Environmental factors disrupting the adaptive advantage of fire-trait syndromes

Fire regimes show substantial variability among ecosystems, with a fundamental contrast between surface and crown fires. While surface fires predominantly consume understory vegetation, crown fires involve the combustion of canopy fuels. This distinction is therefore central to understanding fire-driven ecosystem dynamics and to designing effective wildfire risk management strategies.

Ongoing climate change is expected to further reshape fire regimes by altering temperature and moisture conditions and by driving shifts in species distributions. These processes may indirectly modify fire behaviour by changing fuel structure, continuity, and overall landscape flammability.

Within this context, plant functional traits provide a valuable lens through which to interpret fire–vegetation interactions. They not only respond to environmental filtering but also actively shape ecosystem functioning. Two traits in particular—branch shedding (the ability to shed dead lower branches) and serotiny (the retention of mature cones that open after exposure to high temperatures)—have been proposed as key adaptive strategies influencing fire regimes. However, there is limited understanding of whether environmental factors can effectively cancel the adaptive advantages conferred by these traits, which, if occurring frequently, might substantially alter ecosystem dynamics.

To explore these issues, we integrated forest information from the Spanish Forest Map with fire severity data from the European Forest Fire Information System (EFFIS). Our analysis focused on pine species dominating coniferous forests across the western Mediterranean region. We examined how branch shedding and serotiny relate to crown fire occurrence, and how these relationships are modulated by stand-level attributes such as successional stage, shrubs abundance, and the occurrence of extreme drought during the fire season.

Our results indicate that the effectiveness of these trait-based strategies is, at least in the western Mediterranean, strongly contingent on forest stand conditions and suggests that climate change might disrupt the current spatial consistency of these long-established  fire-traits relationships.