Urbanization increases the complexity of soil microbial interaction networks

Urbanization reshapes soil ecosystems, yet its impacts on the composition and interactions of soil microbial communities remain insufficiently understood. Here, we use high-throughput sequencing to profile bacteria, fungi, and protists across four representative habitat types of different urbanization level-campuses, roadside greenbelts, suburban unmanaged lands, and concrete pavements in four Chinese cities spanning a broad latitudes (Changchun, Beijing, Hangzhou, Haikou). Vegetated habitats consistently structure microbial communities, whereas concrete pavements form a distinct disturbed habitat with the lowest microbial richness. Bacterial richness is highest in campuses and roadside greenbelts, while fungal and protistan richness peaks in suburban unmanaged lands. Despite regional variation, communities under similar vegetation types show convergent compositions, jointly shaped by regional climate and land-use intensity. Bacterial assemblages are more sensitive to environmental variation than fungi and protists. Proteobacteria dominate bacteria communities, whereas fungal and protistan communities display marked habitat specificity. Co-occurrence networks complexity peaks in roadside greenbelts, remains stable in suburban unmanaged lands and collapses significantly in concrete pavements. Microbial diversity patterns are strongly associated with temperature, soil pH, and latitude. Together, these results demonstrate that environmental conditions and urbanization intensity drive the biogeography and interaction patterns of soil microbiomes, providing insights for ecological restoration and urban green-space management.