Comparative assessment of microbial activity and biomass in paired forest and agricultural soils

A forest soil located in the “Parco Nazionale del Cilento e del Vallo di Diano”, Salerno, Italy, has been partly converted to a crop field by deforestation and a deep tillage (mouldboard plowing), characterized by an inversion of soil profile at a depth of 1 m, followed by plowing. In this study, we compare soil quality in a crop field and in the adjacent unchanged forest. Soil samples were collected from the two sites few months after the use change and characterized for main chemical (pH, electrical conductivity, organic C, total N, available P, cation exchange capacity) and microbiological (enzyme activities related to cycles of major nutrients, catabolic response profiles, microbial and fungal biomass) properties. We found a depletion of 50 % in soil organic C content in the crop field in comparison with forest, which indicates that the quality of the top layer of the soil decreased, with consequent deep alteration of the C cycle. The drop of organic matter content determined serious effects on soil microbial activity. Microbial and fungal biomass, as well as all enzyme activities, were decreased. The soil catabolic response profiles showed a significant reduction in functional diversity in the cultivated compared to the forest soil. Among the investigated properties, dehydrogenase and β-galactosidase activities, ergosterol content and catabolic evenness showed the highest sensitivity to the soil use change, suggesting that they could be assumed as indicators of the stress induced by this use change.