The assembly process and co-occurrence patterns of soil microbial communities at a lead smelting site.

The potential toxic elements of the site are diverse and complex, seriously threatening the land utilization potential and soil ecological function. Microbial community is critical to maintaining ecosystem function, their assembly processes and diversity play an essential role in predicting changes in soil ecological function. However, our understanding of the mechanisms that shape community composition and successional direction in complex polluted environments is very limited. In this study, to explore the mechanisms driving community assembly and symbiosis in different contaminated regional environments, the biological characteristics of bacterial and fungal communities in four different polluted areas of a typical lead smelting site were studied. Contamination by PTEs appears to increase microbial networks, as well as altering microbial community composition, with relative abundance of dominant phyla such as Actinomycetes and Acidobacteria decreasing, whilst Proteobacteria and Ascomycota increased, this indicated that communities may shift from K-strategy to r-strategy and become opportunistic. Dispersal limitation (DL, 42 %-86 %), drift (Dr, 8 %-37 %) and homogeneous selection (HoS, 1 %-31 %) proved to be the important community assembly process. The top ten bins controlling the contribution of different biological processes were identified, and the relative abundance of these bacterial and fungal taxa varied with CPI. Collectively, our results suggest that CPI and nutrient availability regulate soil bacterial and fungal community assembly processes. The results of this study provide potential guidance for community regulation in the process of ecological restoration and mitigating degraded soils at smelting sites.