Investigating the Effects of Elevation on Microbial Communities and Soil Properties at Fanjing Mountain, China

Elevation is one of the most influential factors affecting soil characteristics and microbial communities in forest ecosystems. Nevertheless, there is no consensus on how soil characteristics, soil microbials, and their relationships response to the elevation of the mountain ecosystem. We investigated the soil physicochemical characteristics, the activity of soil enzymes, and the microbial community at elevational sites from 600 to 2400 m above sea level (asl) in the western slopes of the Fanjing Mountain ecosystem, China. The soil microbial communities were determined by high throughput 16S rRNA and ITS amplicon sequencing. The results demonstrated that soil total nitrogen (TN) showed a slight decrease, whereas total phosphorus (TP) and total potassium (TK) gradually tended to increase with increasing elevation. The large macroaggregates (>2 mm) accounted for the largest proportion of the aggregate fraction (66.23%–76.13%) in the 0–10 cm soil layer with elevation. The average values of the soil electrical conductivity (EC), soil organic carbon (SOC), and cation exchange capacity (CEC) concentration in the 0–60 cm layer undulated with increasing elevation, and the highest values were observed at 1500–1800 m asl and 1800–2100 m asl, respectively. The activities of soil urease, sucrase, acid phosphatase, and catalase clearly differed (p < 0.05) with increasing elevation, and the minimum values were found at 2100–2400 m asl. Interesting, with increasing soil depth, the values of these factors tended to decrease, indicating surface aggregation. In addition, the soil microbial (bacterial and fungal) community diversity exhibited a single-peak pattern with elevation. Our results also revealed that the soil bacterial and fungal communities varied significantly at different elevation sites. The bacterial communities were dominated by the phyla Acidobacteria, Pseudomonadota, and Chloroflexi, and the phyla Basidiomycota and Ascomycota dominated the fungal communities. The Pearson and redundancy analyses revealed that the SOC, TP, four soil enzymes, and soil aggregates were significant factors influencing the soil microbial community. In conclusion, soil properties and enzyme activities jointly explained the elevational pattern of the soil microbial community in the Fanjing Mountain. The results of this study provide insights into the influence of elevation on soil characteristics, microbial communities, and their relationships in the Fanjing Mountain ecosystem.