Effetti della siccità sulla rigenerazione post-incendio della foresta mediterranea in Catalogna (Spagna)

Over the course of evolution, plants have developed several resilience strategies, in order to withstand fires; these are for example resprouting, from surviving tissues, or fire stimulated seed recruitment. Plants’ ability to regenerate after a fire is fundamental for the conservation of forest biomes; however, this regeneration is likely to be affected by the increased aridity and frequency of drought due to the ongoing and expected climate change. In this thesis, I studied forest post-fire regeneration along a climate gradient, to look at the changes in dominance of different post-fire regeneration strategies, depending on the occurrence of pre- and post-fire drought periods. I analyzed data from two consecutive Spanish Forest Inventories (SNFI2 & SNFI3), in Catalonia, which are approximately 10 years apart. The plot’s variables considered were basal area of adult trees, and sapling (i.e., young trees) density. I defined 2 macro climatic areas, dry sub-humid and semi-arid, based on the Aridity Index. Pre- and post-fire drought events were identified using SPEI (Standardized Precipitation Evapotranspiration Index) for the growing season (September to June). Plots burned between the 2 inventories were selected using the Catalan fire perimeters dataset, provided by GENCAT (Generalitat de Catalunya) Department of Climate Action, Food and Rural Agenda. I found, in the dry sub-humid zone for 3SNFI, a significant difference in resprouter to seeder dominance (i.e., the fraction of resprouters to seeders basal area) between plots that experienced severe pre-fire drought and plots that did not, showing that resprouter post-fire response is sensitive to pre-fire drought events. I also found, considering all climatic zones, that seeder regeneration is sensitive to post-fire drought: the difference in seeder saplings density between the 2 inventories is lower for plots that experienced post-fire drought than for plots that did not.