Quantitative classification of plant communities in the modern Yellow River Delta.

Plant communities in the modern Yellow River Delta are studied by the methods of TWINSPAN(Two-Way Indication Species Analysis) and DCA(Detrended Correspondence Analysis) in this paper.TWINSPAN classification results show that the vegetation in the study area is divided into three large groups of communities dominated by the species Suaeda salsa,Tamarix chinensis and herbage,which includes 12 community types.Three species diversity indices are used to study the changes in species richness,evenness and diversity in different communities. Diversity and richness indices increase gradually from the communities S.salsa and T.chinensis to herbage,but species evennesses fluctuate greatly in the communities S.salsa and T.chinensis.However evenness fluctuation is little in herbaceous community.Results of ordination by DCA reflect that the plant community distribution patterns are affected by environmental factors such as soil salt content and hydrological situation.In the area with high soil salt content,species composition is single and community structure is simple.In the area with low soil salt content,species composition increases and community structure is complex.