Objective  This study aimed to explore the effects of the alterations in soil physicochemical properties on microbial structure and diversity driven by the land-use changes, thus providing a theoretical basis for land use management of the Napahai Plateau wetlands.

  Method  The Illumina high-throughput sequencing technology was applied to determine the composition and diversity of soil microbial communities across the different land-use patterns (i.e., grazing grassland, cultivated land, and a natural swamp wetland (CK)). A Mantel test was also utilized to reveal the impacts of the changes in soil physicochemical environments on microbial communities.

  Result  ① In contrast to natural swamp wetland, tillage and grazing activities significantly reduced soil water content, organic matter, and total nitrogen and available nitrogen, but increased total phosphorus, carbon to nitrogen ratio, and bulk density (P < 0.05). ② Tillage and grazing activities significantly increased the α-diversities of soil bacterial and fungal communities (P < 0.05), and the β-diversity was different between the three land-use types (P < 0.01). ③ Tillage and grazing activities significantly changed soil bacterial and fungal structures. Tillage increased the relative abundances (21.07%-123.61%) of Proteobacteria, Firmicutes and Chlorobacteria, while those of Acidobacteria, Actinobacteria, and Gemmatimonadetes decreased by 62.7%-75.29%. Tillage reduced the relative abundances (71.33%-96.47%) of Ascomycetes, Basidiomycetes, and Zygomycetes, while those of unclassified fungi increased by 722.97%. Grazing activities increased the relative abundances of Verrucomicrobia (57.46%) and Planctomycetes (179.12%), but reduced those (16.23%-67.16%) of Proteobacteria, Bacteroidetes and Gemmatimonadetes (P < 0.05). Grazing activities significantly increased the relative abundances of Basidiomycetes (34.57%) and Ascomycetes (105.94%), while they decreased the abundances of Zygomycetes (93.90%) and unclassified fungi phylum (45.66%). ④ The results from Mantel test showed that soil water content, organic matter, and total nitrogen were the main factors determining the changes in soil microbial diversity, while soil phosphorus, potassium and pH were the drivers of the alterations in bacterial and fungal structures.

  Conclusion  Tillage and grazing activities primarily increased wetland draining and total phosphorus concentration, and decreased soil carbon and nitrogen nutrients, which led to the change of microbial metabolic-type composition as well as the increase of microbial diversity.