Fungal but not bacterial β-diversity decreased after 38-year-long grazing in a southern grassland

Aims Livestock grazing greatly affects the soil environments and soil microbial community, potentially driving significant biodiversity losses. Yet, how soil microbial communities respond to grazing remains relatively unknown in southern grasslands. This study hypothesized that long-term grazing alters soil microbial community composition and reduces microbial diversity by changing underlying soil properties. Methods To assess the impact of long-term grazing on soil properties, bacterial and fungal diversity and microbial community composition were investigated in replicate grazed (38 years of moderate intensity grazing) and ungrazed plots in a subtropical grassland, China. Results Fungal β-diversity was more sensitive to long-term grazing than bacterial β-diversity, with fungal β-diversity decreasing by 28.8%. No significant differences in soil bacterial or fungal α-diversity were detected between grazed and ungrazed plots. Additionally, long-term grazing altered microbial community composition, altering the relative abundance of specific microbial taxa. For bacteria, the relative abundance of Actinobacteriota (41.9%) increased and Acidobacteriota decreased (−22.3%). For fungi, grazing increased the relative abundance of Mortierellomycota (108.1%) and decreased Basidiomycota (−79.5%). Changes in both bacterial and fungal community composition were well explained by available phosphorus, dissolved organic nitrogen, dissolved organic carbon, soil organic carbon, total soil nitrogen, and NH 4 + -N. Conclusions Our study showed that fungal β-diversity decreased after long-term grazing, necessitating changes to grazing management practices to foster soil biodiversity conservation and functions in southern grasslands.