Distribution and Potential Metabolic Functions of Soil Actinobacteria in Degraded Alpine Grassland on the Northern Tibetan Plateau

Actinobacteria play major roles in human health and soil nutrient biogeochemical cycles, which are important for environmental protection. On the northern Qinghai–Tibet Plateau, the Qiangtang Alpine Grasslands have recently become degraded to varying degrees due to global climate changes and human disturbances. Here, we compared the community diversity, composition, and potential metabolic functions of Actinobacteria in soil from different degradation conditions through Illumina MiSeq sequencing. The soil Actinobacteria community structure in the Qiangtang Alpine Grasslands of northern Tibet was dominated by Nocardioides, Gaiella, Solirubrobacter, and Pseudonocardia, with evidence of previously unidentified taxa. Compared with non-degraded and severely degraded grasslands, the moderately degraded grassland had the highest soil Actinobacteria alpha-diversity, and the community composition showed significant differences between degraded grasslands with different degrees of degradation. The interactions between Actinobacteria and KO functions predominantly show negative correlations, but significant positive correlations outnumber significant negative ones. This study showed that Actinobacteria diversity and potential ecological functions in the alpine grasslands of northern Tibet decreased with grassland degradation due to the loss of vegetation cover. Therefore, it is necessary to effectively manage and protect the Qiangtang Alpine Grasslands on the northern Tibetan Plateau.