Abstract: To explore the effects of warming and grazing on the niche and interspecific association of species in the community in alpine meadow,four treatments were set up:Annual warming,Grazing,Annual warming with Grazing,and Control groups. The "Levins" method was used to calculate the niche breadth and niche overlap of the dominant species to other ones. The Variance ratio (VR),chi-square test,Association coefficient (AC) and Ochiai (OI) indices were used to analyze the interspecific association between the dominant species in the community. The results showed that the annual warming,grazing and annual warming with grazing increased the niche width of dominant species in general. The annual warming and annual warming with grazing reduced the niche overlap of major species. By the Chi square test,the 45.5%,41.8%,47.3% and 45.5% of the 55 species pairs composed of 11 dominant species displayed positive association under the four different treatments,respectively. The association coefficient showed that 54.5%,58.2%,52.7% and 54.5% of species pairs were negatively linked under the four different treatments,respectively. The OI index showed that both the annual warming and grazing treatments increased the OI values of the main species. Based on the interspecific association analysis,the annual warming and grazing strengthened the interspecific competition and the interspecific relationship in the community with a trend of regressive succession.

Key words: Simulated warming, Grazing, Alpine Meadow, Niche, Interspecific association

摘要： 为了探明增温和放牧对群落中物种生态位和种间联结的影响,本研究设置全年增温、放牧、放牧全年增温和对照组4种处理。采用"Levins"方法计算优势物种的生态位宽度和生态位重叠值,使用方差比率法(Variance ratio,VR)、卡方检验、联结系数(Association coefficient,AC)和Ochiai(OI)指数分析了种间联结性。结果表明,全年增温、放牧和放牧全年增温处理在总体上增加了优势种的生态位宽度;全年增温和放牧全年增温处理使主要物种生态位重叠值降低;χ²检验表明11个优势物种所组成的55个种对在四种处理下,分别有45.5%,41.8%,47.3%和45.5%的种对表现出正联结性;联结系数AC值表明,四种处理下分别有54.5%,58.2%,52.7%和54.5%的种对呈负联结;OI指数表明,全年增温和放牧处理使得主要物种OI值增大。通过种间联结分析发现,全年增温和放牧使群落内种间竞争加强,种间关系变紧密,呈现逆向演替的趋势。

关键词: 增温, 放牧, 高寒草甸, 生态位, 种间联结