Quantitative Studies of the Effects of Trampling on Typical Steppe of Huanxian in Eastern Gansu,China Response of Underground Biomass to Grazing Trampling in Steppe Grassland of Huanxian County,Gansu Province,Northwestern China Evaluation on trampling of grazed Gansu wapiti (Cervus elaphus kansuensis Po cock) and its effects on soil property in winter grazing land A study on soil erodibility in a combined experimental trampling and simulated rainfall experiment on a Stipa bungeana steppe in Huanxian County, Gansu Province, China