中文摘要：

为探究云雾山天然草地30年恢复演替过程中优势草种的生态位动态,通过典型样方调查,运用Levins和Pianka公式分别对封育5年、9年、14年、18年和30年天然草地的主要物种生态位进行了分析.结果表明：不同封育年限草地的物种组成与群落类型具有明显差异,阿尔泰狗哇花（Heteropappus altaicus）、大针茅（Stipa grandis）、二裂委陵菜（Potentilla bifurca）和百里香（Thymus mongolicus）4个种群生态位总宽度较大,且在5个不同封育年限草地均有出现.云雾山原建群种长芒草（Stipa bungeana）生态位宽度也较大,但在封育30年样方中未发现其分布.不同封育年限各物种生态位宽度排序和其总宽度排序并不相同,封育5年、9年和14年的草地中生态位宽度最大的分别是长芒草、甘肃蒿（Artemisia gansuensis）和猪毛蒿（A.scoparia）,封育18年和30年草地大针茅最大.随着封育年限增加,优势物种的生态位宽度出现波动,大针茅的生态位宽度随封育年限增加呈现“升降升”的动态变化,封育5～18年,长芒草生态位宽度变化表现为先降后升,甘青针茅（S.przewalskyi）只在封育30年样地出现,但其生态位宽度仅次于大针茅.种群间生态位重叠与不同封育年限草地种群生态位宽度无线性关系,封育9年草地种群间的生态位重叠指数均值最大,封育14年和30年草地的生态位重叠指数均值呈递增趋势.随着封育年限的增加,草地生态系统逐渐得到恢复,种间竞争也随之增加.

英文摘要：

In order to explore the niche dynamics of dominant species during 30 years restoration process of natural grassland in Yunwu Mountain,the ecological niches of the main species in different enclosure years were calculated using Levin＇s and Pianka＇s indices,based on the field survey data got by “quadrat method”.Results showed that the species composition and community types differed among the grasslands of different enclosure years.The niche breadths of Heteropappus altaicus,Stipa grandis,Potentilla bifurca and Thymus mongolicus,which appeared in the grasslands of five treatments,were larger than that of other species.Stipa bungeana that used to be a dominant species of Yunwu Mountain with large niche breadth was not found in the quadrats of 30 year enclosure grassland.The species with largest niche breadth in grasslands of enclosure 5-year,9-year,14-year,18-year and 30-year were Stipa bungeana,Artemisia gansuensis,Artemisia scoparia,Stipa grandis and Stipa grandis,respectively.The niche breadth of dominant species fluctuated with the increase of enclosure years.The niche breadth of Stipa grandis showed “up-down-up” trend along with the increasing of enclosure years.The niche breadth of Stipa bungeana initially declined then increased after 18 year enclosure.The niche breadth of Stipa przewalskyi,which appeared only in 30-year enclosure plots,ranked only second to Stipa grandis.There was no a linear relationship between the niche overlap and niche breadth of tested species in the grasslands at different enclosure years.The average value of niche overlap indices was the largest in 9-year enclosure grassland.The grassland ecosystem was gradually restored with long time enclosure.Meanwhile,interspecific competition was also increased.