Abstract: To investigate the effects of different grazing intensities on soil enzyme activities in a Stipa breviflora desert steppe and the driving factors， this study was based on a Stipa breviflora desert steppe and established four grazing intensity levels： no grazing （CK）， light grazing （LG）， moderate grazing （MG）， and heavy grazing （HG）. The effects of different grazing intensities on the activities of β-D-cellobiohydrolase， β-1，4-N-acetylglucosaminidase， and alkaline phosphatase were analyzed， along with species richness， aboveground net primary productivity （ANPP）， and soil pH， saturated water content， bulk density， organic carbon， available nitrogen， and available phosphorus. The results showed that with the increase of grazing intensity， the three soil enzyme activities， species richness， aboveground net primary productivity， soil organic carbon， available nitrogen， and available phosphorus all significantly decreased （P<0.05）， whereas soil bulk density was significantly increased. The Random Forest model indicated that available nitrogen and available phosphorus were the primary drivers regulating soil enzyme activities. Grazing suppresses soil enzyme activities primarily by decreasing available nutrients. This study provides a theoretical basis for the conservation and ecological restoration of desert steppes. In grassland management and utilization， measures such as controlling stocking rates and implementing seasonal grazing exclusion can be adopted.

Key words: Grazing intensity, Desert steppe, Soil enzyme activities, Species richness

摘要： 为探讨不同放牧强度对短花针茅（Stipa breviflora）荒漠草原土壤酶活性的影响及其因素，本研究基于短花针茅荒漠草原，设置不放牧（No grazing， CK）、轻度放牧（Light grazing， LG）、中度放牧（Moderate grazing， MG）和重度放牧（Heavy grazing， HG）4个梯度，分析了不同放牧强度对β-D-纤维素酶、β-1，4-N-乙酰氨基葡萄糖苷酶和碱性磷酸酶活性的影响，并结合物种丰富度、地上净初级生产力及土壤pH值、饱和含水量、容重、有机碳、速效氮、速效磷等因子。结果表明：随放牧强度增加，三种土壤酶活性、物种丰富度、地上净初级生产力、土壤有机碳、速效氮及速效磷均显著降低（P<0.05），容重则显著上升（P<0.05）。随机森林模型显示，速效氮与速效磷是调控土壤酶活性的主要驱动因子。放牧主要通过降低速效养分含量抑制土壤酶活性。本研究为荒漠草原保护与生态恢复提供了理论依据，草地管理利用中可采取控制载畜率、季节性休牧等措施。

关键词: 放牧强度, 荒漠草原, 土壤酶活性, 物种丰富度