中文摘要：

不同强度、季节的放牧是草地生态系统中主要的放牧管理措施,在生物多样性维持以及生态过程发挥中起着重要的作用,然而,关于青藏高原东缘高寒草甸地区放牧对土壤线虫群落的研究甚少。本文调查了放牧（轻度、中度和重度）对植物群落、土壤理化性质和线虫群落的影响。结果表明：植物群落、土壤理化性质和线虫群落受到放牧、时间以及放牧和时间共同作用的影响;食细菌线虫、植物凋落物生物量、根生物量、土壤含水量、土壤有机碳含量在轻度放牧草地内最高（p〈0.0 5）;杂类草生物量在中度放牧草地内最高;杂食线虫数量在重度放牧地内最低（p〈0.05）。植物群落和土壤特性与土壤线虫群落有明显的相关关系（p〈0.05）。结构方程模型显示食草动物主要通过植物群落影响植食和食细菌线虫,进一步的研究应针对植物群落多样性以及个体特征对线虫群落的影响。

英文摘要：

【Objective】The Tibetan Plateau has a unique function in physical environment and ecosystem because of its unique geographical features. Grazing is the main practice of management of grassland ecosystems and plays a crucial role in maintaining biodiversity and ecological processes. So volumes of researches have been reported on plant communities and soil physicochemical properties of the grasslands in the Tibetan Plateau,however,little has on the impacts of grazing on diversity of soil nematodes in this alpine regions,although soil nematodes play an important role in process of the ecosystem. The unique properties of the alpine grassland mean that grazing may have impacts distinct from what the other terrestrial ecosystems have on soil nematode communities. It is,therefore,critical to do more researches on impacts of grazing on population and biodiversity of the soil nematode communities in this region and how grazing affects soil nematode communities,through altering plant communities or soil physicochemical properties.【Method】In this study effects of grazing on soil nematode communities,plant communities and soil physicochemical properties,relative to degree of grazing（light,Moderate and heavy）were explored. Effects of timing of sampling and grazing management and their joint effects on these indices were analyzed via repeated measurements and ANOVA. Changes in biomass of the nematode communities and the plant communities and soil physicochemical properties were observed and the data gathered were analyzed to explore relative importance of alternative pathways of the effect of grassing on nematode communities with the structural equation modeling（SEM）method.【Result】The effects of grazing on nematode communities,plant communities and soil physicochemical properties were related to degree of grazing,time of sampling and their interactions. Population of bacterivores nematodes,biomass of plant roots,biomass of plant litter,soil moisture content and soil organic carbon content were all the highes