Abstract: 【Objective】The objective of this study is to reveal the effects of grazing intensity on the community structure and diversity of different soil fauna in alpine meadow ecosystems.【Method】The investigations were conducted on the soil faunal communities and soil environment of alpine meadows under different grazing intensities (light grazing, LG, 15 sheep/hm²; medium grazing, MG, 22 sheep/hm²; heavy grazing, HG, 36 sheep/hm²; no grazing, NG) in September 2014 in Hongyuan county, northwest Sichuan. Epigeic arthropods were investigated using Vortis sinensis with sampling area 0.2 m² and preserved in 75% alcohol. The soil cores were used to collect soil samples from 0-5, 5-10 and 10-15 cm layers. Two soil samples were collected from each layer. The Tullgren and Baermann methods were used to extract soil arthropods and soil nematodes, respectively, from soil samples. 【Result】 The principal component analysis (PCA) results showed that the community structure of the three kinds of soil fauna in no grazing treatment differed from those of grazing treatments, indicating that the community structure of soil fauna can be affected by grazing. Community structure of soil nematodes in the three grazing treatments were differed clearly from each other, the similar phenomenon was also found for epigeic and soil arthropods. The community densities of soil arthropods and nematodes in grazing treatments were greater than those in no grazing treatment (P＜0.01). The minimum values of community density of epigeic arthropods were recorded in the light grazing treatment and the maximum values of community group number were observed in the heavy grazing treatment (P＞0.05). Shannon index and Pielou index fluctuated among the treatments, and the maximum values of Shannon index and Pielou index were observed in the no grazing treatment, the minimum values in the light treatment (P＜0.05). The Shannon index and group number of soil arthropods increased then reduced with increasing grazing intensity, and the values of Shannon index and group number were greater in light grazing treatments than in other grazing treatments (P＜0.01), but Pielou index changed with no significance (P＞0.05). The maximum values of soil nematode community group number were observed in the light grazing treatment, Shannon index of soil nematodes significantly reduced with increasing grazing intension with the maximum values observed in the no grazing treatment; Pielou index were lower before increase, and the maximum values of Pielou index were observed in the no grazing treatment. One-Way ANOVA results showed that diversity indexes of soil nematodes differed significantly between the four grazing treatments (P＜0.05). The densities and Shannon index of epigeic and soil arthropods were significantly correlated to some soil chemical properties (P＜0.05 or P＜0.01), but the density and Shannon index of soil nematodes were significantly correlated to some soil chemical properties and grazing intensity. 【Conclusion】The results suggested that different groups of soil fauna respond differently to grazing intensity; The heavy, medium and light grazing benefit, respectively, the epigeic arthropods, soil arthropods and soil nematodes, indicating that selecting an appropriate kind of soil fauna is very important to evaluate the effects of grazing intensity on grassland ecosystems.

Key words: grazing intensity, alpine grassland, epigeic arthropods, soil arthropods, soil nematode