若尔盖高原泥炭沼泽湿地土壤细菌群落空间分布及其驱动机制

Abstract

了解高原泥炭沼泽湿地生态系统土壤微生物群落结构组成、多样性及空间分布特征对认识高原湿地生态特征及演化过程至关重要。利用高通量测序技术，在局域尺度上研究了四川若尔盖高原泥炭沼泽湿地土壤细菌群落结构与多样性特征。通过进一步测定土壤及植物基本理化指标，量化采样点之间的地理距离，比较了细菌群落不同成员（稀有种和丰富种）的空间周转差异，分析了土壤环境变量和空间因子对细菌群落结构的相对贡献。结果表明：若尔盖泥炭土壤细菌群落主要由绿弯菌门（Chloroflexi）（26.25%）、变形菌门（Proteobacteria）（23.21%）、厚壁菌门（Firmicutes）（10.56%）等优势物种门类组成；土壤细菌群落结构表现出较强的空间依赖关系，群落结构相似性随采样点地理距离增加而逐渐降低，细菌群落的周转速率表现为总细菌群落 > 丰富种 > 稀有种；Mantel检验结果显示，地上生物量与细菌群落呈极显著相关性（P<0.01），其中，影响稀有种空间分布特征的环境因子还包括土壤硫含量、活性磷、Mn和土壤pH值；方差分解分析表明，局域尺度上的土壤因子对若尔盖高原泥炭沼泽土壤细菌群落构建的相对贡献大于空间因子，土壤异质性是影响微生物空间分布特征的关键因素。研究为开展高原湿地泥炭土壤微生物多样性调查及揭示微生物群落构建机制提供了重要参考。;Identifying the microbial community composition, diversity, and spatial distributional features in samples collected from the plateau peat wetlands is important to understand the ecological characteristics and evolutionary processes of plateau wetland ecosystems. In this study, by using high-throughput sequencing technology, we studied soil bacterial community composition and structure as well as bacterial diversity at the local scale of geographic spaces in the peat wetlands of Zoige Plateau, which are located in Sichuan province, China. The basic plant and soil properties were tested and the geographic distances between the pairwise sampling points were quantified. Additionally, the spatial turnover of the different members of bacterial communities (i.e., endemic taxa and ubiquitous taxa) was compared, and the relative contributions of the different environmental variables and spatial factors to the bacterial community composition and structure were analyzed. The results showed that Chloroflexi, Proteobacteria, and Firmicutes were the most dominant bacteria in the peat wetlands of Zoige Plateau, and the relative abundance of these dominant phyla was 26.25%, 23.21%, and 10.56%, respectively. Soil bacterial community compositions were strongly related to the spatial distances. The composition similarity of bacterial communities gradually decreased with the increase in geographical distances between the pairwise sampling points, and bacterial community compositions showed a decreasing order in their spatial turnover rates as follows:the total bacterial community > ubiquitous community > endemic community. The results of Mantel test analysis showed that the above-ground biomass exerted the most significant effect on the bacterial community composition and structure (P<0.01); meanwhile, soil sulfur content, soil active phosphorus content, soil manganese content, as well as soil pH also affected the spatial distribution of endemic taxa. Variation partition analysis showed that, at the local scale of geographic spaces, edaphic factors played more important role than spatial factors in shaping the composition and structure of soil bacterial communities in the peat wetlands of Zoige Plateau. Especially, soil heterogeneity was the key factor that affected the spatial distributions of soil microbial communities. The present work provides an important reference for investigating soil microbial diversity in the plateau peat wetlands and also provides a theoretical basis for revealing the mechanisms of microbial community assembles over geographic spaces in the plateau wetlands.