Physical and Chemical Properties of Soils Derived from Different Parent Rocks Mediate Microbial Carbon Cycling

Parent rock is a key factor contributing to differences in soil physical and chemical properties. However, the mechanism of microbial carbon cycle mediated by soils with different physical and chemical properties based on parent rock are unclear. In this study, the physical and chemical properties of weathering soils of different parent rocks and the characteristics of soil carbon content were analysed. The composition of soil bacteria and fungi and the genes associated with carbon cycle were analysed via genome sequencing. The results showed that the highest abundance and diversity of soil microbes was detected in purple sandstone, followed by limestone and the least in basalt. Further, the predominant bacterial phyla in the three parent rocks were Proteobacteria, Chloroflexi, Acidobacteria, and Actinobacteria. The predominant fungi were those belonging to phyla Basidiomycota, Ascomycota, and Mortierellomycota. Soil organic carbon (SOC) and available nitrogen (AN), available potassium(AK) and available phosphorus (AP) were the main factors affecting the composition of soil bacteria, while soil soil water content (SWC) pH and AP were the main factors affecting the composition of soil fungi. Similarly, the relative abundance of functional genes associated with soil carbon cycle was the greatest in the purple sandstone, followed by limestone and the least in basalt. The variation in relative abundance of the genes was correlated with the soil physico-chemical properties, especially soil SWC, pH, and AP, which limited carbon metabolism of the soil microbes. Our results show that soil physical and chemical properties of the parental rock regulate microbial composition and carbon cycling.