The aim of this study was to evaluate the relationships among changes in the soil microstructure, soil physicochemical traits and microbial communities during desertification. Soil samples were collected from grasslands at different stages of desertification, from an area of the Tibetan Plateau. Soil aggregate fractionation and soil physicochemical properties were analysed using standard methods, and the abundance and diversity of bacteria associated with different aggregate fractions were estimated by quantitative PCR and Illumina Miseq amplicon sequencing. Sequential changes in response to desertification stages were detected in the analysed features. For instance, soil nutrients, microbial biomass C and N, water content and pH initially changed during the light desertification stage; then, the soil aggregation decreased during the intermediate stages; and finally, bacterial abundance and diversity decreased during heavy and severe desertification stages. During grassland desertification, vegetation coverage positively influenced soil aggregation by affecting soil properties (e.g., pH and SOC), whereas bacterial communities in FMi (free microaggregates) and FSC (free silt and clay) were negatively related to soil aggregation. This study reports novel information concerning the desertification process and the sequential modification of soil traits and interactions among soil physical properties (aggregate composition), soil nutrients and the soil microbial community in the grasslands of the Tibetan Plateau.

中文翻译：

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青藏高原草地荒漠化过程中土壤理化性质，细菌群落和聚集体的变化

这项研究的目的是评估荒漠化过程中土壤微观结构变化，土壤理化特性和微生物群落之间的关系。从青藏高原地区的荒漠化不同阶段的草地收集土壤样品。使用标准方法分析土壤聚集体的分馏和土壤理化性质，并通过定量PCR和Illumina Miseq扩增子测序评估与不同聚集体组分相关的细菌的丰度和多样性。在分析的特征中检测到对荒漠化阶段的响应顺序变化。例如，在轻度荒漠化阶段，土壤养分，微生物生物量碳和氮，水分和pH值最初发生了变化。然后，中期土壤团聚减少；最后，在严重和严重的荒漠化阶段，细菌的丰度和多样性下降。在草地荒漠化期间，植被覆盖度通过影响土壤性质（例如pH和SOC）对土壤聚集产生积极影响，而FMi（游离微聚集体）和FSC（游离淤泥和粘土）中的细菌群落与土壤聚集呈负相关。这项研究报告了有关荒漠化过程和土壤性状的顺序改变以及青藏高原草原上土壤物理性质（集合成分），土壤养分和土壤微生物群落之间相互作用的新信息。在草地荒漠化期间，植被覆盖度通过影响土壤性质（例如pH和SOC）对土壤聚集产生积极影响，而FMi（游离微聚集体）和FSC（游离淤泥和粘土）中的细菌群落与土壤聚集呈负相关。这项研究报告了有关荒漠化过程和土壤性状的顺序改变以及青藏高原草原上土壤物理性质（集合成分），土壤养分和土壤微生物群落之间相互作用的新信息。在草地荒漠化期间，植被覆盖度通过影响土壤性质（例如pH和SOC）对土壤聚集产生积极影响，而FMi（游离微聚集体）和FSC（游离淤泥和粘土）中的细菌群落与土壤聚集呈负相关。这项研究报告了有关荒漠化过程和土壤性状的顺序改变以及青藏高原草原上土壤物理性质（集合成分），土壤养分和土壤微生物群落之间相互作用的新信息。