Jean-Marc Limousin

France-Puéchabon

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A partial rainfall exclusion experiment has been established in 2003 to anticipate the response of the ecosystem to a continuous reduction of precipitation (European project MIND, Mediterranean Terrestrial Ecosystems and Increasing Drought). The experiment was set up on four 140m² plots (14 x 10m) situated on a flat area, so that lateral flow of water is negligible and replicated three times. The first treatment is a control, the second is subjected to a 30% throughfall exclusion, the third is thinned with 33% of the basal area removed and the fourth is thinned and subjected to throughfall exclusion (dry-thinned). On the dry and dry-thinned treatment plots, throughfall exclusion is achieved using 14 m long and 0.19 m wide PVC gutters covering 33% of the ground area under canopy, with the aim to exclude 33% of the throughfall. On the control plot and the thinned plot, identical gutters have been set up upside down so that the albedo and the micro-climate of the forest understory are the same in all treatments. As the experiment has been functioning continuously since 2003, it is currently one of the world longest rainfall manipulation experiment in a forest ecosystem, which allows to study tree and ecosystem acclimation to drought from short to medium term. One of the replicated block is equipped with a scaffold that allows access to the canopy at two levels (shaded leaves and sunlit leaves). Continuous measurements of soil water content, soil temperature, tree sapflow and tree growth have been recorded since the start of the experiment. Field campaigns are regularly performed by the research team for manual measurements.

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