Abstract: In order to study the effects of grassland degradation on vegetation and soil microorganisms,alpine grassland in Luqu county,Gannan prefecture was taken as the research object. The indexes of plant species,vegetation height,coverage,species richness and fresh grass yield in grassland at different degree of degradation were investigated. And the indexes of soil respiration intensity,soil microbial biomass carbon content and soil respiration entropy were measured. The results showed that with the aggravation of grassland degradation,the plant species in alpine grassland tended to decrease,and the species of dominant plants changed,such as Ligularia virgaurea,Oxytropis ochrocephala,Thermopsis lanceolata and other poisonous weeds appeared. And the vegetation height,coverage,plant number,fresh grass yield and other indicators showed a downward trend. The indexes of soil basal respiration and induced respiration,soil microbial biomass carbon and soil metabolic entropy all decreased at different degrees. The content of soil total phospholipid fatty acid (PLFA),soil bacteria and actinomycetes decreased,while the content of fungi increased. The soil microbial community structure changed and the pressure index increased. The correlation analysis showed that there were different degrees of correlation between vegetation and soil microorganisms. Soil fungi and microbial pressure index were negatively correlated with vegetation and other factors of soil microorganisms,while other factors were positively correlated. This study shows that the succession of vegetation is closely related to the change of soil microorganism in alpine grassland degradation.

Key words: Alpine grassland, Grassland degradation, Vegetation characteristics, Soil respiration, PLFA

摘要： 为研究草地退化对植被和土壤微生物的影响，本试验以甘南州碌曲县高寒草地为研究对象，调查研究不同退化程度草地植被特征，并测定土壤微生物呼吸、土壤微生物量碳、土壤微生物代谢熵及土壤微生物群落结构变化。结果表明：随着草地退化程度的加重，高寒草地植物种类减少，优势植物种类发生变化，植被高度、盖度、植株数、鲜草产量下降；土壤基础呼吸和诱导呼吸、土壤微生物量碳及土壤代谢熵等指标均有不同程度的下降；土壤总磷脂脂肪酸（Phospholipid fatty acid，PLFA）、土壤细菌、放线菌含量减少，真菌含量增多，土壤微生物群落结构发生变化，压力指数增高；植被与土壤微生物各指数呈一定的相关性。本研究说明高寒草地退化过程中植被演替与土壤微生物变化密切相关。

关键词: 高寒草地, 草地退化, 植被特性, 土壤呼吸, PLFA