Joint International Research Laboratory of Global Change and Water Cycle, State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, China; State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, China.
Joint International Research Laboratory of Global Change and Water Cycle, State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, China.
Sci Total Environ. 2022 Nov 15;847:157446. doi: 10.1016/j.scitotenv.2022.157446. Epub 2022 Jul 18.
Alpine meadows and alpine steppes are two major grassland types distributed on the Tibetan Plateau. Due in large part to the differences in hydrothermal and nutrient conditions following the thawing of lakeshore permafrost, alpine meadows and alpine steppes which are characterized by disparate above- and below-ground biomass, could emerge together in the grassland transition zone between meadows and steppes of the Tibetan Plateau. Bacterial communities are essential components of alpine grassland ecosystems and respond rapidly to environmental changes. Despite their ecological significance, it remains poorly elucidated whether and how the assembly patterns of bacterial communities differed between alpine meadows and alpine steppes. Here, to disentangle the assembly mechanisms of bacterial communities from alpine meadows and alpine steppes, we collected samples from three diverse habitats (i.e., sediments, rhizosphere soils and bulk soils) in both alpine meadow and steppe ecosystems on the Tibetan Plateau. Our results indicated that in both meadows and steppes, rhizosphere bacterial communities exhibited higher alpha-diversity but lower beta-diversity compared to the bacterial communities in sediments and bulk soils. However, the close relationships of bacterial communities between different habitats weakened from meadows to steppes. Null model analysis indicated that the importance of environmental selection shaping bacterial community assemblages in all habitats decreased from meadows to steppes, whereas the role of dispersal limitation showed an opposite pattern. Moreover, pH was the primary driver of phylogenetic turnover of bacterial communities in the steppes across all habitats, whereas the dominant drivers of phylogenetic turnover of bacterial communities in meadows varied with habitat types. Overall, our findings provide novel insights into understanding the differences in microbial communities between meadows and steppes in the grassland transition zone on the Tibetan Plateau.
高山草甸和高山草原是分布在青藏高原上的两种主要草原类型。由于湖滨多年冻土融化后水热和养分条件的差异，在青藏高原的草甸与草原过渡带，具有不同地上和地下生物量特征的高山草甸和高山草原可以同时出现。细菌群落是高山草原生态系统的重要组成部分，对环境变化反应迅速。尽管它们具有生态意义，但仍不清楚高山草甸和高山草原的细菌群落组装模式是否以及如何存在差异。在这里，为了厘清高山草甸和高山草原细菌群落的组装机制，我们从青藏高原的高山草甸和草原生态系统中三个不同的生境（即沉积物、根际土壤和土壤本体）中收集了样本。我们的研究结果表明，在高山草甸和高山草原中，根际细菌群落的α多样性较高，而β多样性较低，与沉积物和土壤本体中的细菌群落相比。然而，不同生境之间细菌群落的紧密关系从高山草甸到高山草原逐渐减弱。零模型分析表明，在所有生境中，环境选择对细菌群落组装的重要性从高山草甸到高山草原逐渐降低，而扩散限制的作用则呈现相反的模式。此外，pH 值是驱动高山草原所有生境中细菌群落系统发育周转的主要因素，而驱动高山草甸中细菌群落系统发育周转的主要因素则随生境类型而变化。总体而言，我们的研究结果为理解青藏高原草甸与草原过渡带微生物群落之间的差异提供了新的见解。
