Influence of pedogenesis factors on soil microbial communities

Most of the studies in soil microbiology focused exclusively on the soil surface, conversely, scarce is the knowledge about the nature of the microbial communities inhabiting the deeper soil horizons. The main aim of the present study was to investigate the impact of soil forming factors and, in turn, of soil physical and chemical properties on bacterial community harbouring within the soil horizons. The study was conducted in the Frignano Park, located in the Northern Apennines (Italy). Four sites were selected along an altitudinal transect ranging from 700 to 1,350 m a.s.l.. In each site, soil profiles were dug till parent material under different land use (i.e., pasture, forest), the identified horizons were sampled and analyzed for microbial community by Next-Generation Sequencing and main physical-chemical properties. The findings showed the predominance of Firmicutes, Actinobacteriota, Acidobacteriota, Proteobacteriota, Chloroflexi, Planctomycetota, and Verrucomicrobiota. Soil pH and lithology were found as the main factor for shaping soil bacterial diversity and community composition. Indeed, it was observed that Firmicutes were dominant in hydromorphic soils while Acidobacteriota were mostly found in acidic soils and in those where the acidification is currently occurring. While more alkaline soils were characterized by the abundance of the Actinobacteriota. In summary, this study showed that among the soil physicochemical factors, pH was the main factor explaining the variation in bacterial communities.