Effect of yak grazing intensity on characteristics of plant communities and forage quality in Gannan alpine meadow

To study the effects of the intensity of yak grazing on the characteristics of plant communities and forage quality in alpine meadows under the effect of long-term yak grazing in the Qinghai-Tibetan Plateau (Maqu County, Gansu Province), this study analyzed aboveground and belowground biomass, species richness, density of plant communities, surface soil water content at a depth of 0-10 cm, soil temperature, nutritive quality of forage, and correlation among other aspects. The results showed that: 1) Yak grazing significantly (P<0.01) affected above- and belowground biomass. Aboveground biomass was the highest in the non-grazed area (418.15 g·m-2 ); contrastingly, belowground biomass was significantly higher (P<0.05) in the farm with high-intensity grazing compared with the other area. 2) The density of plant communities and proportion of the biomass of edible grass were not significantly (P>0.05) affected by grazing, while species richness was significantly reduced in the farms with moderate and high-intensity grazing compared with the non-grazed area. Moreover, surface soil water content at a depth of 0-10 cm was significantly (P<0.05) lower in the farm with high-grazing intensity compared with the non-grazed area, and contrastingly soil temperature was significantly higher. 3) The intensity of yak grazing similarly affected forage quality; however, the difference was not significant (P<0.05) under the effect of long-term yak grazing. Therefore, yak grazing with moderate intensity may effectively promote the growth of underground biomass, which potentially affects different economic groups, biomass proportion, and forage quality, and maintains the health of the ecosystem.