Factors influencing the bacterial community assembly in the soil of a salt marsh in the desert steppe dominated by Sophora alopecuroides

Abstract:

[Background] Salt marshes in desert steppe are an important part of terrestrial ecosystems, and soil moisture and salinity changes are important factors affecting the soil bacterial community assembly in this ecosystem. [Objective] The soil bacterial community assembly is a continuous ecological process dominated by deterministic and stochastic processes. Revealing the assembly mechanism of soil bacterial communities in salt marshes of desert steppe helps to deepen our understanding about the importance of microorganisms as key ecosystem factors. [Methods] The physicochemical properties were measured for the soil samples collected near the Kushuihu lake (NL) and far from the Kushuihu lake (FL), a typical salt marsh area of the desert steppe in central Ningxia. High-throughput sequencing was performed to analyze the bacterial information. [Results] NL and FL sampling sites presented significant water-salt gradients. The NL soil samples had higher pH, water content, and electrical conductivity than the FL soil samples. Proteobacteria, Actinobacteriota, Firmicutes, Bacteroidota, and Myxococcota were the dominant phyla in the soil samples. As the water-salt gradient increased, the relative abundance of Proteobacteria increased, while that of Actinobacteriota and Firmicutes decreased. Most of the members belong to the phyla had obvious correlations with water-salt changes. In addition, the soil bacterial network in the FL sites had stable network relationship. From the NL to FL sampling sites, the soil bacterial community gradually became being dominated by stochastic factors and was influenced by soil pH, electrical conductivity, and environmental variables. [Conclusion] The changes in soil moisture and salinity in salt marshes of desert steppe altered the soil bacterial community structure. Soil bacterial communities improved the survival under stress by strategies such as niche occupation. The assembly of bacterial communities is a continuum consisting of stochastic and deterministic processes, which are influenced by environmental changes. The results reveal the response characteristics of bacterial community structure and interrelationship to environmental changes in salt marshes of desert steppe and clarify the assembly mechanism and influencing factors of soil bacterial community, providing a theoretical reference for related studies.