Pyro-ecophysiology of 11 woody Karst species: Leaf flammability analysis reveals fire-safe species for green firebreaks development

Climate change is intensifying wildfire frequency and severity in Mediterranean ecosystems, creating urgent needs for effective fire management strategies. Green firebreaks based on fire-resistant vegetation represent a promising approach, but require species-specific flammability assessments. We evaluated leaf moisture-dependent flammability of 11 dominant woody species in a Mediterranean karst ecosystem to identify potential candidates for green firebreak establishment. For each species, we conducted laboratory leaf flammability tests by measuring ignition vulnerability curves (IVCs), which relate leaf ignition probability at different moisture content levels, quantified as Live Fuel Moisture Content (LFMC) and Relative Water Content (RWC). Contemporarily, we monitored species-specific LFMC variation during summer drought in the field. Species-specific IVCs revealed critical LFMC thresholds corresponding to different ignition probability. Results showed marked interspecific variability in flammability, with Specific Leaf Area (SLA) being positively correlated with both maximum moisture content and LFMC at 50 % ignition probability. Species clustered into distinct vulnerability groups: high-risk species (Robinia pseudoacacia, Acer campestre, Acer monspessulanum) required minimal dehydration for ignition, while fire-resistant species (Quercus pubescens, Prunus mahaleb, Pistacia terebinthus, Ailanthus altissima) maintained high moisture content under drought and also required severe dehydration for ignition. These findings provide quantitative tools for species selection in fire management and demonstrate how plant hydraulic strategies determine landscape-scale fire vulnerability in Mediterranean karst ecosystems.