Arbuscular Mycorrhizal Fungi （AMF） play an important role in maintaining the function of grassland ecosystems. Grazing is one of the main utilization modes of grasslands， which has a profound effect on the symbiotic relationship between plants and AMF. However， the regulatory effects of grazing on the Stipa breviflora-AMF symbiosis and its driving mechanisms remain unknown. This study， conducted in the S. breviflora grassland of Inner Mongolia， examined the effects of different grazing intensities—no grazing， light grazing （LG）， moderate grazing （MG）， and heavy grazing （HG）—on the AMF colonization rate in S. breviflora roots. The results revealed a significant decline in the AMF colonization rate with increasing grazing intensity. The colonization rates were 65.89%， 59.89%， 52.89% and 41.33% under different grazing intensities， respectively. Spore density and hyphal length density decreased with increasing grazing intensity. In addition， increased grazing intensity led to longer total root length and smaller root diameter in S. breviflora， along with higher soil density and pH but lower soil organic carbon and available phosphorus. However， soil moisture and nitrate nitrogen content peaked under light grazing. Soil nitrate nitrogen and available phosphorus were identified as the primary factors influencing the reduction in AMF colonization. In conclusion， grazing negatively affects AMF colonization in desert steppes by decreasing nitrogen and phosphorus nutrient effectiveness in the soil. This study provides empirical data and theoretical insights that support the development of sustainable grazing management strategies to maintain the health and resilience of desert steppe ecosystems.

Desert steppe  /  Grazing  /  Stipa breviflora  /  Mycorrhizal infection rate