soil microbial diversity

To explore the effect of land-use intensification on bacterial and fungal ecological patterns, including diversity, composition, and co-occurrence networks in the Karst cultivated soils. In this research, we defined land-use intensity according to planting frequency as uncultivated land (Uncultivated soil) < commonly cultivated land (Maize soil < Cabbage soil < Cocozelle soil). We integrated data on soil microbial community, and environmental factors to investigate ecological patterns of bacteria and fungi in cultivated land using 16S rRNA, ITS sequencing, and network analysis. Soil organic matter, alkali-hydrolyzable nitrogen, total nitrogen, alpha diversity of bacteria and fungi reduced with an increase in land-use intensity in commonly cultivated land. The concentration of these indicators was higher than in uncultivated land, while the abundance of pathogens showed an opposite trend. Bacteria exhibited wider niches and relatively more taxa than fungi, and they had the nodes, edges, and Keystone taxa in co-occurrence networks. Beta diversity of bacteria and fungi were significantly different under different land-use intensities in commonly cultivated land. Mantel test and RDA analysis both indicated that total nitrogen was an important driver of bacteria and fungi. Whereas, functional predictions indicated that land-use intensification would decrease the soil nitrogen fixation capacity. Combined with the reduction in soil nitrogen content and co-occurrence network complexity, the increase in pathogenic bacteria in commonly cultivated land clearly demonstrates that land-use intensification will bring negative effects on the soil. These findings have significances for formulating a reasonable land use intensity management program to prevent land degradation in Karst area.