关键词: 生态用地, 湖泊型流域, 长江流域, 动态度, 转移矩阵

Abstract: The area of lake type watershed (LTW) accounts for more than 30% of the Yangtze River basin, and the change of its ecological land plays an important role in regulating the water ecological environment of the Yangtze River. Based on the land use data of 229 LTWs in the Yangtze River system from 1980 to 2015, the temporal and spatial change characteristic of ecological land in recent decades was analyzed by using the methods of ecological land area and its proportion, improved comprehensive dynamic degree, transfer matrix, and spatial operation. The results showed that the change of ecological land use in the LTWs presented a three-stage trend of "first gradually increasing, then fluctuating and stable, and finally rapidly decreasing"; Woodland and grassland showed a downward trend, while wetland showed an upward trend; The comprehensive dynamic degree of ecological land in the LTWs presented a state of "wave-like vibration". From the perspective of lake size classification, the total area of ecological land in the four types of LTW was quite different. The watershed ecological land corresponding to small lakes was the least, followed by large and medium-sized lakes, while the watershed ecological land area of super large lakes was the largest. Although the ecological land change trend in different types of LTWs was first rising and then declining, the corresponding turning points appeared in different years. From the perspective of different regions of the Yangtze River system, compared with 1980, the ecological land of the LTW in the source, middle, and lower regions increased in 2015, while the ecological land of the LTW in the upper regions decreased; The transfer amount within ecological land was the least, and the transfer amount between ecological land and non-ecological land and the transfer amount within nonecological land accounted for more than 42% of the total transfer amount. The transfer of ecological land was the most complex and intense in the middle region, followed by the lower region, the source region and the upper region were relatively gentle and simple. Before 2000, the main reasons for the change of ecological land were cutting trees, developing agriculture and animal husbandry and reclaiming land from lakes. After 2000, the main reasons were returning farmland to forests and building reservoirs. The increase of construction land, i. e., urban expansion, was one of the main reasons for the decrease of ecological land for most LTWs from 2010 to 2015.

Key words: ecological land, lake-basin, Yangtze River basin, dynamic degree, transfer matrix