ObjectiveThe Horqin Sandy Land is located in agro-pastoral ecotone of northern China, and its species composition and diversity patterns are quite vulnerable to the changes of human disturbance and environmental factors. Because of the fast development of agriculture and animal husbandry industry in recent years, human disturbance has become an essential role in the Horqin Sandy Land. However, further systematic studies are needed to understand the relative influence of grazing disturbance and environmental factors on the α, β and γ diversity of plant communities in the Horqin Sandy Land.

MethodThe grazing disturbance data and environmental data of 44 sampling points were used to study the distribution characteristics of the α, β and γ diversity of plant communities and their main influencing factors in the Horqin Sandy Land by one-way ANOVA, simple linear regression analysis, polynomial regression analysis, and variance decomposition.

Result(1) The α, β and γ diversity of plant communities declined as grazing intensity increased, and the peak species diversity appeared under grazing exclusion. There was a significant difference in the α, β and γ diversity of plant communities among different grazing intensities (P <0.05). The α, β and γ diversity under heavy grazing intensity were significantly lower than that under grazing exclusion (P < 0.05). (2) The α diversity of plant communities had a significantly negative correlation with grazing intensity and mean temperature of the hotest month (P < 0.01), and a positive correlation with mean diurnal range, soil organic carbon and soil total phosphorus (P < 0.01); it had a significant U-shaped relationship with mean annual precipitation, and a hump-shaped relationship with mean temperature of the coldest month and soil total nitrogen (P < 0.05). The β diversity of plant communities had a significantly negative correlation with grazing intensity, potential evapotranspiration, and mean temperature of the coldest month (P < 0.05), and a positive correlation with mean annual precipitation (P < 0.05). The γ diversity of plant communities had a significantly negative correlation with grazing intensity (P < 0.001), and a positive correlation with soil organic carbon and soil total nitrogen (P < 0.01). (3) Grazing disturbance was the main influencing factor affecting the α and β diversity of plant communities; the synergism between grazing disturbance and soil factors was the main influencing factor affecting the γ diversity of plant communities.

ConclusionGrazing disturbance has a critical effect on species diversity of plant communities in the Horqin Sandy Land. Therefore, in order to enhance biodiversity conservation and restore the degraded ecosystem in the Horqin Sandy Land, local government should formulate polices to forbid overgrazing and enhance supervision to reduce the occurrence of grazing without permission.