中文摘要：

以不同退化梯度的高寒草地土壤为研究对象,研究草地退化对不同层次（0～10cm、10～20cm和20～30cm）土壤物理、化学和生物学特征的影响。结果表明：江河源区高寒生态条件下草地退化对土壤物理、化学和生物学性质具有相对一致的影响,随草地退化程度的加重,各土层土壤含水量和水稳性团聚体百分数逐渐下降,土壤容重则呈增加趋势。草地退化导致土壤各种营养物质含量（除全钾）、土壤微生物群落和土壤酶活性显著下降,其中土壤有机质、速效氮、过氧化氢酶、脲酶、磷酸酶、土壤细菌、真菌和微生物总量在0～10cm土层表现为未退化〉轻度退化〉中度退化〉重度退化,而土壤全氮、全磷、速效钾和放线菌数量在0～10cm土层表现为轻度退化〉未退化〉中度退化〉重度退化,在10～30cm土层,则表现为严重退化草地的有些指标有一定程度升高。相关性分析结果表明,各种土壤酶和微生物群落之间呈显著或极显著正相关（除土壤脲酶和中性磷酸酶之间无显著相关性外）;土壤水分,容重、有机碳、全氮、速效氮、速效钾与各种土壤酶和各种微生物均具有显著相关性;水稳性团聚体与各种微生物和中性磷酸酶具有显著相关性。

英文摘要：

The series of physical,chemical,biological properties and their relationships of Alpine pasture soil of three layers（0-10,10-20,20-30 cm） at four different degradation successional stages（undegraded,lightly degraded,moderately degraded and heavily degraded） in the headwater region of Yangtze and Yellow rivers were analyzed in this study.The results showed that under the ecological conditions of the Qing-hai Tibetan Plateau,Alpine meadow degradation had consistent effects on soil physical,chemical and biological properties.With increased meadow degradation grades,soil bulk density at all of the 0-30 cm layers showed a increasing trend,while soil moisture content and water stable aggregates（ 0.25 mm） content at three layers decreased significantly.Soil organic carbon contents as well as available N,the activities of soil enzymes（catalase,urease,neutral phosphatase）,the quantities of soil microorganisms（Bacteria,Fungi and total Microorganisms） at 0-10 cm and 10-20 cm soil layers showed a decreasing trend with meadow degradation.Soil total N,P,available K,quantities of soil actinomycetes at 0-10 cm and 10-20 cm soil layers were increased in lightly degradation meadow but decreased in moderately and heavily degraded meadows compared with no degradation meadow.There were significantly（P 0.05 or P 0.01） positive relationships between the quantities of soil microorganisms（Bacteria,Fungi and Actinomycetes）,the activities of three mentioned soil enzymes（except for soil urease and neutral phosphatase related insignificant）;three mentioned soil enzymes and three soil microorganisms groups were significantly related to the soil moisture content,bulk density,organic C,total N,available N and available K;soil water stable aggregates were also significantly related to soil microorganisms groups and neutral phosphatase.