Grazing exclusion changes the complexity and stability but not the α-diversity of the microbial community in a desert steppe

Abstract

Grazing exclusion (GE), to achieve ecological restoration, has a significant impact on plant community features and soil physicochemical qualities, including soil fertility. Whereas, the responses of soil microbial diversity, complexity, and stability to GE in a water-limited desert steppe remain poorly understood. GE of different durations (14 and 20 years) was implemented in a desert steppe of central Inner Mongolia in this study. Changes in soil physicochemical properties and chemical stoichiometry were observed with increasing restoration time, accompanied by variations in the composition of the microbial community. GE did not alter α-diversity, but it did change the microbial community structure and composition, with significant differences between those in the topsoil and subsoil. A symbiotic network analysis revealed a gradual increase in the complexity of soil bacterial and fungal networks with the increasing GE duration, and that the rate of change was greater in the bacterial than in the fungal community, with greater changes in the latter in the subsoil than in the topsoil. There was no significant change in the stability of the bacterial network under GE whereas the stability of the surface fungal network increased and then decreased, and the underlying stability increased significantly. The Zi-Pi plots and CCA (Canonical Correlation Analysis) analysis revealed important roles for the bacterial phyla Actinobacteriota, Proteobacteria, and Chloroflexi as well as for the fungal phyla Ascomycota, Mortierellomycota, and Basidiomycota in the response of the soil to environmental variations. Available nitrogen and the carbon to nitrogen ratio were the environmental determinants to affect the structure of topsoil fungal community (P < 0.05). As for the subsoil, available phosphorus and above-ground biomass were the environmental determinants to affect its structure (P < 0.05; P < 0.01). Our findings highlighted the critical role of ecosystem restoration duration in shaping soil microbial community in water-stressed steppes. Specifically, the duration significantly influenced the complexity and stability of these community. Furthermore, the community exhibited differential adaptive responses to environmental changes.