Soil properties and species composition under different grazing intensity in an alpine meadow on the eastern Tibetan Plateau, China

As the main form of land use and human disturbance of grassland, livestock grazing has great influences on the soil resources and plant communities. This study observed the variation of soil properties and community characteristics of four treatments of different grazing intensity (no grazing, UG; light grazing, LG; moderate grazing, MG; and heavy grazing, HG) in an alpine meadow of Sichuan Province on the northeastern margin of the Tibetan Plateau. The results showed that grazing increased the pH, soil bulk density (BD), and contents of total carbon (TC) and total nitrogen (TN), and the BD increased while the others decreased with the grazing intensity. At the community level, with the increase of the grazing intensity, the vegetation coverage (R-2 = 0.61, P < 0.001), mean height of community (R-2 = 0.37, P < 0.001), aboveground biomass (R-2 = 0.54, P < 0.001), litter biomass (R-2 = 0.84, P < 0.001), and percentage of aboveground biomass of palatable grasses to total biomass (R-2 = 0.74, P < 0.001) significantly decreased, while the belowground biomass (R-2 = 0.72, P < 0.001) and the root/shoot (R/S) ratio (R-2 = 0.65, P < 0.001) increased. The species richness was the greatest at LG and the total biomass at UG. With grazing, the dominant species of the plant community shifted from palatable grasses (Gramineae and Cyperaceae) to unpalatable grasses (Compositae and Ranunculaceae). Based on the results, LG may be the optimal grassland management mode to be used in the long time in the alpine meadow of the Tibetan Plateau.