Response of major species to grazing mode in an alpine grassland

To explore the response of major alpine grassland species to grazing mode, the prevalence and individual characteristics of species belonging to four functional groups were measured through a manipulated grazing experiment in an alpine grassland in the Qinghai Lake Basin. The manipulated grazing experiment included yak and Tibetan sheep grazing along with mixed-species grazing (MG) featuring different ratios of yak to sheep (1 ꞉ 6, 1 ꞉ 4, and 1 ꞉ 2, abbreviated as MG 1 ꞉ 6,MG 1 ꞉ 4, and MG 1 ꞉ 2, respectively) and a control treatment. The results showed that 1) compared with the control treatment, the frequency of species with high palatability and large biomass decreased under all grazing modes, whereas the frequency of species with low palatability and low height increased, especially under MG 1 ꞉ 2. The height of all species decreased under all grazing modes; 2) the individual weights of graminoid, legume, and palatable forbs decreased under grazing, but that of low-tufted sedges and forbs increased; and 3) the mass-height ratio of each functional group was higher than that of the control treatment, except for Stipa purpurea and Koeleria macrantha. Thus, the response of alpine grassland plants to grazing was significant (P < 0.05) at the species level, and significant differences (P < 0.05) also existed between species; however, the response at the functional-group level was insignificant (P > 0.05). Compared to other grazing treatments, MG 1 ꞉ 2 had a significant impact on the frequency and individual characteristics of each functional group and species.