The effect of grazing disturbance on soil properties in desert steppe.

The effect of different grazing intensity(nongrazed,light grazing,moderate grazing and heavy grazing) on soil physical properties and chemical properties was conducted in a desert steppe in Ningxia.Grazing disturbance had significant effect on soil physical properties and chemical properties in desert steppe.Soil moisture and porosity decreased with the increase of grazing intensity,while soil bulk density and pH showed a sharp linear increase with grazing intensity increasing.As compared with nongrazed plots,grazed plots(heavy grazing,moderate grazing and light grazing) resulted in significant decrease of soil moisture(0-30 cm) and porosity by 21.1%,12.0%,4.7% and 3.2%,2.5%,2.1%.With the increase of soil depth,soil moisture increased under different grazing intensity.Soil organic carbon and C/N decreased with grazing intensity increasing.Compared with nongrazed plots,heavy grazing decreased soil organic carbon of 0-10 cm and 10-20 cm by 20.6% and 14.1%,and soil C/N decreased by 43.4% and 34.1%,respectively.With the increase of grazing intensity,soil total phosphorus,available phosphorus and total kalium increased,while soil electric conductivity and soil total nitrogen decreased after an initial increase.It was suggested that reasonable grazing can improve soil structure and soil nutrient in desert steppe and restrain the degradation of soil in desert steppe.