Effects of prescribed burning on soil microbial community and vegetation in pine plantations of Southern Italy

Prescribed burning application for fire risk reduction, pasture improvement and conservation of natural habitats of Community interest, is increasing throughout Europe. Monitoring ecological effects of prescribed burning on different ecosystems and on different ecosystem components are crucial issues to evaluate the sustainability of this practice. Aim of this study was to evaluate the effect of prescribed burning, applied for the first time in Campania Region (Southern Italy), on both vegetation and soil microbial community, the last playing a major role in nutrient cycling. Prescribed fire was applied to two pine plantations of Cilento e Vallo di Diano National Park in order to reduce fine fuel load and spatial fuel continuity. The study sites were characterized, respectively, by the dominance of Pinus pinaster, in an internal hilly area, and by the dominance of P. halepensis, in a coastal area. Untreated nearby areas were used as control in both plantations. The impact of prescribed burning on some physical (water holding capacity), chemical (pH, organic carbon) and biological (microbial biomass, fungal mycelium and microbial activity) parameters was monitored. In both plantations and at different time since burn (3-5 hours, 11-12 days, 55-56 days and 161-162 days), samples were collected from the fermentation layer and the 5 cm of soil beneath in 6 randomly selected plots of both burned and unburned areas. The effect of fire on vegetation was evaluated by means of floristic composition assessed before and after the treatment. Furthermore, in the P. halepensis plantation the main structural and biometric parameters of the shrubs and soil seed bank were measured before and after the treatment. In the fermentation layer, total microbial biomass showed a statistically significant reduction in both plantations during the whole study period, while microbial activity showed an overall increment. No effect was generally observed in the fungal component and in the organic carbon of the fermentation layer. Soil was usually not altered by the treatment. So far, prescribed fire did not affect tree vitality. Moreover, no significant difference was observed in terms of individual mortality of understorey plants; all the survived shrubs reacted positively to the treatment producing new resprouts. With regard to soil seed bank, no difference was evidenced in terms of floristic composition while an enhanced germination occurred mainly in Erica arborea seeds.