Potential impacts of climate change on grassland productivity at French sites

Given the recognized importance of grasslands to the global carbon budget, a simulation study was performed using the model PASIM to extrapolate potential impacts of altered climate regimes on grassland resources. An array of scenarios was sketched to be representative of climate/soil/plant/management interactions at 12 French sites. SRES climate change projections for near (2020-2049) and far (2070-2099) future were constructed using a range of climate models and settings which mark the limits of uncertainty associated with current climate modelling. PASIM was employed to generate a variety of outputs related to biomass productivity and C budget. Based on alternative scenarios, air temperature rise by ~1-4 °C to the end of 21st century, combined with increasing CO2 levels, translates into increased yields although generally accompanied by decreased precipitations. The latter is likely the main cause of the larger variability of yield observed from year to year under modified climate. A more complex response was observed for spatial and temporal variation of soil organic C. The risk of general driest conditions associated with climate change may not be reflected in yield and C losses due to concurrent effects of increased atmospheric CO2 concentrations, but calls for consideration of water resources depletion. Margins for adaptations can be explored in terms of crop management (e.g., effects of different cutting dates or grazing periods)