“交通廊道蔓延”视角下山地城市典型样带空间格局梯度分析

空间可达性的强弱在一定程度上决定着土地利用变化的方向和强度,因此交通的廊道作用对城市化进程发挥着重要作用。以重庆市轨道交通三号线沿线双侧各3000 m缓冲样带为研究区,采用面向对象分类方法将四期Landsat TM/ETM遥感影像进行土地利用制图,选择核密度估算、指数分析和梯度分析的空间分析方法,研究交通廊道的变化及其对区域空间格局变化的影响。研究表明,研究期内,样带空间的组分和格局发生了较为明显的变化。道路的空间变化和区域空间格局的变化表现出较为明显的梯度性:道路密度、土地利用的变化强度随距离交通主干道距离的远近依次减弱,道路密度等级范围内的土地利用变化强度随等级的降低出现由弱到强再转弱的特征。

Spatial pattern gradient analysis of a transect in a hilly urban area in China from the perspective of transportation corridor sprawl

The improvement of accessibility determines the intensity of land use change. In the past 20 years in China, the development of transportation has accelerated the process of urbanization and land use change. A 6-km distance between two sides of the Chongqing Rail Transit Line 3 was selected as the study area. The research focused mainly on the following key points: (1) how the spatial pattern changed during the study period; (2) how the spatial characteristics of the traffic network changed in the hilly area during the period of rapid development; and (3) how the gradient characteristics of land use changed at different road-density-levels.Chongqing Rail Transit Line 3 was selected as the control line of the study transect. Line 3, the longest single monorail in the world by track length, runs north-south and links districts separated by the two main rivers in Chongqing, the Yangtze (Chángjiāng) and the Jialing (Jiālíngjiāng). Six buffer zones of 500 m (totaling 3 km) were generated along each side of the line.The object-based classification of remote sensing data was applied to map land use. Kernel density estimation (KDE), landscape indices, and gradient analysis were adopted to determine the corridor effect on regional land use. Gradient analysis based on landscape metrics analysis is widely used to study landscape pattern changes in response to rapid urbanization. To discover the relationship of traffic networks and changes in urban patterns of the study area, several landscape metrics were computed along the transect that crosses Chongqing.The results indicate that built-up areas and arable land were the most changed land use types. The urban area expanded from 6550.20 hm² to 21077.37 hm². Conversely, the arable land decreased from 27884.07 hm² to 15929.10 hm². The changes of road location and land use showed an obvious gradient character, whereby road density and intensity of land use decreased as the distance to Transit Line 3 increased. The transfer of land use changed from weak to strong then to weak.The traffic corridor effect was obvious in Chongqing, a typical hilly city in China. The Chongqing traffic transect in this study clearly illustrates the relationship between regional traffic conditions and urban development. The comparison of buffer zones, road density levels, and land use is an effective way to identify the network character and ecological problems caused by rapid urbanization. This study also effectively quantified the impact of traffic expansion on shaping urban character.