Estimation of Urban Land System Stability of River Valley——A Case Study of the Four Districts in Suburbs of Lanzhou City
以兰州为例，利用遥感数据分析了河谷型城市土地利用的时空变化及驱动机制，发现建设用地与耕地、草地、林地之间的转换是关键，城市化降低了土地系统稳定性。
The estimation of urban land system stability is based on the reasonable arrangements of urban land-use, the optimization of land structure system, and the achievement of sustainable utilization of land resources. This paper, taking Lanzhou city, the valley-basin city in Northwest China for example, introduced flow analysis and activity analysis of land utilization, and analyzed the spatiotemporal dynamic characteristics of land utilization and its driving mechanism in research areas by the measure model of land use change and principal component analysis, based on Landsat remote sensing image data. The research shows that:(1) In the research area, less unused land resources and reserved land resources, and the lower proportion of forest land, grassland and water area have the greater ecological risk;(2) Transformable relationships among the construction land, cultivated land, grassland and forest land are key relationships of the transition of land utilization, which has determined change characteristics of land utilization in the research area;(3) The land use change shows the class character. With the rapid development of social economy, the fast promotion of urbanization has increased the entropy of land system and decreased its stability.