Urban soil health improves with green infrastructure and reduced pathogen risks

Urban land-use change significantly alters soil microbial communities, with consequences for ecosystem functionality and public health. However, the ecological and health-related outcomes of converting cropland into urban green infrastructure remain poorly characterized. In this study, we examined how three land-use types, afforestation, constructed wetlands, and urban infrastructure, affect soil bacterial diversity, community assembly, and pathogen risk over a three-year period (2019-2023). Using full-length 16S rRNA sequencing, enzyme activity assays, network analysis, and a composite pathogen risk index, we found that green infrastructure markedly enhanced bacterial diversity and community stability. For example, constructed wetlands increased bacterial richness and phylogenetic diversity by over 5 % and 8 %, respectively, and promoted deterministic community assembly. They also exhibited the lowest pathogen risk index (0.312), representing a 50.94 % reduction compared to the initial cropland. In afforested soils, more than 80 % of the pathogenic taxa present in 2023 were inherited from the 2021 community, indicating stabilization over time. In contrast, maize-wheat rotation croplands retained over 85 % of earlier pathogenic taxa and had the highest risk index, likely due to continuous organic fertilization. Pathogen-bacterial interaction networks in croplands were more complex and fragmented, whereas green infrastructure supported simpler, more stable interactions. These findings highlight the role of green infrastructure in reducing soil-borne pathogen risks while supporting microbial diversity, offering actionable insights for sustainable land management and urban public health planning.