Elevated CO2 maintains grassland net carbon uptake under a future heat and drought extreme

Jacques Roy (1) , Catherine Picon-Cochard (2) , Angela Augusti (2) , Marie-Lise Benot (3) , Lionel Thiery , Olivier Darsonville (2) , Damien Landais (1) , Clément Piel (1) , Marc Defossez , Sebastien Devidal (1) , Christophe Escape (1) , Olivier Ravel (1) , Nathalie Fromin (4) , Florence Volaire (4) , Alexandru Milcu (1, 4) , Michael Bahn (5) , Jean-François J.-F. Soussana (6)

1 Écotron Européen de Montpellier
2 UREP - Unité de recherche sur l'Ecosystème Prairial
3 BioGeCo - Biodiversité, Gènes & Communautés
4 CEFE - Centre d’Ecologie Fonctionnelle et Evolutive
5 Universität Innsbruck [Innsbruck]
6 CODIR - Collège de Direction

Extreme climatic events (ECEs) such as droughts and heat waves are predicted to increase in intensity and frequency and impact the terrestrial carbon balance. However, we lack direct experimental evidence of how the net carbon uptake of ecosystems is affected by ECEs under future elevated atmospheric CO2 concentrations (eCO2). Taking advantage of an advanced controlled environment facility for ecosystem research (Ecotron), we simulated eCO2 and extreme cooccurring heat and drought events as projected for the 2050s and analyzed their effects on the ecosystem-level carbon and water fluxes in a C3 grassland. Our results indicate that eCO2 not only slows down the decline of ecosystem carbon uptake during the ECE but also enhances its recovery after the ECE, as mediated by increases of root growth and plant nitrogen uptake induced by the ECE. These findings indicate that, in the predicted near future climate, eCO2 could mitigate the effects of extreme droughts and heat waves on ecosystem net carbon uptake.

Domaines: Biodiversité et Ecologie; Milieux et Changements globaux; Interactions entre organismes; Ecosystèmes

Jacques Roy, Catherine Picon-Cochard, Angela Augusti, Marie-Lise Benot, Lionel Thiery, et al.. Elevated CO2 maintains grassland net carbon uptake under a future heat and drought extreme. Proceedings of the National Academy of Sciences of the United States of America, 2016, 113 (22), pp.6224-6229. ⟨10.1073/pnas.1524527113⟩. ⟨hal-02127043⟩