Abstract
Land types and ways of utilization significantly influence soil microbial communities in arid and semi-arid regions, which are vital for nutrient cycling and ecosystem functionality. In this study, the soil bacterial and fungal communities of five land types, including natural grasslands, farmlands, artificial grasslands, uncultivated lands, and riverbeds in the semi-arid lower reaches of the Heihe River, China, were investigated. Farmlands exhibited the highest bacterial Chao1 richness and Shannon diversity, while uncultivated soils had the lowest bacterial Chao1 richness. Fungal diversity was highest in uncultivated soils compared to farmlands. Principal coordinate analysis (PCoA) showed distinct microbial community structures across land types, with Actinobacteria, Proteobacteria, Firmicutes, and Chloroflexi dominating bacterial communities, and Ascomycota and Basidiomycota dominating fungal communities. Life history strategies revealed distinct patterns between bacterial and fungal communities within farmland soils and artificial grassland soils. Microbial community assembly in natural grasslands was primarily deterministic, with limited stochastic influence, while farmlands exhibited mixed assembly processes. Co-occurrence network analysis showed more stable and cooperative microbial networks in natural grasslands, while farmland networks were more competitive and reliant on key species. These findings provide important insights into the role of land use in shaping microbial diversity and ecosystem function, offering guidance for sustainable land management in semi-arid oasis regions.