Effects of grazing on plant biomass and soil nutrient in desert steppe

Effects of grazing on plant diversity,biomass and characteristics of soil nutrients were examined in a desert steppe in Ningxia.The result indicates that the grazing has significant effects on plant diversity,evenness and richness.With the increase of grazing intensity,the plant diversity and evenness are decreased after an initial increase and are the highest in the light grazing plots.As compared with the ungrazed plots,the grazed plots(heavy grazing,moderate grazing and light grazing) result in significant decreases of the aboveground and belowground biomass by 43.8%,42.0%,15.4% and 27.7%,16.2%,11.9%.With the increase of the grazing intensity,soil total nitrogen is decreased after an initial increase,and soil organic carbon is decreased.Compared with the grazed plots,soil organic carbon is increased by 18.1% in the ungrazed plots,while total phosphorus,available phosphorus and total potassium are decreased by 21.1%,51.9% and 11.0%,respectively.The effects of soil organic carbon on aboveground biomass and belowground biomass are more significant than those of other soil properties(total nitrogen,total phosphorus,total potassium and available potassium).The soil environment and nutrients are influenced by grazing disturbance to reflect plant diversity,community biomass change of desert steppe.