Soil pH determines the alpha diversity but not beta diversity of soil fungal community along altitude in a typical Tibetan forest ecosystem

Despite their symbiotic relationship with trees and the vital role as decomposer in forest, soil fungi received limited attention regarding their changes with altitude in forest ecosystems. This study aimed to determine the diversity patterns of soil fungi along an altitudinal gradient on Mt. Shegyla, a typical forest ecosystem on the Tibetan Plateau. High-throughput barcoded pyrosequencing and quantitative PCR approaches were employed to measure the community composition, diversity, and abundance patterns of soil fungal 18S ribosomal RNA (rRNA) gene in 20 samples collected along the altitudinal gradient of Mt. Shegyla. Abundant taxa in the fungal community were Agaricomycetes and Leotiomyceta on Mt. Shegyla. Fungal abundance decreased significantly with increasing altitude. Beta diversity of the fungal community, as measured using weighted UniFrac distance, was significantly related to altitude. Significant correlation was observed between altitude and alpha diversity including richness and phylodiversity, but not with evenness. Network analysis revealed that Ceramothyrium and Clavulina were two important hubs in the community, and an uncultured fungal taxon that previously detected in glacier forefront dominated this network. Distance-based linear model identified soil pH as the dominant driver which significantly related with fungal alpha diversity including richness, phylodiversity, and evenness. However, fungal abundance and the first component of PCoA on weighted UniFrac matrix (beta diversity) did not change significantly with pH. These results provided strong evidence that soil pH was the dominant driver for structuring altitudinal alpha diversity pattern but not beta diversity pattern or community abundance of soil fungi in this typical forest on the Tibetan Plateau.