Diversity patterns and drivers of soil bacterial and fungal communities along elevational gradients in the Southern Himalayas, China

Elucidating the diversity patterns and drivers of soil microbes at high altitudes contributes to understanding the role microbes play in ecosystem services, but little is known about the soil microbial diversity, richness and abundance patterns across elevations on the Tibetan Plateau. This study was conducted to explore the shifts of forest soil bacterial and fungal community diversities and the regulating factors along an elevation gradient (2980-4050 m a.s.l.) in the Southern Himalayas of China. Illumina sequencing of 16S rRNA and ITS1, and quantitative real-time PCR were used to determine soil bacterial and fungal communities, coupled with plant diversity survey and edaphic properties analysis. The results revealed that plant alpha-diversity reached the highest level at an elevation of 3255 m and subsequently decreased with higher elevations; while soil bacterial alpha-diversity and fungal richness reached the lowest at 3590 m and 3772 m respectively, then increased with higher elevations; soil microbial abundance decreased with increasing elevation. The soil pH was the main driver of the elevation-related soil bacterial richness, diversity, and abundance. Soil nutrients contributed most to the fungal richness, diversity, and abundance. The total phosphorus content was the optimal predictor of fungal richness and abundance, while nitrate levels determined the fungal diversity. The community structures of bacteria and fungi differed significantly among elevations (Pbacteria = 0.001, Pfungi = 0.001). The elevation and edaphic properties (including the contents of soil organic matter and pH) controlled the elevation patterns of soil bacterial community structures and explained 56.1 % of the total variation. In contrast, edaphic properties (including SOC, TP and pH) primarily shaped the elevation patterns of soil fungal community structures and explained 38.7 % of the total variation. This study provides comprehensive insights into soil microbial geography associated with the biogeochemical cycling on the Tibetan Plateau.