Abstract: Basic ecological characteristics including water body,soil and plants as well as their correlations in an enclosed estuary and centre of Dongting Lake were systematically studied by field investigation of the sampling belt from Liumen Gate to Xiaoxi Lake.Results indicate that in the enclosed estuary the flow was slow and the water was low in transparency,whereas in the centre of the lake,just the contrary;the water in the enclosed estuary was higher in nutritional level and conductivity than the water in the centre;the soil in the centre was higher in organic matter and nitrogen content than the soil in the enclosed estuary;and the enclosed estuary was not fit for aquatic plants to survive in while the centre was the main habitat of aquatic plants.Further correlation analysis shows that mutual effects and interactions existed between the two zones in biological,soil and hydraulic characteristics.Transparency was significantly correlated with water flow velocity（α=0.05）.Species richness,biomass,and biodiversity were significantly correlated with water flow velocity and transparency,respectively（α=0.01）,and with soil total N（α=0.05）.Water flow velocity was the key factor in regulating ecological characteristics.

Key words: estuary, central lake, ecological characteristic, Dongting Lake