外来入侵杂草空心莲子草对植物生物多样性的影响

Effect of Alternanthera philoxeroides,an invasive exotic weed,on plant biodiversity.

利用样方法调查了南京市空心莲子草(Alternantheraphiloxeroides)生长生境中杂草的种类和分布。结果表明,南京市秋季空心莲子草分布样点有杂草30科101种,其中以禾本科、菊科、蓼科居多。主成分分析表明,影响杂草分布的主要因素是土壤水分条件和人为干扰强度。经Q型分析, 24个样点可划分为3个聚类群:聚类群Ⅰ包括的样点均分布在路边和田边开阔地以及小河、小沟和湖的岸边,以马唐、狗尾草和牛筋草为优势种;聚类群Ⅱ的样点都是农田隔离带如田埂以及农田中的沟壑,以波斯婆婆纳、碎米莎草、野塘蒿和铁苋菜为优势种;聚类群Ⅲ的样点以菜地和果园为主,以马唐、香附子、马齿苋和黄鹌菜为优势种。分析了空心莲子草重要值与物种丰富度之间的关系,当空心莲子草重要值大于1. 5时,样方物种丰富度随重要值的增加而减小。2者之间具有显著相关性,表明空心莲子草的入侵对生物多样性有不利影响。

A survey was conducted with the square intercept method on species and distribution of weeds in habitats where Alternanthera philoxeroides (Mart.)Griseb.grew in Nanjing.Principal component analysis (PCA) of the collected data showed that there were 101 weed species belonging to 30 families recorded in autumn in the region,and that the most important factors affecting the distribution of weed species were soil humidity and human activities.According to the two factors,all the samples were divided into three groups.Group I,including the samples collected from roadsides,open spaces beside the fields and shores of rivers,ditches and lakes,was dominated with weed species such as Digitaria sanguinalis,Setaria viridis and Eleusine indica.Group Ⅱ,consisting of the samples located on ridges and furrows in the fields,was dominated with weed species,like Veronica persica,Conyza bonariensis and Acalypha australis.And Group III of the samples gathered from orchards and kaleyards,which lacked management and moisture,was dominated with species,like Digitaria sanguinalis,Portulaca oleracea and Cyperus rotundus.The analysis of relationship between the importance value of Alligator weed and species diversity of the samples showed that when the former reaches 1.5,the latter decreased with the rise of the former,demonstrating a significant correlation between them,which suggests that the invasion of Alligator weed is harmful to biodiversity.