Functional responses of Mediterranean flora to fire: A community‐scale perspective

Abstract

Fire regime is predicted to change, particularly in Mediterranean climate regions, towards more severe and frequent fire events. From a predictive perspective, trait‐based ecology offers a comprehensive framework to characterize vegetation responses to fire. Since fires induce erosion and decrease soil nutrients, species' functional traits and their distribution at community level should reflect these changes. Despite a vast literature focused on plant traits involved in resistance to fire, quantification of community trait responses to fire is lacking, particularly for traits that are linked to resource strategies. Here, we emphasis on plant traits related to morphology (height, specific leaf area, stem and wood density) and resource acquisition strategies (leaf nitrogen, leaf dry mass, seed dry mass). We compiled three different databases compiling vegetation, fire and functional traits for the flora of Southern France. We analysed the relationships between these three components at both species and community levels. Fire numbers and area burnt did not impact species trait distributions. At community level, a clear pattern emerged between the number of fires and the distribution of different traits considered, with two main axes: on the positive PC2 axis vegetative height and seed mass; and on negative PC1 axis leaf carbon and positive PC1 axis nitrogen content and leaf area. We also showed that vegetative height is positively correlated to the aridity index distribution in the region studied. Synthesis: We analysed the relationships among fire, vegetation and functional traits, at both species and community levels. Altogether, there are highly significant direct relationships between the number of fires and leaf area (negatively) as well as seed mass (positively). For woody communities, wood density is also highly positively significant related to the number of fires. Overall, these findings suggest that fire may have an important impact on the functional response of plant communities, while not apparent when looking at individual species. Further, this research paves new ground to better understand the mechanisms behind trait convergence and the way plant communities respond to different environmental pressures.