Abstract: Grazing and frost heaving raised grass mounds embedded in gentle grasslands in the alpine meadow of western Sichuan plateau. In this paper,soil samples were collected along a gradient of soil moisture to analyze the differences in physicochemical properties between raised grass mounds and gentle grasslands,and compare the differences in species richness and coverage between the two habitats to determine whether raised grass mounds is a type of microhabitat that is more prone to degradation. The results showed:Soil porosity,bulk density,water content,available nutrient,total nutrient and organic matter content of the two habitats were significantly different (P<0.05). The differences in the upper layer of soil (0~10 cm) were larger than the lower layer (10~20 cm),and the degradation of upper soil was more obvious when compare to the changes of physicochemical properties of the lower layer. The soil physical properties of the two habitats were the most different under arid conditions,while the soil chemical properties are the most different under wet conditions and the soil physical properties were firstly changed during the habitat degradation process. The effect of soil water content on soil physicochemical properties,species richness and vegetation coverage was greater than habitat types. As the degree of aridification continues to increase,the species diversity of the raised grass mounds was significantly reduced,so the raised grass mounds are more susceptible to degraded microhabitat types.

Key words: Alpine meadow, Raised grass mound, Gentle grassland, Soil moisture content

摘要： 川西高原高寒草甸受放牧践踏和冻胀作用影响，形成了许多凸起草丘镶嵌于平缓草地之间。本文沿土壤水分梯度采集土样，分析凸起草丘和平缓草地土壤理化性质差异，并比较两种生境物种丰富度和盖度的差异，以确定凸起草丘是否为更易退化的微生境类型。结果表明：两种生境的土壤孔隙度、容重、含水率、有效养分、全效养分、有机质含量均有显著差异（P<0.05），且土壤上层（0~10 cm）的差异大于下层（10~20 cm），与下层土壤理化性质的变化相比，上层土壤退化更明显。两种生境间的土壤物理性质在干旱条件下差异最大，而土壤化学性质在湿润条件下差异最大，在生境退化过程中首先是土壤物理性质发生改变。土壤含水率对土壤理化性质、物种丰富度、植被盖度的影响比生境类型产生的影响更大。随着生境干旱化程度增加，凸起草丘物种多样性明显降低，凸起草丘是更易退化的微生境类型。

关键词: 高寒草甸, 凸起草丘, 平缓草地, 土壤含水率