Abstract:

The plant community characteristics and their responses to the slope,the physical and chemical soil properties were investigated from 2009 to 2011 in the water level fluctuation zone of the Xiaojiang River in the Three Gorges Reservoir.The results showed that there were 146 species of vascular plants.Herbaceous plant was the most abundant type with 134 species.The dominances of 19 species plants were above 002,such as Xanthium sibiricum,Cyperus rotundus,Cynodon dactylon,Digitaria sanguinalis,Imperata cylindrical,Daucus carota,Comnyza Canadensis and so on.The slope affected the soil depth and the soil density,and then influenced the spatial distribution of species.The results by using the simple linear regression analysis showed that the fresh weight was highly negatively correlated with the slope (P＜005),and significantly positively correlated with the total nitrogen (P＜001),total phosphorus (P＜005),total potassium (P＜001),available nitrogen (P＜001) and available potassium (P＜0.01).However,the fresh weight did not significantly correlated with the soil pH (P ＞005) and the soil available phosphorus (P＞005).The results by using the multiple stepwise regression analysis exhibited that the main environmental factors influencing the fresh weight were the soil density and the total nitrogen.The results by applying the redundancy analysis (RDA) showed that the key environmental variables affecting the important value of species were the elevation and the available nitrogen.The dominances of species varied from 2009 to 2011.The dominances of C.dactylon,Polygonum hydropiper and Eclipt prostrate increased.However,the dominances of Arthraxon hispidus,Bidens pilosa,Artemisia annua and Artemisia argyi decreased