Spatial and temporal changes of lake wetlands in Jianghan Plain after the implementing of 'thirty-six-word policy'

摘要

After the cataclysm of the Yangtze River in 1998, the State Council put forward the "thirty-six-word policy" for harnessing large rivers and lakes. Jianghan Plain is one of the main areas to get harnessed according to the policy. Based on the CAS land use databases of 1995, 2000, 2005 and 2010, the spatial changes information of lakes in Jianghan Plain were captured and analyzed under the ARCGIS platform or by indexes of landscape ecology. The results show that: From 1995 to 2010, the area of lake wetlands has been grown constantly; Transitions from farmland and unused land to lake were dominant for the increase of lake area, while so were the transitions reversely; Lake wetlands were divided into two categories (lake and pond) to be analyzed according to the area of every lake wetland patch, lakes mainly increased in the area while ponds mainly increased in the number of patches. Ponds are not as curved as lakes in shape and more dispersed than lakes; Lakes became less curved and concentrated with the augment of the area of lake wetlands. The shape of pond wetlands changed little and its distribution became a little concentrated with the increasing number of pond wetlands. During the three five-year analyzed, the increase of wetlands of Jianghan Plain was notable during the period of from 2000 to 2005, though the area of wetlands increased during all the three periods.