Abstract:From May to October 2011,sample-plot survey and soil sampling analysis have been carried out in 128 quadrats of vegetation in 33 sample areas in the middle and lower reaches of the Fenhe River.TWINSPAN was applied to classify the phytocoenosium,and canonical correspondence analysis (CCA) was used to analyze the distribution relation between soil factor and phytocoenosium,in order to reveal the relationship between species diversity and soil factor of phytocoenosium in the middle and lower reaches of the Fenhe River.The results shows that:(1)In the middle and lower reaches of the Fenhe River,121 kinds of plants have been discovered which belong to 33 families and 81 genera,of which Compositae,Gramineae,Chenopodiaceae and Polygonaceae plants are the most,accounting for 24.79%,14.05%,8.26% and 7.43% of the total number,respectively.The distribution frequency of Phragmites australis is the highest which reaches to 49%.(2)TWINSPAN indicates that 33 sample areas in the middle and lower reaches of the Fenhe River are divided into 8 coenotypes (Ⅰ~Ⅷ).(3)Patrick richness index and Shannon-Wiener index variation tendency of phytocoenosium in the middle and lower reaches of the Fenhe River are similar,while Simpson index shows a contrary tendency with the change pattern of Patrick richness index and Shannon-Wiener index;the variation tendency of Pielou evenness index is different from other three indexes.(4)Most of the content differences of soil water content and rapidly available potassium content in the middle and lower reaches of the Fenhe River reach significant level among different sample areas of different coenotypes.The soil nutrients are characterized by apparent moderate nonuniform spatial distribution.(5)The content of soil organic matter and species Simpson index,soil total nitrogen and Pielou evenness index have significant negative correlation in the middle and lower reaches of the Fenhe River basin.(6)The result of CCA ranking demonstrates that soil water content,rapidly available phosphorus and rapidly available potassium content are the most important environmental factors which influence vegetation type distribution.