中文摘要：

运用典型样地法，对塔里木河中游30个天然植被样地的群落结构和数量特征做了调查分析。结果表明：（1）塔里木河中游沙吉力克、沙子河、乌斯满、阿其河、铁依孜五个断面的天然植物隶属11科，20属，22种。（2）塔里木河中游植物群落结构可分三层，即乔木层、灌木层与草本层。但这种乔、灌、草的三层现象不明显。生境条件差，植物对环境利用不充分。（3）荒漠植物群落物种多样性水平较低，群落结构简单，物种组成单一。从多样性指数的数量特征来看，Simpson多样性指数的变化范围为0．47～0．609，Shannon-Wiener指数变化范围0．849～1．302；Menhinick丰富度指数的变化范围为2．309～3．175，Margalef2．731～5．461；JSW均匀度指数的变化范围为0．6～0．778．JSI指数的变化范围0．633～0．805。五个断面盖度的变化范围是0．259—0．563。

英文摘要：

The Tarim River is the longest inland river in China and the Tarim River basin is one of the uttermost arid areas of China. There are natural species belts composed of arbors, shrubbery and herbage along the river. The plants distributed at the Tarim River basin has good capability to acclimate to drought, sandy, windy and salty conditions. It plays a very important role of protecting oasis and manmade oasis. Based on the data obtained from 30 plots of natural plant communities in the middle reaches of Tarim River, the paper analyzed the community structure and species diversity. The results show that （1） there are only 11 families, 20 genera and 22 species at five sections of Tieyizi, Aqike, Wusiman, Shazihe, and Shajilike region. Among those 22 species, Leguminosae and Compositae are the main families, which take up 40.9% of species. The dominant plant species are Arbors of Populus euphratica, Shrubbery of Tamarix ramosissima, Tamarix hispida, and Herbage of Phragmites communis, Poacynum hendersonii, Alhagi sparsifol, Karelinia caspic, Glycyrrhiza inflate, etc ; （2） the paper used Simpson and Shannon-Wiener index, Menhinick and Margalef index, and JSW and JSI index to calculate the species diversity indices. The ecosystem is deteriorating, with Simpson index changed from 0.609 to 0.47, Shannon-Wiener from 0. 849 to 1. 302, Menhinick index changed from 2. 309 to 3. 175, Margalef index from 2. 731 to 5. 461, JSW index changed from 0.78 to 0.62, JSI from 0. 633 to 0. 805, and the mount of species changed from 12 to 9. General speaking, the community with better habitat, evenness index is lower. However, in the habitat with lower richness index, the species distribution is more uniform. According to analysis, the habitat of Wusiman section is better than others. On the contrary, Shajilike section is the worst. The results suggest that much more attentions should be paid to the ecosystem of the middle Tarim River and effective protections should be enforced to the existing plant communities.