空心莲子草入侵对乡土植物群落组成及植物多样性的影响

Impacts of the invasion of Alternanthera philoxeroides on the species composition and diversity of native vegetation community

系统研究了空心莲子草Alternanthera philoxeroides入侵对江西省上饶市郊区乡土植物群落物种种类组成及物种多样性的影响。选取20个有空心莲子草入侵的样方,并在与之相距5 m处选取等面积的没有或有很少空心莲子草植株的20个样方作为对照,应用Simpson指数、Shannon-Wiener指数、Pielou指数和Alatalo均匀度指数分析了空心莲子草入侵乡土植物群落的多样性变化格局。结果表明:1)所有样方中共计出现59种植物,隶属于29科,在试验样方中出现的物种数量和种类都低于在对照样方中出现的物种数量和种类。2)试验样方和对照样方的物种重要值分布存在较大的差异,表明在空心莲子草入侵的胁迫下,群落物种格局发生了变化。3)分析了空心莲子草重要值与多样性指数、均匀度指数的关系。当空心莲子草重要值小于29.7时,乡土植物多样性指数和均匀度指数都随空心莲子草重要值的增加而增加,而空心莲子草重要值大于29.7时,各项指数都随重要值的增加而减小,当空心莲子草重要值大于64.3时,各项指数急剧下降。表明空心莲子草的入侵可影响乡土植物群落物种多样性,并产生正向影响和负向影响,当空心莲子草入侵量达到一定的阈值,将导致乡土植物多样性下降。

The influence of invasive Alternanthera philoxeroides on local vegetation community composition and biodiversity was systematically studied in the suburb of Shangrao city, Jiangxi province. 20 plots which were invaded by A. philoxeroides, were established. One plot which was none or a few A. philoxeroides individuals selected as control plot with a distance of 5 m from others. The pattern of local community biodiversity was analyzed by Simpson index, Shannon-Wiener index, Pielou index, and Alatalo index. The results showed that. 1） There were totally 59 species in all plots which were subordinated to 29 families. The numbers of species in tested plots were lower than those in the control; 2） There were significant differences of the importance value distribution between the tested and control plots, indicating that the patterns of the species in the local vegetation community changed under the invasion of A. philoxeroides; 3） Analysis of relationship between importance value and biodiversity indices of the local community revealed that Simpson index; Shannon-wiener index~ Pielou index and Alatalo index were all increased before the importance value of A. philoxeroides reached 29.7, then reduced when the importance value was higher than 64.3, all the indices decreased sharply. This indicated that the invasion of A. philoxeroides had the positive effect and negative effect on the local vegetation community biodiversity. The local community biodiversity could reduce when the invasion of A. philoxeroides reached a threshold.