塔里木河下游荒漠植物群落物种多样性及其结构特征分析

以29块植物群落调查样地资料为基础，采用物种多样性指数、丰富度和均匀度由高到低指数对塔里木河下游植物群落的物种多样性及群落结构进行分析。结果表明，研究区共有植物10科14属，出现频率居于前3位的植物依次为柽柳、黑果枸杞和胡杨；重要值以胡杨为最大（0．384），其次为柽柳（0．230），盐生草为最小（0．002）；优势建群植物胡杨主要分布在与河道垂直距离500m范围内。沿河道从英苏至阿拉干断面，地下水位逐渐下降，物种多样性总体呈下降趋势，群落结构由乔木-灌木-草本转为以乔木-灌木为主；随与河道垂直距离增加，群落密度和盖度均呈现先增加后减少的变化趋势，植物群落结构由乔木-灌木、乔木-灌木-草本逐渐演变为灌木-草本或单一的灌木结构。

Species Diversity and Structural Characters of Desert Plant Communities in Lower Reaches of Tarim River.

Based on the data of plant communities collected from 29 sampling sites, species diversities and structures of the natural plant communities in the lower reaches of the Tarim River were analyzed from the angle of different environmen- tal gradients, using species diversity, richness and evenness indices. Results show that （ 1 ） the study area had a total of 14 genera of plants, belonging to 10 families, with Tamarix ramosissima, Lycium ruthenicum and Populus euphratica being the first three in frequency of occurrence and P. euphratica being the highest （0. 384 ） , T. ramosissima the next highest （0. 230） and Halogeton arachnoideus the lowest （0. 002） in the importance value, and P. euphratica being dominant spe- cies was mainly distributed in areas less than 500 m from the river. （2） Groundwater tables along the fiver lowered from the upper reaches to the lower reaches, except for the Yiganbujima Section, and so did the species diversity on the whole and arbor-shrub-herb-dominated communities were gradually changed into arbor-shrub-dominated one; while getting farther away from the river, the communities first increased and then decreased in density and coverage, and the plant community structures gradually shifted from arbor-shrub and arbor-shrub-herb to shrub-herb or shrub.