Effects of Different Altitudes on Castanopsis hystrix, the Top Community-Building Species in Southern Subtropical China: Rhizospheric Soil Chemical Properties and Soil Microbiota

Castanopsis hystrix, a dominant canopy species in the subtropical forests of south China, is renowned for its high natural regeneration ability. Therefore, this paper took C. hystrix as the subject of study. Examining the variations in microbial diversity and community composition within the soil rhizosphere of C. hystrix across different elevation gradients, we explored how this community-forming species impacts soil microbial diversity and community structure and how soil microorganisms respond to changes in soil physicochemical properties due to altitude gradients. The results show: (1) soil samples from five altitudes established 1078 fungal OTU and 5595 bacterial OTUs. (2) Basidiomycota and ascomycota are dominant fungal groups in the soil, with Acidobacteria being the predominant bacteria for C. hystrix. (3) As altitude increases, fungal communities' richness and diversity index peaks at 849 m; for bacterial communities, the richness index peaks at 387 m and the diversity index at 670 m. (4) Total phosphorus (TP), nitrate nitrogen (NO3--N), hydrolyzed nitrogen (HN), total nitrogen (TN), and organic matter (SOM) are significant environmental factors affecting fungal community structure. At the same time, available potassium (AK) significantly influences the composition of bacterial communities. The study underscores the intricate relationship between altitude, soil properties, and microbial diversity, offering insights into how C. hystrix contributes to ecosystem resilience. Recommendations include enhancing phosphorus supplementation and controlling nitrogen deposition to maintain forest ecological integrity, additionally, the supply of potassium in the soil should also be a key consideration. Further research is necessary to understand the broader implications for biodiversity conservation and adaptive management strategies in the face of climate change.