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IntroductionBurrowing activities of plateau pikas cause widespread bare patches in alpine meadows on the Qinghai-Tibet Plateau, affecting the plant community composition and forage production. However, it is not clear how these bare patches influence the main forage composition in alpine meadows.MethodsTherefore, we investigated the plant communities in bare patches (BP) and neighboring control plots (CK) in alpine meadows in Maqu county in the Gannan region of China.ResultsOur results showed that plant communities in the CK plots differed from those in the BP plots. The sedge cover, number of sedge species and number of grass species were all significantly higher in the CK plots compared to the BP plots. However, grass cover and its dry weight were significantly higher in the BP plots. Grass cover and the grass dry weight in the BP plots were 1.859 times and 1.802 times higher than that in the CK plots across the five sites, respectively. Grasses also had a significantly higher cover and dry weight than sedge in the BP plots, grass cover was 66.5 times higher than the sedge cover, and the grass dry weight was 68.242 times that of the sedge dry weight. Therefore, bare patches resulting from plateau pika burrowing activity significantly increase the grass/sedge ratio in alpine meadows.DiscussionA potential explanation is that grasses have a stronger reproductive potential than sedges in bare soil. This has implications for pasture yields since grasses have a higher biomass per unit area compared to sedges in alpine meadows.

Vegetation is a crucial component of any ecosystem and to preserve the health and stability of grassland ecosystems, species diversity is important. The primary form of grassland use globally is livestock grazing, hence many studies focus on how plant diversity is affected by the grazing intensity, differential use of grazing time and livestock species. Nevertheless, the impact of the grazing time on plant diversity remains largely unexplored. We performed a field survey on the winter pastures in alpine meadows of the Qinghai-Tibetan Plateau (QTP) to examine the effects of grazing time on the vegetation traits. Livestock species, grazing stocking rates and the initiation time of the grazing were similar, but termination times of the grazing differed. The grazing termination time has a significant effect on most of the vegetation traits in the winter pastures. The vegetation height, above-ground biomass, and the Graminoids biomass was negatively related to the grazing termination time in the winter pastures. In contrast, vegetation cover and plant diversity initially increased and subsequently decreased again as the grazing termination time was extended. An extension of the grazing time did not have any effect on the biomass of forbs. Our study is the first to investigate the effects of grazing during the regrowth period on vegetation traits and imply that the plant diversity is mediated by the grazing termination time during the regrowth period in winter pastures. These findings could be used to improve the guidelines for livestock grazing management and policies of summer and winter pasture grazing of family pastures on the QTP from the perspective of plant diversity protection.

Although grazing is the most common use of grassland, the ecological function of grassland far exceeds its productivity. Therefore, the protection of plant diversity is of the utmost importance and cannot be ignored. Existing research on the effect of grazing on grassland mainly focuses on grazing intensity and the type of livestock, but the consequences of the timing of the grazing on the vegetation community remains unclear. We investigated plant community characteristics of winter pastures in alpine meadow with different grazing termination times (grazing before and during the grassland greenup periods) in Maqu County, eastern QTP. The results showed that vegetation height, coverage, aboveground biomass and Graminoid biomass were lower in grassland when grazing happened during the greenup period compared to grassland where grazing was terminated before the greenup period. However, the total plant species richness and forbs richness were higher in grassland with grazing during the greenup period compared to grassland without grazing during the greenup period. Our structural equation modeling reveals a potential indirect implication for the total plant species richness and forbs richness of winter pastures mainly through a decrease in the vegetation coverage and grass biomass abundance. Our findings imply that grazing during the grassland greenup period may facilitate the maintenance of plant diversity in winter pastures. These findings have important implications for grassland ecosystem functioning and for the conservation of plant diversity.