A total rainfall exclusion experiment has been designed to simulate the effect of an extreme climatic event on the functioning and the vulnerability of the ecosystem. In 2007, a mobile rainfall shelter was installed 1m above the canopy in order to modify rainfall seasonality by removing all the precipitation during a 6-month period (ANR project Drought+). The 20 x 15 m rainfall shelter moves along two 60 m rails to cover alternatively 3 plots of 20m each : two droughted plots are situated at either ends of the railing, while the middle plot is a standby position for the shelter when it does not rain. This design allows to cover the rainfall exclusion plots only during the rain events without modifying the forest microclimate. A late autumn drought was simulated in 2008 by removing all the precipitation from July to December, and an early spring drought was simulated in 2009 by excluding the precipitation from February to July. The experimental set-up will next be used to simulate an extreme drought event until tree or at least branch mortality happens.
Funding
2007- 2010 Drought+ (ANR Milieu et climat N°ANR-06-VULN-003-01, France)