Ensemble modelling of carbon fluxes in grasslands and croplands
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Author
Sándor, Renáta
Ehrhardt, Fiona
Grace, Peter
Recous, Sylvie
Smith, Pete
Snow, Val
Soussana, Jean-François
Basso, Bruno
Bathia, Arti
Brilli, Lorenzo
Dorich, Christopher D.
Doro, Luca
Fitton, Nuala
Grant, Brian
Harrison, Matthew Tom
Kirschbaum, Miko U.F.
Klumpp, Katja
Laville, Patricia
Léonard, Joel
Martin, Raphaël
Massad, Raia-Silvia
Moore, Andrew
Myrgiotis, Vasileios
Pattey, Elizabeth
Rolinski, Susanne
Sharp, Joanna
Skiba, Ute
Smith, Ward
Wu, Lianhai
Zhang, Qing
Bellocchi, Gianni
Publication date
2020-04-25ISSN
0378-4290
Abstract
Croplands and grasslands are agricultural systems that contribute to land–atmosphere exchanges of carbon (C). We evaluated and compared gross primary production (GPP), ecosystem respiration (RECO), net ecosystem exchange (NEE) of CO2, and two derived outputs - C use efficiency (CUE=-NEE/GPP) and C emission intensity (IntC= -NEE/Offtake [grazed or harvested biomass]). The outputs came from 23 models (11 crop-specific, eight grassland-specific, and four models covering both systems) at three cropping sites over several rotations with spring and winter cereals, soybean and rapeseed in Canada, France and India, and two temperate permanent grasslands in France and the United Kingdom. The models were run independently over multi-year simulation periods in five stages (S), either blind with no calibration and initialization data (S1), using historical management and climate for initialization (S2), calibrated against plant data (S3), plant and soil data together (S4), or with the addition of C and N fluxes (S5). Here, we provide a framework to address methodological uncertainties and contextualize results. Most of the models overestimated or underestimated the C fluxes observed during the growing seasons (or the whole years for grasslands), with substantial differences between models. For each simulated variable, changes in the multi-model median (MMM) from S1 to S5 was used as a descriptor of the ensemble performance. Overall, the greatest improvements (MMM approaching the mean of observations) were achieved at S3 or higher calibration stages. For instance, grassland GPP MMM was equal to 1632 g C m−2 yr-1 (S5) while the observed mean was equal to 1763 m-2 yr-1 (average for two sites). Nash-Sutcliffe modelling efficiency coefficients indicated that MMM outperformed individual models in 92.3 % of cases. Our study suggests a cautious use of large-scale, multi-model ensembles to estimate C fluxes in agricultural sites if some site-specific plant and soil observations are available for model calibration. The further development of crop/grassland ensemble modelling will hinge upon the interpretation of results in light of the way models represent the processes underlying C fluxes in complex agricultural systems (grassland and crop rotations including fallow periods).
Document Type
Article
Document version
Accepted version
Language
English
Subject (CDU)
631 - Agriculture in general
Pages
56
Publisher
Elsevier
Is part of
Field Crops Research
Citation
Sándor, Renáta, Fiona Ehrhardt, Peter Grace, Sylvie Recous, Pete Smith, Val Snow, and Jean-François Soussana et al. 2020. "Ensemble Modelling Of Carbon Fluxes In Grasslands And Croplands". Field Crops Research 252: 107791. Elsevier BV. doi:10.1016/j.fcr.2020.107791.
Grant agreement number
EC/FP5/EVK2-CT-2001-00105/EU/Sources and sinks of greenhouse gases from managed european grasslands and mitigtion scenarios/GREENGRASS
EC/FP6/505572/EU/Assessment of the European Terrestrial Carbon Balance/CARBOEUROPE-IP
EC/FP6/17841/EU/The nitrogen cycle and its influence on the European greenhouse gas balance/NITROEUROPE IP
Program
Cultius Extensius Sostenibles
This item appears in the following Collection(s)
- ARTICLES CIENTÍFICS [2831]
Except where otherwise noted, this item's license is described as http://creativecommons.org/licenses/by-nc-nd/4.0/