Abstract:

Based on the product of MOD13Q1 of MODIS (Moderate Resolution Imaging Spectroradiometer),this paper dealt with 322 available images from 2003 to 2016 by using decision tree classification method,and then got a time-based series of classified data about water,mud flats,grassland,and reed of wetland in East Dongting Lake.It analyzed the degree of accuracy of the classification results,and the annual and interannual variation trends of water and grassland of wetland,as well as the key driving factors,summarized that:(1)it is acceptable of the degree of accuracy which was calculated from the classification results by using the decision tree method on the series data of MODIS images from East Dongting Lake.(2)There is no significant interannual variety of the area of water and grassland of wetland from 2003 to 2016,when the construction and operation of the Three Gorges Dam was underway.(3)Area of water and grassland of wetland varies with the hydrological rhythm,and there is an extremely significant negative correlation between them.This paper proposed that,water level is the key factor of the ecosystem of East Dongting Lake,it is crucial to keep it in a reasonable range to maintain the health of ecosystem.

Key words: the lower and middle reaches of the Yangtze River, East Dongting Lake, decision tree classification method, wetland, MODIS, the Three Gorges Dam