Microbial community assembly and co-occurrence relationships in the shallow groundwater of intensive vegetable cultivation and rural areas in the Huaibei Plain, China

Microbial communities are crucial contributors to the cycling of elements within groundwater systems. However, limited research has been conducted on the composition and assembly mechanisms of microbial communities in groundwater within the intensively cultivated vegetable areas (IVCs) of the Huaibei Plain, as well as the relationships between microbial communities and hydrogeochemical parameters. Therefore, in this study, the structure and assembly process of prokaryotic microorganisms in the groundwater of IVCs and rural areas (RAs) in the Huaibei Plain of China were investigated, and the factors influencing the microbiota structure, function, and assembly process in IVC and RA groundwater were assessed based on hydrogeochemistry, co-occurrence network analysis, and null modeling analysis. The main findings indicate that groundwater from IVCs significantly increase NO 3 -N concentrations, compareed with RA groundwater. Despite considerable similarity in groundwater microbial community composition between the IVCs and RA regions, significant differences were identified in a subset of microbial taxa across phylogenetic levels from phylum to genus. However, the groundwater in the IVC had a higher abundance of microorganisms related to nitrification at the genus level. Co-occurrence network analysis demonstrated that the microbial communities in the RA groundwater exhibited more the percentage of positively correlated edges, and the key species in the microbial communities of IVC groundwater were related to nitrogen and sulfur cycling. The null model analysis results indicated that dispersal limitation in stochastic processes dominated the assembly of groundwater microbial communities in the IVCs and RAs. Multivariate statistical analysis identified that pH is the key environmental factor controlling the groundwater microbial community composition and assembly process in IVCs. These findings contribute to a deeper understanding of the influence of IVCs on groundwater physicochemical properties and microbial community assembly mechanisms.