东江流域近20年土地利用变化的时空差异特征分析

根据1990年、2000年和2009年3期LandsatTM/ETM影像的土地利用分类结果,综合运用地理信息系统空间分析工具、变化指数对比分析等技术和方法,对东江流域1990年-2009年间的土地利用变化及其区域差异特征进行了分析。结果表明:①1990年以来,东江流域土地利用变化的特点表现为城市化过程显著、非城镇用地结构变化明显,以及林地和灌草地大为减少的总体特征;②流域的上游、中游、下游三个区域在1990年-2000年和2000年-2009年两个时段,城镇用地增加量表现出相同的空间分异特征,而年增长率却表现出不同的空间分异特征,其中非城镇用地的转化在3个区域差异明显,自然植被退缩的程度表现为下游>上游>中游;③东江流域2000年-2009年时段的土地利用变化速度较之1990年-2000年时段整体上有所缓和,但在程度上仍具有区域差异性,显示出土地利用程度进一步向高度集约化发展;④人口增加、经济增长、区域发展政策的变化叠加在区域自然差异之上是东江流域土地利用变化及区域差异产生的主要原因。

Characteristics of the Spatial-Temporal Differences of Land Use Changes in the Dongjiang River Basin from 1990 to 2009

The environment in the Dongjiang River basin has received much attention in recent years due to its role in providing freshwater to cities including Heyuan, Huizhou, Dongguan, ShenZhen, and in part Hong Kong. It is widely recognized that land use change is a major cause of environmental changes. The Dongjiang River basin has undergone rapid urbanization along with growing economy during the recent two decades, which, in turn, has led to great regional land use changes over space and time. In this paper, the spatial-temporal characteristics of the land use change in the basin from 1990 to 2009 were quantified and comprehensively analyzed through performing change detection on the basis of interpretation of Landsat TM/ETM+ imageries acquired in 1990, 2000, and 2009. Some quantitative indexes were adopted, involving land use net change, annual change rate, and transition matrix. Results show that: 1) significant land use changes have taken place in the basin during the period 1990-2009, implying that the region has been experiencing processes of rapid urbanization and a prominent adjustment of the land use structure, which were demonstrated by increases in human-related land use, e.g., the urban built-up areas and decreases in natural land use types, e.g., woodland, brushwood, and grassland; 2) there existed obvious regional differentiation in land use change across the basin during the study period, which can be further divided into two phrases. For the first phrase, 1990-2000, the annual growth rate of the urban build-up land varied over the basin, showing the rate in the middle reaches > the upper reaches > the lower reaches. For the second phrase, 2000-2009, this rate in a decreasing order was the upper reaches > the middle reaches > the lower reaches, showing a slightly different magnitude of the change for the two phrases. Meanwhile, the decreasing extent of the natural land use types shows a trend as the lower reaches > the upper reaches > the middle reaches; 3) comparing with the period 1990-2000, the period 2000-2009 exhibited a more marked decrease in the amount of land use change and a decrease in the annual change rate; and 4) population growth, rapid economic development, and regional development strategies and policies are probably three major drivers for the spatial-temporal land use changes occurring in the basin. In the end, several measures for sustainable land use, encompassing natural vegetation conservation, land-use planning and management, restoration of wetlands, arable land protection, and ecological and environmental protection were given.