中文摘要：

在宁夏荒漠草原选取围封禁牧（NG）、轻度放牧（LG）、中度放牧（MG）和重度放牧（HG）4个放牧强度,研究不同放牧强度对土壤物理和化学性状的影响。结果表明,放牧干扰对荒漠草原土壤物理和化学性状影响显著。土壤含水量和孔隙度随着放牧强度的增加呈显著降低趋势,而土壤容重和pH值呈线性增加趋势。重度、中度、轻度放牧0～30cm土壤含水量和孔隙度比围封禁牧分别降低了21.1%,12.0%,4.7%和3.2%,2.5%,2.1%。不同放牧强度土壤含水量随着土壤深度的增加均呈显著增加趋势。随着放牧强度的增加,土壤有机碳和C/N降低。重度放牧0～10和10～20cm土壤有机碳比围封禁牧分别降低了20.6%和14.1%,土壤C/N分别降低了43.4%和34.1%。土壤全磷、速效磷和全钾含量随着放牧强度增加呈增加趋势,而土壤电导率和全氮含量呈先增加后降低趋势。合理放牧可以改善荒漠草原土壤结构和养分性状,有利于遏制荒漠草原土壤的退化。

英文摘要：

The effect of different grazing intensity （nongrazed, light grazing, moderate grazing and heavy graz- ing） 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 mois- ture 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.%, 12.0%, 4.7% and 3.2%, 2.5%, 2.1%. With the increase of soil depth, soil moisture in- creased under different grazing intensity. Soil organic carbon and C/N decreased with grazing intensity increas ing. 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