Are trait responses of tree species across pyroregions indicative of fire-modulated plant functional strategies?

Abstract

Fire disturbance is a global eco-evolutionary force affecting plant species persistence and distribution. Pyrogeographic studies so far have identified pyroregions based on their similarity in climate and fire regime parameters. However, which fire-related traits tend to promote or hinder plant species persistence and distribution in different pyroregions remains underexplored. We implement a trait-based approach focusing on 38 tree species in the Mediterranean Basin (Italy), testing whether 1) species distribution across different pyroregions is associated with fire regime, 2) species in different pyroregions exhibit distinct fire-related trait values and, if so, 3) trait differences suggest better abilities to cope with fire and aridity in species distributed in more fire-prone and arid regions (e.g. thicker bark). We ran multivariate analyses (Correspondence Analysis) and linear models (Standardized Major Axis, Ordinary Least Squares) to address our goals. Findings tend to positively answer our questions, emphasizing the importance of including fire-related traits in pyroregionalization studies. Noticeably, the most fire-prone pyroregions collapse into one region from a functional perspective, with species characterized by trait values indicative of adaptations to fire and aridity. A trait-based approach may contribute to refine pyroregionalization exercises while proving useful for management purposes, such as identifying species or life histories whose traits may facilitate their persistence in the face of future, likely exacerbating, fire regimes.