Linking Plant Community Characteristics and Soil Properties Under Grazing Disturbance in a Desert Steppe Ecosystem

Grazing is a key driver of structural and functional changes in desert steppe ecosystems. Soil nutrients are essential for plant growth, and grazing can alter soil nutrient availability through herbivory and trampling, which, in turn, may affect plant communities. However, the responses of plant communities and their functional groups to soil properties under different grazing intensities remain elusive. This study examined variations in plant community characteristics, including biomass, quantitative traits, and species diversity, under a gradient of grazing intensities. Species were classified into functional groups, and their corresponding soil physicochemical properties were analyzed. The results showed that aboveground biomass was highest under no grazing and light grazing, and lowest under extreme grazing. Height and coverage of annual and biennial forbs and perennial grasses declined sharply with increasing grazing intensity. Species richness and diversity indices reached their minimum values under heavy grazing, while Simpson's dominance index peaked. Soil analysis revealed that available nitrogen and available phosphorus declined with increasing grazing intensity. Pearson correlation analysis revealed positive relationships between available nitrogen, available phosphorus, and plant α-diversity, biomass, and basic traits. Structural equation modeling further showed that grazing not only directly affected plant communities but also influenced them indirectly through reductions in soil available nitrogen and available phosphorus. In conclusion, regulating grazing intensity to maintain soil nutrient availability may be important for sustaining the stability and functioning of desert steppe ecosystems.