中文摘要：

以东江干流河岸带为案例研究区,借助回归分析和冗余分析（RDA）,从不同尺度探讨了研究区内河岸带植物群落物种α多样性和β多样性的空间分布模式及其影响因子。结果表明：①Patrick指数、Shannon-Wiener指数、Simpson指数和Pielou指数等指示群落α多样性的指数沿东江干流河岸带的变化情况相似,从下游至上游总体上均呈现出逐渐上升趋势,其中除Pielou指数外,另三种指数的回归拟合均达显著水平（P〈0.05）;②以Bray-Curtis指数表示的群落β多样性在上、中、下游不同样地间群落相似性整体较低（均值仅0.17）,经广义可加模型（GAM）拟合后呈先增加后下降趋势,其中β多样性相对高值点出现于中、下游区域;③相邻样地间Bray-Curtis指数显示该干流的群落β多样性具较强波动性;④经RDA排序揭示的群落分异主要影响因素,首推纬度与海拔的叠加效应,表征为群落样地沿第一轴从左到右按下、中、上游顺序清晰排布;⑤下游群落物种多样性较低,外来物种入侵程度较高,中游次之,上游情况与下游相反;⑥东江干流的物种多样性与入侵植物对群落的侵入程度,以及与土壤总磷、总氮、pH值、有机质等营养要素均呈负相关关系,其中又以土壤总磷的影响最为突出。

英文摘要：

Based on an investigation into the riparian vegetation along Dongjiang River, this paper revealed the features of alpha and beta diversities in riparian communities. The environmental factors influencing the communities were also examined using multivariate regression analysis, redundancy analysis （RDA） and general additive model （GAM） methods. Four alpha diversity indices and four invasion indices were included in our analysis. The results show that the four alpha diversity indices appeared in similar forms, revealing a uniform upward trend from the lower- to mid- to upper-reaches, except for the Patrick index that did not pass the significance test. Beta diversity as revealed by the Bray-Curtis index showed only a weak similarity between and among the communities from one sample site to another. Variations in species composition among communities along the riparian zone were caused by environmental factors such as the geographical features of latitude and elevation, soil physical and chemical features of total phosphorus （TP） and total nitrogen （TN）, and pH. All invasion indices shown in the ordination diagram expressed a clear trend, from the left to the right, and hence separated the sample sites into the lower reach cluster （with abundant alien species and lower diversity）, middle reach cluster （with moderate alien species and moderate diversity） and upper reach cluster （with fewer alien species and higher diversity）. These results suggest that human activities, at least in the lower reaches, are the main reasons for habitat and species composition changes in communities and invasion by alien species.