对三江源区不同退化演替阶段的高寒草甸土壤酶活性和微生物群落结构进行分析，结果表明：1） 土壤微生物种类和数量并不随着高寒草甸的退化而降低，而是在中度退化阶段达到最高；2）不同退化演替过程，中度退化阶段土壤微生物的结构更加复杂；3）不同土层中，0?10 cm 土壤微生物的多样性更加丰富，其群落结构能更好地适应外界环境的变化；4）5种土壤酶的酶活性均随土层深度的增加而显著降低(P<0. 05)。在不同退化演替阶段，碱性磷酸酶的活性随演替的进行而显著降低(P<0. 05)；蛋白酶和多酚氧化酶的酶活性最大值出现在中度退化演替阶段，最小值则在未退化阶段（原生植被）出现；蔗糖酶和脲酶活性在4个演替阶段中均无显著变化(P>0. 05)。不同酶活性对外界环境变化敏感性不同，蛋白酶、碱性磷酸酶和多酚氧化酶具有较高的敏感性，而脲酶和蔗糖酶活性的敏感性较低；5）土壤酶活性与土壤微生物在高寒草甸不同退化演替阶段具有显著相关性(P<0. 05)。土壤酶活性、土壤微生物群落结构可以作为一个综合指标，来指示三江源区高寒草甸的演替阶段和退化程度。

An analysis was carried out on the soil enzyme activities and the soil microbial community structure of alpine meadows in the headwater area of the Yellow River,the Yangtze River and the Lancang River at four successional degraded stages （NS: Normal Steppe,LD: Light Degradation, MD: Moderate Degradation, HD: Heavy Degradation) using the colorimetric method and phospholipids fatty acid (PLFA). 1) The species and quantity of soil microbes did not reduce with degradation of the alpine meadow and they reached the highest level at MD. 2) The soil microbial structure at MD was the most complex one among the four stages. 3) The soil microbial diversity in the 0-10 cm layer was richer than that at 10 - 20 cm，which made the microbial community structure better adapted to the changes of ambient environment. 4) The activities of all five enzymes decreased significantly (P<0. 05) with soil depth and the activity of alkali phosphatase decreased considerably as the alpine meadow degraded (P<0. 05). The maximum activities of protease and polyphenol oxidase appeared at MD, with the minimum in NS,but the activities of invertase and urease (P>0. 05) seldom changed in any of the four stages. Enzyme activities responded differently to changes of the ambient environment. Alkali phosphatase, protease and polyphenol were more sensitive than invertase and urease. 5) There was a significant correlation between soil enzyme activities and soil microbes at successional degraded stages of the alpine meadow (P<0. 05). Soil enzyme activities and soil microbial community structure could be comprehensive indicators to show the stage of succession and the degree of degradation on the alpine meadows in the headwater areas of the three rivers.