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Abstract: The aim of the study was to examine soil microbial activity and functional diversity in different parts of coastal landscapes influenced by recurring saltwater intrusion in the Ravenna area (Italy). For this reason, seven profiles were selected in the San Vitale Pinewood, in low-lying interdune spot and next to dune crests and swales. Soils were classified as Typic Psammaquent, Typic Ustipsamment, Aquic Ustipsamment and Sodic Psammaquent. Chemical, physical and biochemical properties of soil horizons, such as microbial biomass metabolic quotient and enzyme activity, were determined to examine the effects of soil salinity and sodicity levels on microbial activity and functional diversity. The various soils and horizons could be split into distinct groups based on Differential Function Analysis of their properties. Cellulase, xylosidase and arylsulfatase showed a peak of their activity in surface horizons of sodic soils. α-glucosidase activity also was high in deeper horizons of those soils. Moreover, functional diversity, evaluated through calculation of Shannon''s diversity index, was higher in the surface and deeper horizons of saline soils than non-saline soils. Conversely, soil with shallow water-table showed similar enzyme activity to soil located in the highest spots of the dune system. However, the highest values of specific activity (per unit of organic carbon) recorded in the deep horizons of the Typic Ustipsamment soil suggested more efficient hydrolytic activity of organic substrates due to oxygenation of soil. In conclusion, hydromorphic conditions in these soils influence the efficiency of organic substrate hydrolysis while soil salinity and sodicity increase both biochemical activity and functional diversity of microbial communities. [Copyright &y& Elsevier]

Abstract: This study reports a comparative analysis of soil enzyme activities (β-glucosidase, protease, urease, arylsulphatase, phosphatase and fluorescein diacetate hydrolase), ATP, total N and organic matter contents in three vegetal successional stages (meadow, low shrubland and high maquis) of a Mediterranean ecosystem in the Natural Reserve of Castel Volturno (Campania, Italy). Because water availability is a major limiting factor of soil microbial activity in Mediterranean ecosystems, the analysis was performed in late spring (May), after the rainy period, and in early autumn (October), after the long dry summer. A significant decrease in protease, arylsulphatase, urease and β-glucosidase activities was observed in meadow soil in the autumn sampling, probably due to the prolonged summer drought. Combining the values measured in the two sampling dates, the high maquis tended to have higher levels of enzymes activities than shrubland and meadow. Notably, high maquis had significantly higher phosphatase and arylsulphatase activities than shrubland and meadow and, in addition, a higher ATP content compared to meadow. Drastic changes were observed in EA/ATP ratios between the sampling periods in the meadow and shrubland, suggesting changes in the efficiency of microbial community more likely linked to climatic fluctuations than to the successional stage. The more stable EA/ATP ratio in the maquis probably reflects a constant contribution of microbial biomass to enzyme secretion. In conclusion, our results point to an increase in soil microbial activity accompanying the succession from meadow to high maquis that probably reflects a parallel increase in soil functions. Nevertheless, spatial heterogeneity and, more important, temporal variations in soil activities often may obscure differences related to the plant cover type. [Copyright &y& Elsevier]