title: Effect of climate change, CO2 trends, nitrogen addition, and land-cover and management intensity changes on the carbon balance of European grasslands.
abstract: Several lines of evidence point to European managed grassland ecosystems being a sink of carbon. In this study, we apply ORCHIDEE-GM a process-based carbon cycle model that describes specific management practices of pastures and the dynamics of carbon cycling in response to changes in climatic and biogeochemical drivers. The model is used to simulate changes in the carbon balance [i.e., net biome production (NBP)] of European grasslands over 1991-2010 on a 25 km × 25 km grid. The modeled average trend in NBP is 1.8-2.0 g C m(-2)  yr(-2) during the past two decades. Attribution of this trend suggests management intensity as the dominant driver explaining NBP trends in the model (36-43% of the trend due to all drivers). A major change in grassland management intensity has occurred across Europe resulting from reduced livestock numbers. This change has 'inadvertently' enhanced soil C sequestration and reduced N2 O and CH4 emissions by 1.2-1.5 Gt CO2 -equivalent, offsetting more than 7% of greenhouse gas emissions in the whole European agricultural sector during the period 1991-2010. Land-cover change, climate change and rising CO2 also make positive and moderate contributions to the NBP trend (between 24% and 31% of the trend due to all drivers). Changes in nitrogen addition (including fertilization and atmospheric deposition) are found to have only marginal net effect on NBP trends. However, this may not reflect reality because our model has only a very simple parameterization of nitrogen effects on photosynthesis. The sum of NBP trends from each driver is larger than the trend obtained when all drivers are varied together, leaving a residual - nonattributed - term (22-26% of the trend due to all drivers) indicating negative interactions between drivers.
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnement, UMR8212, CEA-CNRS-UVSQ, Gif-sur-Yvette, 91191, France.|Sorbonne Universités (UPMC, Univ Paris 06)-CNRS-IRD-MNHN, LOCEAN/IPSL, 4 place Jussieu, Paris, 75005, France.
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Chang
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnement, UMR8212, CEA-CNRS-UVSQ, Gif-sur-Yvette, 91191, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Ciais
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnement, UMR8212, CEA-CNRS-UVSQ, Gif-sur-Yvette, 91191, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Viovy
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnement, UMR8212, CEA-CNRS-UVSQ, Gif-sur-Yvette, 91191, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Vuichard
authors.affiliation: Commonwealth Scientific and Industrial Research Organisation, Agriculture Flagship, St. Lucia, QLD, 4067, Australia.
authors.forename: Mario
authors.initials: M
authors.lastname: Herrero
authors.affiliation: Ecosystems Services and Management Program, International Institute for Applied Systems Analysis, Laxenburg, 2361, Austria.
authors.forename: Petr
authors.initials: P
authors.lastname: Havlík
authors.affiliation: Laboratoire de Météorologie Dynamique, Institute Pierre Simon Laplace, Paris, 75005, France.|Sino-French Institute of Earth System Sciences, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China.
authors.forename: Xuhui
authors.initials: X
authors.lastname: Wang
authors.affiliation: Sorbonne Universités (UPMC, Univ Paris 06)-CNRS-IRD-MNHN, LOCEAN/IPSL, 4 place Jussieu, Paris, 75005, France.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Sultan
authors.affiliation: INRA, Grassland Ecosystem Research Unit, UREP, Clermont-Ferrand, 63100, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Soussana
mesh_terms: D000383:Agriculture / Q000379:methods*; D000397:Air Pollution; D000818:Animals; D002244:Carbon / Q000737:chemistry; D057486:Carbon Cycle; D002245:Carbon Dioxide; D057231:Climate Change; D005060:Europe; D065948:Grassland; D058751:Livestock; D008962:Models, Theoretical; D009584:Nitrogen / Q000737:chemistry; D012987:Soil / Q000737:chemistry
chemical_list: D012987:Soil; D002245:Carbon Dioxide; D002244:Carbon; D009584:Nitrogen
keywords: European grassland; ORCHIDEE-GM; carbon balance; climate change; land-cover change; management intensity