Dynamic Analysis of Typical Wetland in Dongting Lake during 1987-2004

Dongting Lake wetland occupies an important position in Chinese lakes and wetlands,which has undergone a wide range of reclaiming land from lakes and RETURNING.The present study selected three December TM remote sensing images in 1987,1995,and 2004,and classified them through the decision tree classification method.The type of land use transition matrix was calculated and the area change of typical types of wetlands in Dongting Lake was analyzed rationally in detail.By analyzing the dynamic change of typical wetland in Dongting Lake area between 1987-2004,this study were planned to understand the status of natural wetlands and artificial wetlands transformed into each other before and after the RETURNING,and to provide data support for wetland conservation of Dongting Lake in the future.The results showed that during 1987-2004,the constructed wetlands were reduced,while natural wetlands exhibited growth,mainly in the marsh land and reed beach.The growth rate of the marsh land was 23.85 km2/a,and the growth rate of the reed beach was 1.97 km2/a.In the years 1987-1995,natural wetlands degraded heavily,while wetlands generally showed growth.From 2004 to 1995,in the natural wetlands,the overall change of waters and mud sand was not obvious,while the reed beach and marsh showed growth,and constructed wetlands showed a degradation trend.The RETURNING works has played a certain role in wetlands protection,but there is still some phenomenon of reclaiming land from lakes,the implementation of the project has not been completely implemented.