Role of fire on soil organic matter turnover and microbial activity in a mediterranean burned area.

This study examined the effects of light and intense experimental fires and of wildfire on the soil microbial biomass and activity and on organic carbon turnover in a coastal area of southern Italy. Wildfire, that mainly affected plant cover, caused a rise in the input of organic matter to the soil, but did not significantly influence total microbial biomass nor fungal mycelia. In contrast experimental fires developing on the soil surface caused a decrease in the organic carbon as well as in total microbial biomass and fungal mycelia. All types of fires resulted in an increased soil potential respiration and metabolic quotient (qCO2: mg CO2-C mg-1 Cmic 10 d-1). Moreover, increases in the coefficient of endogenous mineralization (CEM: mg CO2-C g-1 Corg 10 d-1) after experimental fires and increases in the soil CO2 emission after wildfire were also observed. The data suggest that burned soils may be an important source of carbon for the atmosphere.