Ability of soil bacterial composition as an indicator of levels of soil erosion in a badland

Abstract

Calanchi (plural of calanco) are typical Italian badlands created by a combination of morphogenetic processes (rill and interrill erosion, gullying, piping, and mass movements) mainly originated by the effect of water. Calanchi are characterized by the sparse and patchy distribution of vegetation, and, in interplant areas, the soil surface is colonized by an association of organisms known as biological soil crust (BSC). A morphometric analysis of 45 basins in the studied calanchi area, based on a high-resolution digital elevation model, showed those basins are sediment removal systems characterized by rapid and relevant erosion processes. The goal of the current research is to evaluate the bacterial composition of BSC and to recognize its signature of land degradation processes in soil samples by a microbiological analysis (culture-dependent and culture-independent approaches). Soil bacterial distribution was investigated by a culture-independent approach, applying Illumina technology in soils with different vegetation cover. Four species were detected in site A (bare soil). In sites B (sparse vegetation) and C (densely vegetated soil) 19 and 18 bacterial taxa were detected, respectively. Sites B and C were characterized by 17 species in common. The microbial communities detected at sites B and C are typical of environments unable to support vegetation and microorganisms that are not specialized to live in these environments. Biodiversity analysis of the bacterial communities of biocrusts, done using richness and evenness indices, confirmed that the composition of the BSC communities can be a signature of the intensity of soil erosion processes.