Phenological response to drought in Quercus ilex: thinning as mitigation tool

Abstract: Mediterranean forests will be greatly affected by climate change, which is expected to have changes in the timing of some phenological events. In this context, management practices could improve ecosystem resilience to disturbances. This study tested the response of an experimental drought on holm oak phenology and how thinning could mitigate its effects. The study was performed in the Puechabon Forest (Southern France) using 4 experimental treatments on 120 m² plots: control (C), thinning (T, -30% basal area), drought (D, -30% precipitation) and drought + thinning (DT). Plots are part of the Experimentation in Ecosystem Research European infrastructure. We analyzed development of Quercus ilex leaves in spring over 2003-2013 period. Phenology was affected by the treatment, being C plot the earliest, DT plot the latest and T and D plots reached intermediate values. Regarding the phenophases length, we only found differences for the last one (expanding leaves and enduring) reaching drought plots (D and DT) the lowest values. Moreover, synchrony was highest for drought plots (D and DT). These phenological differences amongst treatments, could affect growth and acorn production with important ecological consequences.