+ 33 4 34 35 98 94 ecotron@cnrs.fr


To study and understand the impact of climate change and extreme climate events on a mid-mountain grassland ecosystem by analyzing their carbon and water cycles continuously over more than two years.

Number of rooms used

  •  12

Project Duration

  •  24 months

Extreme summer climate event in the future: impact on the net CO2 and water flows of a mountain meadow


Jacques Roy ; Damien Landais ; Clément Piel ; Christophe Escape ; Sebastien Devidal ; Olivier Ravel ; Philippe Didier; Angela Augusti; Jean François Soussana; Catherine Picon Cochard; Florence Volaire; Michael Bahn 



Ecotron – UREP – CEFE – Institute of Ecology University of Innsbruk Austria



  • Biogeochemical cycles (carbon storage, water and nitrogen balance…)
  • Biodiversity (soil and vegetation)
  • Quantity and quality of green biomass

Extreme weather events are expected to be more frequent and more intense in a few decades, but they will also occur in a different climatic context from the current one.  At the Montpellier Ecotron, we studied the response of intact meadow monoliths (1m², 60 cm deep) taken from a plateau meadow in the French Massif Central. In the first year, the meadows were acclimatized to the average climatic conditions of the years around 2050 (+ 4 °C and – 56 mm for summer rainfall). The second year, the same climate was maintained, but in half of the experimental units, we imposed a summer drought and heat wave (50% reduction in rainfall for one month, then 100% reduction for two weeks with a 3.4°C increase in temperature). A treatment with CO2 (520 vs 380 µmol/mol/mol) was crossed with the climatic treatment.

Net fluxes of CO2 were measured continuously during the second year of the experiment. The extreme climatic event induced total canopy senescence regardless of the CO2 treatment. The interactive effect of the CO2 elevation with the drought treatment was significant at the onset of the drought and particularly significant in the fall after the recovery period, with net photosynthesis twice as high in the treatment (extreme climate + CO2) than in the control. Integrated over the year, the high level of CO2 totally dampened the impact of the extreme climatic event on the net exchanges of CO2. These results are discussed with the evapotranspiration and soil moisture data.