Abstract: [Objective] The project aims to determine the height,coverage,density and aboveground biomass of the dominant plant species of grassland communities in different months and calculate the important values and analyze the dynamic change of diversity indexes in the northern slope of Tianshan mountain.[Method] The meter ampere quadrates of different grassland types were set based on the crossing method,and community characteristic parameters were monitored from spring to autumn.[Result] There were some differences in the important values of different grassland types.The whole trend of important value from may to september showed decreasing trend;especially forage grass of Stipa capillata,Festuca ovina decreased obviously than the forbs important value.The plant community height,coverage and aboveground biomass showed high trend in late spring and early summer while low from August to September.The statistical results showed that the trend of diversity indexes was increasing first and then decreasing and then increasing,such as Simpson index D and Shannon-Wiener index H,evenness index Esw and richness index R,And Simpson index D and Shannon-Wiener index H and species richness R to aboveground biomass were significantly positively correlated,and evenness index to aboveground biomass was not significantly negatively correlated.[Conclusion] The preliminary study of the quantity characteristics of the plant communities in different grassland types showed a trend of increasing first and then decreasing with the seasonal variation and the species diversity increased firstly and then decreased.The results can provide data for supporting the rational utilization of grassland.

摘要： [目的]针对天山北坡山地草原不同群落类型,测定不同月份间草地群落植物优势种的高度、盖度、密度、地上生物量,计算重要值,分析多样性指数的动态变化.[方法]在不同草地类型上设立固定监测样地,十字交叉法设立定点1 m×1 m样方,从牧草返青期至结实期每月定期测定植物群落高度、盖度、密度及地上生物量.[结果]植物群落的高度、盖度、地上生物量在5～9月期间均表现出春末夏初高,8、9月低的动态变化规律;不同草地类型主要优势种重要值存在一定差异,5-9月重要值呈逐渐降低趋势,尤其是家畜喜食的牧草,如针茅、羊茅的重要值降低较为明显,而杂类草重要值未呈现出一定的规律性;群落Simpson指数D和Shannon-Wiener指数H、均匀度指数Esw和丰富度指数R均表现出升高-降低-再升高的趋势,且Simpson指数D和Shannon-Wiener指数H及物种丰富度R与地上生物量呈显著正相关,而均匀度指数与地上生物量呈不显著负相关.[结论]不同草地型问的植物群落数量特征随季节变化呈先升高后降低趋势,物种多样性呈先升高后降低再升高的月动态变化规律,研究结果可为合理利用草地提供数据支持.