Unreasonable grassland use has degraded the alpine meadow on the Qinghai-Tibetan Plateau in the past half a century, and approximately 32.1% of the degraded meadows degenerated to bare grassland. Artificial grassland reconstruction is a widespread measure for rebuilding the grassland ecosystems of these bare grasslands. However, does the soil microbe community structure improve with the aboveground vegetation restoration? Which microflora are more sensitive to environmental changes are not unclear. Thus, we analyzed four artificial grasslands established for different years on extreme-degraded (ED) grasslands of the alpine meadows. These artificial grasslands were rationally utilized by grazing Tibetan sheep and Yak from December to April and were completely grazing-prohibited in other seasons. In 2017, four plots of approximately 2400 m² for each artificial restoration grassland (3, 6, 9, and 12 years) were selected as treatments with non-degraded (ND) and ED meadows as controls. The potential predictors and regulators for soil microbial community structures and functions in the alpine meadows were evaluated. The results showed that artificial restoration did not affect soil microbe community compositions but dramatically changed the community constructions. The bacterial community structure was more sensitive to artificial interference than fungal. Actinobacteria, Acidobacteria, and Mortierellomycota could be used as indicators of environmental changes. Compared with ED grassland, the soil microbial biomass carbon increased significantly by 29.5% and 33.7% in 6 and 9 years grasslands, respectively. The species richness and below-ground biomass of grassland vegetation play a decisive role in soil microbial community and functional structures, while the soil water content and organic carbon, and soil elemental balance play a regulating role. Moreover, the abundance of soil bacteria with ureolysis and nitrogen fixation functions decreased significantly in grassland degradation, and soil pH played a major regulatory role. In conclusion, the vegetation and soil of artificial grasslands were in good condition after 6 years of artificial restoration. However, all the indexes declined to different degrees after 12 years of establishment, and the grassland ecosystem faced the risk of secondary degradation. The mixed sowing of many plant species with developed root systems should be adopted when artificially restoring degenerated alpine grasslands. Simultaneously, soil organic material supplementation and the balanced application of nitrogen and phosphorus fertilizers are recommended.

中文翻译：

---

植被群落特征的变化导致退化高寒草甸耕作过程中土壤微生物群落和功能的重建


近半个世纪以来，不合理的草地利用使青藏高原高山草甸退化，约 32.1% 的退化草甸退化为裸草地。人工草地重建是这些裸草地重建草原生态系统的广泛措施。然而，土壤微生物群落结构是否会随着地上植被的恢复而改善？哪些微生物群落对环境变化更敏感尚不清楚。因此，我们分析了在高山草甸的极端退化 （ED） 草原上建立的 4 个不同年份的人工草地。这些人工草原在 12 月至 4 月期间被藏羊和牦牛合理利用，其他季节完全禁止放牧。2017 年，选择每个人工恢复草地（3、6、9 和 12 年）的四个约 2400 m² 的样地作为处理，以未退化 （ND） 和 ED 草甸作为对照。评估了高寒草甸土壤微生物群落结构和功能的潜在预测因子和调节因子。结果表明，人工恢复不会影响土壤微生物群落组成，但显着改变了群落结构。细菌群落结构对人工干扰比真菌更敏感。放线菌门、酸杆菌门和森霉菌门可用作环境变化的指标。与ED草地相比，6 年和 9 年生草地土壤微生物量碳分别显著增加 29.5% 和 33.7%。 草地植被的物种丰富度和地下生物量对土壤微生物群落和功能结构起决定性作用，而土壤含水量和有机碳以及土壤元素平衡起调节作用。此外，在草地退化中，具有尿解和固氮功能的土壤细菌丰度显著降低，土壤 pH 值起主要调节作用。综上所述，人工草地的植被和土壤经过 6 年的人工恢复后处于良好状态。然而，建立12年后，各指标均出现不同程度的下降，草地生态系统面临次生退化的风险。人工恢复退化的高寒草原时，应采用多种根系发达的植物物种混播。同时，建议土壤有机物质补充和氮磷肥的均衡施用。