Short-term responses of ecosystem multifunctionality to fire severity are modulated by fire-induced impacts on plant and soil microbial communities

This study represents a first attempt to shed light into the mechanisms that modulate the response of ecosystem multifunctionality (EMF) to fire severity in post-fire landscapes. We specifically investigated the role played by fireinduced changes on above and belowground communities in the modulation of EMF responses at short-term after fire. For this purpose, we estimated EMF using an averaging approach from three ecosystem functions (carbon regulation, decomposition and soil fertility) and their standardized functional indicators in field plots burned at low and high fire severity 1-year after a wildfire occurred in a Mediterranean ecosystem in the central region of Spain. Plant taxonomic and functional richness, and the bacterial and fungal taxonomic richness, were measured in the plots as community properties with a potential intermediate control over fire severity effects on EMF. The ecological effects of fire severity on above and belowground communities were important in shaping EMF as evidenced by Structural Equation Modeling (SEM). Indeed, the evidenced shrinkage exerted by high fire severity on EMF at short-term after fire was not direct, but modulated by fire-induced effects on the plant functional richness and the microbial taxonomic richness. However, EMF variation was more strongly modulated by indirect effects of fire severity on the biodiversity of soil microbial communities, than by the effects on the plant communities. Particularly, the fungal community exerted the strongest intermediate control (standardized SEM [3 coefficient = 0.62), which can be linked to the differential response of bacterial ([3 = -0.36) and fungal ([3 = -0.84) communities to fire severity evidenced here. Our findings demonstrate that the effects of fire severity on above and belowground communities are important drivers of shortterm ecosystem functioning. Efforts tailored to secure the provision of multiple functions should be focused on promoting the recovery on soil microbial communities under high-severity scenarios.