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急尖长苞冷杉(Abies georgei var.smithii)是西藏东南部高山林线区森林群落的主要建群树种,分布于色季拉山海拔3 600～4 400m区域,为阴坡高山林线的优势树种。在藏东南色季拉山东坡急尖长苞冷杉林林线附近海拔4 000～4 400m地带进行样地样方调查的基础上,分析急尖长苞冷杉群落的物种组成、物种丰富度(S)、Simpson指数(D)、Shannon-Wiener指数(H’)、均匀度指数(Ea)、Jaccard指数(Cj)、Cody指数(βc)以及种群结构与生长特征。结果表明:1)在林线5个海拔的调查样地中,共有种子植物26种,分属16科20属;随海拔梯度的升高,植物的科、属、种的数量总体呈减少趋势,灌木层和草本层的丰富度亦呈相似的趋势;2)林线附近的灌木层和草本层植物的α多样性与海拔总体呈负相关;3)在生境转折带的4 100～4 200m之间Jaccard指数(Cj)最低,Cody指数与海拔呈负相关;4)林线附近的急尖长苞冷杉种群总体呈稳定的金字塔型结构;5)在林线附近,海拔4 200m的急尖长苞冷杉的分布与生长状况相对较优。
Abies georgei var.smithii is the dominant tree species of forest communities in the southeastern part of Tibet, covering an area of 3 600 ~ 4 400 m above Sejila Mountain, which is the advantage of shady alpine timberline species. Based on the sampling plots of 4 000 ~ 4 400 m above sea level near Abies forests on the east slope of Sejila Mountain, southeast Tibetan Plateau, the species composition, species richness (S Simpson index, Shannon-Wiener index, Ea, Jaccard index, Cody index and population structure and growth characteristics. The results showed that: 1) There were 26 species of seed plants in 5 survey plots of Linxian, belonging to 16 families and 20 genera. With the elevation gradient increasing, the number of plants, genera and species decreased overall , And the richness of shrub layer and herb layer also showed a similar trend. 2) The α diversity of shrub layer and herb layer near the forestline was negatively correlated with the altitude. 3) In the habitat transition zone, (Cj) was the lowest, and Cody index was negatively correlated with altitude. (4) The population of Abies georgei var. Fimbriatum near the forest line was generally stable pyramidal structure. (5) Near the forest line, the sharp point The distribution and growth of long-bred fir are relatively better.