Effects of seasonal grazing on spatial distribution characteristics of forage biomass in an alpine meadow on the Qinghai-Tibet Plateau

Alpine meadow are one of the main grassland types on the Qinghai-Tibet Plateau, and are of great significance to local peoples’ lives as a national ecological barrier. Four seasonal yak pastures in an alpine meadow of Maqu County, Gansu Province, were selected as research objects, and the effect of seasonal grazing on the spatial distribution of forage biomass was explored. The results showed that the coefficient of variation of aboveground biomass of plant communities in non-grazing plots and continuous grazing plots was higher than that in other seasonal pastures (29.06% and 29.02%, respectively). The coefficient of variation of root to shoot ratio and belowground biomass of plant communities in non-grazing plots was the highest, at 34.46% and 35.73%, respectively. Moreover, it was the lowest for pasture in spring, at 9.16% and 13.12% respectively. The aboveground biomass of summer pasture and continuous grazing plots was significantly lower than that of the pasture in the other three seasons, at 194.52 and 167.94 g·m⁻², respectively, but the root to shoot ratio showed the opposite trend. Grazing reduced the belowground biomass of the summer, winter, and four-season continuous grazing plots, but the effect was not significant. The contribution of the aboveground biomass of Leguminosae to the belowground biomass was the lowest. The aboveground biomass of others, Cyperaceae, and Compositae accounted for 40%, 31%, and 30% of the belowground biomass, respectively. The aboveground biomass of Ranunculaceae and Gramineae could explain the variation in the root to shoot ratio by 42% and 41%, respectively. Therefore, the aboveground biomass of Compositae and others can suitably predict the alpine meadow plant community’s belowground biomass on the Qinghai-Tibet Plateau, and the aboveground biomass of Gramineae and Ranunculaceae can predict the root to shoot ratio of plant communities in the region. These results provide a theoretical and technical basis for alpine meadow utilization and grazing management.