Physiological and Regenerative Plant Traits Explain Vegetation Regeneration under Different Severity Levels in Mediterranean Fire-Prone Ecosystems

In Mediterranean fire-prone ecosystems, plant functional traits and burn severity have decisive roles in post-fire vegetation recovery. These traits may reflect plant fitness to fire regimes in the Mediterranean Basin. The aim of this study was to evaluate the effect of burn severity on post-fire vegetation regeneration through plant functional (physiological and regenerative) traits in two Mediterranean ecosystems: one more humid and colder (Cabrera in Leon province, NW Spain), and another characterized by a longer summer drought (Gatova in Valencia province, SE Spain). A total of 384 and 80 field plots (2 m x 2 m) were fixed in Cabrera and Gatova, respectively. In each burned plot, we quantified burn severity by means of the composite burn index (CBI), differentiating three severity levels (low, moderate, and high), and evaluated post-fire vegetation regeneration one and two years after wildfires. We measured the percentage cover of each species and classified them according to physiological (specific leaf area and N-2-fixing capacity) and regenerative traits (reproductive strategy, bud bank location, and heat-stimulated germination). The main results showed that in Cabrera, burn severity had significant effects on vegetation cover independently of plant functional traits. In Gatova, burn severity effects differed among functional traits. In this site, the cover of plants with low specific leaf area and without heat-stimulation and N-2-fixing capacity was negatively related to burn severity. On the contrary, the cover of N-2-fixers and species with resprouting ability and heat-stimulated germination rose with increasing burn severity. In general, vegetation cover showed a more pronounced increased over time in the more humid area, mainly under the effect of high severity. The results of this research highlighted the importance of the use of plant functional traits as a driver to understand the response of different ecosystems to current fire regimes, which could be relevant for pre- and post-fire management.

Automated summary

This study evaluated the impact of burn severity on post-fire vegetation recovery in two Mediterranean ecosystems in Spain and found that plant functional traits played a crucial role in this process. The results indicated that different ecosystems responded differently to burn severity, highlighting the importance of considering plant traits in fire management strategies.