东苕溪喜旱莲子草群落研究

Alternanthera philoxeroides community in the eastern Tiaoxi River

通过对浙江省东苕溪江8个河段喜旱莲子草Alternanthera philoxeroides的群落及伴生植物群落结构进行调查的基础上,分析该入侵种在不同河流段生境中的重要值及对入侵地物种多样性的影响.结果表明：在东苕溪流域,喜旱莲子草茎长平均为41.85～62.83 cm,节间距平均为4.00～6.28 cm,平均分枝数为6.35～82.00个.临安市东湖村采样点喜旱莲子草重要值最高,为56.09％;但伴生植物种类最少,为2种.杭州市余杭区陡家门采样点该入侵种重要值较低,但伴生种种类最多（8种）.随着喜旱莲子草重要值的升高,群落Simpson多样性指数和Shannon-Wiener指数呈下降趋势,表明随着喜旱莲子草种群的扩散,区域内其他物种逐渐受到排挤.在伴生植物种类较少的取样点,喜旱莲子草相对密度较大,如杭州市余杭区安溪镇、临安市里畈水库下游和临安市东湖村苕溪北路段（相对密度分别为40.00％,39.85％和37.50％）,Pielou均匀度指数较低,这都说明喜旱莲子草的扩散降低了当地的物种多样性.喜旱莲子草对苕溪江植物种类和分布已经产生较大的影响.

Recently, A lternanthera philoxeroides, an invasive species, is found to distributed widly in eastern Tiaoxi River which is as an important source of drinking water in Hangzhou City. The widely distribution of A. philoxeroides will be result in the water ecological security. So it has an important significance to study the distribution of A. philoxeroides community in eastern Tiaoxi River, as well as to find the effect on local species＇ diversity. In this study, random sampling method was used. One 100 m2 sample plot at eight reaches of the eastern Tiaoxi River was designed, in which five 0.25 m2 quadrats were chose to as be sampling sites. The morphological characteristics and the associated communities of A. philoxeroides at eight reaches of the eastern Tiaoxi River, Zhejiang Province were studied, and the importance and influence on plant diversity at eight sites were analyzed using Simpson＇s diversity, Shannon-Wiener, and Pielou Evenness Indexes. Results showed that stem length varied from 41.85 to 62.83 cm, average distance between nodes varied from 4.00 to 6.28 cm, and average number of branches ranged from 6.35 to 82.00. At the Donghu Village site of Lin＇an City, the highest important value was 56.09% with the least number of associated significant relevance between the importance value of A. philoxeroides and the species number of associated species （P〉0.05）. Nevertheless, there were significantly correlations between the associated species number and three diversity indexes （Simpson＇s diversity, ,Shannon-Wiener indexes, and Pielou Even ness Index） （P〈0.05）. Our results indicate A. philoxeroides has affected the local plant species diversity of the eastern Tiaoxi River. And the water ecological security of east Tiaoxi River is being threated by invasive species A. philoxeroides.