The combined role of plant cover and fire occurrence on soil properties reveals response to wildfire in the Mediterranean basin

Climate change has strongly increased the fire frequency in Mediterranean forests causing changes in soil bacterial, fungal and microarthropod communities. Fire impacts on soil properties depend on vegetation covers. In this framework, the aim of this research was to evaluate the effects of fire on bacterial, fungal communities and microarthropod community in soils under trees and shrubs in a Mediterranean area. Surface soil cores were sampled in unburnt and burnt (three years since fire occurrence) patches in the Vesuvius National Park trees (Quercus ilex L. and Pinus nigra L.) and shrubs (Ginesta sp., Myrtus communis L., Laurus nobilis L.). Samples were analyzed for abiotic (pH, water content and concentrations of C, N, C-org, P, NO2-, NH4+ and P-avail) and biotic (bacterial and fungal biomasses, and density, taxa richness, diversity, evenness and QBS-ar of microarthropods) properties. Results showed that, three years since fire, the abiotic properties were recovered in shrub stands but not yet in tree stands. Fire stimulated the development of bacteria only in shrub stands; no effects were observed for the fungal community in both shrub and tree stands; the amount and the taxa richness of microarthropods recovered to the values of the pre-fire conditions in both the stands. In conclusion, in the investigated area, fire differently impacted the vegetation covers, making soils under trees more similar to shrubs with the consequence to reduce the differences between the vegetation covers.