Soil bacterial and fungal communities respond differently to post-fire restoration treatments

Wildfires are increasing in frequency and severity in Mediterranean forests, intensifying the need for effective post-fire management strategies that support long-term ecosystem recovery. While the effects of wildfire and post-fire interventions on soil physicochemical properties are relatively well documented, their long-term impacts on soil microbial communities, key drivers of ecosystem functioning, remain poorly understood. In this study, we assessed long-term differences in soil bacterial and fungal communities associated with wildfire and post-fire management in a Mediterranean pine forest six years after a high-severity fire. We evaluated bacterial and fungal communities under salvage logging and straw mulching, applied individually and in combination, using high-throughput DNA metabarcoding of soil samples. Our results showed persistent differences between burnt soils and nearby unburnt reference soils six years after the fire, with contrasting responses between bacteria and fungi, i.e., bacterial communities under the combined mulching and salvage logging treatment were more similar to those in unburnt reference soils, whereas fungal communities remained structurally distinct across all burnt treatments. The combined mulching and salvage logging treatment was also associated with lower fungal alpha diversity than that observed in unburnt reference soils, while salvage logging alone showed no comparable patterns. These findings highlight contrasting long-term trajectories of soil microbial communities following wildfire and post-fire management and emphasize the need to consider belowground biodiversity when designing restoration strategies in fire-prone Mediterranean ecosystems.