Decoupled diversity patterns in microbial geographic distributions on the arid area (the Loess Plateau)

Abstract

Soil microbes are essential to biogeochemical cycling, soil organic matter decomposition and climate regulation in terrestrial ecosystems. The biogeography of soil bacteria and fungi lags behind in animals and plants, especially in arid areas with alkaline conditions. Understanding the biogeographic of soil microbes and the interactions with environmental factors will provide new insights into the ecosystem functions and services droved by soil bacteria and fungi. Therefore, we chose 48 dryland sites from two transects (north-south and east-west transects) on the Loess Plateau (an arid area) to determine soil bacterial and fungal diversity and community compositions in response to environmental factors and geographic distance. The results showed that soil organic carbon enhanced soil fungal diversity rather than soil bacterial diversity, while soil bacterial diversity was not affected by the environmental factors on the Loess Plateau. The significant associations between the abundance of main bacteria and fungi and soil pH, suggesting that soil pH was the predominant factor affecting soil microbial community structure. In the alkaline soils (pH = 7.4–9.1), soil bacterial community compositions were limited by soil pH, while soil fungal community composition was less sensitive in response to the alterations in soil pH, revealing soil fungi has a wider optimal pH range than bacteria. Compered to historical contingencies, local environment mainly controlled the geography of bacteria and fungi in soils. On the Loess Plateau, soil microbial communities diverge most by soil pH, especially for soil bacteria. These results provide a well understanding of soil microbial geography and associated biogeochemical cycling in arid areas with higher soil pH.