Variations of microbial communities and enzyme activities in rhizosphere and non-rhizosphere soils of aged Loropetalum chinense forests in karst rocky mountains during dry and rainy seasons

To understand the seasonal changes and influencing factors of soil biological activity in karst areas, we investigated the changes in rhizosphere and non-rhizosphere soil microbial communities and enzyme activity of the Loropetalum chinense community in the aged forest stage of karst areas, as well as their relationships with environmental factors. The results were as follows:(1)During the rainy season, the pH value, organic matter, total carbon, total nitrogen, total potassium, total phosphorus contents, and alkaline phosphatase, catalase, and urease activities of rhizosphere soil were lower than those of non-rhizosphere soil, indicating that nutrient leaching in rhizosphere soil was more severe and affected the activity of related enzymes. In contrast, the changes in dry season were nutrient enrichment strategies adopted by rhizosphere soil for healthy plant growth.(2)The diversities of fungi in rhizosphere and non-rhizosphere soils were both significantly higher in the dry season than in the rainy season; the bacterial diversity of non-rhizosphere soil was significantly higher in the rainy season than in the dry season, but the seasonal differences in bacterial diversity of rhizosphere soil were not significant. Regardless of the dry and rainy seasons, the dominant fungal phyla in rhizosphere and non-rhizosphere soils were Ascomycota, Mortierellomycota, and Basidiomycota, while the dominant bacterial phyla were Actinobacteriota, Proteobacteria, and Acidobacteriota. The seasonal changes had significant differences in the structure of microbial communities in rhizosphere and non-rhizosphere soils.(3)The dominant factors of rhizosphere and non-rhizosphere soil microbial communities varied in different seasons. During the rainy season, the rhizosphere soil exhibited pH, catalase and alkaline phosphatase activities, while non-rhizosphere soil exhibited catalase, alkaline phosphatase, cellulase activities, and total potassium content; during the dry season, the rhizosphere soil exhibited catalase activity and soil water content, while non-rhizosphere soil exhibited cellulase and sucrase activity. In addition, soil enzyme activity was significantly correlated with carbon, nitrogen, phosphorus, potassium, and soil water content.(4)Compared to bacteria, fungal functions in rhizosphere and non-rhizosphere soils were more sensitive to seasonal changes. In summary, the adaptive strategies adopted for microbial communities and enzyme activities in rhizosphere and non-rhizosphere soils during the rainy and dry seasons are significantly different. The research results provide theoretical references for vegetation restoration and soil succession in karst areas.