Growth Stage-Dependent Variation in Soil Quality and Microbial Diversity of Ancient Gleditsia sinensis

The environment monitoring of forest is vital for the ecosystem sustainable management, especially soil quality. Ancient Gleditsia sinensis is one of the most distributed ancient trees in Shaanxi. Comprehensive soil evaluate is important for the ancient tree protection. In this study, we selected the most distributed ancient tree Gleditsia sinensis and immature tree to compare the effect of growth stage to soil quality and soil bacteria. Most ancient tree soil nutrients were in good condition compared with immature tree. The bacterial community were composed with Proteobacteria (27.55%), Acidobacteriota (16.82%), Actinobacteriota (15.77%), Gemmatimonadota (6.82%), Crenarchaeota (4.61%), Bacteroidota (4.41%), Firmicutes (4.32%), Chloroflexi (4.28%), Planctomycetota (3.24%) and Verrucomicrobiota (3.04%). The level 2 ancient tree (300–400 years old) was different in bacterial community diversity. SOC and STN were important to level 2 (300–400 years old Gleditsia sinensis), and other levels were opposite. Our results suggested that the ancient tree management should not be lumped together.