Résumé
Climate models forecast, for the coming future, an increase in frequency of extremes events, such as heat waves and severe droughts. In grassland ecosystem most of the carbon is stored in the soil and its flux toward the soil is the second larger among all ecosystems. Soil CO2 efflux derives from two main components, autotrophic respiration being associated with root and rhizosphere respiration and heterotrophic respiration associated with the turnover of soil organic matter by microorganisms. The aim of this work was to evaluate the vulnerability of a grassland ecosystem under summer extreme events in a context of future climate and the possible mitigation effect of increased CO2. In particular, we studied the extreme event effects on soil efflux and on its autotrophic and heterotrophic components.