Abstract: In order to reveal the changes of herbaceous community diversity with altitude gradient,the similarity and stability of community structure in the middle reaches of the Yarlung Zangbo River,the species diversity and stability index were measured in this study using survey data of 7 altitudinal gradients. The results showed that:(1) In 140 quadrates,39 species of herbs were recorded,belonging to 20 families and 33 genera,of which Poaceae was the most dominant species,followed by Asteraceae. (2) Astragalus strictus and Aster tataricus had strong adaptability to habitats. Pteridium aquilinum distributed below 3800 m,and Rhodiola rosea distributed above 4000 m. The distribution of herbaceous plants was greatly affected by habitat conditions such as altitude,latitude and longitude and soil. (3) The species richness reached the highest in the range of 3600-3800 m altitude,which was a suitable living area for herbaceous communities. (4) According to the Jaccard index,the community similarity was high when the altitude was below 3600 m. (5) From the perspective of community stability index and diversity index,there was no direct correlation between plant community diversity and community stability. This study,conducted sampling and observation research on herbaceous plants in the middle reaches of the Yarlung Zangbo River,could comprehensively show the relationship between species distribution,spatial composition and altitude factors of herbaceous plants in the study area,and provide scientific theoretical basis for the protection and sustainable utilization of biodiversity in the study area in the future.

Key words: Diversity and similarity index, Correlation analysis, Community stability index, Altitude

摘要： 为揭示雅鲁藏布江中游段草本植物群落多样性与海拔因子的关系、群落结构的相似性及稳定性。本研究利用7个海拔梯度的调查数据，测算物种的多样性及稳定性指数。结果表明：(1)在140个样方中，共记录到草本植物39种，隶属20科33属，其中禾本科(Poaceae)植物为的第1优势种，其次为菊科(Asteraceae)。(2)笔直黄芪(Astragalus strictus)和紫菀(Aster tataricus)对生境适应性较强。蕨类(Pteridium aquilinum)分布在3800 m以下，红景天(Rhodiola rosea)分布在4000 m以上。草本植物的分布受海拔，经纬度及土壤等生境条件的制约影响较大。(3)物种丰富度在海拔3600~3800 m范围内达到最高，为草本群落适宜的生存区。(4)从Jaccard指数来看，海拔在3600 m以下时群落相似性高。(5)从群落稳定性指数与多样性指数来看，植物群落多样性的高低与群落稳定性没有直接相关性。本研究对雅鲁藏布江中游草本植物进行采样观测研究，能够全面地展现研究区草本植物的物种分布、空间组成等整体概况与海拔因子的关系，为今后研究区生物多样性的保护和可持续利用提供科学理论依据。

关键词: 多样性及相似性指数, 相关性分析, 群落稳定性指数, 海拔