A new bioclimatic model calibrated with vegetation for Mediterranean forest areas

Water availability is one of the main factors explaining flora composition and growth in Mediterranean regions, where it may decline with climate change. Our goal was to develop a model for forest site assessment in Mediterranean environments, focusing on water availability to assess potential vegetation composition and productivity in any places, whatever their level of disturbance. We designed a statistical model, using global climatic and geographic variables, as well as detailed local topographic and edaphic variables, to compute a bioclimatic index for Mediterranean forest environments. This model was calibrated in France with a flora index from 325 old forests. The model explained 80.3% of the flora index variance. The method fills a gap in existing models, bridging scales from the region to forest sites. Beyond its theoretical aspect, it was designed to allow practical tools to be derived from it for decision-making and management, such as the assessment of climate change impact on vegetation, and of forest productivity. Its development and adaptation is possible in other Mediterranean regions, and in any region where water is one of the main limiting factors.