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作 者 ：林金成, 强胜

期 刊 ：植物生态学报 2006年 30卷 4期 页码：585-592

关键词：空心莲子草；杂草分布；主成分分析；聚类分析；物种多样性；

Keywords:Alternanthera philoxeroides, Weed distribution, Principal component analysis, Cluster analysis, Species diversity,

摘 要 ：空心莲子草（Alternanthera philoxeroides）是目前我国危害最为严重的外来植物之一 。利用样方法调查了南京市春季有空心莲子草分布的不同生境下杂草的种类和分布情况，用主成分分析及聚类分析法进行数据处理分析，目的是研究空心莲子草对杂草群落组成和物种多样性的影响。结果表明，南京市春季有空心莲子草分布的样点杂草有36科142种，其中禾本科、菊科、蓼科最多；影响空心莲子草及伴生杂草分布、发生的主要因素是土壤水分条件和人为干扰强度。依据这两个因素的不同，可将样点划分为4个聚类群，比较了各聚类群物种多样性指数，结果显示：各聚类群里随着空心莲子草重要值的升高，Simpson优势度指数也逐步上升，表明空心莲子草的优势度得到加强；Shannon-Weiner指数和Pielou均匀度指数均逐渐下降，说明了群落的物种多样性持续降低，原来的优势种危害加大，空心莲子草的入侵影响群落结构，使物种多样性降低。

Abstract:Background and Aims The growing frequency and impact of biological invasions worldwide
threaten biodiversity, ecosystem functioning, resource availability, national economies,
and human health. Alternanthera philoxeroides is one of the most harmful invasive species
and has caused great economic and ecological losses. This species has caused great harm to
agriculture, fisheries, as well as to landscapes and native biodiversity, and, at times,
has completely overrun and dominated an entire terrestrial ecosystem. It also can form
dense tangled mats that float on the water surface of ponds or lakes and shade indigenous
aquatic vegetation from sunlight, and thus replace native species. Previous studies have
shown that A. philoxeroides can reduce the biodiversity of plants on paddy field ridges,
but there have been no other studies on the effects of A. philoxeroides on biodiversity in
other habitats. In this study, we conducted a survey of the species and their distributions
in different weedy habitats that were invaded by A. philoxeroides in Nanjing during the
spring and early summer season in order to interpret the relationship between its
occurrence and the environments and elucidate the impact of its invasion on plant
diversity. 
Methods The abundance, coverage and frequency of each weed population were quantified using
the square intercept method in 27 plots. The importance value of each weed was calculated
as the sum of the relative abundance, relative coverage and relative frequency. We recorded
142 weed species that belonged to thirty-six families. The data were analysed using
principal component analysis (PCA) in SPSS . Thirty_eight out of 142 weed species that had
more than 20% frequency occurred in 27 samples were used in the analysis. 
Key Results The results showed that the most important factors affecting the occurrence and
distribution of weed species were the levels of human disturbance and the soil humidity.
According to these two factors, all samples were divided into four groups. Group I included
samples collected from experimental fields, and the dominant weed species were Capsella
burss-pastoris, Veronica persica and Stellaria media. Group II included samples located in
rape farmland which have high soil humidity, and the dominant weed species were Galium
aparine var. tenerum, Conyza bonariensis, and Roegneria kamoji. Group III included samples
located in public parks or under trees, and the dominant weed species were Vicia sativa,
Beckmannia syzigachne, and Geranium carolinianum. The last group was mainly composed of
samples distributed on wastelands and waysides which were non_managed or non_irrigated
farmland, and the dominant weed species were Erigeron annuus, and Veronica arvensis. The
change in the density of Alligator weed and other weeds in the different habitats were
analysed. The results showed that the importance value of Alligator weed was high when the
soil humidity was relatively high and the intensity of human disturbance was not too great,
indicating that Alligator weed has a strong ability to adapt to different habitats. There
were different dominants in the different plant communities, which means human disturbance
and soil humidity had a key effect on the communities that were composed of a mixture of
Alligator and other weeds. When species diversity indices of each group were compared, it
was found that although species richness and Simpson’s index increased slightly from group
I to group IV, but the Shannon-Wiener index and the Pielou evenness index decreased with an
increase in the average importance value of Alligator weed. 
Conclusions These results indicated that the species composition of the weed community had
changed, and the species diversity gradually decreased with increasing dominance of the
invasive Alligator weed. These results clearly showed that the invasion of Alligator weed
had a negative affect on biodiversity.

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