Although fire is widely regarded as a disturbance, it is also recognized as an important driver of biodiversity, with its effects varying across ecosystems and fire regimes. As global change is expected to alter wildfire activity worldwide, understanding how fire influences biodiversity has become increasingly relevant. A major challenge is that vegetation and fire interact through feedbacks, whereby plant community composition influences fire occurrence and, in turn, is reshaped by it.

To investigate how these feedbacks affect biodiversity, we analyzed the compositional and functional diversity of simulated plant communities across a gradient of fire frequencies. We extended an existing vegetation model to represent species-rich communities and parameterized it for Boreal and Mediterranean ecosystems. Fire events occurred stochastically, with average frequencies determined by community flammability, while species differed in their responses to fire, generating dynamic vegetation–fire feedbacks.

Across both ecosystems, fire generally promoted both compositional and functional diversity, with diversity typically peaking at intermediate fire frequencies. Although the two diversity dimensions were positively correlated, they did not reach their maxima in the same communities. This suggests that some degree of functional similarity among species may be necessary to support the highest levels of species richness. These results stem from the vegetation- fire feedback, highlighting its importance for predicting ecosystem responses to global change, including biodiversity losses and wildfire regime shifts.