本文以重庆市主城区为例,通过GIS构建城市用地变化模型对重庆市城市用地20年来的时空演变规律进行了分析,分别对其城市用地利用程度、城市用地多样性和城市用地重心变化进行了评价,并考虑人口和海拔因素,讨论了重庆市城市用地发展的主要特点。结果表明:(1)重庆市主城区城市用地中耕地面积最多,其次是林地,城市景观所占比例较轻。2000-2007年城市用地变化速率最强,耕地先增后减,林地先减后增,建设用地、水体和草地持续增加。(2)城市用地类型间转化关系反映区域内相应人为活动:1986-1995年,研究区有较多的毁林造田、毁草造田等农业开垦活动,城市化进程缓慢;1995-2000年,毁林造田、毁草造田等活动减轻,城市化扩张加快;2000-2007年,研究区的城市化进程剧烈。三峡工程蓄水对区域用地影响明显,淹没低海拔的部分地类。研究区的退耕还林、退耕还草等森林工程效果显著。(3)1986-2007年,耕地和林地重心迁移规律相反,二者关系紧密。未来的城市建设用地的重心偏向于北部的"两江新区"。城市用地利用程度逐渐加剧,北部土地利用程度更剧烈。城市用地类型多样化程度增加,城市用地类型多样化分布表现为东低西高,建设用地对区域城市用地类多样化影响显著。(4)城市用地变化受城镇人口和海拔影响明显,城镇人口的增加,加剧了城市 用地利用程度和结构的多样化;重庆主城区受地势影响明显,城市用地变化集中在低海拔的槽地和平坝区,导致研究区形成多个城市核心,呈"汤圆"散状分布。

Based on GIS, we analyzed the urban land use change of Chongqing main city zone from 1986 to 2007, and evaluated the urban land use degrees, land use diversity and the transfer of urban land use cores. At last, we analyzed the driving factor of the urban land use from population and elevation. The results showed: (1) the cultivated land and the wood land were more than the other land types, showing a low ratio of urban landscape. From 2000 to 2007, it had the fastest speed of the land variation, the cultivated land increased firstly and then decreased, the wood land decreased firstly and then increased, the water body, construction land and grass land were kept increasing. (2) The result of land transfer corresponded to human activities in some degrees, i.e. from 1986 to 1995, there were some agricultural activities (damage of wood land and grass land for cultivated land), and the urban expansion was very slow; from 1995 to 2000, these destroy activities were reduced, and the urban expansion was speeded up; from 2000 to 2007, urban expansion was very rapid. At the same time, there were some complex disturbances by humans: the urbanization was intense, the Three Gorges Project affected regional land impoundment obviously, and some lower lands were submerged. The effect of "Green for Grain" is remarkable. (3) From 1986 to 2007, the shift of cultivated land core and wood land core was opposite and the two cores were closely related. The core of future urban construction land would be in the "New District along the Two Rivers" in the north of the city. The degree of urban land use will increase gradually, especially in the northern part. The diversification of land use types increased gradually, too, with a pattern of lower in the east and higher in the west, and it was strongly impacted by the construction land changes. (4) The population and the altitude are closely related to the urban land use change. Urban population increased sharply, leading to the diversification in the degree and structure of urban land use. In the main city zone of Chongqing, topography is the primary impact factor. Construction land was located in the lower belts and plain regions, making a scattered distribution of urban cores which is different from Beijing, Shanghai and other big cities.