Soil micro-biological indicators separated land use practices in contrast to abiotic soil properties at the 50 km scale under summer warm Mediterranean climate in northern Italy

Abstract

Soil abiotic properties represent important framing conditions of ecosystems and soil microbiological biomass and microbial activity are the biological driving forces that respond sensitive to environmental impacts. In environmental research and monitoring programmes, approaches for spatial classification were elaborated poorly. Therefore, soil abiotic and microbiological indicators were clustered for a 2965km2 region in northern Italy with the aim to identify the key spatial characteristics. Forty one sampling points for 30cm soil depth were selected at the European Grid of the Land Use Cover Area frame Statistical survey (LUCAS). Soil abiotic indicators included physical (clay content and soil bulk density) and chemical (Cd, Pb and Hg content, organic carbon and total nitrogen) properties. The values varied between 3–47g clay 100g−1 soil, 1.27–1.62Mgm−3, 0.69–3.47g organic C 100g−1 soil and 0.07–0.31g total N 100g−1 soil. Our cluster analysis with the abiotic characteristics separated two core classes derived from four clusters. In contrast, soil microbiological indicators including microbial carbon, respiration values and microbial energetic quotients, separated three well-defined core classes derived from five clusters. The microbial properties values ranged between 24–431μg microbial Cg−1 soil and 0.08–1.82μgCO2-Cg−1soilh−1 and corresponded to those in other European agricultural soils. The three soil microbiological classes separated low, typical and high ranges for soil microbial biomass (values <120, 50–250 and >320μg microbial Cg−1 soil), for soil respiration rates (values <0.4, 0.4–0.7, and >1.4μgCO2-Cg−1soilh−1) for metabolic quotient (values <3.5, 3.5–5.0, >5.0, mg CO2-Cg−1Cmich−1) and for microbial C to organic C ratio (values <0.7, 0.5–1.7 and >1.0%). The soil microbiological indicators responded more evidently to land cover and soil management practices while soil abiotic indicators that referred mainly to the framing conditions such as geology and climatic conditions.