Alcornocales Natural Park
The rainfall exclusion experiment of the Alcornocales Natural Park (southern Spain) involves two different sites about 5 km apart: Gamir and Marrufo. Gamir is a closed forest dominated by the Mediterranean oaks Quercus suber and Quercus canariensis, whereas Marrufo is an open woodland dominated by Quercus suber and Olea europaea var. sylvestris. Both forests are invaded by the exotic soil-borne pathogen Phytophthora cinnamomi.
We established 6 plots of 20×15 m at each site during early spring 2016 (12 plots in total). These plots were specifically built to reduce the amount of rainfall by 30%. This percentage corresponds to the average reduction of rainfall according to a restrictive future climate change scenario for southern Spain (model CMIP5 for the scenario RCP 8.5 for the period 2081-2100 in comparison with the period 1986-2005). Three of these plots had a structure of rainfall exclusion whereas the other three were assigned to control. The rainfall exclusion treatment was formed by a metal structure supporting plastic PVC gutters that covered 30% of the plot area in order to exclude a similar amount of natural precipitation.On the control plots, identical gutters were placed upside down to make the albedo and the understory microclimate as similar as possible in both treatments. All plots were selected to have similar conditions in terms of slope, aspect and number of trees.