The Quantitative Classification and Ordination of Natural Vegetation Populus euphratica Oliv.Forests Growing on the Banks of Ejina River

The classification and ordination of Populus euphratica Oliv.community on the banks of Ejina River in Inner Mongolia were studied by using the two-way indicator species analysis(TWINSPAN)and distended canonical correspondence analysis(DCA).Eight quadrats selected from the community were classified into four associations by TWINSPAN,and ecological environment of each association was discribed.The results of DCCA ordination were tested and verified by the results of TWINSPAN.The ordinate and abscissa of DCCA ordination indicates the gradi- ent variations of ground water level,air relative humidity,and soil humidity to elevation of each association.Fur- thermore,the results of DCCA ordination and environment factor correlation analysis showed that the ground water was the crucial environment factor among the all to the distribution of plant community.