Partial rainfall exclusion

An experimental system of partial exclusion of precipitation was set up in 2003 to anticipate the ecosystem’s response to a continuous reduction in precipitation (European MIND project, Mediterranean Terrestrial Ecosystems and Increasing Drought). The experiment was set up on four 140 m² (14 x 10 m) plots located on a flat area to minimize lateral water run-off, and replicated three times.

• The first treatment is the reference
• The second is subject to a 30% throughfall exclusion
• The third is thinned with 33% of basal area removed
• The fourth is thinned and dry-thinned.

On plots with “dry” and “dry-thinned” treatment, the exclusion of infiltrated precipitation is achieved using PVC gutters 14 m long and 0.19 m wide, covering 33% of the ground surface under the canopy, with the aim of excluding 33% of infiltrated precipitation. On the control and thinned plots, identical gutters were installed in reverse, so as to maintain the same albedo and microclimate for the undergrowth in all treatments. As the experiment has been running continuously since 2003, it is currently one of the world’s longest-running experiments manipulating precipitation in a forest ecosystem, making it possible to study the acclimatization of trees and the ecosystem to drought in the short and medium term.

One of the replicated blocks is equipped with scaffolding that provides access to the canopy at two levels: shaded leaves and sunlit leaves. Continuous measurements of soil water content, soil temperature, tree sap flow, and tree growth have been recorded since the beginning of the experiment. The research team regularly conducts field campaigns to perform manual measurements.

Continuous measurement