The Study On Communities Structure And Diversity Of Plant In Deganba Jiangjin Segment In The Upper Reaches Of Yangzi River

Riparian ecosystems are in the riparian zone,which belongs to sensitive border. Riparian vegetation system plays a very important role on Reducing the degree of soil erosion, channel stabilization, habitat protection and water quality improvement by filtering and trapping sediment, water and nutrients and so on, to coordinate horizontal and vertical flow of matter and energy. So studying riparian vegetation is of great significance for the protection a nd maintenance of the function and role of the integrity and continuity of riparian.It is used Braun-Blanquet filed method to survey the structure and diversity of phytocoenosiumy in Deganba Jiangjing segment in the upper area of Yangzi River.By surveying phytocoenosiumy and analyzing the relationship between plants and environments, it Reveals composition, type, distribution, diversity of Deganba riparian flora and other characteristics, specific results are as followings:1. According to the analysis of the floristic features in riparian zone of Deganba, we found that the species of plants are poor, the composition of floristic are easy. The composition of biotype is herb which contains20families,37genus and44species. Among the three transects, in pre-flood season, the specie and quantity of pant in transect A are less than transect B and C. But after flood season, the species and quantities of three transects are the same. Compared the phytocoenosium in riparian zone of main stream in Three Gorges,vegetation in riparian zone of main urban zone of Chong Qing and its landscape plant, it is known that the species and quantity of plant in the whole research area are poor. The results show that the riparian zone of Deganba are interfered seriously by human activities.2.Using the TWINSPAN to analyze the types of the phytocoenosis in riparian zone of Deganba, it can divided into two part:pre-flood and after-flood.The results show that there are three vegetation in riparian zone of Deganba: D.Arundinacea Beauv and Polygonum lapathifolium;Cynodondactylon Pers and Polygonum lapathifolium; Cynodondactylon Pers. After flood, there are two phytocoenosis in riparian zone of De ganba:D.Arundinacea Beauv and Polygonum lapathifolium;Cynodondactylon Pers and Polygonum lapathifolium; Cynodondactylon Pers. Compared the phytocoenosium in riparian zone of main stream in Three Gorges,vegetation in riparian zone of main urban zone of Chong Qing and its landscape plant, the results show that no matter pre-flood and after-flood, the composition of vegetation is very simple, just has grass. Meanwhile, the types of the phytocoenosium are just two or three types.3.According to analysis of the diversity of the vegetation in riparian zone of De ganba, the results shows that the change trend of diversity of vegetation can show the structure types, level of organization, developmental stage, the stabilization and heterogeneity. The research results show that the structures of the vegetation in this research area are simple, the composition of vegetation are less, the plants are pygmyism and sparse and the level of diversity are low. From the difference of the seasons, in the pre-flood, the diversity of the vegetation of A simple is lower than B and C simples, and the differences are huge. But simple B and simple C are the same. In the after flood, the diversity of vegetation are the same. The reason is that simple B and simple C are influenced by the flood seriously.Meanwhile, some other reasons, like climate, are the important factors. Among them, Simple A is farmland, interfered by the human very serious, such as farmlands, is rarely affected by the flood.So no matter in the pre-flood or after-flood, the diversity of the vegetation of simple A keeps the same. he index of richness of the vegetation in riparian zone is between2.00-21.00.The index of diversity of the Shannon-Wiener is between0.47-2.46.The index of diversity of Simpson is0.63-0.99.The dominance of Simpson is between0.79-0.39.It shows the structures of the vegetation are simple, the composition of vegetation are less in De ganba. Although the species of plants are as many as20families,37genus and44species, the composition of it is herb which looks very poor.