中文摘要：

以地处青海湖北岸三角城种羊场附近高寒退化的紫花针茅草原为对象,研究了施肥对植物群落盖度、物种多样性和植物类群的影响。结果表明：施肥后的第2年（2012年）和第3年（2013年）群落的总盖度显著高于施肥前（2011年）（P〈0.05）,且随着施肥年限的增加,群落的盖度也增加,但不同处理增加的幅度不一致;与不施肥相比,不同的施肥处理在2年和第3年物种丰富度逐渐减小;施肥后Simpson指数、Shannon指数、Pielou均匀度指数的变化无明显规律;不同植物类群对施肥的响应亦不同,施肥后第2年和第3年不同施肥处理间禾草类和杂类草生物量均显著增加（P〈0.05）,而莎草类和豆科变化不明显。

英文摘要：

Effects of nitrogen （ N）, phosphorus （ P ） and potassium （K） fertilizations on plant community coverage, plant diversity and economic herbage groups in a degraded alpine steppe on the northern shore of Qinghai Lake was examined during 2011-2013 in the present study. The three-year results showed that the total plant community coverage of fertilized treatments in the second （2012） and third year （2013） was significantly higher than that in the first year （2011）. Meanwhile, plant community coverage also increased as the fertilization continued, but different fertilization treatments showed distinct responses in comparison with no fertilization treatment. All fertilization treatments reduced the species richness of community, and the species richness de- creased as the fertilization continued. However, there was no consistent pattern in the change of Simpson index, Shannon index and Pielou evenness index after fertilization. Different economic groups responded distinctly to fertilization. The aboveground biomass of grass and forb species in- creased significantly （P 〈 0.05 ） in the second and third years after fertilization, while that of sedge and legume species had no obvious change after fertilization.