Bacterial and fungal community assembly in relation to soil nutrients and plant growth across different ecoregions of shrubland in Shaanxi, northwestern China

Abstract

Revealing soil microbial community assembly and associated influencing factors is essential for understanding the diversity and functioning of terrestrial ecosystems. Yet how soil microbial communities respond to environmental factors and plant traits in natural shrub ecosystems has received little attention. Therefore, we explored the diversity and assembly mechanisms of soil bacterial and fungal communities across four ecoregions of natural shrubland in Shaanxi Province, northeastern China. Soil chemical properties, climatic variable, and plant growth traits of dominant shrub species were analyzed to determine their relationships with local soil microbial communities. The results indicated that soil bacteria and fungi in the four ecoregions had divergent diversity patterns. The microbial community composition was significantly affected by soil pH, nutrients, and mean annual precipitation. Bacterial community assembly was mainly driven by variable selection (a deterministic process) in the Loess Plateau and the southern slope of Qinling Mountains, or by stochastic processes in the Mu Us Desert and the northern slope of Qinling Mountains. Fungal community assembly was primarily influenced by variable selection in different ecoregions, except for the Mu Us Desert. A highly connected subnetwork of microorganisms did not exist in the desert, but in the southern mountain slope the microbial network did harbor remarkably critical nodes. Bacterial keystone taxa that belonged to Chloroflexi were most relevant to shrub biomass traits. Our findings have implications for predicting the structure of microbial communities in shrubland soils in response to environmental change and their potential impact on plant growth. This study could improve our understanding of soil bacterial and fungal diversity and community assembly patterns in natural shrublands.