are known to affect microbial dynamics, metabolism and biogeochemistry in the oceans 8–10 , remains largely unexplored in soil. Here, we aimed to investigate how viruses influence microbial ecology and carbon metabolism in peatland soils along a permafrost thaw gradient in Sweden. We recovered 1,907 viral populations (genomes and large genome fragments) from 197 bulk soil and size-fractionated metagenomes, 58% of which were detected in metatranscriptomes and presumed to be active. In silico predictions linked 35% of the viruses to microbial host populations, highlighting likely viral predators of key carbon-cycling microorganisms, including methanogens and methanotrophs. Lineage-specific virus/host ratios varied, suggesting that viral infection dynamics may differentially impact microbial responses to a changing climate. Virus-encoded glycoside hydrolases, including an endomannanase with confirmed functional activity, indicated that viruses influence complex carbon degradation and that viral abundances were significant predictors of methane dynamics. These findings suggest that viruses may impact ecosystem function in climate-critical, terrestrial habitats and identify multiple potential viral contributions to soil carbon cycling.
BibTeX:
@article{Emerson2018,
  author = {Emerson, Joanne B. and Roux, Simon and Brum, Jennifer R. and Bolduc, Benjamin and Woodcroft, Ben J. and Jang, Ho Bin and Singleton, Caitlin M. and Solden, Lindsey M. and Naas, Adrian E. and Boyd, Joel A. and Hodgkins, Suzanne B. and Wilson, Rachel M. and Trubl, Gareth and Li, Changsheng and Frolking, Steve and Pope, Phillip B. and Wrighton, Kelly C. and Crill, Patrick M. and Chanton, Jeffrey P. and Saleska, Scott R. and Tyson, Gene W. and Rich, Virginia I. and Sullivan, Matthew B.},
  title = {Host-linked soil viral ecology along a permafrost thaw gradient},
  journal = {Nature Microbiology},
  publisher = {Springer Nature},
  year = {2018},
  volume = {3},
  number = {8},
  pages = {870--880},
  doi = {10.1038/s41564-018-0190-y}
}
Ericson Y, Falck E, Chierici M, Fransson A, Kristiansen S, Platt SM, Hermansen O and Myhre CL (2018), "Temporal Variability in Surface Water pCO2 in Adventfjorden (West Spitsbergen) With Emphasis on Physical and Biogeochemical Drivers", Journal of Geophysical Research: Oceans., jul, 2018. Vol. 123(7), pp. 4888-4905. American Geophysical Union (AGU).
Abstract: Seasonal and interannual variability in surface water partial pressure of CO2 (pCO2) and air-sea CO2 fluxes from a West Spitsbergen fjord (IsA Station, Adventfjorden) are presented, and the associated driving forces are evaluated. Marine CO2 system data together with temperature, salinity, and nutrients, were collected at the IsA Station between March 2015 and June 2017. The surface waters were undersaturated in pCO2 with respect to atmospheric pCO2 all year round. The effects of biological activity (primary production/respiration) followed by thermal forcing on pCO2 were the most important drivers on a seasonal scale. The ocean was a sink for atmospheric CO2 with annual air-sea CO2 fluxes of −36 ± 2 and −31 ± 2 g Ctextperiodcenteredm−2textperiodcenteredyear−1 for 2015–2016 and 2016–2017, respectively, as estimated from the month of April. Waters of an Arctic origin dominated in 2015 and were replaced in 2016 by waters of a transformed Atlantic source. The CO2 uptake rates over the period of Arctic origin waters were significantly higher (2 mmol Ctextperiodcenteredm−2textperiodcenteredday−1) than the rates of the Atlantic origin waters of the following year.
BibTeX:
@article{Ericson2018,
  author = {Ericson, Y. and Falck, E. and Chierici, M. and Fransson, A. and Kristiansen, S. and Platt, S. M. and Hermansen, O. and Myhre, C. L.},
  title = {Temporal Variability in Surface Water pCO2 in Adventfjorden (West Spitsbergen) With Emphasis on Physical and Biogeochemical Drivers},
  journal = {Journal of Geophysical Research: Oceans},
  publisher = {American Geophysical Union (AGU)},
  year = {2018},
  volume = {123},
  number = {7},
  pages = {4888--4905},
  doi = {10.1029/2018JC014073}
}
Erkkilä KM, Ojala A, Bastviken D, Biermann T, Heiskanen J, Lindroth A, Peltola O, Rantakari M, Vesala T and Mammarella I (2018), "Methane and carbon dioxide fluxes over a lake: Comparison between eddy covariance, floating chambers and boundary layer method", Biogeosciences., jan, 2018. Vol. 15(2), pp. 429-445.
Abstract: Freshwaters bring a notable contribution to the global carbon budget by emitting both carbon dioxide (CO2) and methane (CH4) to the atmosphere. Global estimates of freshwater emissions traditionally use a wind-speed-based gas transfer velocity, kCC (introduced by Cole and Caraco, 1998), for calculating diffusive flux with the boundary layer method (BLM). We compared CH4 and CO2 fluxes from BLM with kCC and two other gas transfer velocities (kTE and kHE), which include the effects of water-side cooling to the gas transfer besides shear-induced turbulence, with simultaneous eddy covariance (EC) and floating chamber (FC) fluxes during a 16-day measurement campaign in September 2014 at Lake Kuivajärvi in Finland. The measurements included both lake stratification and water column mixing periods. Results show that BLM fluxes were mainly lower than EC, with the more recent model kTE giving the best fit with EC fluxes, whereas FC measurements resulted in higher fluxes than simultaneous EC measurements. We highly recommend using up-to-date gas transfer models, instead of kCC, for better flux estimates. textlessbrtextgreatertextlessbrtextgreater BLM CO2 flux measurements had clear differences between daytime and night-time fluxes with all gas transfer models during both stratified and mixing periods, whereas EC measurements did not show a diurnal behaviour in CO2 flux. CH4 flux had higher values in daytime than night-time during lake mixing period according to EC measurements, with highest fluxes detected just before sunset. In addition, we found clear differences in daytime and night-time concentration difference between the air and surface water for both CH4 and CO2. This might lead to biased flux estimates, if only daytime values are used in BLM upscaling and flux measurements in general. textlessbrtextgreatertextlessbrtextgreater FC measurements did not detect spatial variation in either CH4 or CO2 flux over Lake Kuivajärvi. EC measurements, on the other hand, did not show any spatial variation in CH4 fluxes but did show a clear difference between CO2 fluxes from shallower and deeper areas. We highlight that while all flux measurement methods have their pros and cons, it is important to carefully think about the chosen method and measurement interval, as well as their effects on the resulting flux.
BibTeX:
@article{Erkkilae2018,
  author = {Erkkilä, Kukka Maaria and Ojala, Anne and Bastviken, David and Biermann, Tobias and Heiskanen, Jouni and Lindroth, Anders and Peltola, Olli and Rantakari, Miitta and Vesala, Timo and Mammarella, Ivan},
  title = {Methane and carbon dioxide fluxes over a lake: Comparison between eddy covariance, floating chambers and boundary layer method},
  journal = {Biogeosciences},
  year = {2018},
  volume = {15},
  number = {2},
  pages = {429--445},
  url = {https://www.biogeosciences.net/15/429/2018/},
  doi = {10.5194/bg-15-429-2018}
}
Faiola CL, Buchholz A, Kari E, Yli-Pirilä P, Holopainen JK, Kivimäenpää M, Miettinen P, Worsnop DR, Lehtinen KE, Guenther AB and Virtanen A (2018), "Terpene Composition Complexity Controls Secondary Organic Aerosol Yields from Scots Pine Volatile Emissions", Scientific Reports., feb, 2018. Vol. 8(1) Springer Nature.
Abstract: Secondary organic aerosol (SOA) impact climate by scattering and absorbing radiation and contributing to cloud formation. SOA models are based on studies of simplified chemical systems that do not account for the chemical complexity in the atmosphere. This study investigated SOA formation from a mixture of real Scots pine (Pinus sylvestris) emissions including a variety of monoterpenes and sesquiterpenes. SOA generation was characterized from different combinations of volatile compounds as the plant emissions were altered with an herbivore stress treatment. During active herbivore feeding, monoterpene and sesquiterpene emissions increased, but SOA mass yields decreased after accounting for absorption effects. SOA mass yields were controlled by sesquiterpene emissions in healthy plants. In contrast, SOA mass yields from stressed plant emissions were controlled by the specific blend of monoterpene emissions. Conservative estimates using a box model approach showed a 1.5- to 2.3-fold aerosol enhancement when the terpene complexity was taken into account. This enhancement was relative to the commonly used model monoterpene, "α-pinene". These results suggest that simplifying terpene complexity in SOA models could lead to underpredictions in aerosol mass loading.
BibTeX:
@article{Faiola2018,
  author = {Faiola, C. L. and Buchholz, A. and Kari, E. and Yli-Pirilä, P. and Holopainen, J. K. and Kivimäenpää, M. and Miettinen, P. and Worsnop, D. R. and Lehtinen, K. E.J. and Guenther, A. B. and Virtanen, A.},
  title = {Terpene Composition Complexity Controls Secondary Organic Aerosol Yields from Scots Pine Volatile Emissions},
  journal = {Scientific Reports},
  publisher = {Springer Nature},
  year = {2018},
  volume = {8},
  number = {1},
  doi = {10.1038/s41598-018-21045-1}
}
Fares S, Conte A and Chabbi A (2018), "Ozone flux in plant ecosystems: new opportunities for long-term monitoring networks to deliver ozone-risk assessments", Environmental Science and Pollution Research. Vol. 25(9), pp. 8240-8248. Springer Nature.
Abstract: Ozone (O3) is a photochemically formed reactive gas responsible for a decreasing carbon assimilation in plant ecosystems. Present in the atmosphere in trace concentrations (less than 100 ppbv), this molecule is capable of inhibiting carbon assimilation in agricultural and forest ecosystems. Ozone-risk assessments are typically based on manipulative experiments. Present regulations regarding critical ozone levels are mostly based on an estimated accumulated exposure over a given threshold concentration. There is however a scientific consensus over flux estimates being more accurate, because they include plant physiology analyses and different environmental parameters that control the uptake—that is, not just the exposure—of O3. While O3 is a lot more difficult to measure than other non-reactive greenhouse gases, UV-based and chemiluminescence sensors enable precise and fast measurements and are therefore highly desirable for eddy covariance studies. Using micrometeorological techniques in association with latent heat flux measurements in the field allows for the partition of ozone fluxes into the stomatal and non-stomatal sinks along the soil-plant continuum. Long-term eddy covariance measurements represent a key opportunity in estimating carbon assimilation at high-temporal resolutions, in an effort to study the effect of climate change on photosynthetic mechanisms. Our aim in this work is to describe potential of O3 flux measurement at the canopy level for ozone-risk assessment in established long-term monitoring networks.
BibTeX:
@article{Fares2018,
  author = {Fares, Silvano and Conte, Adriano and Chabbi, Abad},
  title = {Ozone flux in plant ecosystems: new opportunities for long-term monitoring networks to deliver ozone-risk assessments},
  journal = {Environmental Science and Pollution Research},
  publisher = {Springer Nature},
  year = {2018},
  volume = {25},
  number = {9},
  pages = {8240--8248},
  doi = {10.1007/s11356-017-0352-0}
}
Fassbender AJ, Rodgers KB, Palevsky HI and Sabine CL (2018), "Seasonal Asymmetry in the Evolution of Surface Ocean pCO2 and pH Thermodynamic Drivers and the Influence on Sea-Air CO2 Flux", Global Biogeochemical Cycles. Vol. 32(10), pp. 1476-1497. American Geophysical Union (AGU).
Abstract: It has become clear that anthropogenic carbon invasion into the surface ocean drives changes in the seasonal cycles of carbon dioxide partial pressure (pCO2) and pH. However, it is not yet known whether the resulting sea-air CO2 fluxes are symmetric in their seasonal expression. Here we consider a novel application of observational constraints and modeling inferences to test the hypothesis that changes in the ocean's Revelle factor facilitate a seasonally asymmetric response in pCO2 and the sea-air CO2 flux. We use an analytical framework that builds on observed sea surface pCO2 variability for the modern era and incorporates transient dissolved inorganic carbon concentrations from an Earth system model. Our findings reveal asymmetric amplification of pCO2 and pH seasonal cycles by a factor of two (or more) above preindustrial levels under Representative Concentration Pathway 8.5. These changes are significantly larger than observed modes of interannual variability and are relevant to climate feedbacks associated with Revelle factor perturbations. Notably, this response occurs in the absence of changes to the seasonal cycle amplitudes of dissolved inorganic carbon, total alkalinity, salinity, and temperature, indicating that significant alteration of surface pCO2 can occur without modifying the physical or biological ocean state. This result challenges the historical paradigm that if the same amount of carbon and nutrients is entrained and subsequently exported, there is no impact on anthropogenic carbon uptake. Anticipation of seasonal asymmetries in the sea surface pCO2 and CO2 flux response to ocean carbon uptake over the 21st century may have important implications for carbon cycle feedbacks.
BibTeX:
@article{Fassbender2018,
  author = {Fassbender, Andrea J. and Rodgers, Keith B. and Palevsky, Hilary I. and Sabine, Christopher L.},
  title = {Seasonal Asymmetry in the Evolution of Surface Ocean pCO2 and pH Thermodynamic Drivers and the Influence on Sea-Air CO2 Flux},
  journal = {Global Biogeochemical Cycles},
  publisher = {American Geophysical Union (AGU)},
  year = {2018},
  volume = {32},
  number = {10},
  pages = {1476--1497},
  doi = {10.1029/2017GB005855}
}
Finco A, Coyle M, Nemitz E, Marzuoli R, Chiesa M, Loubet B, Fares S, Diaz-Pines E, Gasche R and Gerosa G (2018), "Characterization of ozone deposition to a mixed oak-hornbeam forest - Flux measurements at five levels above and inside the canopy and their interactions with nitric oxide", Atmospheric Chemistry and Physics., dec, 2018. Vol. 18(24), pp. 17945-17961. Copernicus GmbH.
Abstract: A 1-month field campaign of ozone (textlessspan classCombining double low line"inline-formula"textgreaterO3textless/spantextgreater) flux measurements along a five-level vertical profile above, inside and below the canopy was run in a mature broadleaf forest of the Po Valley, northern Italy. The study aimed to characterize textlessspan classCombining double low line"inline-formula"textgreaterO3textless/spantextgreater flux dynamics and their interactions with nitrogen oxides (textlessspan classCombining double low line"inline-formula"textgreaterNOtextlessitextgreaterxtextless/itextgreatertextless/spantextgreater) fluxes from the forest soil and the atmosphere above the canopy. Ozone fluxes measured at the levels above the canopy were in good agreement, thus confirming the validity of the constant flux hypothesis, while below-canopy textlessspan classCombining double low line"inline-formula"textgreaterO3textless/spantextgreater fluxes were lower than above. However, at the upper canopy edge textlessspan classCombining double low line"inline-formula"textgreaterO3textless/spantextgreater fluxes were surprisingly higher than above during the morning hours. This was attributed to a chemical textlessspan classCombining double low line"inline-formula"textgreaterO3textless/spantextgreater sink due to a reaction with the nitric oxide (NO) emitted from soil and deposited from the atmosphere, thus converging at the top of the canopy. Moreover, this mechanism was favored by the morning coupling between the forest and the atmosphere, while in the afternoon the fluxes at the upper canopy edge became similar to those of the levels above as a consequence of the in-canopy stratification. Nearly 80 % of the textlessspan classCombining double low line"inline-formula"textgreaterO3textless/spantextgreater deposited to the forest ecosystem was removed by the canopy by stomatal deposition, dry deposition on physical surfaces and by ambient chemistry reactions (33.3 % by the upper canopy layer and 46.3 % by the lower canopy layer). Only a minor part of textlessspan classCombining double low line"inline-formula"textgreaterO3textless/spantextgreater was removed by the understorey vegetation and the soil surface (2 %), while the remaining 18.2 % was consumed by chemical reaction with NO emitted from soil. The collected data could be used to improve the textlessspan classCombining double low line"inline-formula"textgreaterO3textless/spantextgreater risk assessment for forests and to test the predicting capability of textlessspan classCombining double low line"inline-formula"textgreaterO3textless/spantextgreater deposition models. Moreover, these data could help multilayer canopy models to separate the influence of ambient chemistry vs. textlessspan classCombining double low line"inline-formula"textgreaterO3textless/spantextgreater dry deposition on the observed fluxes.
BibTeX:
@article{Finco2018,
  author = {Finco, Angelo and Coyle, Mhairi and Nemitz, Eiko and Marzuoli, Riccardo and Chiesa, Maria and Loubet, Benjamin and Fares, Silvano and Diaz-Pines, Eugenio and Gasche, Rainer and Gerosa, Giacomo},
  title = {Characterization of ozone deposition to a mixed oak-hornbeam forest - Flux measurements at five levels above and inside the canopy and their interactions with nitric oxide},
  journal = {Atmospheric Chemistry and Physics},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {18},
  number = {24},
  pages = {17945--17961},
  doi = {10.5194/acp-18-17945-2018}
}
Fischer M, Zenone T, Trnka M, Orság M, Montagnani L, Ward EJ, Tripathi AM, Hlavinka P, Seufert G, Žalud Z, King JS and Ceulemans R (2018), "Water requirements of short rotation poplar coppice: Experimental and modelling analyses across Europe", Agricultural and Forest Meteorology., mar, 2018. Vol. 250-251, pp. 343-360.
Abstract: Poplars are among the most widely used short rotation woody coppice (SRWC) species but due to their assumed high water use, concerns have been raised with respect to large-scale exploitation and potentially detrimental effects on water resources. Here we present a quantitative analysis of the water requirements of poplar SRWC using experimental data and a soil water balance modelling approach at three different sites across Europe. We used (i) eddy covariance (EC) measurements (2004–2006) at an irrigated SRWC grown on a previous rice paddy in northern Italy, (ii) Bowen ratio and energy balance (BREB) measurements (2008–2015) and EC (2011–2015) at a SRWC in rain-fed uplands in the Czech Republic, and (iii) EC measurements (2010–2013) at a SRWC on a previous agricultural land with a shallow water table in Belgium. Without any calibration against water balance component measurements, simulations by the newly developed soil water balance model R-4ET were compared with evapotranspiration (ET) measurements by EC and BREB with a resulting mean root mean square error (RMSE) of 0.75 mm day−1. In general, there was better agreement between EC and the model (RMSE = 0.66 mm day−1) when EC data were adjusted for lack of energy balance closure. A comparison of the simulated and measured soil water content yielded a mean RMSE of 0.03 m3 m−3. The mean annual crop coefficient, i.e. the ratio between actual and reference ET, was 0.82 (ranging from 0.65 to 0.95) while the monthly maxima reached 1.16. These values indicated that ET of poplar SRWC was significantly lower than ET of a well-watered grass cover at the annual time scale, but exceeded ET of the reference cover at shorter time scales during the growing season. We show that the model R-4ET is a simple, yet reliable tool for the assessment of water requirements of existing or planned SRWC. For very simple assessments on an annual basis, using a crop coefficient of 0.86 (adjusted to a sub-humid climate), representing an average value across the three sites in years with no evident drought stress, is supported by this analysis.
BibTeX:
@article{Fischer2018,
  author = {Fischer, Milan and Zenone, Terenzio and Trnka, Miroslav and Orság, Matěj and Montagnani, Leonardo and Ward, Eric J. and Tripathi, Abhishek Mani and Hlavinka, Petr and Seufert, Günther and Žalud, Zdeněk and King, John S. and Ceulemans, Reinhart},
  title = {Water requirements of short rotation poplar coppice: Experimental and modelling analyses across Europe},
  journal = {Agricultural and Forest Meteorology},
  year = {2018},
  volume = {250-251},
  pages = {343--360},
  url = {http://linkinghub.elsevier.com/retrieve/pii/S0168192317304860},
  doi = {10.1016/j.agrformet.2017.12.079}
}
Franz D, Acosta M, Altimir N, Arriga N, Arrouays D, Aubinet M, Aurela M, Ayres E, López-Ballesteros A, Barbaste M, Berveiller D, Biraud S, Boukir H, Brown T, Brömmer C, Buchmann N, Burba G, Carrara A, Cescatti A, Ceschia E, Clement R, Cremonese E, Crill P, Darenova E, Dengel S, D'Odorico P, Filippa G, Fleck S, Fratini G, Fuß R, Gielen B, Gogo S, Grace J, Graf A, Grelle A, Gross P, Grönwald T, Haapanala S, Hehn M, Heinesch B, Heiskanen J, Herbst M, Herschlein C, Hörtnagl L, Hufkens K, Ibrom A, Jolivet C, Joly L, Jones M, Kiese R, Klemedtsson L, Kljun N, Klumpp K, Kolari P, Kolle O, Kowalski A, Kutsch W, Laurila T, De Ligne A, Linder S, Lindroth A, Lohila A, Longdoz B, Mammarella I, Manise T, Jiménez SM, Matteucci G, Mauder M, Meier P, Merbold L, Mereu S, Metzger S, Migliavacca M, Mölder M, Montagnani L, Moureaux C, Nelson D, Nemitz E, Nicolini G, Nilsson MB, De Beeck MO, Osborne B, Löfvenius MO, Pavelka M, Peichl M, Peltola O, Pihlatie M, Pitacco A, Pokorný R, Pumpanen J, Ratié C, Rebmann C, Roland M, Sabbatini S, Saby NP, Saunders M, Schmid HP, Schrumpf M, Sedlák P, Ortiz PS, Siebicke L, Šigut L, Silvennoinen H, Simioni G, Skiba U, Sonnentag O, Soudani K, Soulé P, Steinbrecher R, Tallec T, Thimonier A, Tuittila ES, Tuovinen JP, Vestin P, Vincent G, Vincke C, Vitale D, Waldner P, Weslien P, Wingate L, Wohlfahrt G, Zahniser M and Vesala T (2018), "Towards long-Term standardised carbon and greenhouse gas observations for monitoring Europe's terrestrial ecosystems: A review", International Agrophysics., dec, 2018. Vol. 32(4), pp. 439-455.
Abstract: Research infrastructures play a key role in launching a new generation of integrated long-Term, geographically distributed observation programmes designed to monitor climate change, better understand its impacts on global ecosystems, and evaluate possible mitigation and adaptation strategies. The pan-European Integrated Carbon Observation System combines carbon and greenhouse gas (GHG; CO 2 , CH 4 , N 2 O, H 2 O) observations within the atmosphere, terrestrial ecosystems and oceans. High-precision measurements are obtained using standardised methodologies, are centrally processed and openly available in a traceable and verifiable fashion in combination with detailed metadata. The Integrated Carbon Observation System ecosystem station network aims to sample climate and land-cover variability across Europe. In addition to GHG flux measurements, a large set of complementary data (including management practices, vegetation and soil characteristics) is collected to support the interpretation, spatial upscaling and modelling of observed ecosystem carbon and GHG dynamics. The applied sampling design was developed and formulated in protocols by the scientific community, representing a trade-off between an ideal dataset and practical feasibility. The use of open-Access, high-quality and multi-level data products by different user communities is crucial for the Integrated Carbon Observation System in order to achieve its scientific potential and societal value.
BibTeX:
@article{Franz2018,
  author = {Franz, Daniela and Acosta, Manuel and Altimir, Núria and Arriga, Nicola and Arrouays, Dominique and Aubinet, Marc and Aurela, Mika and Ayres, Edward and López-Ballesteros, Ana and Barbaste, Mireille and Berveiller, Daniel and Biraud, Sébastien and Boukir, Hakima and Brown, Timothy and Brömmer, Christian and Buchmann, Nina and Burba, George and Carrara, Arnaud and Cescatti, Allessandro and Ceschia, Eric and Clement, Robert and Cremonese, Edoardo and Crill, Patrick and Darenova, Eva and Dengel, Sigrid and D'Odorico, Petra and Filippa, Gianluca and Fleck, Stefan and Fratini, Gerardo and Fuß, Roland and Gielen, Bert and Gogo, Sébastien and Grace, John and Graf, Alexander and Grelle, Achim and Gross, Patrick and Grönwald, Thomas and Haapanala, Sami and Hehn, Markus and Heinesch, Bernard and Heiskanen, Jouni and Herbst, Mathias and Herschlein, Christine and Hörtnagl, Lukas and Hufkens, Koen and Ibrom, Andreas and Jolivet, Claudy and Joly, Lilian and Jones, Michael and Kiese, Ralf and Klemedtsson, Leif and Kljun, Natascha and Klumpp, Katja and Kolari, Pasi and Kolle, Olaf and Kowalski, Andrew and Kutsch, Werner and Laurila, Tuomas and De Ligne, Anne and Linder, Sune and Lindroth, Anders and Lohila, Annalea and Longdoz, Bernhard and Mammarella, Ivan and Manise, Tanguy and Jiménez, Sara Maraón and Matteucci, Giorgio and Mauder, Matthias and Meier, Philip and Merbold, Lutz and Mereu, Simone and Metzger, Stefan and Migliavacca, Mirco and Mölder, Meelis and Montagnani, Leonardo and Moureaux, Christine and Nelson, David and Nemitz, Eiko and Nicolini, Giacomo and Nilsson, Mats B. and De Beeck, M. O.M. and Osborne, Bruce and Löfvenius, Mikaell Ottosson and Pavelka, Marian and Peichl, Matthias and Peltola, Olli and Pihlatie, Mari and Pitacco, Andrea and Pokorný, Radek and Pumpanen, Jukka and Ratié, Céline and Rebmann, Corinna and Roland, Marilyn and Sabbatini, Simone and Saby, Nicolas P.A. and Saunders, Matthew and Schmid, Hans Peter and Schrumpf, Marion and Sedlák, Pavel and Ortiz, Penelope Serrano and Siebicke, Lukas and Šigut, Ladislav and Silvennoinen, Hanna and Simioni, Guillaume and Skiba, Ute and Sonnentag, Oliver and Soudani, Kamel and Soulé, Patrice and Steinbrecher, Rainer and Tallec, Tiphaine and Thimonier, Anne and Tuittila, Eeva Stiina and Tuovinen, Juha Pekka and Vestin, Patrik and Vincent, Gaëlle and Vincke, Caroline and Vitale, Domenico and Waldner, Peter and Weslien, Per and Wingate, Lisa and Wohlfahrt, Georg and Zahniser, Mark and Vesala, Timo},
  title = {Towards long-Term standardised carbon and greenhouse gas observations for monitoring Europe's terrestrial ecosystems: A review},
  journal = {International Agrophysics},
  year = {2018},
  volume = {32},
  number = {4},
  pages = {439--455},
  url = {https://content.sciendo.com/view/journals/intag/32/4/article-p439.xml},
  doi = {10.1515/intag-2017-0039}
}
Fratini G, Sabbatini S, Ediger K, Riensche B, Burba G, Nicolini G, Vitale D and Papale D (2018), "Eddy covariance flux errors due to random and systematic timing errors during data acquisition", Biogeosciences., sep, 2018. Vol. 15(17), pp. 5473-5487. Copernicus GmbH.
Abstract: Modern eddy covariance (EC) systems collect high-frequency data (10-20Hz) via digital outputs of instruments. This is an important evolution with respect to the traditional and widely used mixed analog/digital systems, as fully digital systems help overcome the traditional limitations of transmission reliability, data quality, and completeness of the datasets. However, fully digital acquisition introduces a new problem for guaranteeing data synchronicity when the clocks of the involved devices themselves cannot be synchronized, which is often the case with instruments providing data via serial or Ethernet connectivity in a streaming mode. In this paper, we suggest that, when assembling EC systems textlessqtextgreaterin-housetextless/qtextgreater, aspects related to timing issues need to be carefully considered to avoid significant flux biases. By means of a simulation study, we found that, in most cases, random timing errors can safely be neglected, as they do not impact fluxes significantly. At the same time, systematic timing errors potentially arising in asynchronous systems can effectively act as filters leading to significant flux underestimations, as large as 10%, by means of attenuation of high-frequency flux contributions. We characterized the transfer function of such textlessqtextgreaterfilterstextless/qtextgreater as a function of the error magnitude and found cutoff frequencies as low as 1Hz, implying that synchronization errors can dominate high-frequency attenuations in open- and enclosed-path EC systems. In most cases, such timing errors neither be detected nor characterized a posteriori. Therefore, it is important to test the ability of traditional and prospective EC data logging systems to assure the required synchronicity and propose a procedure to implement such a test relying on readily available equipment.
BibTeX:
@article{Fratini2018,
  author = {Fratini, Gerardo and Sabbatini, Simone and Ediger, Kevin and Riensche, Brad and Burba, George and Nicolini, Giacomo and Vitale, Domenico and Papale, Dario},
  title = {Eddy covariance flux errors due to random and systematic timing errors during data acquisition},
  journal = {Biogeosciences},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {15},
  number = {17},
  pages = {5473--5487},
  doi = {10.5194/bg-15-5473-2018}
}
Fusaro L, Mereu S, Salvatori E, Agliari E, Fares S and Manes F (2018), "Modeling ozone uptake by urban and peri-urban forest: a case study in the Metropolitan City of Rome", Environmental Science and Pollution Research. Vol. 25(9), pp. 8190-8205. Springer Nature.
Abstract: Urban and peri-urban forests are green infrastructures (GI) that play a substantial role in delivering ecosystem services such as the amelioration of air quality by the removal of air pollutants, among which is ozone (O3), which is the most harmful pollutant in Mediterranean metropolitan areas. Models may provide a reliable estimate of gas exchanges between vegetation and atmosphere and are thus a powerful tool to quantify and compare O3 removal in different contexts. The present study modeled the O3 stomatal uptake at canopy level of an urban and a peri-urban forest in the Metropolitan City of Rome in two different years. Results show different rates of O3 fluxes between the two forests, due to different exposure to the pollutant, management practice effects on forest structure and functionality, and environmental conditions, namely, different stressors affecting the gas exchange rates of the two GIs. The periodic components of the time series calculated by means of the spectral analysis show that seasonal variation of modeled canopy transpiration is driven by precipitation in peri-urban forests, whereas in the urban forest seasonal variations are driven by vapor pressure deficit of ambient air. Moreover, in the urban forest high water availability during summer months, owing to irrigation practice, leads to an increase in O3 uptake, thus suggesting that irrigation may enhance air phytoremediation in urban areas.
BibTeX:
@article{Fusaro2018,
  author = {Fusaro, Lina and Mereu, Simone and Salvatori, Elisabetta and Agliari, Elena and Fares, Silvano and Manes, Fausto},
  title = {Modeling ozone uptake by urban and peri-urban forest: a case study in the Metropolitan City of Rome},
  journal = {Environmental Science and Pollution Research},
  publisher = {Springer Nature},
  year = {2018},
  volume = {25},
  number = {9},
  pages = {8190--8205},
  doi = {10.1007/s11356-017-0474-4}
}
García OE, Schneider M, Ertl B, Sepúlveda E, Borger C, Diekmann C, Wiegele A, Hase F, Barthlott S, Blumenstock T, Raffalski U, Gómez-Peláez A, Steinbacher M, Ries L and De Frutos AM (2018), "The MUSICA IASI CH4 and N2O products and their comparison to HIPPO, GAW and NDACC FTIR references", Atmospheric Measurement Techniques., jul, 2018. Vol. 11(7), pp. 4171-4215. Copernicus GmbH.
Abstract: This work presents the methane (CH4) and nitrous oxide (N2O) products as generated by the IASI (Infrared Atmospheric Sounding Interferometer) processor developed during the project MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water). The processor retrieves CH4 and N2O with different water vapour and water vapour isotopologues (as well as HNO3) and uses a single a priori data set for all the retrievals (no variation in space and time). Firstly, the characteristics and errors of the products are analytically described. Secondly, the products are comprehensively evaluated by comparisons to the following reference data measured by different techniques and from different platforms as follows: (1) aircraft CH4 and N2O profiles from the five HIAPER Pole-to-Pole Observation (HIPPO) missions; (2) continuous in situ CH4 and N2O observations performed between 2007 and 2017 at subtropical and mid-latitude highmountain observatories (Izaña Atmospheric Observatory and Jungfraujoch, respectively) in the framework of the WMO-GAW (World Meteorological Organization-Global Atmosphere Watch) programme; (3) ground-based FTIR (Fouriertransform infrared spectrometer) measurements made between 2007 and 2017 in the framework of the NDACC (Network for the Detection of Atmospheric Composition Change) at the subtropical Izaña Atmospheric Observatory, the mid-latitude station of Karlsruhe and the Kiruna polar site. The theoretical estimations and the comparison studies suggest a precision for the N2O and CH4 retrieval products of about 1.5-3% and systematic errors due to spectroscopic parameters of about 2 %. The MUSICA IASI CH4 data offer a better sensitivity than N2O data. While for the latter the sensitivity is mainly limited to the UTLS (upper troposphere- lower stratosphere) region, for CH4 we are able to prove that at low latitudes the MUSICA IASI processor can detect variations that take place in the free troposphere independently from the variations in the UTLS region.We demonstrate that the MUSICA IASI data qualitatively capture the CH4 gradients between low and high latitudes and between the Southern Hemisphere and Northern Hemisphere; however, we also find an inconsistency between low- and high-latitude CH4 data of up to 5 %. The N2O latitudinal gradients are very weak and cannot be detected. We make comparisons over a 10-year time period and analyse the agreement with the reference data on different timescales. The MUSICA IASI data can detect day-to-day signals (only in the UTLS), seasonal cycles and long-term evolution (in the UTLS and for CH4 also in the free troposphere) similar to the reference data; however, there are also inconsistencies in the long-term evolution connected to inconsistencies in the used atmospheric temperature a priori data. Moreover, we present a method for analytically describing the a posteriori-calculated logarithmic-scale difference of the CH4 and N2O retrieval estimates. By correcting errors that are common in the CH4 and N2O retrieval products, the a posteriori-calculated difference can be used for generating an a posteriori-corrected CH4 product with a theoretically better precision than the original CH4 retrieval products. We discuss and evaluate two different approaches for such a posteriori corrections. It is shown that the correction removes the inconsistencies between low and high latitudes and enables the detection of day-to-day signals also in the free troposphere. Furthermore, they reduce the impact of short-term atmospheric dynamics, which is an advantage, because respective signals are presumably hardly comparable to model data. The approach that affects the correction solely on the scales on which the errors dominate is identified as the most efficient, because it reduces the inconsistencies and errors without removing measurable real atmospheric signals. We give a brief outlook on a possible usage of this a posterioricorrected MUSICA IASI CH4 product in combination with inverse modelling.
BibTeX:
@article{Garcia2018,
  author = {García, Omaira E. and Schneider, Matthias and Ertl, Benjamin and Sepúlveda, Eliezer and Borger, Christian and Diekmann, Christopher and Wiegele, Andreas and Hase, Frank and Barthlott, Sabine and Blumenstock, Thomas and Raffalski, Uwe and Gómez-Peláez, Angel and Steinbacher, Martin and Ries, Ludwig and De Frutos, Angel M.},
  title = {The MUSICA IASI CH4 and N2O products and their comparison to HIPPO, GAW and NDACC FTIR references},
  journal = {Atmospheric Measurement Techniques},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {11},
  number = {7},
  pages = {4171--4215},
  doi = {10.5194/amt-11-4171-2018}
}
Gielen B, Acosta M, Altimir N, Buchmann N, Cescatti A, Ceschia E, Fleck S, Hörtnagl L, Klumpp K, Kolari P, Lohila A, Loustau D, Maraʼnon-Jimenez S, Manise T, Matteucci G, Merbold L, Metzger C, Moureaux C, Montagnani L, Nilsson MB, Osborne B, Papale D, Pavelka M, Saunders M, Simioni G, Soudani K, Sonnentag O, Tallec T, Tuittila ES, Peichl M, Pokorny R, Vincke C and Wohlfahrt G (2018), "Ancillary vegetation measurements at ICOS ecosystem stations", International Agrophysics., dec, 2018. Vol. 32(4), pp. 645-664.
Abstract: The Integrated Carbon Observation System is a Pan-European distributed research infrastructure that has as its main goal to monitor the greenhouse gas balance of Europe. The ecosystem component of Integrated Carbon Observation System consists of a multitude of stations where the net greenhouse gas exchange is monitored continuously by eddy covariance measurements while, in addition many other measurements are carried out that are a key to an understanding of the greenhouse gas balance. Amongst them are the continuous meteorological measurements and a set of non-continuous measurements related to vegetation. The latter include Green Area Index, aboveground biomass and litter biomass. The standardized methodology that is used at the Integrated Carbon Observation System ecosystem stations to monitor these vegetation related variables differs between the ecosystem types that are represented within the network, whereby in this paper we focus on forests, grasslands, croplands and mires. For each of the variables and ecosystems a spatial and temporal sampling design was developed so that the variables can be monitored in a consistent way within the ICOS network. The standardisation of the methodology to collect Green Area Index, above ground biomass and litter biomass and the methods to evaluate the quality of the collected data ensures that all stations within the ICOS ecosystem network produce data sets with small and similar errors, which allows for inter-comparison comparisons across the Integrated Carbon Observation System ecosystem network.
BibTeX:
@article{Gielen2018,
  author = {Gielen, Bert and Acosta, Manuel and Altimir, Nuria and Buchmann, Nina and Cescatti, Alessandro and Ceschia, Eric and Fleck, Stefan and Hörtnagl, Lukas and Klumpp, Katja and Kolari, Pasi and Lohila, Annalea and Loustau, Denis and Maraʼnon-Jimenez, Sara and Manise, Tanguy and Matteucci, Giorgio and Merbold, Lutz and Metzger, Christine and Moureaux, Christine and Montagnani, Leonardo and Nilsson, Mats B. and Osborne, Bruce and Papale, Dario and Pavelka, Marian and Saunders, Matthew and Simioni, Guillaume and Soudani, Kamel and Sonnentag, Oliver and Tallec, Tiphaine and Tuittila, Eeva Stiina and Peichl, Matthias and Pokorny, Radek and Vincke, Caroline and Wohlfahrt, Georg},
  title = {Ancillary vegetation measurements at ICOS ecosystem stations},
  journal = {International Agrophysics},
  year = {2018},
  volume = {32},
  number = {4},
  pages = {645--664},
  url = {https://content.sciendo.com/view/journals/intag/32/4/article-p645.xml},
  doi = {10.1515/intag-2017-0048}
}
Goris N, Tjiputra JF, Olsen A, Schwinger J, Lauvset SK and Jeansson E (2018), "Constraining projection-based estimates of the future North Atlantic carbon uptake", Journal of Climate. Vol. 31(10), pp. 3959-3978. American Meteorological Society.
Abstract: The North Atlantic is one of the major sinks for anthropogenic carbon in the global ocean. Improved understanding of the underlying mechanisms is vital for constraining future projections, which presently have high uncertainties. To identify some of the causes behind this uncertainty, this study investigates the North Atlantic's anthropogenically altered carbon uptake and inventory, that is, changes in carbon uptake and inventory due to rising atmospheric CO2 and climate change (abbreviated as Cant*-uptake and Cant*-inventory). Focus is set on an ensemble of 11 Earth system models and their simulations of a future with high atmospheric CO2. Results show that the model spread in the Cant*-uptake originates in middle and high latitudes. Here, the annual cycle of oceanic pCO2 reveals inherent model mechanisms that are responsible for different model behavior: while it is SST-dominated for models with a low future Cant* -uptake, it is dominated by deep winter mixing and biological production for models with a high future Cant*-uptake. Models with a high future Cant*-uptake show an efficient carbon sequestration and hence store a large fraction of their contemporary North Atlantic Cant*-inventory below 1000-m depth, while the opposite is true for models with a low future Cant*-uptake. Constraining the model ensemble with observation-based estimates of carbon sequestration and summer oceanic pCO2 anomalies yields later flattening of the Cant*-uptake than previously estimated. This result highlights the need to depart from the concept of unconstrained model ensembles in order to reduce uncertainties associated with future projections.
BibTeX:
@article{Goris2018,
  author = {Goris, Nadine and Tjiputra, Jerry F. and Olsen, Are and Schwinger, Jörg and Lauvset, Siv K. and Jeansson, Emil},
  title = {Constraining projection-based estimates of the future North Atlantic carbon uptake},
  journal = {Journal of Climate},
  publisher = {American Meteorological Society},
  year = {2018},
  volume = {31},
  number = {10},
  pages = {3959--3978},
  doi = {10.1175/JCLI-D-17-0564.1}
}
Gourlez de la Motte L, Mamadou O, Beckers Y, Bodson B, Heinesch B and Aubinet M (2018), "Rotational and continuous grazing does not affect the total net ecosystem exchange of a pasture grazed by cattle but modifies CO2 exchange dynamics", Agriculture, Ecosystems and Environment., feb, 2018. Vol. 253, pp. 157-165. Elsevier BV.
Abstract: Grassland carbon budgets are known to be greatly dependent on management. In particular, grazing is known to directly affect CO2 exchange through consumption by plants, cattle respiration, natural fertilisation through excreta, and soil compaction. This study investigates the impact of two grazing methods on the net ecosystem exchange (NEE) dynamics and carbon balance, by measuring CO2 fluxes using eddy covariance in two adjacent pastures located in southern Belgium during a complete grazing season. Rotational (RG) grazing consists of an alternation of rest periods and short high stock density grazing periods. Continuous grazing (CG) consists of uninterrupted grazing with variable stocking rates. To our knowledge, this is the first study to assess the impact of these grazing methods on total net ecosystem exchange and CO2 exchange dynamics using eddy covariance. The results showed that NEE dynamics were greatly impacted by the grazing method. Following grazing events on the RG parcel, net CO2 uptake on the RG parcel was reduced compared to the CG parcel. During the following rest periods, this phenomenon progressively shifted towards a higher assimilation for the RG treatment. This behaviour was attributed to sharp biomass changes in the RG treatment and therefore sharp changes in plant photosynthetic capacity. We found that differences in gross primary productivity at high radiation were strongly correlated to differences in standing biomass. In terms of carbon budgets, no significant difference was observed between the two treatments, neither in cumulative NEE, or in terms of estimated biomass production. The results of our study suggest that we should not expect major benefits in terms of CO2 uptake from rotational grazing management when compared to continuous grazing management in intensively managed temperate pastures.
BibTeX:
@article{GourlezdelaMotte2018,
  author = {Gourlez de la Motte, Louis and Mamadou, Ossénatou and Beckers, Yves and Bodson, Bernard and Heinesch, Bernard and Aubinet, Marc},
  title = {Rotational and continuous grazing does not affect the total net ecosystem exchange of a pasture grazed by cattle but modifies CO2 exchange dynamics},
  journal = {Agriculture, Ecosystems and Environment},
  publisher = {Elsevier BV},
  year = {2018},
  volume = {253},
  pages = {157--165},
  url = {http://linkinghub.elsevier.com/retrieve/pii/S0167880917305017 https://doi.org/10.1016/j.agee.2017.11.011},
  doi = {10.1016/j.agee.2017.11.011}
}
Groh J, Slawitsch V, Herndl M, Graf A, Vereecken H and Pütz T (2018), "Determining dew and hoar frost formation for a low mountain range and alpine grassland site by weighable lysimeter", Journal of Hydrology., aug, 2018. Vol. 563, pp. 372-381. Elsevier BV.
Abstract: Non-rainfall events like dew or hoar frost formation are often neglected in the water budget, because either assumed to be too small or their determination requires time consuming and difficult measurements. These events supply in many dryland ecosystems a substantial amount of water, but their role for northern humid ecosystems is largely unknown. There is a general need to quantify the ecological relevance for ecosystems of the water amount from dew and hoar frost formation. Weighable precision lysimeters were used to determine dew and hoar frost formation for a low mountain range and alpine grassland site for the hydrological years 2013–2015. Together dew and hoar frost formation ranged on a yearly basis between 42.1 and 67.7 mm, which corresponds to 4.2–6% of the total annual amount of precipitation. In drier months dew and hoar frost contributed up to 16.1% of total monthly precipitation amount. In winter months dew and hoar frost formation contributed up to 38% to the total monthly precipitation amount. Our investigation suggests, that dew and hoar frost formation are of ecological importance during droughts as well as cold periods. The amounts and seasonal patterns of dew and hoar frost formation could be predicted relatively well, based on standard meteorological variables with the Penman-Monteith equation. However, our results also showed, that the surface energy balance model from Penman-Monteith underestimated the amount of dew and hoar frost during colder periods and specific meteorological site conditions (i.e. high wind speeds at night). The mean underestimation between calculated and measured dew and hoar frost on a yearly scale were 63.2% and 16.6% at Rollesbroich and Gumpenstein, respectively. Dew and hoar frost formation contributes substantially to the water budgets of a low mountain range and alpine grassland.
BibTeX:
@article{Groh2018,
  author = {Groh, Jannis and Slawitsch, Veronika and Herndl, Markus and Graf, Alexander and Vereecken, Harry and Pütz, Thomas},
  title = {Determining dew and hoar frost formation for a low mountain range and alpine grassland site by weighable lysimeter},
  journal = {Journal of Hydrology},
  publisher = {Elsevier BV},
  year = {2018},
  volume = {563},
  pages = {372--381},
  doi = {10.1016/j.jhydrol.2018.06.009}
}
Groot Zwaaftink CD, Henne S, Thompson RL, Dlugokencky EJ, Machida T, Paris JD, Sasakawa M, Segers A, Sweeney C and Stohl A (2018), "Three-dimensional methane distribution simulated with FLEXPART 8-CTM-1.1 constrained with observation data", Geoscientific Model Development., nov, 2018. Vol. 11(11), pp. 4469-4487. Copernicus GmbH.
Abstract: A Lagrangian particle dispersion model, the FLEXible PARTicle dispersion chemical transport model (FLEXPART CTM), is used to simulate global three-dimensional fields of trace gas abundance. These fields are constrained with surface observation data through nudging, a data assimilation method, which relaxes model fields to observed values. Such fields are of interest to a variety of applications, such as inverse modelling, satellite retrievals, radiative forcing models and estimating global growth rates of greenhouse gases. Here, we apply this method to methane using 6 million model particles filling the global model domain. For each particle, methane mass tendencies due to emissions (based on several inventories) and loss by reaction with OH, Cl and O(1D), as well as observation data nudging were calculated. Model particles were transported by mean, turbulent and convective transport driven by 1° × 1° ERA-Interim meteorology. Nudging is applied at 79 surface stations, which are mostly included in the World Data Centre for Greenhouse Gases (WDCGG) database or the Japan-Russia Siberian Tall Tower Inland Observation Network (JR-STATION) in Siberia. For simulations of 1 year (2013), we perform a sensitivity analysis to show how nudging settings affect modelled concentration fields. These are evaluated with a set of independent surface observations and with vertical profiles in North America from the National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory (ESRL), and in Siberia from the Airborne Extensive Regional Observations in SIBeria (YAK-AEROSIB) and the National Institute for Environmental Studies (NIES). FLEXPART CTM results are also compared to simulations from the global Eulerian chemistry Transport Model version 5 (TM5) based on optimized fluxes. Results show that nudging strongly improves modelled methane near the surface, not only at the nudging locations but also at independent stations. Mean bias at all surface locations could be reduced from over 20 to less than 5 ppb through nudging. Near the surface, FLEXPART CTM, including nudging, appears better able to capture methane molar mixing ratios than TM5 with optimized fluxes, based on a larger bias of over 13 ppb in TM5 simulations. The vertical profiles indicate that nudging affects model methane at high altitudes, yet leads to little improvement in the model results there. Averaged from 19 aircraft profile locations in North America and Siberia, root mean square error (RMSE) changes only from 16.3 to 15.7 ppb through nudging, while the mean absolute bias increases from 5.3 to 8.2 ppb. The performance for vertical profiles is thereby similar to TM5 simulations based on TM5 optimized fluxes where we found a bias of 5 ppb and RMSE of 15.9 ppb. With this rather simple model setup, we thus provide three-dimensional methane fields suitable for use as boundary conditions in regional inverse modelling as a priori information for satellite retrievals and for more accurate estimation of mean mixing ratios and growth rates. The method is also applicable to other long-lived trace gases.
BibTeX:
@article{GrootZwaaftink2018,
  author = {Groot Zwaaftink, Christine D. and Henne, Stephan and Thompson, Rona L. and Dlugokencky, Edward J. and Machida, Toshinobu and Paris, Jean Daniel and Sasakawa, Motoki and Segers, Arjo and Sweeney, Colm and Stohl, Andreas},
  title = {Three-dimensional methane distribution simulated with FLEXPART 8-CTM-1.1 constrained with observation data},
  journal = {Geoscientific Model Development},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {11},
  number = {11},
  pages = {4469--4487},
  doi = {10.5194/gmd-11-4469-2018}
}
Grossiord C, Sevanto S, Bonal D, Borrego I, Dawson TE, Ryan M, Wang W and McDowell NG (2018), "Prolonged warming and drought modify belowground interactions for water among coexisting plants", Tree Physiology., sep, 2018. Vol. 39(1), pp. 55-63. Oxford University Press (OUP).
Abstract: Understanding how climate alters plant-soil water dynamics, and its impact on physiological functions, is critical to improved predictions of vegetation responses to climate change. Here we analyzed how belowground interactions for water shift under warming and drought, and associated impacts on plant functions. In a semi-arid woodland, adult trees (piñon and juniper) and perennial grasses (blue grama) were exposed to warming and precipitation reduction. After 6 years of continuous treatment exposure, soil and plant water isotopic composition was measured to assess plant water uptake depths and community-level water source partitioning. Warming and drought modified plant water uptake depths. Under warming, contrasting changes in water sources between grasses and trees reduced belowground water source partitioning, resulting in higher interspecific competition for water. Under drought, shifts in trees and grass water sources to deeper soil layers resulted in the maintenance of the naturally occurring water source partitioning among species. Trees showed higher water stress, and reduced water use and photosynthesis in response to warming and drought. This case study demonstrates that neighboring plants shift their competitive interactions for water under prolonged warming and drought, but regardless of whether changes in moisture sources will result in increased competition among species or maintained partitioning of water resources, these competitive adaptations may easily be overridden by climate extremes.
BibTeX:
@article{Grossiord2018,
  author = {Grossiord, Charlotte and Sevanto, Sanna and Bonal, Damien and Borrego, Isaac and Dawson, Todd E. and Ryan, Max and Wang, Wenzhi and McDowell, Nate G.},
  editor = {Whitehead, David},
  title = {Prolonged warming and drought modify belowground interactions for water among coexisting plants},
  journal = {Tree Physiology},
  publisher = {Oxford University Press (OUP)},
  year = {2018},
  volume = {39},
  number = {1},
  pages = {55--63},
  doi = {10.1093/treephys/tpy080}
}
Hari P, Noe S, Dengel S, Elbers J, Gielen B, Kerminen VM, Kruijt B, Kulmala L, Lindroth A, Mammarella I, Petäjä T, Schurgers G, Vanhatalo A, Kulmala M and Bäck J (2018), "Prediction of photosynthesis in Scots pine ecosystems across Europe by a needle-level theory", Atmospheric Chemistry and Physics., sep, 2018. Vol. 18(18), pp. 13321-13328. Copernicus GmbH.
Abstract: Photosynthesis provides carbon for the synthesis of macromolecules to construct cells during growth. This is the basis for the key role of photosynthesis in the carbon dynamics of ecosystems and in the biogenic CO2 assimilation. The development of eddy-covariance (EC) measurements for ecosystem CO2 fluxes started a new era in the field studies of photosynthesis. However, the interpretation of the very variable CO2 fluxes in evergreen forests has been problematic especially in transition times such as the spring and autumn. We apply two theoretical needle-level equations that connect the variation in the light intensity, stomatal action and the annual metabolic cycle of photosynthesis. We then use these equations to predict the photosynthetic CO2 flux in five Scots pine stands located from the northern timberline to Central Europe. Our result has strong implications for our conceptual understanding of the effects of the global change on the processes in boreal forests, especially of the changes in the metabolic annual cycle of photosynthesis.
BibTeX:
@article{Hari2018,
  author = {Hari, Pertti and Noe, Steffen and Dengel, Sigrid and Elbers, Jan and Gielen, Bert and Kerminen, Veli Matti and Kruijt, Bart and Kulmala, Liisa and Lindroth, Anders and Mammarella, Ivan and Petäjä, Tuukka and Schurgers, Guy and Vanhatalo, Anni and Kulmala, Markku and Bäck, Jaana},
  title = {Prediction of photosynthesis in Scots pine ecosystems across Europe by a needle-level theory},
  journal = {Atmospheric Chemistry and Physics},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {18},
  number = {18},
  pages = {13321--13328},
  doi = {10.5194/acp-18-13321-2018}
}
Hauck J (2018), "Unsteady seasons in the sea", Nature Climate Change., jan, 2018. Vol. 8(2), pp. 97-98. Springer Nature.
Abstract: Ocean uptake of CO2 slows the rate of anthropogenic climate change but comes at the cost of ocean acidification. Observations now show that the seasonal cycle of CO2 in the ocean also changes, leading to earlier occurrence of detrimental conditions for ocean biota.
BibTeX:
@article{Hauck2018,
  author = {Hauck, Judith},
  title = {Unsteady seasons in the sea},
  journal = {Nature Climate Change},
  publisher = {Springer Nature},
  year = {2018},
  volume = {8},
  number = {2},
  pages = {97--98},
  doi = {10.1038/s41558-018-0069-1}
}
He YC, Tjiputra J, Langehaug HR, Jeansson E, Gao Y, Schwinger J and Olsen A (2018), "A Model-Based Evaluation of the Inverse Gaussian Transit-Time Distribution Method for Inferring Anthropogenic Carbon Storage in the Ocean", Journal of Geophysical Research: Oceans. Vol. 123(3), pp. 1777-1800. American Geophysical Union (AGU).
Abstract: The Inverse Gaussian approximation of transit time distribution method (IG-TTD) is widely used to infer the anthropogenic carbon (Cant) concentration in the ocean from measurements of transient tracers such as chlorofluorocarbons (CFCs) and sulfur hexafluoride (SF6). Its accuracy relies on the validity of several assumptions, notably (i) a steady state ocean circulation, (ii) a prescribed age tracer saturation history, e.g., a constant 100% saturation, (iii) a prescribed constant degree of mixing in the ocean, (iv) a constant surface ocean air-sea CO2 disequilibrium with time, and (v) that preformed alkalinity can be sufficiently estimated by salinity or salinity and temperature. Here, these assumptions are evaluated using simulated “model-truth” of Cant. The results give the IG-TTD method a range of uncertainty from 7.8% to 13.6% (11.4 Pg C to 19.8 Pg C) due to above assumptions, which is about half of the uncertainty derived in previous model studies. Assumptions (ii), (iv) and (iii) are the three largest sources of uncertainties, accounting for 5.5%, 3.8% and 3.0%, respectively, while assumptions (i) and (v) only contribute about 0.6% and 0.7%. Regionally, the Southern Ocean contributes the largest uncertainty, of 7.8%, while the North Atlantic contributes about 1.3%. Our findings demonstrate that spatial-dependency of Δ/Г, and temporal changes in tracer saturation and air-sea CO2 disequilibrium have strong compensating effect on the estimated Cant. The values of these parameters should be quantified to reduce the uncertainty of IG-TTD; this is increasingly important under a changing ocean climate.
BibTeX:
@article{He2018,
  author = {He, Yan Chun and Tjiputra, Jerry and Langehaug, Helene R. and Jeansson, Emil and Gao, Yongqi and Schwinger, Jörg and Olsen, Are},
  title = {A Model-Based Evaluation of the Inverse Gaussian Transit-Time Distribution Method for Inferring Anthropogenic Carbon Storage in the Ocean},
  journal = {Journal of Geophysical Research: Oceans},
  publisher = {American Geophysical Union (AGU)},
  year = {2018},
  volume = {123},
  number = {3},
  pages = {1777--1800},
  doi = {10.1002/2017JC013504}
}
Henson SA, Humphreys MP, Land PE, Shutler JD, Goddijn-Murphy L and Warren M (2018), "Controls on Open-Ocean North Atlantic ΔpCO2 at Seasonal and Interannual Time Scales Are Different", Geophysical Research Letters., sep, 2018. Vol. 45(17), pp. 9067-9076. American Geophysical Union (AGU).
Abstract: The North Atlantic is a substantial sink for anthropogenic CO2. Understanding the mechanisms driving the sink's variability is key to assessing its current state and predicting its potential response to global climate change. Here we apply a time series decomposition technique to satellite and in situ data to examine separately the factors (both biological and nonbiological) that affect the sea-air CO2 difference (ΔpCO2) on seasonal and interannual time scales. We demonstrate that on seasonal time scales, the subpolar North Atlantic ΔpCO2 signal is predominantly correlated with biological processes, whereas seawater temperature dominates in the subtropics. However, the same factors do not necessarily control ΔpCO2 on interannual time scales. Our results imply that the mechanisms driving seasonal variability in ΔpCO2 cannot necessarily be extrapolated to predict how ΔpCO2, and thus the North Atlantic CO2 sink, may respond to increases in anthropogenic CO2 over longer time scales.
BibTeX:
@article{Henson2018,
  author = {Henson, Stephanie A. and Humphreys, Matthew P. and Land, Peter E. and Shutler, Jamie D. and Goddijn-Murphy, Lonneke and Warren, Mark},
  title = {Controls on Open-Ocean North Atlantic ΔpCO2 at Seasonal and Interannual Time Scales Are Different},
  journal = {Geophysical Research Letters},
  publisher = {American Geophysical Union (AGU)},
  year = {2018},
  volume = {45},
  number = {17},
  pages = {9067--9076},
  doi = {10.1029/2018GL078797}
}
Hodgkins SB, Richardson CJ, Dommain R, Wang H, Glaser PH, Verbeke B, Winkler BR, Cobb AR, Rich VI, Missilmani M, Flanagan N, Ho M, Hoyt AM, Harvey CF, Vining SR, Hough MA, Moore TR, Richard PJ, De La Cruz FB, Toufaily J, Hamdan R, Cooper WT and Chanton JP (2018), "Tropical peatland carbon storage linked to global latitudinal trends in peat recalcitrance", Nature Communications., sep, 2018. Vol. 9(1) Springer Nature.
Abstract: Peatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-surface low-latitude peat has lower carbohydrate and greater aromatic content than near-surface high-latitude peat, creating a reduced oxidation state and resulting recalcitrance. This recalcitrance allows peat to persist in the (sub)tropics despite warm temperatures. Because we observed similar declines in carbohydrate content with depth in high-latitude peat, our data explain recent field-scale deep peat warming experiments in which catotelm (deeper) peat remained stable despite temperature increases up to 9 °C. We suggest that high-latitude deep peat reservoirs may be stabilized in the face of climate change by their ultimately lower carbohydrate and higher aromatic composition, similar to tropical peats.
BibTeX:
@article{Hodgkins2018,
  author = {Hodgkins, Suzanne B. and Richardson, Curtis J. and Dommain, René and Wang, Hongjun and Glaser, Paul H. and Verbeke, Brittany and Winkler, B. Rose and Cobb, Alexander R. and Rich, Virginia I. and Missilmani, Malak and Flanagan, Neal and Ho, Mengchi and Hoyt, Alison M. and Harvey, Charles F. and Vining, S. Rose and Hough, Moira A. and Moore, Tim R. and Richard, Pierre J.H. and De La Cruz, Florentino B. and Toufaily, Joumana and Hamdan, Rasha and Cooper, William T. and Chanton, Jeffrey P.},
  title = {Tropical peatland carbon storage linked to global latitudinal trends in peat recalcitrance},
  journal = {Nature Communications},
  publisher = {Springer Nature},
  year = {2018},
  volume = {9},
  number = {1},
  doi = {10.1038/s41467-018-06050-2}
}
Honkanen M, Tuovinen JP, Laurila T, Mäkelä T, Hatakka J, Kielosto S and Laakso L (2018), "Measuring turbulent CO2 fluxes with a closed-path gas analyzer in a marine environment", Atmospheric Measurement Techniques., sep, 2018. Vol. 11(9), pp. 5335-5350. Copernicus GmbH.
Abstract: In this study, we introduce new observations of sea-air fluxes of carbon dioxide using the eddy covariance method. The measurements took place at the Utö Atmospheric and Marine Research Station on the island of Utö in the Baltic Sea in July-October 2017. The flux measurement system is based on a closed-path infrared gas analyzer (LI-7000, LI-COR) requiring only occasional maintenance, making the station capable of continuous monitoring. However, such infrared gas analyzers are prone to significant water vapor interference in a marine environment, where CO2 fluxes are small. Two LI-7000 analyzers were run in parallel to test the effect of a sample air drier which dampens water vapor fluctuations and a virtual impactor, included to remove liquid sea spray, both of which were attached to the sample air tubing of one of the analyzers. The systems showed closely similar (R2 Combining double low line 0.99) sea-air CO2 fluxes when the latent heat flux was low, which proved that neither the drier nor the virtual impactor perturbed the CO2 flux measurement. However, the undried measurement had a positive bias that increased with increasing latent heat flux, suggesting water vapor interference. For both systems, cospectral densities between vertical wind speed and CO2 molar fraction were distributed within the expected frequency range, with a moderate attenuation of high-frequency fluctuations. While the setup equipped with a drier and a virtual impactor generated a slightly higher flux loss, we opt for this alternative for its reduced water vapor cross-sensitivity and better protection against sea spray. The integral turbulence characteristics were found to agree with the universal stability dependence observed over land. Nonstationary conditions caused unphysical results, which resulted in a high percentage (65 %) of discarded measurements. After removing the nonstationary cases, the direction of the sea-air CO2 fluxes was in good accordance with independently measured CO2 partial pressure difference between the sea and the atmosphere. Atmospheric CO2 concentration changes larger than 2 ppm during a 30 min averaging period were found to be associated with the nonstationarity of CO2 fluxes.
BibTeX:
@article{Honkanen2018,
  author = {Honkanen, Martti and Tuovinen, Juha Pekka and Laurila, Tuomas and Mäkelä, Timo and Hatakka, Juha and Kielosto, Sami and Laakso, Lauri},
  title = {Measuring turbulent CO2 fluxes with a closed-path gas analyzer in a marine environment},
  journal = {Atmospheric Measurement Techniques},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {11},
  number = {9},
  pages = {5335--5350},
  doi = {10.5194/amt-11-5335-2018}
}
Hooghiem JJ, De Vries M, Been HA, Heikkinen P, Kivi R and Chen H (2018), "LISA: A lightweight stratospheric air sampler", Atmospheric Measurement Techniques., dec, 2018. Vol. 11(12), pp. 6785-6801. Copernicus GmbH.
Abstract: We developed a new lightweight stratospheric air sampler (LISA). The LISA sampler is designed to collect four bag samples in the stratosphere during a balloon flight for CO 2 , CH 4 and CO mole fraction measurements. It consists of four multi-layer foil (MLF) sampling bags, a custommade manifold, and a diaphragm pump, with a total weight of ∼ 2.5kg. A series of laboratory storage tests were performed to assess the stability of CO 2 , CH 4 and CO mole fractions in both MLF and Tedlar bags. The MLF bag was chosen due to its better overall performance than the Tedlar bag for the three species CO 2 , CH 4 and CO. Furthermore, we evaluated the performance of the pump under low pressure conditions to optimize a trade-off between the vertical resolution and the sample size. The LISA sampler was flown on the same balloon flight with an AirCore in Sodankylä, Finland (67.368° N, 26.633° E, 179ma.s.l.), on 26 April and 4-7 September 2017. A total of 15 stratospheric air samples were obtained during the ascent of four flights. The sample size ranges between 800 and 180mL for the altitude between 12 and 25 km, with the corresponding vertical resolution ranging from 0.5 to 1.5 km. The collected air samples were analysed for CO 2 , CH 4 and CO mole fractions, and evaluated against AirCore retrieved profiles, showing mean differences of 0.84 ppm for CO 2 , 1.8 ppb for CH 4 and 6.3 ppb for CO, respectively. High-accuracy stratospheric measurements of greenhouse gas mole fractions are useful to validate remote sensing measurements from ground and from space, which has been performed primarily by comparison with collocated aircraft measurements (0.15-13 km), and more recently with Air- Core observations (0-30 km). While AirCore is capable of achieving high-accuracy greenhouse gas mole fraction measurements, it is challenging to obtain accurate altitude registration for AirCore measurements. The LISA sampler provides a viable low-cost tool for retrieving stratospheric air samples for greenhouse gas measurements that is complementary to AirCore. Furthermore, the LISA sampler is advantageous in both the vertical resolution and sample size for performing routine stratospheric measurements of the isotopic composition of trace gases.
BibTeX:
@article{Hooghiem2018,
  author = {Hooghiem, Joram J.D. and De Vries, Marcel and Been, Henk A. and Heikkinen, Pauli and Kivi, Rigel and Chen, Huilin},
  title = {LISA: A lightweight stratospheric air sampler},
  journal = {Atmospheric Measurement Techniques},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {11},
  number = {12},
  pages = {6785--6801},
  doi = {10.5194/amt-11-6785-2018}
}
Hufkens K, Filippa G, Cremonese E, Migliavacca M, D'Odorico P, Peichl M, Gielen B, Hörtnagl L, Soudani K, Papale D, Rebmann C, Brown T and Wingate L (2018), "Assimilating phenology datasets automatically across ICOS ecosystem stations", International Agrophysics., dec, 2018. Vol. 32(4), pp. 677-687.
Abstract: The presence or absence of leaves within plant canopies exert a strong influence on the carbon, water and energy balance of ecosystems. Identifying key changes in the timing of leaf elongation and senescence during the year can help to understand the sensitivity of different plant functional types to changes in temperature. When recorded over many years these data can provide information on the response of ecosystems to long-Term changes in climate. The installation of digital cameras that take images at regular intervals of plant canopies across the Integrated Carbon Observation System ecosystem stations will provide a reliable and important record of variations in canopy state, colour and the timing of key phenological events. Here, we detail the procedure for the implementation of cameras on Integrated Carbon Observation System flux towers and how these images will help us understand the impact of leaf phenology and ecosystem function, distinguish changes in canopy structure from leaf physiology and at larger scales will assist in the validation of (future) remote sensing products. These data will help us improve the representation of phenological responses to climatic variability across Integrated Carbon Observation System stations and the terrestrial biosphere through the improvement of model algorithms and the provision of validation datasets.
BibTeX:
@article{Hufkens2018,
  author = {Hufkens, Koen and Filippa, Gianluca and Cremonese, Edoardo and Migliavacca, Mirco and D'Odorico, Petra and Peichl, Matthias and Gielen, Bert and Hörtnagl, Lukas and Soudani, Kamel and Papale, Dario and Rebmann, Corinna and Brown, Tim and Wingate, Lisa},
  title = {Assimilating phenology datasets automatically across ICOS ecosystem stations},
  journal = {International Agrophysics},
  year = {2018},
  volume = {32},
  number = {4},
  pages = {677--687},
  url = {https://content.sciendo.com/view/journals/intag/32/4/article-p677.xml},
  doi = {10.1515/intag-2017-0050}
}
Ibraim E, Wolf B, Harris E, Gasche R, Wei J, Yu L, Kiese R, Eggleston S, Butterbach-Bahl K, Zeeman M, Tuzson B, Emmenegger L, Six J, Henne S and Mohn J (2018), "Attribution of Ntextlesssubtextgreater2textless/subtextgreaterO sources in a grassland soil with laser spectroscopy based isotopocule analysis", Biogeosciences Discussions. , pp. 1-27. Copernicus GmbH.
Abstract: textlessptextgreatertextlessstrongtextgreaterAbstract.textless/strongtextgreater Nitrous oxide (Ntextlesssubtextgreater2textless/subtextgreaterO) is the primary atmospheric constituent involved in stratospheric ozone depletion and contributes strongly to changes in the climate system through a positive radiative forcing mechanism. The atmospheric abundance of Ntextlesssubtextgreater2textless/subtextgreaterO has increased from 270 ppb during the pre-industrial era to approx. 330 ppb in 2018. Even though it is well known that microbial processes in agricultural and natural soils are the major Ntextlesssubtextgreater2textless/subtextgreaterO source, the contribution of specific soil processes is still uncertain. The relative abundance of Ntextlesssubtextgreater2textless/subtextgreaterO isotopocules (textlesssuptextgreater14textless/suptextgreaterNtextlesssuptextgreater14textless/suptextgreaterNtextlesssuptextgreater16textless/suptextgreaterN, textlesssuptextgreater14textless/suptextgreaterNtextlesssuptextgreater15textless/suptextgreaterNtextlesssuptextgreater16textless/suptextgreaterO, textlesssuptextgreater15textless/suptextgreaterNtextlesssuptextgreater14textless/suptextgreaterNtextlesssuptextgreater16textless/suptextgreaterO and textlesssuptextgreater14textless/suptextgreaterNtextlesssuptextgreater14textless/suptextgreaterNtextlesssuptextgreater18textless/suptextgreaterO) carries process-specific in-formation and thus can be used to trace production and consumption pathways. While isotope ratio mass spectroscopy (IRMS) was traditionally used for high-precision measurement of the isotopic composition of Ntextlesssubtextgreater2textless/subtextgreaterO, quantum cascade laser absorption spectroscopy (QCLAS) has been put forward as a complementary technique with the potential for on-site analysis. In recent years, preconcentration combined with QCLAS has been presented as a technique to resolve subtle changes in ambient Ntextlesssubtextgreater2textless/subtextgreaterO isotopic composition.textless/ptextgreater textlessptextgreaterFrom the end of May until the beginning of August 2016, we investigated Ntextlesssubtextgreater2textless/subtextgreaterO emissions from an intensively managed grassland at the study site Fendt in Southern Germany. In total, 612 measurements of ambient Ntextlesssubtextgreater2textless/subtextgreaterO were taken by combining preconcentration with QCLAS analyses, yielding δtextlesssuptextgreater15textless/suptextgreaterNtextlesssuptextgreaterαtextless/suptextgreater, δtextlesssuptextgreater15textless/suptextgreaterNtextlesssuptextgreaterβtextless/suptextgreater, δtextlesssuptextgreater18textless/suptextgreaterO and Ntextlesssubtextgreater2textless/subtextgreaterO concentration with a temporal resolution of approximately one hour and precisions of 0.46 ‰, 0.36 ‰, 0.59 ‰ and 1.24 ppb, respectively. Soil δtextlesssuptextgreater15textless/suptextgreaterN-NOtextlesssubtextgreater3textless/subtextgreatertextlesssuptextgreater−textless/suptextgreater values and concentrations of NOtextlesssubtextgreater3textless/subtextgreatertextlesssuptextgreater−textless/suptextgreater and NHtextlesssubtextgreater4textless/subtextgreatertextlesssuptextgreater+textless/suptextgreater were measured to further constrain possible Ntextlesssubtextgreater2textless/subtextgreaterO-emitting source processes. Furthermore, the concentration footprint area of measured Ntextlesssubtextgreater2textless/subtextgreaterO was determined with a Lagrangian particle dispersion model (FLEXPART-COSMO) using local wind and turbulence observations. These simulations indicated that night-time concentration observations were largely sensitive to local fluxes. While bacterial denitrification and nitrifier denitrification were identified as the primary Ntextlesssubtextgreater2textless/subtextgreaterO-emitting processes, Ntextlesssubtextgreater2textless/subtextgreaterO reduction to Ntextlesssubtextgreater2textless/subtextgreater largely dictated the isotopic composition of measured Ntextlesssubtextgreater2textless/subtextgreaterO. Fungal denitrification and nitrification-derived Ntextlesssubtextgreater2textless/subtextgreaterO accounted for 34–42 % of total Ntextlesssubtextgreater2textless/subtextgreaterO emissions and had a clear effect on the measured isotopic source signatures. This study presents the suitability of on-site Ntextlesssubtextgreater2textless/subtextgreaterO isotopocule analysis for disentangling source and sink processes in-situ and found that at the Fendt site bacterial denitrification/nitrifier denitrification is the major source for Ntextlesssubtextgreater2textless/subtextgreaterO, while Ntextlesssubtextgreater2textless/subtextgreaterO reduction acted as a major sink.textless/ptextgreater
BibTeX:
@article{Ibraim2018,
  author = {Ibraim, Erkan and Wolf, Benjamin and Harris, Eliza and Gasche, Rainer and Wei, Jing and Yu, Longfei and Kiese, Ralf and Eggleston, Sarah and Butterbach-Bahl, Klaus and Zeeman, Matthias and Tuzson, Béla and Emmenegger, Lukas and Six, Johan and Henne, Stephan and Mohn, Joachim},
  title = {Attribution of Ntextlesssubtextgreater2textless/subtextgreaterO sources in a grassland soil with laser spectroscopy based isotopocule analysis},
  journal = {Biogeosciences Discussions},
  publisher = {Copernicus GmbH},
  year = {2018},
  pages = {1--27},
  doi = {10.5194/bg-2018-426}
}
Järveoja J, Nilsson MB, Gažovič M, Crill PM and Peichl M (2018), "Partitioning of the net CO2 exchange using an automated chamber system reveals plant phenology as key control of production and respiration fluxes in a boreal peatland", Global Change Biology. Vol. 24(8), pp. 3436-3451. Wiley.
Abstract: The net ecosystem CO2 exchange (NEE) drives the carbon (C) sink–source strength of northern peatlands. Since NEE represents a balance between various production and respiration fluxes, accurate predictions of its response to global changes require an in depth understanding of these underlying processes. Currently, however, detailed information of the temporal dynamics as well as the separate biotic and abiotic controls of the NEE component fluxes is lacking in peatland ecosystems. In this study, we address this knowledge gap by using an automated chamber system established across natural and trenching/vegetation removal plots to partition NEE into its production (i.e., gross and net primary production; GPP and NPP) and respiration (i.e., ecosystem, heterotrophic and autotrophic respiration; ER, Rh and Ra) fluxes in a boreal peatland in northern Sweden. Our results showed that daily NEE patterns were driven by GPP while variations in ER were governed by Ra rather than Rh. Moreover, we observed pronounced seasonal shifts in the Ra/Rh and above/belowground NPP ratios throughout the main phenological phases. Generalized linear model analysis revealed that the greenness index derived from digital images (as a proxy for plant phenology) was the strongest control of NEE, GPP and NPP while explaining considerable fractions also in the variations of ER and Ra. In addition, our data exposed greater temperature sensitivity of NPP compared to Rh resulting in enhanced C sequestration with increasing temperature. Overall, our study suggests that the temporal patterns in NEE and its component fluxes are tightly coupled to vegetation dynamics in boreal peatlands and thus challenges previous studies that commonly identify abiotic factors as key drivers. These findings further emphasize the need for integrating detailed information on plant phenology into process-based models to improve predictions of global change impacts on the peatland C cycle.
BibTeX:
@article{Jaerveoja2018,
  author = {Järveoja, Järvi and Nilsson, Mats B. and Gažovič, Michal and Crill, Patrick M. and Peichl, Matthias},
  title = {Partitioning of the net CO2 exchange using an automated chamber system reveals plant phenology as key control of production and respiration fluxes in a boreal peatland},
  journal = {Global Change Biology},
  publisher = {Wiley},
  year = {2018},
  volume = {24},
  number = {8},
  pages = {3436--3451},
  doi = {10.1111/gcb.14292}
}
Järvi L, Rannik U, Kokkonen TV, Kurppa M, Karppinen A, Kouznetsov RD, Rantala P, Vesala T and Wood CR (2018), "Uncertainty of eddy covariance flux measurements over an urban area based on two towers", Atmospheric Measurement Techniques. Vol. 11(10), pp. 5421-5438. Copernicus GmbH.
Abstract: The eddy covariance (EC) technique is the most direct method for measuring the exchange between the surface and the atmosphere in different ecosystems. Thus, it is commonly used to get information on air pollutant and greenhouse gas emissions, and on turbulent heat transfer. Typically an ecosystem is monitored by only one single EC measurement station at a time, making the ecosystem-level flux values subject to random and systematic uncertainties. Furthermore, in urban ecosystems we often have no choice but to conduct the single-point measurements in non-ideal locations such as close to buildings and/or in the roughness sublayer, bringing further complications to data analysis and flux estimations. In order to tackle the question of how representative a single EC measurement point in an urban area can be, two identical EC systems - measuring momentum, sensible and latent heat, and carbon dioxide fluxes - were installed on each side of the same building structure in central Helsinki, Finland, during July 2013-September 2015. The main interests were to understand the sensitivity of the vertical fluxes on the single measurement point and to estimate the systematic uncertainty in annual cumulative values due to missing data if certain, relatively wide, flow-distorted wind sectors are disregarded.The momentum and measured scalar fluxes respond very differently to the distortion caused by the building structure. The momentum flux is the most sensitive to the measurement location, whereas scalar fluxes are less impacted. The flow distortion areas of the two EC systems (40-150 and 230-340°) are best detected from the mean-wind-normalised turbulent kinetic energy, and outside these areas the median relative random uncertainties of the studied fluxes measured by one system are between 12% and 28%. Different gap-filling methods with which to yield annual cumulative fluxes show how using data from a single EC measurement point can cause up to a 12% (480Cm 2) underestimation in the cumulative carbon fluxes as compared to combined data from the two systems. Combining the data from two EC systems also increases the fraction of usable half-hourly carbon fluxes from 45% to 69% at the annual level. For sensible and latent heat, the respective underestimations are up to 5% and 8% (0.094 and 0.069TJm 2). The obtained random and systematic uncertainties are in the same range as observed in vegetated ecosystems. We also show how the commonly used data flagging criteria in natural ecosystems, kurtosis and skewness, are not necessarily suitable for filtering out data in a densely built urban environment. The results show how the single measurement system can be used to derive representative flux values for central Helsinki, but the addition of second system to other side of the building structure decreases the systematic uncertainties. Comparable results can be expected in similarly dense city locations where no large directional deviations in the source area are seen. In general, the obtained results will aid the scientific community by providing information about the sensitivity of EC measurements and their quality flagging in urban areas.
BibTeX:
@article{Jaervi2018,
  author = {Järvi, Leena and Rannik, Ullar and Kokkonen, Tom V. and Kurppa, Mona and Karppinen, Ari and Kouznetsov, Rostislav D. and Rantala, Pekka and Vesala, Timo and Wood, Curtis R.},
  title = {Uncertainty of eddy covariance flux measurements over an urban area based on two towers},
  journal = {Atmospheric Measurement Techniques},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {11},
  number = {10},
  pages = {5421--5438},
  doi = {10.5194/amt-11-5421-2018}
}
Jiskra M, Sonke JE, Obrist D, Bieser J, Ebinghaus R, Myhre CL, Pfaffhuber KA, Wängberg I, Kyllönen K, Worthy D, Martin LG, Labuschagne C, Mkololo T, Ramonet M, Magand O and Dommergue A (2018), "A vegetation control on seasonal variations in global atmospheric mercury concentrations", Nature Geoscience., apr, 2018. Vol. 11(4), pp. 244-250. Springer Nature.
Abstract: Anthropogenic mercury emissions are transported through the atmosphere as gaseous elemental mercury (Hg(0)) before they are deposited to Earth's surface. Strong seasonality in atmospheric Hg(0) concentrations in the Northern Hemisphere has been explained by two factors: anthropogenic Hg(0) emissions are thought to peak in winter due to higher energy consumption, and atmospheric oxidation rates of Hg(0) are faster in summer. Oxidation-driven Hg(0) seasonality should be equally pronounced in the Southern Hemisphere, which is inconsistent with observations of constant year-round Hg(0) levels. Here, we assess the role of Hg(0) uptake by vegetation as an alternative mechanism for driving Hg(0) seasonality. We find that at terrestrial sites in the Northern Hemisphere, Hg(0) co-varies with CO2, which is known to exhibit a minimum in summer when CO2 is assimilated by vegetation. The amplitude of seasonal oscillations in the atmospheric Hg(0) concentration increases with latitude and is larger at inland terrestrial sites than coastal sites. Using satellite data, we find that the photosynthetic activity of vegetation correlates with Hg(0) levels at individual sites and across continents. We suggest that terrestrial vegetation acts as a global Hg(0) pump, which can contribute to seasonal variations of atmospheric Hg(0), and that decreasing Hg(0) levels in the Northern Hemisphere over the past 20 years can be partly attributed to increased terrestrial net primary production.
BibTeX:
@article{Jiskra2018,
  author = {Jiskra, Martin and Sonke, Jeroen E. and Obrist, Daniel and Bieser, Johannes and Ebinghaus, Ralf and Myhre, Cathrine Lund and Pfaffhuber, Katrine Aspmo and Wängberg, Ingvar and Kyllönen, Katriina and Worthy, Doug and Martin, Lynwill G. and Labuschagne, Casper and Mkololo, Thumeka and Ramonet, Michel and Magand, Olivier and Dommergue, Aurélien},
  title = {A vegetation control on seasonal variations in global atmospheric mercury concentrations},
  journal = {Nature Geoscience},
  publisher = {Springer Nature},
  year = {2018},
  volume = {11},
  number = {4},
  pages = {244--250},
  doi = {10.1038/s41561-018-0078-8}
}
Jocher G, Marshall J, Nilsson MB, Linder S, De Simon G, Hörnlund T, Lundmark T, Näsholm T, Ottosson Löfvenius M, Tarvainen L, Wallin G and Peichl M (2018), "Impact of Canopy Decoupling and Subcanopy Advection on the Annual Carbon Balance of a Boreal Scots Pine Forest as Derived From Eddy Covariance", Journal of Geophysical Research: Biogeosciences., feb, 2018. Vol. 123(2), pp. 303-325.
Abstract: Apparent net uptake of carbon dioxide (CO2) during wintertime by an ∼ 90 year old Scots pine stand in northern Sweden led us to conduct canopy decoupling and subcanopy advection investigations over an entire year. Eddy covariance (EC) measurements ran simultaneously above and within the forest canopy for that purpose. We used the correlation of above- and below-canopy standard deviation of vertical wind speed (σw) as decoupling indicator. We identified 0.33 m s−1 and 0.06 m s−1 as site-specific σw thresholds for above- and below-canopy coupling during nighttime (global radiation textless20 W m−2) and 0.23 m s−1 and 0.06 m s−1 as daytime (global radiation textgreater20 W m−2) σw thresholds. Decoupling occurred in 53% of the annual nighttime and 14% of the annual daytime. The annual net ecosystem exchange (NEE), gross ecosystem exchange (GEE), and ecosystem respiration (Reco) derived via two-level filtered EC data were −357 g C m−2, −1,138 g C m−2, and 781 g C m−2, respectively. In comparison, both single-level friction velocity (u*) and quality filtering resulted in ˜ 22% higher NEE, mainly caused by ˜ 16% lower Reco. GEE remained similar among filtering regimes. Accounting for changes of CO2 storage across the canopy in the single-level filtered data could only marginally decrease these discrepancies. Consequently, advection appears to be responsible for the major part of this divergence. We conclude that the two-level filter is necessary to adequately address decoupling and subcanopy advection at our site, and we recommend this filter for all forested EC sites.
BibTeX:
@article{Jocher2018,
  author = {Jocher, Georg and Marshall, John and Nilsson, Mats B. and Linder, Sune and De Simon, Giuseppe and Hörnlund, Thomas and Lundmark, Tomas and Näsholm, Torgny and Ottosson Löfvenius, Mikaell and Tarvainen, Lasse and Wallin, Göran and Peichl, Matthias},
  title = {Impact of Canopy Decoupling and Subcanopy Advection on the Annual Carbon Balance of a Boreal Scots Pine Forest as Derived From Eddy Covariance},
  journal = {Journal of Geophysical Research: Biogeosciences},
  year = {2018},
  volume = {123},
  number = {2},
  pages = {303--325},
  url = {http://doi.wiley.com/10.1002/2017JG003988},
  doi = {10.1002/2017JG003988}
}
Juráň S, Edwards-Jonášová M, Cudlín P, Zapletal M, Šigut L, Grace J and Urban O (2018), "Prediction of ozone effects on net ecosystem production of Norway spruce forest", IForest., dec, 2018. Vol. 11(6), pp. 743-750. Italian Society of Sivilculture and Forest Ecology (SISEF).
Abstract: Future ground-level concentrations of phytotoxic ozone are projected to grow in the Northern Hemisphere, at a rate depending on emission scenarios. We explored the likely changes in net ecosystem production (NEP) due to the increasing concentration of tropospheric ozone by applying a Generalized Additive Mixed Model based on measurements of ozone concentration ([O 3 ]) and stomatal ozone flux (FsO 3 ), at a mountainous Norway spruce forest in the Czech Republic, Central Europe. A dataset covering the growing period (May-August 2009) was examined in this case study. A predictive model based on FsO 3 was found to be marginally more accurate than a model using [O 3 ] alone for prediction of the course of NEP when compared to NEP measured by the eddy covariance technique. Both higher [O 3 ] and FsO 3 were found to reduce NEP. NEP simulated at low, pre-industrial FsO 3 (0.5 nmol m -2 s -1 ) was higher by 24.8% as compared to NEP assessed at current rates of FsO 3 (8.32 nmol m -2 s -1 ). However, NEP simulated at high FsO 3 (17 nmol m -2 s -1 ), likely in the future, was reduced by 14.1% as compared to NEP values at current FsO 3 . The interaction between environmental factors and stomatal conductance is discussed in this paper.
BibTeX:
@article{Juran2018,
  author = {Juráň, Stanislav and Edwards-Jonášová, Magda and Cudlín, Pavel and Zapletal, Miloš and Šigut, Ladislav and Grace, John and Urban, Otmar},
  title = {Prediction of ozone effects on net ecosystem production of Norway spruce forest},
  journal = {IForest},
  publisher = {Italian Society of Sivilculture and Forest Ecology (SISEF)},
  year = {2018},
  volume = {11},
  number = {6},
  pages = {743--750},
  doi = {10.3832/ifor2805-011}
}
Jurevics A, Peichl M and Egnell G (2018), "Stand volume production in the subsequent stand during three decades remains unaffected by slash and stump harvest in Nordic forests", Forests., dec, 2018. Vol. 9(12), pp. 770. MDPI AG.
Abstract: The renewable energy policies of the European Union rely on forest biomass in achieving climate mitigation targets. In Sweden, where secondary residues from the forest industries are fully utilized, primary residues following harvest such as stumps and slash offer a potential as an additional biomass source. Stump and slash harvest may, however, have adverse effects on site productivity due to increased nutrient loss from the site which could negatively impact the stand volume production of the subsequent stand. Stand volume production is also affected by seedling survival, seedling input from natural regeneration and management of the regenerated stand. In this study, we evaluate the effects of stump and slash harvest on stand volume production of the subsequent stand based on data from eight experimental sites across Sweden planted with Scots pine (Pinus sylvestris L.) or Norway spruce (Picea abies (L.) Karst.) over period of 31-34 years after clearcut with (1) traditional stem-only harvest; (2) stem and stump harvest; (3) stem and slash harvest; and (4) stem, stump and slash harvest. With the goal to explain treatment differences in stand volume production, treatment effects on site productivity estimated through initial height growth (10-19 years after planting), seedling survival, and input of seedlings through natural regeneration were also analyzed. We found that stand volume production was higher following stump harvest as compared to slash harvest, but stand volume production for the more intense harvest treatments (2)-(4) did not differ from stem-only harvest (1). Initial height growth (i.e., site productivity) did not differ between treatments, but followed the trend in stand volume production with (2) textgreater (4) textgreater (3) textgreater (1). Survival of planted seedlings was not affected by the treatments, whereas natural regeneration after 5 years was significantly increased after both treatments including slash harvest (3) and (4) in comparison to stem-only harvest. However, since most of that natural regeneration was removed in subsequent pre-commercial thinnings, this initial increase did not affect stand volume production. The absence of a significant interaction between treatment and species planted for all independent variables tested suggests that there were no species related response differences. Since the experimental design did not allow for site-level analyses, we cannot exclude the possibility that site-specific harvest treatment effects might have masked general effects across all sites. Thus, slash and stump harvest effects at the site level need to be further studied. These results suggest, at least over a 3-decade perspective, that logging residues like stumps and slash can provide an additional renewable energy source to help achieving climate change mitigation goals in the Nordic countries without depleting the future forest biomass resource.
BibTeX:
@article{Jurevics2018,
  author = {Jurevics, Arnis and Peichl, Matthias and Egnell, Gustaf},
  title = {Stand volume production in the subsequent stand during three decades remains unaffected by slash and stump harvest in Nordic forests},
  journal = {Forests},
  publisher = {MDPI AG},
  year = {2018},
  volume = {9},
  number = {12},
  pages = {770},
  doi = {10.3390/f9120770}
}
Kaisermann A, Ogée J, Sauze J, Wohl S, Jones SP, Gutierrez A and Wingate L (2018), "Disentangling the rates of carbonyl sulfide (COS) production and consumption and their dependency on soil properties across biomes and land use types", Atmospheric Chemistry and Physics., jul, 2018. Vol. 18(13), pp. 9425-9440. Copernicus GmbH.
Abstract: Soils both emit and consume the trace gas carbonyl sulfide (COS) leading to a soil-air COS exchange rate that is the net result of two opposing fluxes. Partitioning these two gross fluxes and understanding their drivers are necessary to estimate the contribution of soils to the current and future atmospheric COS budget. Previous efforts to disentangle the gross COS fluxes from soils have used flux measurements on air-dried soils as a proxy for the COS emission rates of moist soils. However, this method implicitly assumes that COS uptake becomes negligible and that COS emission remains steady while soils are drying. We tested this assumption by simultaneously estimating the soil COS sources and sinks and their temperature sensitivity (Q10); these estimates were based on soil-air COS flux measurements on fresh soils at different COS concentrations and two soil temperatures. Measurements were performed on 27 European soils from different biomes and land use types in order to obtain a large range of physical-chemical properties and identify the drivers of COS consumption and production rates. We found that COS production rates from moist and airdried soils were not significantly different for a given soil and that the COS production rates had Q10 values (3.96±3.94) that were larger and more variable than the Q10 for COS consumption (1.17±0.27). COS production generally contributed less to the net flux at lower temperatures but this contribution of COS production increased rapidly at higher temperatures, lower soil moisture contents and lower COS concentrations. Consequently, measurements at higher COS concentrations (viz. 1000 ppt) always increased the robustness of COS consumption estimates. Across the range of biomes and land use types COS production rates co-varied with total soil nitrogen concentrations (r =0.52, P textless 0.05) and mean annual precipitation (r = 0.53, P textless 0.05), whilst the gross COS uptake rate and the first-order COS hydrolysis rate constant co-varied significantly with the microbial biomass nitrogen (N) content of the soils (r = -0.74 and 0.64, P textless 0.05 and P textless 0.05, respectively). Collectively our findings suggest a strong interaction between soil nitrogen and water cycling on COS production and uptake, providing new insights into how to upscale the contribution of soils to the global atmospheric COS budget.
BibTeX:
@article{Kaisermann2018,
  author = {Kaisermann, Aurore and Ogée, Jérôme and Sauze, Joana and Wohl, Steven and Jones, Sam P. and Gutierrez, Ana and Wingate, Lisa},
  title = {Disentangling the rates of carbonyl sulfide (COS) production and consumption and their dependency on soil properties across biomes and land use types},
  journal = {Atmospheric Chemistry and Physics},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {18},
  number = {13},
  pages = {9425--9440},
  doi = {10.5194/acp-18-9425-2018}
}
Kamp J, Skov H, Jensen B and Sørensen LL (2018), "Fluxes of gaseous elemental mercury (GEM) in the High Arctic during atmospheric mercury depletion events (AMDEs)", Atmospheric Chemistry and Physics., may, 2018. Vol. 18(9), pp. 6923-6938. Copernicus GmbH.
Abstract: Measurements of gaseous elemental mercury (GEM) fluxes over snow surfaces using a relaxed eddy accumulation (REA) system are carried out at the High Arctic site at the Villum Research Station, Station Nord, in North Greenland. Simultaneously, CO2 fluxes are determined using the eddy covariance (EC) technique. The REA system with dual inlets and dual analyzers is used to measure fluxes directly over the snow. The measurements were carried out from 23 April to 12 May during spring 2016, where atmospheric mercury depletion events (AMDEs) took place. The measurements showed a net emission of 8.9 ng m-2 min-1, with only a few minor episodes of net depositional fluxes, from a maximum deposition of 8.1 ng m-2 min-1 to a maximum emission of 179.2 ng m-2 min-1. The data support the theory that gaseous oxidized mercury (GOM) is deposited during AMDEs followed by formation of GEM on surface snow and is re-emitted as GEM shortly after the AMDEs. Furthermore, observation of the relation between GEM fluxes and atmospheric temperature suggests that GEM emission partly could be affected by surface heating. However, it is also clear that the GEM emissions are affected by many parameters.
BibTeX:
@article{Kamp2018,
  author = {Kamp, Jesper and Skov, Henrik and Jensen, Bjarne and Sørensen, Lise Lotte},
  title = {Fluxes of gaseous elemental mercury (GEM) in the High Arctic during atmospheric mercury depletion events (AMDEs)},
  journal = {Atmospheric Chemistry and Physics},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {18},
  number = {9},
  pages = {6923--6938},
  doi = {10.5194/acp-18-6923-2018}
}
Katul G, Peltola O, Grönholm T, Launiainen S, Mammarella I and Vesala T (2018), "Ejective and Sweeping Motions Above a Peatland and Their Role in Relaxed-Eddy-Accumulation Measurements and Turbulent Transport Modelling", Boundary-Layer Meteorology., jul, 2018. Vol. 169(2), pp. 163-184. Springer Nature.
Abstract: The three turbulent velocity components, water vapour (H 2O ), carbon dioxide (CO 2), and methane (CH 4) concentration fluctuations are measured above a boreal peatland and analyzed using conditional sampling and quadrant analysis. The overarching question to be addressed is to what degree lower-order cumulant expansion methods describe transport efficiency and the relative importance of ejections and sweeps to momentum, CH 4, CO 2 and H 2O fluxes across a range of atmospheric flow regimes. The patchy peatland surface creates distinctly different source and sink distributions for the three scalars in space and time thereby adding to the uniqueness of the set-up. The measured and modelled fractional contributions to the momentum flux show that sweep events dominate over ejections in agreement with prior studies conducted in the roughness sublayer. For scalar fluxes, ejections dominate the turbulent fluxes over sweeps. While ejective motions persist longer for momentum transport, sweeping events persist longer for all three scalars. Third-order cumulant expansions describe many of the results detailed above, and the results are surprising given the highly non-Gaussian distribution of CH 4 turbulent fluctuations. Connections between the asymmetric contributions of sweeps and ejections and the flux-transport term arising in scalar turbulent-flux-budget closure are derived and shown to agree reasonably well with measurements. The proposed model derived here is much simpler than prior structural models used to describe laboratory experiments. Implications of such asymmetric contributions on, (i) the usage of the now proliferating relaxed-eddy-accumulation method in turbulent flux measurements, (ii) the constant-flux assumption, and (iii) gradient-diffusion closure models are presented.
BibTeX:
@article{Katul2018,
  author = {Katul, Gabriel and Peltola, Olli and Grönholm, Tiia and Launiainen, Samuli and Mammarella, Ivan and Vesala, Timo},
  title = {Ejective and Sweeping Motions Above a Peatland and Their Role in Relaxed-Eddy-Accumulation Measurements and Turbulent Transport Modelling},
  journal = {Boundary-Layer Meteorology},
  publisher = {Springer Nature},
  year = {2018},
  volume = {169},
  number = {2},
  pages = {163--184},
  doi = {10.1007/s10546-018-0372-4}
}
Kiese R, Fersch B, Baessler C, Brosy C, Butterbach-Bahl K, Chwala C, Dannenmann M, Fu J, Gasche R, Grote R, Jahn C, Klatt J, Kunstmann H, Mauder M, Rödiger T, Smiatek G, Soltani M, Steinbrecher R, Völksch I, Werhahn J, Wolf B, Zeeman M and Schmid H (2018), "The TERENO Pre-Alpine Observatory: Integrating Meteorological, Hydrological, and Biogeochemical Measurements and Modeling", Vadose Zone Journal. Vol. 17(1), pp. 180060. Soil Science Society of America.
Abstract: textcopyright Soil Science Society of America. Global change has triggered several transformations, such as alterations in climate, land productivity, water resources, and atmospheric chemistry, with far reaching impacts on ecosystem functions and services. Finding solutions to climate and land cover change-driven impacts on our terrestrial environment is one of the most important scientific challenges of the 21st century, with far-reaching interlinkages to the socio-economy. The setup of the German Terrestrial Environmental Observatories (TERENO) Pre-Alpine Observatory was motivated by the fact that mountain areas, such as the pre-alpine region in southern Germany, have been exposed to more intense warming compared with the global average trend and to higher frequencies of extreme hydrological events, such as droughts and intense rainfall. Scientific research questions in the TERENO Pre-Alpine Observatory focus on improved process understanding and closing of combined energy, water, C, and N cycles at site to regional scales. The main long-term objectives of the TERENO Pre-Alpine Observatory include the characterization and quantification of climate change and land cover–manage-ment effects on terrestrial hydrology and biogeochemical processes at site and regional scales by joint measuring and modeling approaches. Here we present a detailed climatic and biogeophysical characterization of the TERENO Pre-Alpine Observatory and a summary of novel scientific findings from observations and projects. Finally, we reflect on future directions of climate impact research in this particularly vulnerable region of Germany.
BibTeX:
@article{Kiese2018,
  author = {Kiese, R. and Fersch, B. and Baessler, C. and Brosy, C. and Butterbach-Bahl, K. and Chwala, C. and Dannenmann, M. and Fu, J. and Gasche, R. and Grote, R. and Jahn, C. and Klatt, J. and Kunstmann, H. and Mauder, M. and Rödiger, T. and Smiatek, G. and Soltani, M. and Steinbrecher, R. and Völksch, I. and Werhahn, J. and Wolf, B. and Zeeman, M. and Schmid, H.P.},
  title = {The TERENO Pre-Alpine Observatory: Integrating Meteorological, Hydrological, and Biogeochemical Measurements and Modeling},
  journal = {Vadose Zone Journal},
  publisher = {Soil Science Society of America},
  year = {2018},
  volume = {17},
  number = {1},
  pages = {180060},
  doi = {10.2136/vzj2018.03.0060}
}
Kisel'Ák J, Dušek J and Stehlík M (2018), "Recurrence of CH 4 and CO 2 emissions measured by a non-steady state flow-through chamber system", In AIP Conference Proceedings. Vol. 2046 Author(s).
Abstract: Raw data of methane and carbon dioxide emissions from the sedge-grass marsh ecosystem measured by the non-steady state flow-through chamber system were analyzed using a recurrence plots of a time trajectory returns. The recurrence plots can help to understand process of gases emission and optionally can exploited to characterize the system's behavior. According to recurrence plots we can to state that behavior of system is mostly stochastic with determination parts with chaos transitions.
BibTeX:
@inproceedings{KiselAk2018,
  author = {Kisel'Ák, Jozef and Dušek, Jiří and Stehlík, Milan},
  title = {Recurrence of CH 4 and CO 2 emissions measured by a non-steady state flow-through chamber system},
  booktitle = {AIP Conference Proceedings},
  publisher = {Author(s)},
  year = {2018},
  volume = {2046},
  doi = {10.1063/1.5081566}
}
Kiuru P, Ojala A, Mammarella I, Heiskanen J, Kämäräinen M, Vesala T and Huttula T (2018), "Effects of Climate Change on CO2 Concentration and Efflux in a Humic Boreal Lake: A Modeling Study", Journal of Geophysical Research: Biogeosciences., jul, 2018. Vol. 123(7), pp. 2212-2233. American Geophysical Union (AGU).
Abstract: Climate change may have notable impacts on carbon cycling in freshwater ecosystems, especially in the boreal zone. Higher atmospheric temperature and changes in annual discharge patterns and carbon loading from the catchment affect the thermal and biogeochemical conditions in a lake. We developed an extension of a one-dimensional process-based lake model MyLake for simulating carbon dioxide (CO2) dynamics of a boreal lake. We calibrated the model for Lake Kuivajärvi, a small humic boreal lake, for the years 2013–2014, using the extensive data available on carbon inflow and concentrations of water column CO2 and dissolved organic carbon. The lake is a constant source of CO2 to the atmosphere in the present climate. We studied the potential effects of climate change-induced warming on lake CO2 concentration and air-water flux using downscaled air temperature data from three recent-generation global climate models with two alternative representative concentration pathway forcing scenarios. Literature estimates were used for climate change impacts on the lake inflow. The scenario simulations showed a 20–35% increase in the CO2 flux from the lake to the atmosphere in the scenario period 2070–2099 compared to the control period 1980–2009. In addition, we estimated possible implications of different changes in terrestrial inorganic and organic carbon loadings to the lake. The scenarios with plausible increases of 10% and 20% in CO2 and dissolved organic carbon loadings, respectively, produced increases of 2.1–2.5% and 2.2–2.3% in the annual CO2 flux.
BibTeX:
@article{Kiuru2018,
  author = {Kiuru, Petri and Ojala, Anne and Mammarella, Ivan and Heiskanen, Jouni and Kämäräinen, Matti and Vesala, Timo and Huttula, Timo},
  title = {Effects of Climate Change on CO2 Concentration and Efflux in a Humic Boreal Lake: A Modeling Study},
  journal = {Journal of Geophysical Research: Biogeosciences},
  publisher = {American Geophysical Union (AGU)},
  year = {2018},
  volume = {123},
  number = {7},
  pages = {2212--2233},
  doi = {10.1029/2018JG004585}
}
Knauer J, Zaehle S, Medlyn BE, Reichstein M, Williams CA, Migliavacca M, De Kauwe MG, Werner C, Keitel C, Kolari P, Limousin J and Linderson M (2018), "Towards physiologically meaningful water‐use efficiency estimates from eddy covariance data", Global Change Biology., feb, 2018. Vol. 24(2), pp. 694-710.
BibTeX:
@article{Knauer2018,
  author = {Knauer, Jürgen and Zaehle, Sönke and Medlyn, Belinda E. and Reichstein, Markus and Williams, Christopher A. and Migliavacca, Mirco and De Kauwe, Martin G. and Werner, Christiane and Keitel, Claudia and Kolari, Pasi and Limousin, Jean‐Marc and Linderson, Maj‐Lena},
  title = {Towards physiologically meaningful water‐use efficiency estimates from eddy covariance data},
  journal = {Global Change Biology},
  year = {2018},
  volume = {24},
  number = {2},
  pages = {694--710},
  url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.13893},
  doi = {10.1111/gcb.13893}
}
Kondrik D, Kazakov E and Pozdnyakov D (2018), "A synthetic satellite dataset of textlessitextgreaterE. huxleyitextless/itextgreater spatio-temporal distributions and their impacts on Arctic and Subarctic marine environments (1998–2016)", Earth System Science Data Discussions., oct, 2018. , pp. 1-17. Copernicus GmbH.
Abstract: textlessptextgreatertextlessstrongtextgreaterAbstract.textless/strongtextgreater A 19-year (1998–2016) continuous dataset of coccolithophore textlessitextgreaterE. huxleyitextless/itextgreater distributions and activity in Arctic and Subarctic seas is presented. The dataset is based on optical remote sensing data (mostly OC CCI data) with assimilation of different relevant in-situ observations, preprocessed with authorial algorithms. Alongside with bloom locations, we also provide both detailed information on textlessitextgreaterE. huxleyitextless/itextgreater impacts within the bloom area on marine environments and the subdatasets of quantified coccolith concentrations, particulate inorganic carbon content and COtextlesssubtextgreater2textless/subtextgreater partial pressure in water driven by coccolithophores. All data are presented on a regular 4×4textlessspan class="thinspace"textgreatertextless/spantextgreaterkm grid at a temporal resolution of 8 days. The paper describes the theoretical and methodological basis for all processing and modeling steps. The data are available on Zenodo: textlessa href="https://doi.org/10.5281/zenodo.1402033" target="blank"textgreaterhttps://doi.org/10.5281/zenodo.1402033textless/atextgreater.textless/ptextgreater
BibTeX:
@article{Kondrik2018,
  author = {Kondrik, Dmitry and Kazakov, Eduard and Pozdnyakov, Dmitry},
  title = {A synthetic satellite dataset of textlessitextgreaterE. huxleyitextless/itextgreater spatio-temporal distributions and their impacts on Arctic and Subarctic marine environments (1998–2016)},
  journal = {Earth System Science Data Discussions},
  publisher = {Copernicus GmbH},
  year = {2018},
  pages = {1--17},
  doi = {10.5194/essd-2018-101}
}
Korrensalo A, Kettunen L, Laiho R, Alekseychik P, Vesala T, Mammarella I and Tuittila ES (2018), "Boreal bog plant communities along a water table gradient differ in their standing biomass but not their biomass production", Journal of Vegetation Science., feb, 2018. Vol. 29(2), pp. 136-146. Wiley.
Abstract: Question: Peatlands are globally important for carbon storage due to the imbalance between plant biomass production and decomposition. Distribution of both live standing biomass (BM, dry mass g/m2) and biomass production (BMP, dry mass g m−2 growing season−1) are known to be dependent on the water table (WT). However, the relations of BM and BMP to WT variation are poorly known. Here we investigated, how the above- and below-ground BM and BMP of three different plant functional types (PFTs), dwarf shrubs, sedges and Sphagnum mosses, relate to natural WT variation within an ombrotrophic boreal bog. In addition, we estimated ecosystem-level BMP and compared that with ecosystem net primary production (NPP) derived from eddy covariance (EC) measurements. Location: Siikaneva bog, Ruovesi, Finland. Methods: We quantified above- and below-ground BM and BMP of PFTs along the WT gradient, divided into six plant community types. Plant community scale BM and BMP were up-scaled to the ecosystem level. NPP was derived from EC measurements using a literature-based ratio of heterotrophic respiration to total ecosystem respiration. Results: BM varied from 211 to 979 g/m2 among the plant community types, decreasing gradually from dry to wet community types. In contrast, BMP was similar between plant community types (162–216 g/m2), except on nearly vegetation-free bare peat surfaces where it was low (38 g/m2). Vascular plant BM turnover rate (BMP:BM, per year) varied from 0.14 to 0.30 among the plant community types, being highest in sedge-dominated hollows. On average 56% of the vascular BM was produced below ground. Mosses, when present, produced on average 31% of the total BM, ranging from 16% to 53% depending on community type. EC-derived NPP was higher than measured BMP due to underestimation of certain components. Conclusions: We found that the diversity of PFTs decreases the spatial variability in productivity of a boreal bog ecosystem. The observed even distribution of BMP resulted from different WT optima and BMP:BM of dwarf shrubs, sedges and Sphagnum species. These differences in biomass turnover rate and species responses to environmental conditions may provide a resilience mechanism for bog ecosystems in changing conditions.
BibTeX:
@article{Korrensalo2018,
  author = {Korrensalo, Aino and Kettunen, Laura and Laiho, Raija and Alekseychik, Pavel and Vesala, Timo and Mammarella, Ivan and Tuittila, Eeva Stiina},
  editor = {Roxburgh, Stephen},
  title = {Boreal bog plant communities along a water table gradient differ in their standing biomass but not their biomass production},
  journal = {Journal of Vegetation Science},
  publisher = {Wiley},
  year = {2018},
  volume = {29},
  number = {2},
  pages = {136--146},
  doi = {10.1111/jvs.12602}
}
Korrensalo A, Männistö E, Alekseychik P, Mammarella I, Rinne J, Vesala T and Tuittila ES (2018), "Small spatial variability in methane emission measured from a wet patterned boreal bog", Biogeosciences. Vol. 15(6), pp. 1749-1761. Copernicus GmbH.
Abstract: We measured methane fluxes of a patterned bog situated in Siikaneva in southern Finland from six different plant community types in three growing seasons (2012-2014) using the static chamber method with chamber exposure of 35 min. A mixed-effects model was applied to quantify the effect of the controlling factors on the methane flux.The plant community types differed from each other in their water level, species composition, total leaf area (LAITOT) and leaf area of aerenchymatous plant species (LAIAER). Methane emissions ranged from-309 to 1254 mg m-2 d-1. Although methane fluxes increased with increasing peat temperature, LAITOT and LAIAER, they had no correlation with water table or with plant community type. The only exception was higher fluxes from hummocks and high lawns than from high hummocks and bare peat surfaces in 2013 and from bare peat surfaces than from high hummocks in 2014. Chamber fluxes upscaled to ecosystem level for the peak season were of the same magnitude as the fluxes measured with the eddy covariance (EC) technique. In 2012 and in August 2014 there was a good agreement between the two methods; in 2013 and in July 2014, the chamber fluxes were higher than the EC fluxes.Net fluxes to soil, indicating higher methane oxidation than production, were detected every year and in all community types. Our results underline the importance of both LAIAER and LAITOT in controlling methane fluxes and indicate the need for automatized chambers to reliably capture localized events to support the more robust EC method.
BibTeX:
@article{Korrensalo2018a,
  author = {Korrensalo, Aino and Männistö, Elisa and Alekseychik, Pavel and Mammarella, Ivan and Rinne, Janne and Vesala, Timo and Tuittila, Eeva Stiina},
  title = {Small spatial variability in methane emission measured from a wet patterned boreal bog},
  journal = {Biogeosciences},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {15},
  number = {6},
  pages = {1749--1761},
  doi = {10.5194/bg-15-1749-2018}
}
Kountouris P, Gerbig C, Rödenbeck C, Karstens U, Koch TF and Heimann M (2018), "Atmospheric CO2 inversions on the mesoscale using data-driven prior uncertainties: Quantification of the European terrestrial CO2 fluxes", Atmospheric Chemistry and Physics. Vol. 18(4), pp. 3047-3064.
Abstract: Optimized biogenic carbon fluxes for Europe were estimated from high-resolution regional-scale inversions, utilizing atmospheric CO2 measurements at 16 stations for the year 2007. Additional sensitivity tests with different data-driven error structures were performed. As the atmospheric network is rather sparse and consequently contains large spatial gaps, we use a priori biospheric fluxes to further constrain the inversions. The biospheric fluxes were simulated by the Vegetation Photosynthesis and Respiration Model (VPRM) at a resolution of 0.1° and optimized against eddy covariance data. Overall we estimate an a priori uncertainty of 0.54 GtC yr-1 related to the poor spatial representation between the biospheric model and the ecosystem sites. The sink estimated from the atmospheric inversions for the area of Europe (as represented in the model domain) ranges between 0.23 and 0.38 GtC yr-1 (0.39 and 0.71 GtC yr-1 up-scaled to geographical Europe). This is within the range of posterior flux uncertainty estimates of previous studies using ground-based observations.
BibTeX:
@article{Kountouris2018,
  author = {Kountouris, Panagiotis and Gerbig, Christoph and Rödenbeck, Christian and Karstens, Ute and Koch, Thomas F. and Heimann, Martin},
  title = {Atmospheric CO2 inversions on the mesoscale using data-driven prior uncertainties: Quantification of the European terrestrial CO2 fluxes},
  journal = {Atmospheric Chemistry and Physics},
  year = {2018},
  volume = {18},
  number = {4},
  pages = {3047--3064},
  url = {https://www.atmos-chem-phys.net/18/3047/2018/},
  doi = {10.5194/acp-18-3047-2018}
}
Kovalets I, Avila R, Mölder M, Kovalets S and Lindroth A (2018), "Verification of a One-Dimensional Model of CO 2 Atmospheric Transport Inside and Above a Forest Canopy Using Observations at the Norunda Research Station", Boundary-Layer Meteorology., feb, 2018. Vol. 168(1), pp. 103-126. Springer Nature.
Abstract: A model of CO 2 atmospheric transport in vegetated canopies is tested against measurements of the flow, as well as CO 2 concentrations at the Norunda research station located inside a mixed pine–spruce forest. We present the results of simulations of wind-speed profiles and CO 2 concentrations inside and above the forest canopy with a one-dimensional model of profiles of the turbulent diffusion coefficient above the canopy accounting for the influence of the roughness sub-layer on turbulent mixing according to Harman and Finnigan (Boundary-Layer Meteorol 129:323–351, 2008; hereafter HF08). Different modelling approaches are used to define the turbulent exchange coefficients for momentum and concentration inside the canopy: (1) the modified HF08 theory—numerical solution of the momentum and concentration equations with a non-constant distribution of leaf area per unit volume; (2) empirical parametrization of the turbulent diffusion coefficient using empirical data concerning the vertical profiles of the Lagrangian time scale and root-mean-square deviation of the vertical velocity component. For neutral, daytime conditions, the second-order turbulence model is also used. The flexibility of the empirical model enables the best fit of the simulated CO 2 concentrations inside the canopy to the observations, with the results of simulations for daytime conditions inside the canopy layer only successful provided the respiration fluxes are properly considered. The application of the developed model for radiocarbon atmospheric transport released in the form of 14CO 2 is presented and discussed.
BibTeX:
@article{Kovalets2018,
  author = {Kovalets, Ivan and Avila, Rodolfo and Mölder, Meelis and Kovalets, Sophia and Lindroth, Anders},
  title = {Verification of a One-Dimensional Model of CO 2 Atmospheric Transport Inside and Above a Forest Canopy Using Observations at the Norunda Research Station},
  journal = {Boundary-Layer Meteorology},
  publisher = {Springer Nature},
  year = {2018},
  volume = {168},
  number = {1},
  pages = {103--126},
  doi = {10.1007/s10546-018-0340-z}
}
Kuhn M, Lundin EJ, Giesler R, Johansson M and Karlsson J (2018), "Emissions from thaw ponds largely offset the carbon sink of northern permafrost wetlands", Scientific Reports., jun, 2018. Vol. 8(1) Springer Nature.
Abstract: Northern regions have received considerable attention not only because the effects of climate change are amplified at high latitudes but also because this region holds vast amounts of carbon (C) stored in permafrost. These carbon stocks are vulnerable to warming temperatures and increased permafrost thaw and the breakdown and release of soil C in the form of carbon dioxide (CO2) and methane (CH4). The majority of research has focused on quantifying and upscaling the effects of thaw on CO2 and CH4 emissions from terrestrial systems. However, small ponds formed in permafrost wetlands following thawing have been recognized as hotspots for C emissions. Here, we examined the importance of small ponds for C fluxes in two permafrost wetland ecosystems in northern Sweden. Detailed flux estimates of thaw ponds during the growing season show that ponds emit, on average (±SD), 279 ± 415 and 7 ± 11 mmol C m-2 d-1 of CO2 and CH4, respectively. Importantly, addition of pond emissions to the total C budget of the wetland decreases the C sink by ˜39%. Our results emphasize the need for integrated research linking C cycling on land and in water in order to make correct assessments of contemporary C balances.
BibTeX:
@article{Kuhn2018,
  author = {Kuhn, McKenzie and Lundin, Erik J. and Giesler, Reiner and Johansson, Margareta and Karlsson, Jan},
  title = {Emissions from thaw ponds largely offset the carbon sink of northern permafrost wetlands},
  journal = {Scientific Reports},
  publisher = {Springer Nature},
  year = {2018},
  volume = {8},
  number = {1},
  doi = {10.1038/s41598-018-27770-x}
}
Kunz M, Lavric J, Gerbig C, Tans P, Neff D, Hummelgärd C, Martin H, Rödjegärd H, Wrenger B and Heimann M (2018), "COCAP: A carbon dioxide analyser for small unmanned aircraft systems", Atmospheric Measurement Techniques. Vol. 11(3), pp. 1833-1849. Copernicus GmbH.
Abstract: Unmanned aircraft systems (UASs) could provide a cost-effective way to close gaps in the observation of the carbon cycle, provided that small yet accurate analysers are available. We have developed a COmpact Carbon dioxide analyser for Airborne Platforms (COCAP). The accuracy of COCAP's carbon dioxide (CO2) measurements is ensured by calibration in an environmental chamber, regular calibration in the field and by chemical drying of sampled air. In addition, the package contains a lightweight thermal stabilisation system that reduces the influence of ambient temperature changes on the CO2 sensor by 2 orders of magnitude. During validation of COCAP's CO2 measurements in simulated and real flights we found a measurement error of 1.2gmolgmolg'1 or better with no indication of bias. COCAP is a self-contained package that has proven well suited for the operation on board small UASs. Besides carbon dioxide dry air mole fraction it also measures air temperature, humidity and pressure. We describe the measurement system and our calibration strategy in detail to support others in tapping the potential of UASs for atmospheric trace gas measurements.
BibTeX:
@article{Kunz2018,
  author = {Kunz, Martin and Lavric, Jost and Gerbig, Christoph and Tans, Pieter and Neff, Don and Hummelgärd, Christine and Martin, Hans and Rödjegärd, Henrik and Wrenger, Burkhard and Heimann, Martin},
  title = {COCAP: A carbon dioxide analyser for small unmanned aircraft systems},
  journal = {Atmospheric Measurement Techniques},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {11},
  number = {3},
  pages = {1833--1849},
  doi = {10.5194/amt-11-1833-2018}
}
Landschützer P, Gruber N, Bakker DC, Stemmler I and Six KD (2018), "Strengthening seasonal marine CO2 variations due to increasing atmospheric CO2", Nature Climate Change., jan, 2018. Vol. 8(2), pp. 146-150. Springer Nature.
Abstract: The increase of atmospheric CO2 (ref. 1 ) has been predicted to impact the seasonal cycle of inorganic carbon in the global ocean 2,3, yet the observational evidence to verify this prediction has been missing. Here, using an observation-based product of the oceanic partial pressure of CO2 (p CO2) covering the past 34 years, we find that the winter-to-summer difference of the p CO2 has increased on average by 2.2 ± 0.4 μatm per decade from 1982 to 2015 poleward of 10° latitude. This is largely in agreement with the trend expected from thermodynamic considerations. Most of the increase stems from the seasonality of the drivers acting on an increasing oceanic p CO2 caused by the uptake of anthropogenic CO2 from the atmosphere. In the high latitudes, the concurrent ocean-acidification-induced changes in the buffer capacity of the ocean enhance this effect. This strengthening of the seasonal winter-to-summer difference pushes the global ocean towards critical thresholds earlier, inducing stress to ocean ecosystems and fisheries 4 . Our study provides observational evidence for this strengthening seasonal difference in the oceanic carbon cycle on a global scale, illustrating the inevitable consequences of anthropogenic CO2 emissions.
BibTeX:
@article{Landschuetzer2018,
  author = {Landschützer, Peter and Gruber, Nicolas and Bakker, Dorothee C.E. and Stemmler, Irene and Six, Katharina D.},
  title = {Strengthening seasonal marine CO2 variations due to increasing atmospheric CO2},
  journal = {Nature Climate Change},
  publisher = {Springer Nature},
  year = {2018},
  volume = {8},
  number = {2},
  pages = {146--150},
  doi = {10.1038/s41558-017-0057-x}
}
Laruelle GG, Cai WJ, Hu X, Gruber N, Mackenzie FT and Regnier P (2018), "Continental shelves as a variable but increasing global sink for atmospheric carbon dioxide", Nature Communications., jan, 2018. Vol. 9(1) Springer Nature.
Abstract: It has been speculated that the partial pressure of carbon dioxide (pCO2) in shelf waters may lag the rise in atmospheric CO2. Here, we show that this is the case across many shelf regions, implying a tendency for enhanced shelf uptake of atmospheric CO2. This result is based on analysis of long-term trends in the air-sea pCO2 gradient (ΔpCO2) using a global surface ocean pCO2 database spanning a period of up to 35 years. Using wintertime data only, we find that ΔpCO2 increased in 653 of the 825 0.5° cells for which a trend could be calculated, with 325 of these cells showing a significant increase in excess of +0.5 μatm yr-1 (p textless 0.05). Although noisier, the deseasonalized annual data suggest similar results. If this were a global trend, it would support the idea that shelves might have switched from a source to a sink of CO2 during the last century.
BibTeX:
@article{Laruelle2018,
  author = {Laruelle, Goulven G. and Cai, Wei Jun and Hu, Xinping and Gruber, Nicolas and Mackenzie, Fred T. and Regnier, Pierre},
  title = {Continental shelves as a variable but increasing global sink for atmospheric carbon dioxide},
  journal = {Nature Communications},
  publisher = {Springer Nature},
  year = {2018},
  volume = {9},
  number = {1},
  doi = {10.1038/s41467-017-02738-z}
}
Laudon H and Sponseller RA (2018), "How landscape organization and scale shape catchment hydrology and biogeochemistry: insights from a long-term catchment study", Wiley Interdisciplinary Reviews: Water., nov, 2018. Vol. 5(2), pp. e1265. Wiley.
Abstract: Catchment science plays a critical role in the protection of water resources in the face of ongoing changes in climate, long-range transport of air pollutants, and land use. Addressing these challenges, however, requires improved understand- ing of how, when, and where changes in water quantity and quality occur within river networks. To reach these goals, we must recognize how different catchment features are organized to regulate surface chemistry at multiple scales, from pro- cesses controlling headwaters, to the downstream mixing of water from multiple landscape sources and deep aquifers. Here we synthesize 30-years of hydrologi- cal and biogeochemical research from the Krycklan catchment study (KCS) in northern Sweden to demonstrate the benefits of coupling long-term monitoring with multi-scale research to advance our understanding of catchment function- ing across space and time. We show that the regulation of hydrological and bio- geochemical patterns in the KCS can be decomposed into four, hierarchically structured landscape features that include: (1) transmissivity and reactivity of dominant source layers within riparian soils, (2) spatial arrangement of groundwater input zones that govern water and solute fluxes at reach- to segment-scales, (3) landscape scale heterogeneity (forests, mires, and lakes) that generates unique biogeochemical signals downstream, and (4) broad-scale mixing of surface streams with deep groundwater contributions. While this set of features are perhaps specific to the study region, analogous hierarchical controls are likely to be wide- spread. Resolving these scale dependent processes is important for predicting how, when, and where different environmental changes may influence patterns of surface water chemistry within river networks.
BibTeX:
@article{Laudon2018,
  author = {Laudon, Hjalmar and Sponseller, Ryan A.},
  title = {How landscape organization and scale shape catchment hydrology and biogeochemistry: insights from a long-term catchment study},
  journal = {Wiley Interdisciplinary Reviews: Water},
  publisher = {Wiley},
  year = {2018},
  volume = {5},
  number = {2},
  pages = {e1265},
  doi = {10.1002/wat2.1265}
}
Le Quéré C, Andrew RM, Friedlingstein P, Sitch S, Pongratz J, Manning AC, Ivar Korsbakken J, Peters GP, Canadell JG, Jackson RB, Boden TA, Tans PP, Andrews OD, Arora VK, Bakker DC, Barbero L, Becker M, Betts RA, Bopp L, Chevallier F, Chini LP, Ciais P, Cosca CE, Cross J, Currie K, Gasser T, Harris I, Hauck J, Haverd V, Houghton RA, Hunt CW, Hurtt G, Ilyina T, Jain AK, Kato E, Kautz M, Keeling RF, Klein Goldewijk K, Körtzinger A, Landschützer P, Lefèvre N, Lenton A, Lienert S, Lima I, Lombardozzi D, Metzl N, Millero F, Monteiro PM, Munro DR, Nabel JE, Nakaoka SI, Nojiri Y, Antonio Padin X, Peregon A, Pfeil B, Pierrot D, Poulter B, Rehder G, Reimer J, Rödenbeck C, Schwinger J, Séférian R, Skjelvan I, Stocker BD, Tian H, Tilbrook B, Tubiello FN, Laan-Luijkx IT, Werf GR, Van Heuven S, Viovy N, Vuichard N, Walker AP, Watson AJ, Wiltshire AJ, Zaehle S and Zhu D (2018), "Global Carbon Budget 2017", Earth System Science Data., mar, 2018. Vol. 10(1), pp. 405-448. Copernicus GmbH.
Abstract: Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere-the "global carbon budget"-is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. CO2 emissions from fossil fuels and industry (EFF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (ELUC), mainly deforestation, are based on land-cover change data and bookkeeping models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1δ. For the last decade available (2007-2016), EFF was 9.4±0.5 GtC yr-1, ELUC 1.3±0.7 GtC yr-1, GATM 4.7±0.1 GtC yr-1, SOCEAN 2.4±0.5 GtC yr-1, and SLAND 3.0±0.8 GtC yr-1, with a budget imbalance BIM of 0.6 GtC yr-1 indicating overestimated emissions and/or underestimated sinks. For year 2016 alone, the growth in EFF was approximately zero and emissions remained at 9.9±0.5 GtC yr-1. Also for 2016, ELUC was 1.3±0.7 GtC yr-1, GATM was 6.1±0.2 GtC yr-1, SOCEAN was 2.6±0.5 GtC yr-1, and SLAND was 2.7±1.0 GtC yr-1, with a small BIM of-0.3 GtC. GATM continued to be higher in 2016 compared to the past decade (2007-2016), reflecting in part the high fossil emissions and the small SLAND consistent with El Ninõ conditions. The global atmospheric CO2 concentration reached 402.8±0.1 ppm averaged over 2016. For 2017, preliminary data for the first 6-9 months indicate a renewed growth in EFF of C2.0% (range of 0.8 to 3.0 %) based on national emissions projections for China, USA, and India, and projections of gross domestic product (GDP) corrected for recent changes in the carbon intensity of the economy for the rest of the world. This living data update documents changes in the methods and data sets used in this new global carbon budget compared with previous publications of this data set (Le Quéré et al., 2016, 2015b, a, 2014, 2013). All results presented here can be downloaded from https://doi.org/10.18160/GCP-2017 (GCP, 2017).
BibTeX:
@article{LeQuere2018,
  author = {Le Quéré, Corinne and Andrew, Robbie M. and Friedlingstein, Pierre and Sitch, Stephen and Pongratz, Julia and Manning, Andrew C. and Ivar Korsbakken, Jan and Peters, Glen P. and Canadell, Josep G. and Jackson, Robert B. and Boden, Thomas A. and Tans, Pieter P. and Andrews, Oliver D. and Arora, Vivek K. and Bakker, Dorothee C.E. and Barbero, Leticia and Becker, Meike and Betts, Richard A. and Bopp, Laurent and Chevallier, Frédéric and Chini, Louise P. and Ciais, Philippe and Cosca, Catherine E. and Cross, Jessica and Currie, Kim and Gasser, Thomas and Harris, Ian and Hauck, Judith and Haverd, Vanessa and Houghton, Richard A. and Hunt, Christopher W. and Hurtt, George and Ilyina, Tatiana and Jain, Atul K. and Kato, Etsushi and Kautz, Markus and Keeling, Ralph F. and Klein Goldewijk, Kees and Körtzinger, Arne and Landschützer, Peter and Lefèvre, Nathalie and Lenton, Andrew and Lienert, Sebastian and Lima, Ivan and Lombardozzi, Danica and Metzl, Nicolas and Millero, Frank and Monteiro, Pedro M.S. and Munro, David R. and Nabel, Julia E.M.S. and Nakaoka, Shin Ichiro and Nojiri, Yukihiro and Antonio Padin, X. and Peregon, Anna and Pfeil, Benjamin and Pierrot, Denis and Poulter, Benjamin and Rehder, Gregor and Reimer, Janet and Rödenbeck, Christian and Schwinger, Jörg and Séférian, Roland and Skjelvan, Ingunn and Stocker, Benjamin D. and Tian, Hanqin and Tilbrook, Bronte and Tubiello, Francesco N. and Laan-Luijkx, Ingrid T.Vander and Werf, Guido R.Vander and Van Heuven, Steven and Viovy, Nicolas and Vuichard, Nicolas and Walker, Anthony P. and Watson, Andrew J. and Wiltshire, Andrew J. and Zaehle, Sönke and Zhu, Dan},
  title = {Global Carbon Budget 2017},
  journal = {Earth System Science Data},
  publisher = {Copernicus GmbH},
  year = {2018},
  volume = {10},
  number = {1},
  pages = {405--448},
  url = {https://doi.org/10.5194/essd-10-405-2018 https://www.earth-syst-sci-data.net/10/405/2018/},
  doi = {10.5194/essd-10-405-2018}
}
Ledesma JL, Futter MN, Blackburn M, Lidman F, Grabs T, Sponseller RA, Laudon H, Bishop KH and Köhler SJ (2018), "Towards an Improved Conceptualization of Riparian Zones in Boreal Forest Headwaters", Ecosystems., apr, 2018. Vol. 21(2), pp. 297-315. Springer Nature.
Abstract: The boreal ecoregion supports about one-third of the world's forest. Over 90% of boreal forest streams are found in headwaters, where terrestrial–aquatic interfaces are dominated by organic matter (OM)-rich riparian zones (RZs). Because these transition zones are key features controlling catchment biogeochemistry, appropriate RZ conceptualizations are needed to sustainably manage surface water quality in the face of a changing climate and increased demands for forest biomass. Here we present a simple, yet comprehensive, conceptualization of RZ function based on hydrological connectivity, biogeochemical processes, and spatial heterogeneity. We consider four dimensions of hydrological connectivity: (1) laterally along hillslopes, (2) longitudinally along the stream, (3) vertically down the riparian profile, and (4) temporally through event-based and seasonal changes in hydrology. Of particular importance is the vertical dimension, characterized by a ‘Dominant Source Layer' that has the highest contribution to solute and water fluxes to streams. In addition to serving as the primary source of OM to boreal streams, RZs shape water chemistry through two sets of OM-dependent biogeochemical processes: (1) transport and retention of OM-associated material and (2) redox-mediated transformations controlled by RZ water residence time and availability of labile OM. These processes can lead to both retention and release of pollutants. Variations in width, hydrological connectivity, and OM storage drive spatial heterogeneity in RZ biogeochemical function. This conceptualization provides a useful theoretical framework for environmental scientists and ecologically sustainable and economically effective forest management in the boreal region and elsewhere, where forest headwaters are dominated by low-gradient, OM-rich RZs.
BibTeX:
@article{Ledesma2018,
  author = {Ledesma, José L.J. and Futter, Martyn N. and Blackburn, M. and Lidman, Fredrik and Grabs, Thomas and Sponseller, Ryan A. and Laudon, Hjalmar and Bishop, Kevin H. and Köhler, Stephan J.},
  title = {Towards an Improved Conceptualization of Riparian Zones in Boreal Forest Headwaters},
  journal = {Ecosystems},
  publisher = {Springer Nature},
  year = {2018},
  volume = {21},
  number = {2},
  pages = {297--315},
  doi = {10.1007/s10021-017-0149-5}
}
Leip A, Skiba U, Vermeulen A and Thompson RL (2018), "A complete rethink is needed on how greenhouse gas emissions are quantified for national reporting", Atmospheric Environment., feb, 2018. Vol. 174, pp. 237-240.
BibTeX:
@article{Leip2018,
  author = {Leip, Adrian and Skiba, Ute and Vermeulen, Alex and Thompson, Rona L.},
  title = {A complete rethink is needed on how greenhouse gas emissions are quantified for national reporting},
  journal = {Atmospheric Environment},
  year = {2018},
  volume = {174},
  pages = {237--240},
  url = {http://linkinghub.elsevier.com/retrieve/pii/S1352231017308300},
  doi = {10.1016/j.atmosenv.2017.12.006}
}
Leufen LH and Schädler G (2018), "Calculating the turbulent fluxes in the atmospheric surface layer with neural networks", Geoscientific Model Development Discussions., nov, 2018. , pp. 1-22. Copernicus GmbH.
Abstract: textlessptextgreatertextlessstrongtextgreaterAbstract.textless/strongtextgreater The turbulent fluxes of momentum, heat and water vapour link the Earth's surface with the atmosphere. The correct modelling of the flux interactions between these two systems with very different time scales is therefore vital for climate (resp. Earth system) models. Conventionally, these fluxes are modelled using Monin–Obukhov similarity theory (MOST) with stability functions derived from a small number of field experiments; this results in a range of formulations of these functions and thus also in the flux calculations; furthermore, the underlying equations are non-linear and have to be solved iteratively at each time step of the model. For these reasons, we tried here a different approach, namely using an artificial neural network (ANN) to calculate the fluxes resp. the scaling quantities textlessitextgreaterutextless/itextgreatertextlesssubtextgreater*textless/subtextgreater and textlessitextgreaterθtextless/itextgreatertextlesssubtextgreater*textless/subtextgreater, thus avoiding explicit formulas for the stability functions. The network was trained and validated with multi-year datasets from seven grassland, forest and wetland sites worldwide using the Broyden–Fletcher–Goldfarb–Shanno (BFGS) quasi-Newton backpropagation algorithm and six-fold cross validation. Extensive sensitivity tests showed that an ANN with six input variables and one hidden layer gave results comparable to (and in some cases even slightly better than) the standard method. Similar satisfying results were obtained when the ANN routine was implemented in a one-dimensional stand alone land surface model (LSM), opening the way to implementation in three-dimensional climate models. In case of the one-dimensional LSM, no CPU time was saved when using the ANN version, since the small time step of the standard version required only one iteration in most cases. This could be different in models with longer time steps, e.g. global climate models.textless/ptextgreater
BibTeX:
@article{Leufen2018,
  author = {Leufen, Lukas Hubert and Schädler, Gerd},
  title = {Calculating the turbulent fluxes in the atmospheric surface layer with neural networks},
  journal = {Geoscientific Model Development Discussions},
  publisher = {Copernicus GmbH},
  year = {2018},
  pages = {1--22},
  doi = {10.5194/gmd-2018-263}
}
Li H and Ilyina T (2018), "Current and Future Decadal Trends in the Oceanic Carbon Uptake Are Dominated by Internal Variability", Geophysical Research Letters., jan, 2018. Vol. 45(2), pp. 916-925. American Geophysical Union (AGU).
Abstract: We investigate the internal decadal variability of the ocean carbon uptake using 100 ensemble simulations based on the Max Planck Institute Earth system model (MPI-ESM). We find that on decadal time scales, internal variability (ensemble spread) is as large as the forced temporal variability (ensemble mean), and the largest internal variability is found in major carbon sink regions, that is, the 50–65°S band of the Southern Ocean, the North Pacific, and the North Atlantic. The MPI-ESM ensemble produces both positive and negative 10 year trends in the ocean carbon uptake in agreement with observational estimates. Negative decadal trends are projected to occur in the future under RCP4.5 scenario. Due to the large internal variability, the Southern Ocean and the North Pacific require the most ensemble members (more than 53 and 46, respectively) to reproduce the forced decadal trends. This number increases up to 79 in future decades as CO2 emission trajectory changes.
BibTeX:
@article{Li2018,
  author = {Li, Hongmei and Ilyina, Tatiana},
  title = {Current and Future Decadal Trends in the Oceanic Carbon Uptake Are Dominated by Internal Variability},
  journal = {Geophysical Research Letters},
  publisher = {American Geophysical Union (AGU)},
  year = {2018},
  volume = {45},
  number = {2},
  pages = {916--925},
  doi = {10.1002/2017GL075370}
}
Lindroth A, Holst J, Heliasz M, Vestin P, Lagergren F, Biermann T, Cai Z and Mölder M (2018), "Effects of low thinning on carbon dioxide fluxes in a mixed hemiboreal forest", Agricultural and Forest Meteorology., nov, 2018. Vol. 262, pp. 59-70. Elsevier BV.
Abstract: We used eddy-covariance (EC) measurements of net ecosystem exchange (NEE) above canopy to assess the effects of thinning on CO2 fluxes at the ICOS Sweden site Norunda in central Sweden. This forest site consists of mixed pine and spruce stands approx. 100 years old. The thinning during late autumn 2008, performed in a semi-circle from the mast extending 200 m outwards harvested about 25% of the volume. Measurements were conducted from 2007 to 2016 and thus, above canopy fluxes were recorded two years before and eight years after the thinning. We also measured the net flux from the forest floor with automatic chambers in three locations and with below-canopy EC during shorter periods before and after thinning. The chamber measurements during the first part of the growing season after thinning showed strongly enhanced effluxes in the order of 150–250% of the pre-thinning values. These chamber measurements were made on drier places within the thinned area because waterlogging made it impossible to use chambers at all available locations. The below-canopy EC measurements, which had a larger footprint as compared to the chambers, showed less enhanced fluxes (in the order of 35%). This footprint included also wetter areas. The above canopy EC measurements showed a reduction of daytime net flux by approx. 30% during the first summer after thinning. The median growing season fluxes then slowly increased but were not restored to the pre-thinning levels eight years after thinning. There was also a small decrease in growing season ecosystem respiration during the first summer after thinning and with a continued decreasing trend over time. It was concluded that this decrease in respiration was caused by successively decreasing decomposition of coarse organic substrates resulting from the thinning. This respiration decrease over time persisted even under gradual biomass increase, which otherwise would indicate increasing autotrophic respiration. The light-response and respiration models fitted to all data did not show any trends in daytime or nighttime fluxes so the conclusion was that the trends were caused by the thinning and not because of trends in meteorological drivers. The annual values contrasted with the summertime results since only a minor effect was observed on the annual NEE. Both ecosystem respiration and gross primary productivity were reduced as an effect of thinning. We explained the different summertime versus annual effects to be caused by the decrease in ecosystem respiration since respiration is dominating the NEE during non-growing season periods when photosynthesis is very low or even zero. Our results are a strong indication that the NEE of a forest could be maintained over time with harvesting practices that avoids clear-cutting and thereby enhance the total carbon uptake of forests.
BibTeX:
@article{Lindroth2018,
  author = {Lindroth, Anders and Holst, Jutta and Heliasz, Michal and Vestin, Patrik and Lagergren, Fredrik and Biermann, Tobias and Cai, Zhanzhang and Mölder, Meelis},
  title = {Effects of low thinning on carbon dioxide fluxes in a mixed hemiboreal forest},
  journal = {Agricultural and Forest Meteorology},
  publisher = {Elsevier BV},
  year = {2018},
  volume = {262},
  pages = {59--70},
  doi = {10.1016/j.agrformet.2018.06.021}
}
López-Ballesteros A, Beck J, Bombelli A, Grieco E, Lorencová EK, Merbold L, Brümmer C, Hugo W, Scholes R, Vačkář D, Vermeulen A, Acosta M, Butterbach-Bahl K, Helmschrot J, Kim DG, Jones M, Jorch V, Pavelka M, Skjelvan I and Saunders M (2018), "Towards a feasible and representative pan-African research infrastructure network for GHG observations", Environmental Research Letters., jul, 2018. Vol. 13(8)
Abstract: There is currently a lack of representative, systematic and harmonised greenhouse gas (GHG) observations covering the variety of natural and human-altered biomes that occur in Africa. This impedes the long-term assessment of the drivers of climate change, in addition to their impacts and feedback loops at the continental scale, but also limits our understanding of the contribution of the African continent to the global carbon (C) cycle. Given the current and projected transformation of socio-economic conditions in Africa (i.e. the increasing trend of urbanisation and population growth) and the adverse impacts of climate change, the development of a GHG research infrastructure (RI) is needed to support the design of suitable mitigation and adaptation strategies required to assure food, fuel, nutrition and economic security for the African population. This paper presents the initial results of the EU-African SEACRIFOG project, which aims to design a GHG observation RI for Africa. The first stages of this project included the identification and engagement of key stakeholders, the definition of the conceptual monitoring framework and an assessment of existing infrastructural capacity. Feedback from stakeholder sectors was obtained through three Stakeholder Consultation Workshops held in Kenya, Ghana and Zambia. Main concerns identified were data quality and accessibility, the need for capacity building and networking among the scientific community, and adaptation to climate change, which was confirmed to be a priority for Africa. This feedback in addition to input from experts in the atmospheric, terrestrial and oceanic thematic areas, facilitated the selection of a set of 'essential variables' that need to be measured in the future environmental RI. An inventory of 47 existing and planned networks across the continent allowed for an assessment of the current RIs needs and gaps in Africa. Overall, the development of a harmonised and standardised pan-African RI will serve to address the continent's primary societal and scientific challenges through a potential cross-domain synergy among existing and planned networks at regional, continental and global scales.
BibTeX:
@article{LopezBallesteros2018,
  author = {López-Ballesteros, Ana and Beck, Johannes and Bombelli, Antonio and Grieco, Elisa and Lorencová, Eliška Krkoška and Merbold, Lutz and Brümmer, Christian and Hugo, Wim and Scholes, Robert and Vačkář, David and Vermeulen, Alex and Acosta, Manuel and Butterbach-Bahl, Klaus and Helmschrot, Jörg and Kim, Dong Gill and Jones, Michael and Jorch, Veronika and Pavelka, Marian and Skjelvan, Ingunn and Saunders, Matthew},
  title = {Towards a feasible and representative pan-African research infrastructure network for GHG observations},
  journal = {Environmental Research Letters},
  year = {2018},
  volume = {13},
  number = {8},
  url = {http://iopscience.iop.org/article/10.1088/1748-9326/aad66c},
  doi = {10.1088/1748-9326/aad66c}
}
López-Blanco E, Lund M, Christensen TR, Tamstorf MP, Smallman TL, Slevin D, Westergaard-Nielsen A, Hansen BU, Abermann J and Williams M (2018), "Plant Traits are Key Determinants in Buffering the Meteorological Sensitivity of Net Carbon Exchanges of Arctic Tundra", Journal of Geophysical Research: Biogeosciences., sep, 2018. Vol. 123(9), pp. 2675-2694. American Geophysical Union (AGU).
Abstract: The climate sensitivity of carbon (C) cycling in Arctic terrestrial ecosystems is a major unknown in the Earth system. There is a lack of knowledge about the mechanisms that drive the interactions between photosynthesis, respiration, and changes in C stocks across full annual cycles in Arctic tundra. We use a calibrated and validated model (soil-plant-atmosphere; SPA) to estimate net ecosystem exchange (NEE), gross primary production (GPP), ecosystem respiration (Reco), and internal C processing across eight full years. SPA's carbon flux estimates are validated with observational data obtained from the Greenland Ecosystem Monitoring program in West Greenland tundra. Overall, the model explained 73%, 73%, and 50% of the variance in NEE, GPP, and Reco, respectively, and 85% of the plant greenness variation. Flux data highlighted the insensitivity of growing season NEE to interannual meteorological variability, due to compensatory responses of photosynthesis and ecosystem respiration. In this modelling study, we show that this NEE buffering is the case also for full annual cycles. We show through a sensitivity analysis that plant traits related to nitrogen are likely key determinants in the compensatory response, through simulated links to photosynthesis and plant respiration. Interestingly, we found a similar temperature sensitivity of the trait-flux couplings for GPP and Reco, suggesting that plant traits drive the stabilization of NEE. Further, model analysis indicated that wintertime periods decreased the C sink by 60%, mostly driven by litter heterotrophic respiration. This result emphasizes the importance of wintertime periods and allows a more comprehensive understanding of full annual C dynamics.
BibTeX:
@article{LopezBlanco2018,
  author = {López-Blanco, Efrén and Lund, Magnus and Christensen, Torben R. and Tamstorf, Mikkel P. and Smallman, Thomas L. and Slevin, Darren and Westergaard-Nielsen, Andreas and Hansen, Birger U. and Abermann, Jakob and Williams, Mathew},
  title = {Plant Traits are Key Determinants in Buffering the Meteorological Sensitivity of Net Carbon Exchanges of Arctic Tundra},
  journal = {Journal of Geophysical Research: Biogeosciences},
  publisher = {American Geophysical Union (AGU)},
  year = {2018},
  volume = {123},
  number = {9},
  pages = {2675--2694},
  doi = {10.1029/2018JG004386}
}
Loustau D, Altimir N, Barbaste M, Gielen B, Jiménez SM, Klumpp K, Linder S, Matteucci G, Merbold L, De Beek MO, Soulé P, Thimonier A, Vincke C and Waldner P (2018), "Sampling and collecting foliage elements for the determination of the foliar nutrients in ICOS ecosystem stations", International Agrophysics., dec, 2018. Vol. 32(4), pp. 665-676.
Abstract: The nutritional status of plant canopies in terms of nutrients (C, N, P, K, Ca, Mg, Mn, Fe, Cu, Zn) exerts a strong influence on the carbon cycle and energy balance of terrestrial ecosystems. Therefore, in order to account for the spatial and temporal variations in nutritional status of the plant species composing the canopy, we detail the methodology applied to achieve consistent time-series of leaf mass to area ratio and nutrient content of the foliage within the footprint of the Integrated Carbon Observation System Ecosystem stations. The guidelines and defi-nitions apply to most terrestrial ecosystems.
BibTeX:
@article{Loustau2018,
  author = {Loustau, Denis and Altimir, Nuria and Barbaste, Mireille and Gielen, Bert and Jiménez, Sara Maraʼnón and Klumpp, Katja and Linder, Sune and Matteucci, Giorgio and Merbold, Lutz and De Beek, Marteen Op and Soulé, Patrice and Thimonier, Anne and Vincke, Caroline and Waldner, Peter},
  title = {Sampling and collecting foliage elements for the determination of the foliar nutrients in ICOS ecosystem stations},
  journal = {International Agrophysics},
  year = {2018},
  volume = {32},
  number = {4},
  pages = {665--676},
  url = {https://content.sciendo.com/view/journals/intag/32/4/article-p665.xml},
  doi = {10.1515/intag-2017-0038}
}
Lucas-Moffat AM, Huth V, Augustin J, Brümmer C, Herbst M and Kutsch WL (2018), "Towards pairing plot and field scale measurements in managed ecosystems: Using eddy covariance to cross-validate CO2 fluxes modeled from manual chamber campaigns", Agricultural and Forest Meteorology. Vol. 256-257, pp. 362-378.
Abstract: Manual chamber campaigns are a versatile method to study management effects at plot scale in factorial experiments. The eddy covariance technique has the advantage of continuous measurements but it requires large homogeneous areas. By pairing the two techniques, the uncertainties of the CO2 fluxes modeled from the chamber campaigns can be quantified through cross-validation with the continuous eddy covariance data. This is particularly important in managed ecosystems with high temporal dynamics. At our agricultural site in Northern Germany, we installed both techniques in parallel for two crop cultivation periods, winter oilseed rape in 2012/13 and winter wheat in 2013/14. First, we compared measured net CO2 exchange (NEE) obtained from the closed chambers with the corresponding half-hourly fluxes from the eddy covariance technique. Despite largely different footprints and measurement windows, the measured fluxes were highly correlated (R2 = 0.83 in 2012/13 und R2 = 0.93 in 2013/14). Interpolating from chamber campaigns to the entire measurement period is commonly performed by modeling half-hourly fluxes based on non-linear regressions for photosynthesis and respiration. These modeled fluxes were compared to the fluxes measured with the eddy covariance technique. To understand the observed differences, we performed five modeling setups: 1) Non-linear regressions based algorithm with default settings, 2) non-linear regressions with expert settings, 3) purely empirical modeling with artificial neural networks, 4) cross-validation using eddy covariance measurements as campaign fluxes on original campaign days, and 5) cross-validation on weekly campaign days. The modeled seasonal course of daily NEE agreed well with the eddy covariance measurements for all five setups (R2 from 0.77 to 0.92) but with periods of systematic offsets in the range of ±5 g C m−2 day−1. Though the pattern of the offsets was different, all setups had comparable root mean square errors around 1.5 g C m−2 day-1 despite having opposite limitations. Cross-validation by simulating campaigns with artificial gaps from the continuous eddy dataset in setup 4) and 5) resulted in bias errors of around 0.4 g C m−2 day−1. This translates to a total uncertainty on annual NEE of around ±175 g C m−2 a−1 purely from the modeling, i.e. the interpolation in-between campaigns. By leave-one-campaign-out scenarios, the sensitivity to single campaigns was examined. The mean effect on the annual total was higher for setup 4 (30 g C m−2) with the original number of campaigns than for setup 5 (9 g C m−2) with four times more campaigns. Furthermore, the interpolation in-between the campaigns can be improved by deriving vegetation proxies from the continuous eddy covariance measurements, such as an effective green area index (GAI) presented herein.
BibTeX:
@article{LucasMoffat2018,
  author = {Lucas-Moffat, Antje M. and Huth, Vytas and Augustin, Jürgen and Brümmer, Christian and Herbst, Mathias and Kutsch, Werner L.},
  title = {Towards pairing plot and field scale measurements in managed ecosystems: Using eddy covariance to cross-validate CO2 fluxes modeled from manual chamber campaigns},
  journal = {Agricultural and Forest Meteorology},
  year = {2018},
  volume = {256-257},
  pages = {362--378},
  doi = {10.1016/j.agrformet.2018.01.023}
}
Lund M (2018), "Uncovering the unknown - Climate interactions in a changing arctic tundra", Environmental Research Letters., jun, 2018. Vol. 13(6), pp. 61001. IOP Publishing.
BibTeX:
@article{Lund2018,
  author = {Lund, Magnus},
  title = {Uncovering the unknown - Climate interactions in a changing arctic tundra},
  journal = {Environmental Research Letters},
  publisher = {IOP Publishing},
  year = {2018},
  volume = {13},
  number = {6},
  pages = {61001},
  doi = {10.1088/1748-9326/aac63f}
}
Lundström J, Öhman K and Laudon H (2018), "Comparing buffer zone alternatives in forest planning using a decision support system", Scandinavian Journal of Forest Research., feb, 2018. Vol. 33(5), pp. 493-501. Informa UK Limited.
Abstract: Increased awareness of the connection between forest management activities and negative effects on water quality means that forestry needs to consider its potential impact on the aquatic environment when planning operations. Protective buffer zones are effective, but their design can vary. To be able to incorporate up-to-date scientific theory into practical applications easy-to-use planning tools are needed. In this study, we evaluate different buffer zone alternatives by using the freely available decision support system Heureka. The consequences on both economic and ecological values over a time period of 100 years were evaluated for two buffer zone approaches and three management alternatives within the buffer zones. Results indicated that there is a trade-off between economic and ecological values when managing the buffer zones. To be able to perform the analyses within Heureka, a new tool was developed. This software development provides access to a forest planning tool that can help improve nature conservation.
BibTeX:
@article{Lundstroem2018,
  author = {Lundström, Johanna and Öhman, Karin and Laudon, Hjalmar},
  title = {Comparing buffer zone alternatives in forest planning using a decision support system},
  journal = {Scandinavian Journal of Forest Research},
  publisher = {Informa UK Limited},
  year = {2018},
  volume = {33},
  number = {5},
  pages = {493--501},
  doi = {10.1080/02827581.2018.1441900}
}
Malhotra A, Moore TR, Limpens J and Roulet NT (2018), "Post-thaw variability in litter decomposition best explained by microtopography at an ice-rich permafrost peatland", Arctic, Antarctic, and Alpine Research., jan, 2018. Vol. 50(1), pp. e1415622. Informa UK Limited.
Abstract: Litter decomposition, a key process by which recently fixed carbon is lost from ecosystems, is a function of environmental conditions and plant community characteristics. In ice-rich peatlands, permafrost thaw introduces high variability in both abiotic and biotic factors, both of which may affect litter decomposition rates in different ways. Can the existing conceptual frameworks of litter decomposition and its controls be applied across a structurally heterogeneous thaw gradient? We investigated the variability in litter decomposition and its predictors at the Stordalen subarctic peatland in northern Sweden. We measured in situ decomposition of representative litter and environments using litter bags throughout two years. We found highly variable litter decomposition rates with turnover times ranging from five months to four years. Surface elevation was a strong correlate of litter decomposition across the landscape, likely as it integrates multiple environmental and plant community changes brought about by thaw. There was faster decomposition but also more mass remaining after two years in thawed areas relative to permafrost areas, suggesting faster initial loss of carbon but more storage into the slow-decomposing carbon pool. Our results highlight mechanisms and predictors of carbon cycle changes in ice-rich peatlands following permafrost thaw.
BibTeX:
@article{Malhotra2018,
  author = {Malhotra, Avni and Moore, Tim R. and Limpens, Juul and Roulet, Nigel T.},
  title = {Post-thaw variability in litter decomposition best explained by microtopography at an ice-rich permafrost peatland},
  journal = {Arctic, Antarctic, and Alpine Research},
  publisher = {Informa UK Limited},
  year = {2018},
  volume = {50},
  number = {1},
  pages = {e1415622},
  doi = {10.1080/15230430.2017.1415622}
}
Martínez B, Sanchez-Ruiz S, Gilabert MA, Moreno A, Campos-Taberner M, García-Haro FJ, Trigo IF, Aurela M, Brümmer C, Carrara A, De Ligne A, Gianelle D, Grünwald T, Limousin JM, Lohila A, Mammarella I, Sottocornola M, Steinbrecher R and Tagesson T (2018), "Retrieval of daily gross primary production over Europe and Africa from an ensemble of SEVIRI/MSG products", International Journal of Applied Earth Observation and Geoinformation., mar, 2018. Vol. 65, pp. 124-136. Elsevier BV.
Abstract: The main goal of this paper is to derive a method for a daily gross primary production (GPP) product over Europe and Africa taking the full advantage of the SEVIRI/MSG satellite products from the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) sensors delivered from the Satellite Application Facility for Land Surface Analysis (LSA SAF) system. Special attention is paid to model the daily GPP response from an optimized Montheith's light use efficiency model under dry conditions by controlling water shortage limitations from the actual evapotranspiration and the potential evapotranspiration (PET). The PET was parameterized using the mean daily air temperature at 2 m (Ta) from ERA-Interim data. The GPP product (MSG GPP) was produced for 2012 and assessed by direct site-level comparison with GPP from eddy covariance data (EC GPP). MSG GPP presents relative bias errors lower than 40% for the most forest vegetation types with a high agreement (r textgreater 0.7) when compared with EC GPP. For drylands, MSG GPP reproduces the seasonal variations related to water limitation in a good agreement with site level GPP estimates (RMSE = 2.11 g m−2 day−1; MBE = −0.63 g m−2 day−1), especially for the dry season. A consistency analysis against other GPP satellite products (MOD17A2 and FLUXCOM) reveals a high consistency among products (RMSD textless 1.5 g m−2 day−1) over Europe, North and South Africa. The major GPP disagreement arises over moist biomes in central Africa (RMSD textgreater 3.0 g m−2 day−1) and over dry biomes with MSG GPP estimates lower than FLUXCOM (MBD up to −3.0 g m−2 day−1). This newly derived product has the potential for analysing spatial patterns and temporal dynamics of GPP at the MSG spatial resolutions on a daily basis allowing to better capture the GPP dynamics and magnitude.
BibTeX:
@article{Martinez2018,
  author = {Martínez, B. and Sanchez-Ruiz, S. and Gilabert, M. A. and Moreno, A. and Campos-Taberner, M. and García-Haro, F. J. and Trigo, I. F. and Aurela, M. and Brümmer, C. and Carrara, A. and De Ligne, A. and Gianelle, D. and Grünwald, T. and Limousin, J. M. and Lohila, A. and Mammarella, I. and Sottocornola, M. and Steinbrecher, R. and Tagesson, T.},
  title = {Retrieval of daily gross primary production over Europe and Africa from an ensemble of SEVIRI/MSG products},
  journal = {International Journal of Applied Earth Observation and Geoinformation},
  publisher = {Elsevier BV},
  year = {2018},
  volume = {65},
  pages = {124--136},
  url = {https://doi.org/10.1016/j.jag.2017.10.011 http://linkinghub.elsevier.com/retrieve/pii/S0303243417302301},
  doi = {10.1016/j.jag.2017.10.011}
}
Mauder M, Genzel S, Fu J, Kiese R, Soltani M, Steinbrecher R, Zeeman M, Banerjee T, De Roo F and Kunstmann H (2018), "Evaluation of energy balance closure adjustment methods by independent evapotranspiration estimates from lysimeters and hydrological simulations", Hydrological Processes., dec, 2018. Vol. 32(1), pp. 39-50. Wiley.
Abstract: Non-closure of the surface energy balance is a frequently observed phenomenon of hydrometeorological field measurements, when using the eddy-covariance method, which can be ascribed to an underestimation of the turbulent fluxes. Several approaches have been proposed in order to adjust the measured fluxes for this apparent systematic error. However, there are uncertainties about partitioning of the energy balance residual between the sensible and latent heat flux and whether such a correction should be applied on 30-min data or longer time scales. The data for this study originate from two grassland sites in southern Germany, where measurements from weighable lysimeters are available as reference. The adjusted evapotranspiration rates are also compared with joint energy and water balance simulations using a physically based distributed hydrological model. We evaluate two adjustment methods: the first one preserves the Bowen ratio and the correction factor is determined on a daily basis. The second one attributes a smaller portion of the residual energy to the latent heat flux than to the sensible heat flux for closing the energy balance for every 30-min flux integration interval. Both methods lead to an improved agreement of the eddy-covariance based fluxes with the independent lysimeter estimates and the physically based model simulations. The first method results in a better comparability of evapotranspiration rates, and the second method leads to a smaller overall bias. These results are similar between both sites despite considerable differences in terrain complexity and grassland management. Moreover, we found that a daily adjustment factor leads to less scatter than a complete partitioning of the residual for every half-hour time interval. The vertical temperature gradient in the surface layer and friction velocity were identified as important predictors for a potential future parameterisation of the energy balance residual.
BibTeX:
@article{Mauder2018,
  author = {Mauder, Matthias and Genzel, Sandra and Fu, Jin and Kiese, Ralf and Soltani, Mohsen and Steinbrecher, Rainer and Zeeman, Matthias and Banerjee, Tirtha and De Roo, Frederik and Kunstmann, Harald},
  title = {Evaluation of energy balance closure adjustment methods by independent evapotranspiration estimates from lysimeters and hydrological simulations},
  journal = {Hydrological Processes},
  publisher = {Wiley},
  year = {2018},
  volume = {32},
  number = {1},
  pages = {39--50},
  doi = {10.1002/hyp.11397}
}
Mauder M and Zeeman MJ (2018), "Field intercomparison of prevailing sonic anemometers", Atmospheric Measurement Techniques., jan, 2018. Vol. 11(1), pp. 249-263.
Abstract: Three-dimensional sonic anemometers are the core component of eddy covariance systems, which are widely used for micrometeorological and ecological research. In order to characterize the measurement uncertainty of these instruments we present and analyse the results from a field intercomparison experiment of six commonly used sonic anemometer models from four major manufacturers. These models include Campbell CSAT3, Gill HS-50 and R3, METEK uSonic-3 Omni, R. M. Young 81000 and 81000RE. The experiment was conducted over a meadow at the TERENO/ICOS site DE-Fen in southern Germany over a period of 16 days in June of 2016 as part of the ScaleX campaign. The measurement height was 3 m for all sensors, which were separated by 9 m from each other, each on its own tripod, in order to limit contamination of the turbulence measurements by adjacent structures as much as possible. Moreover, the high-frequency data from all instruments were treated with the same post-processing algorithm. In this study, we compare the results for various turbulence statistics, which include mean horizontal wind speed, standard deviations of vertical wind velocity and sonic temperature, friction velocity, and the buoyancy flux. Quantitative measures of uncertainty, such as bias and comparability, are derived from these results. We find that biases are generally very small for all sensors and all computed variables, except for the sonic temperature measurements of the two Gill sonic anemometers (HS and R3), confirming a known transducer-temperature dependence of the sonic temperature measurement. The best overall agreement between the different instruments was found for the mean wind speed and the buoyancy flux.
BibTeX:
@article{Mauder2018a,
  author = {Mauder, Matthias and Zeeman, Matthias J.},
  title = {Field intercomparison of prevailing sonic anemometers},
  journal = {Atmospheric Measurement Techniques},
  year = {2018},
  volume = {11},
  number = {1},
  pages = {249--263},
  url = {https://www.atmos-meas-tech.net/11/249/2018/},
  doi = {10.5194/amt-11-249-2018}
}
McGloin R, Šigut L, Havránková K, Dušek J, Pavelka M and Sedlák P (2018), "Energy balance closure at a variety of ecosystems in Central Europe with contrasting topographies", Agricultural and Forest Meteorology., jan, 2018. Vol. 248, pp. 418-431.
Abstract: A long-standing problem in micrometeorology is that at most eddy covariance sites around the world, the sum of the sensible and latent heat flux measurements is less than the available energy, resulting in the so-called energy balance closure problem. This study utilised the national network of eddy covariance towers in the Czech Republic to examine the degree of energy balance closure at sites covering a wide variety of vegetation types and terrain complexities. The degree of energy balance closure at each site varied depending on the method used to calculate the closure fraction. When the closure was computed using linear regressions of half-hourly sums of turbulent heat fluxes against half-hourly available energy values, closure ranged from 0.68 (beech forest) to 0.81 (spruce forest). However, when closure was computed using the bulk energy balance ratio method, values ranged from 0.61 to 0.73. Highest closure occurred in moderately unstable atmospheric conditions, while closure also increased with increases in the correlation coefficients for vertical wind velocity and water vapour, and vertical wind velocity and sonic temperature. Lowest closure was found at a beech forest in the Carpathian Mountains, where evidence suggested that the complex topography to the south of the eddy covariance tower was influencing the airflow and resulting in poor energy balance closure results. Energy balance closure was also particularly low at a rapeseed cropland, and this was attributed to the low frequency of moderately unstable to strongly unstable conditions at the site.
BibTeX:
@article{McGloin2018,
  author = {McGloin, Ryan and Šigut, Ladislav and Havránková, Kateřina and Dušek, Jiří and Pavelka, Marian and Sedlák, Pavel},
  title = {Energy balance closure at a variety of ecosystems in Central Europe with contrasting topographies},
  journal = {Agricultural and Forest Meteorology},
  year = {2018},
  volume = {248},
  pages = {418--431},
  url = {http://linkinghub.elsevier.com/retrieve/pii/S0168192317303234},
  doi = {10.1016/j.agrformet.2017.10.003}
}
Menegat A, Milberg P, Nilsson AT, Andersson L and Vico G (2018), "Soil water potential and temperature sum during reproductive growth control seed dormancy in Alopecurus myosuroides Huds.", Ecology and Evolution., jun, 2018. Vol. 8(14), pp. 7186-7194. Wiley.
Abstract: The sustainable management of unwanted vegetation in agricultural fields through integrated weed control strategies requires detailed knowledge about the maternal formation of primary seed dormancy, to support the prediction of seedling emergence dynamics. This knowledge is decisive for the timing of crop sowing and nonchemical weed control measures. Studies in controlled environments have already demonstrated that thermal conditions and, to some extent, water availability during seed set and maturation has an impact on the level of dormancy. However, it is still unclear if this applies also under field conditions, where environmental stressors and their timing are more variable. We address this question for Alopecurus myosuroides in south-western Sweden. We quantified the effects of cumulated temperature and precipitation as well as soil water potential during the reproductive growth phase of A myosuroides on primary seed dormancy under field conditions. Empirical models differing in focal time intervals and, in case of soil water potential, focal soil depths were compared regarding their predictive power. The highest predictive power for the level of primary dormancy of A. myosuroides seeds was found for a two-factorial linear model containing air temperature sum between 0 and 7 days before peak seed shedding as well as the number of days with soil water potential below field capacity between 7 and 35 days before peak seed shedding. For soil water potential, it was found that only the top 10 cm soil layer is of relevance, which is in line with the shallow root architecture of A. myosuroides. We conclude that for this species the level of dormancy depends on the magnitude and timing of temperature and water availability during the reproductive growth phase. Water availability appears to be more important during maternal environmental perception and temperature during zygotic environmental perception.
BibTeX:
@article{Menegat2018,
  author = {Menegat, Alexander and Milberg, Per and Nilsson, Anders T.S. and Andersson, Lars and Vico, Giulia},
  title = {Soil water potential and temperature sum during reproductive growth control seed dormancy in Alopecurus myosuroides Huds.},
  journal = {Ecology and Evolution},
  publisher = {Wiley},
  year = {2018},
  volume = {8},
  number = {14},
  pages = {7186--7194},
  doi = {10.1002/ece3.4249}
}
Meredith LK, Boye K, Youngerman C, Whelan M, Ogée J, Sauze J and Wingate L (2018), "Coupled Biological and Abiotic Mechanisms Driving Carbonyl Sulfide Production in Soils", Soil Systems., jun, 2018. Vol. 2(3), pp. 37. MDPI AG.
Abstract: Understanding soil production of the trace gas carbonyl sulfide (OCS) is key to its use as a tracer of ecosystem function. Underlying its application is the observation that vascular plants consume atmospheric OCS via their stomatal pores in proportion with CO2 photosynthesis and that soil fluxes of OCS are negligible in comparison. Recent soil-centered studies demonstrate that soils can produce OCS and contribute as much as a quarter of the atmospheric terrestrial flux. Despite the potential widespread importance of soil OCS emissions, insufficient data exist to predict variations in OCS production across ecosystems, and the chemical and biological drivers of OCS production are virtually unknown. In this study, we address this knowledge gap by investigating variables controlling OCS soil production including soil physical and chemical properties, microbial community composition, and sulfur speciation in two independent surveys. We found that soil OCS production was nearly ubiquitous across the 58 sites, increased exponentially with temperature, and was insensitive to visible light conditioning. Soil pH, N, and C/N were predictors of OCS soil production rates in both soil surveys. Patterns in soil S speciation and predicted microbial S-cycling pathways both pointed to S-containing amino acids such as cysteine and methionine and their derivatives as potential precursors for OCS production. Elevated sulfate levels were associated with OCS production in some soils. This study provides new mechanistic insight into OCS production in soils and presents strategies to represent soil OCS fluxes that facilitate the use of OCS as a tracer for leaf-level processes related to carbon and water cycling.
BibTeX:
@article{Meredith2018,
  author = {Meredith, Laura K. and Boye, Kristin and Youngerman, Connor and Whelan, Mary and Ogée, Jérôme and Sauze, Joana and Wingate, Lisa},
  title = {Coupled Biological and Abiotic Mechanisms Driving Carbonyl Sulfide Production in Soils},
  journal = {Soil Systems},
  publisher = {MDPI AG},
  year = {2018},
  volume = {2},
  number = {3},
  pages = {37},
  doi = {10.3390/soilsystems2030037}
}
Montagnani L, Grünwald T, Kowalski A, Mammarella I, Merbold L, Metzger S, Sedlák P and Siebicke L (2018), "Estimating the storage term in eddy covariance measurements: The ICOS methodology", International Agrophysics., dec, 2018. Vol. 32(4), pp. 551-567.
Abstract: In eddy covariance measurements, the storage flux represents the variation in time of the dry molar fraction of a given gas in the control volume representative of turbulent flux. Depending on the time scale considered, and on the height above ground of the measurements, it can either be a major component of the overall net ecosystem exchange or nearly negligible. Instrumental configuration and computational procedures must be optimized to measure this change at the time step used for the turbulent flux measurement. Three different configurations are suitable within the Integrated Carbon Observation System infrastructure for the storage flux determination: separate sampling, subsequent sampling and mixed sampling. These configurations have their own advantages and disadvantages, and must be carefully selected based on the specific features of the considered station. In this paper, guidelines about number and distribution of vertical and horizontal sampling points are given. Details about suitable instruments, sampling devices, and computational procedures for the quantification of the storage flux of different GHG gases are also provided.
BibTeX:
@article{Montagnani2018,
  author = {Montagnani, Leonardo and Grünwald, Thomas and Kowalski, Andrew and Mammarella, Ivan and Merbold, Lutz and Metzger, Stefan and Sedlák, Pavel and Siebicke, Lukas},
  title = {Estimating the storage term in eddy covariance measurements: The ICOS methodology},
  journal = {International Agrophysics},
  year = {2018},
  volume = {32},
  number = {4},
  pages = {551--567},
  url = {https://content.sciendo.com/view/journals/intag/32/4/article-p551.xml},
  doi = {10.1515/intag-2017-0037}
}
Mozaffar A, Schoon N, Bachy A, Digrado A, Heinesch B, Aubinet M, Fauconnier ML, Delaplace P, du Jardin P and Amelynck C (2018), "Biogenic volatile organic compound emissions from senescent maize leaves and a comparison with other leaf developmental stages", Atmospheric Environment., mar, 2018. Vol. 176, pp. 71-81.
Abstract: Plants are the major source of Biogenic Volatile Organic Compounds (BVOCs) which have a large influence on atmospheric chemistry and the climate system. Therefore, understanding of BVOC emissions from all abundant plant species at all developmental stages is very important. Nevertheless, investigations on BVOC emissions from even the most widespread agricultural crop species are rare and mainly confined to the healthy green leaves. Senescent leaves of grain crop species could be an important source of BVOCs as almost all the leaves senesce on the field before being harvested. For these reasons, BVOC emission measurements have been performed on maize (Zea mays L.), one of the most cultivated crop species in the world, at all the leaf developmental stages. The measurements were performed in controlled environmental conditions using dynamic enclosures and proton transfer reaction mass spectrometry (PTR-MS). The main compounds emitted by senescent maize leaves were methanol (31% of the total cumulative BVOC emission on a mass of compound basis) and acetic acid (30%), followed by acetaldehyde (11%), hexenals (9%) and m/z 59 compounds (acetone/propanal) (7%). Important differences were observed in the temporal emission profiles of the compounds, and both yellow leaves during chlorosis and dry brown leaves after chlorosis were identified as important senescence-related BVOC sources. Total cumulative BVOC emissions from senescent maize leaves were found to be among the highest for senescent Poaceae plant species. BVOC emission rates varied strongly among the different leaf developmental stages, and senescent leaves showed a larger diversity of emitted compounds than leaves at earlier stages. Methanol was the compound with the highest emissions for all the leaf developmental stages and the contribution from the young-growing, mature, and senescent stages to the total methanol emission by a typical maize leaf was 61, 13, and 26%, respectively. This study shows that BVOC emissions from senescent maize leaves cannot be neglected and further investigations in field conditions are recommended to further constrain the BVOC emissions from this important C4 crop species.
BibTeX:
@article{Mozaffar2018,
  author = {Mozaffar, A. and Schoon, N. and Bachy, A. and Digrado, A. and Heinesch, B. and Aubinet, M. and Fauconnier, M. L. and Delaplace, P. and du Jardin, P. and Amelynck, C.},
  title = {Biogenic volatile organic compound emissions from senescent maize leaves and a comparison with other leaf developmental stages},
  journal = {Atmospheric Environment},
  year = {2018},
  volume = {176},
  pages = {71--81},
  url = {http://linkinghub.elsevier.com/retrieve/pii/S1352231017308658},
  doi = {10.1016/j.atmosenv.2017.12.020}
}
Mzobe P, Berggren M, Pilesjö P, Lundin E, Olefeldt D, Roulet NT and Persson A (2018), "Dissolved organic carbon in streams within a subarctic catchment analysed using a GIS/ remote sensing approach", PLoS ONE., jul, 2018. Vol. 13(7), pp. e0199608. Public Library of Science (PLoS).
Abstract: Climate change projections show that temperature and precipitation increases can alter the exchange of greenhouse gases between the atmosphere and high latitude landscapes, including their freshwaters. Dissolved organic carbon (DOC) plays an important role in greenhouse gas emissions, but the impact of catchment productivity on DOC release to subarctic waters remains poorly known, especially at regional scales. We test the hypothesis that increased terrestrial productivity, as indicated by the normalized difference vegetation index (NDVI), generates higher stream DOC concentrations in the Stordalen catchment in subarctic Sweden. Furthermore, we aimed to determine the degree to which other generic catchment properties (elevation, slope) explain DOC concentration, and whether or not land cover variables representing the local vegetation type (e.g., mire, forest) need to be included to obtain adequate predictive models for DOC delivered into rivers. We show that the land cover type, especially the proportion of mire, played a dominant role in the catchment's release of DOC, while NDVI, slope, and elevation were supporting predictor variables. The NDVI as a single predictor showed weak and inconsistent relationships to DOC concentrations in recipient waters, yet NDVI was a significant positive regulator of DOC in multiple regression models that included land cover variables. Our study illustrates that vegetation type exerts primary control in DOC regulation in Stordalen, while product