The melting of permafrost and the degradation of alpine meadow ecosystems caused by climate warming and high-intensity human activities have imposed serious threats to local and global ecological security. In order to estimate the effects of climate warming and grazing interference on the photosynthesis and respiration of alpine meadow plant community in permafrost regions, warming – infrared radiator is applied to simulate the climate warming (increasing temperature by +2°С). The winter grazing level is simulated by mowing the aboveground biomass of all plants. The responses of permafrost meadow community in terms of photosynthesis, respiration, surface soil temperature and moisture, as well as the carbon balance to simulated different climate warming and grazing level were analyzed and discussed. The results showed that: (1) the surface soil temperature in climate warming and grazing plots is significantly higher than in Ck plots (P < 0.01); (2) warming and warming + grazing plots enhanced community photosynthesis and respiration (P < 0.01); (3) warming and warming + grazing treatments increased community aboveground biomass (P < 0.05); (4) the photosynthetic rate increased in the second year, then decreased in the third year when both temperature and grazing level increased during the growing season. However, the ecosystem respiration increasingly increased year by year; (5) compared with the control groups, warming and grazing treatments resulted in an increase in carbon sequestration of the permafrost meadow community during the growing season.

Legume–grass mixtures are widely used to improve productivity and soil quality in alpine grasslands; however, their effects on soil fungal communities and the underlying mechanisms remain unclear. In this study, a two-factor field experiment (species richness (three, four, and five species) × legume–grass ratio (4:6, 3:7 and 2:8)) was conducted in an alpine artificial grassland on the Qinghai–Tibetan Plateau. Soil fungal communities were assessed using high-throughput sequencing combined with multivariate analyses. The results showed that Ascomycota, Mortierellomycota, and Basidiomycota were the dominant fungal phyla. Both species composition and seeding ratio significantly influenced fungal community structure and α-diversity primarily through indirect pathways mediated by plant community characteristics and soil properties. Plant height and soil total phosphorus (TP) were identified as key drivers of fungal α-diversity. Specifically, the four-species mixture (Z2) at a 3:7 legume–grass ratio resulted in relatively higher and more stable aboveground biomass and improved soil nutrient status, whereas increasing species richness to five species did not further enhance these benefits. Overall, our findings indicate that optimizing species composition and legume–grass ratio, rather than simply increasing species richness, is more effective for regulating soil fungal diversity and ecosystem function.

Climate change and human activities are increasing the disturbance to alpine meadows in Qinghai-Tibet Plateau, these changes are reducing the abundance of previously-dominant Gramineae and sedges, with forbs establishing dominance through secondary succession. Forbs replaced native Gramineae and sedges as dominant species. To explain the formation mechanism of this succession, this paper studied the seed characteristics of 14 common plants in alpine meadow communities, including seed number, 1000-grain weight, germination rate, pappus characteristics, fall velocity. It is revealed that seed pappus characteristics are the key factors in determining the dominance of species on the secondary bare land of degraded alpine meadows. The results of the comprehensive evaluation method show that Asteraceae have higher diffuse ability than Gramineae, sedges, Apiaceae and Leguminosae due to lower falling speed of Asteraceae, caused by their pappus. The redundancy analysis results further explain the reasons for the emergence of corresponding dominant species in different degradation stages of alpine meadows. These results are helpful for understanding changes in plant communities in alpine meadows under grazing disturbance. They also provide a theoretical basis for the sustainable utilization and management of the alpine meadow ecosystem and restoration of degraded grassland.

The degradation of alpine meadows on the Qinghai–Tibet Plateau has seriously affected the structure and productivity of grassland communities. In this experiment, a sample area was set up in Keqihetan of Zexiong Village, Youganning Town, Henan County, Mongolian Autonomous Prefecture. The degraded alpine meadow was divided into three plaque types, bare patches (BP), short-term recovered patches (SRP), and long-term recovered patches (LRP), and Native alpine meadows (NM) as controls, in order to reveal the effects of grassland degradation on community structure and aboveground/belowground biomass allocation in alpine meadow. Here, we measured total biomass (TCB), aboveground biomass (AGB), belowground biomass (BGB), and root/shoot ratio (R/S) of alpine meadows on the Qinghai–Tibetan Plateau and investigated plant community cover and height. The results showed that with the restoration of the patchy alpine meadow, the height decreased first and then increased, the amount of AGB increased first and then decreased, while the coverage and BGB increased in turn, and BGB decreased with the deepening of soil depth. We also found that R/S decreased first and then increased with the patch recovery of the alpine meadow. The overall distribution of AGB and BGB belongs to allometric growth distribution, but the native meadow belongs to isometric growth distribution, while other recovery stages belong to allometric growth distribution. By studying the biomass and its distribution of degraded grassland, we can understand the impact of grassland degradation on the community structure and productivity of the alpine meadow.