荒漠草原盐沼湿地苦豆子土壤细菌群落构建机制及其影响因素

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

摘要:

【背景】荒漠草原盐沼湿地是陆地生态系统的重要组成部分，土壤水分和盐分变化是影响该生态系统土壤细菌群落构建的重要因素。【目的】土壤细菌群落构建是由确定性和随机性主导的连续生态过程，阐明荒漠草原盐沼湿地土壤细菌群落的构建机制对于加深微生物作为关键生态系统因子重要性的理解具有积极意义。【方法】以宁夏中部典型荒漠草原盐沼苦水湖湿地为研究对象，对近湖边（near the lake，NL）和远离湖边（far from the lake，FL）苦豆子群落土壤理化特性进行测定并结合土壤细菌高通量测序分析。【结果】NL和FL样地具有明显的水盐梯度变化，NL样地土壤pH、含水量和电导率均显著高于FL样地；变形菌门、放线菌门、厚壁菌门、拟杆菌门和黏菌门是研究区域土壤细菌群落的优势菌门，变形菌门相对丰度随水盐梯度上升而升高，放线菌门和厚壁菌门相对丰度则随之下降，门下成员大多与水盐变化具有明显的相关性；此外，FL样地土壤细菌网络则具有稳定的网络关系；随着NL样地向FL样地的延伸，土壤细菌群落由随机过程主导，并且受pH、电导率和环境变量的影响。【结论】荒漠草原盐沼湿地水分和盐分的变化改变了土壤细菌群落结构；土壤细菌群落通过生态位占据等策略提高逆境下的生存能力；细菌群落构建是随机过程和确定性过程组成的连续统一体，同样受环境变化的影响。本结果揭示了荒漠草原盐沼湿地细菌群落结构和相互关系对环境变化的响应特征，同时阐明了该区土壤细菌群落的构建机制及影响因素，也为相关科学研究提供了一定理论参考。

关键词:盐沼湿地;苦豆子群落;土壤细菌;网络关系;群落构建

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.

Key words:salt marsh;Sophora alopecuroides-dominated community;soil bacteria;network relationship;community assembly