岩溶山地城市扩展空间差异的地形效应

The Effect of Karst Mountain Physiognomy on Spatial Process of Urbanization in Guiyang City

利用贵阳市1976年MSS影像,1986年、1996年TM影像,2006年CBERS影像和1∶5万DEM等,对喀斯特山地地貌背景及地形条件与贵阳城市化空间过程的时空分异特征的相互关系进行深入分析。土地扩展集中指数表明地貌分布直接影响城市在不同方向上的扩展分布,建设用地的扩展主要发生在起伏度小于30m的平缓地形区;对比贵阳城市扩展斑块,新生斑块密度整体上要高于延展斑块密度;城市几何中心轨迹呈西北—东南来回移动。这说明贵阳城市扩展整体受地形条件影响较大,向盆周山丘缓坡→盆地外围的岩溶山地垭口、谷地、小型山间盆地坝子和岩溶丘原面拓展,城市扩展不能连片发展,只能在较为平缓的地带分散扩展,各分区城市扩展强度最高值均在5～15km的缓冲区内。同时城市空间放射状指数表明城市形态虽然狭长,但城市化过程中紧凑度水平逐渐升高。

Taking Guiyang as an example, a thorough analysis was carried out to reveal the relations of the karst mountain physiognomy and the spatial-temporal distribution characteristic of the spatial process of urban expansion in Guiyang, based on the MSS image of Guiyang in 1976, Landsat images in 1986, 1996 and CBERS image in 2006, as well as geomorphologic characteristics, 1：50,000 DEM. Some analytical indexes such as relief degree of land surface, concentration index of land expansion, urban spatial radial shape index, etc. were introduced to describe the spatial differentiation of urban land expansion. The results show that the karst mountain physiognomy has serious restrictions to urban expansion of Guiyang. Concentration index of land expansion shows that the topographic distribution has direct impact on the expansion of distribution of landscape of the city in different directions. The expansion of construction land was mainly generated in fiat terrain of the area where relief degree of land surface was less than 30 m. Comparsion of all the expansion patches of Guiyang city indicated that the density of new patches was higher than the density of extended patches. The geometric centers of urban area in Guiyang city has been transforming from northwest to southeast. First, the expansion of the city mainly generated along the gentle slope around the basin, and then the expansion generated along the karst mountain pass, valley land and small intermountain fiat out of the basin; the expansion of the city was dispersed in fiat area; and the maximum expansion intensity of the city was in 5-15km buffer in various partitions.