Canonical correspondence analysis of relationship between botanical characters of exotic weeds and their environmental factors
外来入侵种植物学性状和环境因子间关系的典范对应分析

In the suburb of Jinhua City,Zhejiang Province,China,73 sites were sampled in the different habitats,the ecological importance values of the weeds in these sites were surveyed,and 34 morphological and ecological characters of exotic weeds,12 environmental factors in these sites were also recorded.The potential relationship between characters of exotic weeds and their environmental factors,and the relationship between the distribution of exotic weeds and the environmental factors were determined by canonical correspondence analysis(CCA) based on the obtained data.The main results are as follows:(1) among the 73 sites,69 sites were invaded by exotic weeds(totally 32 species);the mean number of the exotic weed species per site was 4.68;(2)The CCA ordination showed that soil water content,sandiness quantity,slope,canopy,soil tillage intension,the grazing frequency,the distance from residential area,the interference effect of buildings and the traffic frequency were the main factors influencing the distribution of exotic weeds;(3) the exotic weeds,which are stemless or perennials,or have rhizomes,vegetative reproduction and bilateral symmetry flowers,were often recorded in the soil with higher water content;(4) in woodland,the weeds are often biennials,toxic,or have rhizome,scramble stem,thorn and thick leaves;(5) the weeds in the soil frequently ploughed are often annuals,or have fruits such as pod,nut and utricle;(6) in the residential areas or the environments with heavy traffic,the exotic species are often toxic,or have utricle,larger seeds.