关键词: 放牧, 植物功能群, 土壤因子, mantel检验, 结构方程模型, 天山北坡

Abstract: Aims Grassland ecosystem provides an important guarantee for the survival and development of human beings, and is also an important foundation for grassland animal husbandry. Grassland plant community is the main body of grassland ecosystem, however, there is a lack of research on the change rule of plant functional groups and their response to environmental factors under different grazing intensity. Methods In order to deeply understand the change rules of grassland plant communities and soil physicochemical factors under different grazing disturbance treatments as well as the interaction relationship between the two, this paper takes the grassland in the middle part of the north slope of Tianshan Mountain under different grazing intensities as the research object, and analyzes the characteristics of plant communities and soil physicochemical properties under different grazing treatments based on the field plant surveys and the analysis of soil physicochemical properties indoors. Important findings The results showed that the main dominant species of grassland plant communities in the lightly grazed and ungrazed samples were perennial grasses and sedge-like forbs, and the main dominant species in the heavily grazed sample was drunken horseweed. Compared with the heavily grazed treatment, the ungrazed treatment significantly increased the height, cover, density and plant diversity index of the grassland plant community (p < 0.05), as well as soil factors such as soil organic carbon, total nitrogen, phosphorus and potassium, quick-acting nitrogen, phosphorus and potassium and soil water content, and the light grazing significantly increased the aboveground biomass of the functional groups of perennial grasses, perennial legumes, sedges and miscellaneous grasses (p < 0.05). And the aboveground biomass of toxic grasses under heavy grazing treatment was significantly higherthan that of light grazing and ungrazed treatment (p < 0.05). Mantel test and structural equation modeling showed that plant community traits, functional groups and community diversity were significantly correlated with soil organic carbon, quick-acting nitrogen, quick-acting potassium, all-phosphorus, all-kilograms, soil capacity, and soil water content (p < 0.05). Grazing can directly affect the basic traits, functional groups and diversity of grassland plants (p＜0.05), and can also indirectly affect the basic traits, functional groups and diversity of plants by increasing the soil capacity and decreasing the soil nutrients, so that increasing the soil nutrients plays a crucial role in maintaining the stable growth of grassland plant communities in the middle part of the north slope of Tianshan Mountain. This study provides new insights into the relationship between grassland plant communities and soil factors under grazing disturbance, and provides a theoretical basis for the rational utilization of grassland plant resources on the northern slopes of Tianshan Mountain.

Key words: Grazing disturbance, Plant functional groups, Soil factors, Mantel test, Structural equation modeling, North slope of Tianshan Mountain