Abstract

Current climate change is related to increasing frequency and intensity of droughts in the Mediterranean basin. This climate dryness entails a serious impact on the drought-sensitive forests, several of them considered as hot spots of biodiversity. Adaptive management, as experimental thinning, may increase tree-level resources availability, but the long-term stand-level effectiveness of this approach at sustaining forest ecosystem functioning remains uncertain. Here we attempt to place experimental thinning in a climate change context, using as experimental system the drought-sensitive fir Abies pinsapo. We conducted a long-term study (2004-2019), focus on tree basal area increment and quantified the extent to that thinning improved drought resistance, recovery and resilience to drought in the remaining trees. The results support that after the thinning (2004) there was an increase of the BAI in all the studied populations (+21% in Control, +103% in 30% thinning and +135% in 60% thinning ). However, when studying the response of the Abies pinsapo forest strategies after an extreme period of drought, it showed a general decline in resistance values for dry periods ( -49% Control, -45% Intensity 30%, -54 Intensity 60%) as well as for the Resilience values (-19% Control, -25% Intensity 30%, -42% Intensity 60%), contrary to the Recovery values where all plots increased significantly (+61% Control, +34% Intensity 30%, 27% Intensity 60%).

Density reduction provides a promising strategy for minimizing climate change effects on drought-sensitive tree species by improving resources availability to the remaining trees.