The Grain for Green Program Promotes Soil Organic Matter Accumulation and Improves Soil Fungal Diversity in the Southwestern Karst Region

Soil microorganisms play pivotal roles in terrestrial ecological processes. However, how soil microbial biomass and community characteristics respond to changes in land utilization in karst regions remains largely unknown. The present study investigated the impacts of land-use change on soil chemical properties, microbial community structure, and biomass in a karst region of southwest China across four land-use types: shrubland (natural vegetation restoration), plantation forest (managed vegetation restoration), orchards, and croplands. Vegetation restoration increased microbial biomass carbon and microbial biomass nitrogen. Shrubland had the highest bacterial and fungal abundance and fungal diversity; in addition, the soil microbial community structure differed significantly among land-use types. The dominant bacterial phyla were Actinobacteria, Proteobacteria, Acidobacteria, and Chloroflexi, whereas Ascomycota was the predominant fungal phylum, with its abundance declining significantly following vegetation restoration. Soil properties, including soil organic matter and available phosphorus, were strongly associated with microbial community composition and diversity in karst areas. The findings of this study are essential for gaining a deeper understanding of how changes in land-use affect soil properties and microbial dynamics, and provide valuable insights for ecological restoration and agricultural management in karst regions.