Functional diversity of the microbial community in Mediterranean maquis soils as affected by fires

Fire is a disturbance in the Mediterranean region associated with frequent drought periods, and can affect the soil microbial community, which plays a fundamental role in nutrient cycling. In the present study the effect of low- and high-severity experimental fires on the soil microbial community was evaluated in an Italian Mediterranean maquis. Burned and unburned soils were compared for functional diversity, specific activities, microbial biomass, fungal mycelia and fungal fraction of microbial carbon, during the first year after fire. In the first week after fire, changes in the functional diversity were observed in burned soils, differing also between low- and high-severity fires. Respiration responses to specific organic compounds were generally lower in burned soils during the whole study period, with a percentage of changed responses from 2 to 70%. The general reduction in burned soils of the fungal fraction of microbial carbon (19–61%) and active mycelia (16–55%), together with the increase in microbial biomass carbon (29–42%) during the first 3 months after fire, suggest a larger and longer effect of fire on fungi than on bacteria. The results indicate a rapid recovery of functional diversity in soil after burning despite the persistent reduction of microbial community activity and the change in its structure.