Variation of soil microbial communities in alpine meadows across different degradation degrees and related environmental drivers in the Sanjiangyuan Region, China

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Alpine meadow degradation threatens regional ecology and pastoral sustainability. This study compared the influence of different degradation degrees (no, light, moderate, and severe degradation) on soil microbial communities, physicochemical properties, and enzyme activities in the Sanjiangyuan region, and explored correlations between soil microbial communities and environmental factors. Using Illumina MiSeq high-throughput sequencing, we found that as degradation increased, soil pH increased significantly, while soil moisture and nutrient contents decreased. Soil enzyme activities, such as leucine aminopeptidase and cellulase were increased, while N-acetyl- β-d-glucosidase, glucosidase, polyphenol oxidase, urease, acid proteinase, and acid phosphatase decreased significantly. Dominant microbial communities included fungal genera Hygrocybe, Archaeorhizomyces, and Mycena, and bacterial genera RB41, Pseudomonas, and Sphingomonas. The Shannon diversity index showed a revealed V-shaped pattern for fungal diversity with the minimum in moderate-degradation meadow, while bacterial diversity declined. Moreover, the relative abundance of microorganisms varied significantly with degradation degree. Bacterial communities consistently demonstrated greater stability compared to fungal communities across. Moreover, redundancy analysis indicated that fungal communities, including Hygrocybe, Archaeorhizomyces, and Mycena, exhibited strong positive associations with organic matter (OM), total nitrogen (TN), total phosphorus (TP), nitrate nitrogen (NN), and glucosidase, while being strongly negatively correlated with pH and cellobiohydrolase. In contrast, bacterial communities, specifically RB41 and Sphingomonas, showed strong positive correlations with pH and soil cellulase (CBH), but negative associations with OM, TN, TP, NN, and soil glucosidase (BG). Pseudomonas displayed opposing trends. These findings provide a scientific basis for understanding the relationship among the different degradation degrees in alpine meadows and their corresponding soil microbial communities and environmental factors.

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