城市群视角下空间联系与城市扩张的关联分析

在城市群发展的不同阶段,城市扩张表现出不同的时空特征。从城市群视角研究城市扩张的时空规律,对于理解城市扩张与城市群网络化组织结构之间的复杂耦合关系具有重要意义。本文以长江三角洲城市群为例,基于交通网络、引力模型和空间句法模型,结合1980、1990、2000和2010年Landsat遥感影像提取建设用地扩张信息,计算城市扩张强度与速度指标;采用核心城市可达性与空间相互作用力强度分析城市的交通网络区位;采用空间句法模型计算城市交通网络的通达性和城市在城市群交通路网中的地位。结果表明：城市扩张强度与核心城市可达性、核心城市空间相互作用力强度、空间句法变量指标呈正相关关系。城市扩张速度与上述指标在第一阶段(1980-1990年)和第二阶段(1990-2000年)呈正相关关系;但在第三阶段(2000-2010年)整体表现为负相关,分布在城市群外围、交通路网联系程度较低的城市扩张速度更快,呈现出空间收敛的趋势。表明城市群中的城市空间联系在城市扩张中起到重要但又不断演变的作用,研究结果对于长三角城市群规划和其他城市群城市扩张调控具有借鉴意义。

Spatial linkage and urban expansion:An urban agglomeration perspective

Urban expansion displays varied spatial characteristics in different periods of urban agglomeration development. Studying the spatial and temporal patterns of urban expansion from the perspective of urban agglomeration is important for understanding the complex relationship between urban expansion and network structure of urban agglomerations. In this study we analyzed urban expansion in the Yangtze River Delta urban agglomeration based on road network, a gravity model, and a space syntax model. Construction land expansion was obtained from Landsat remote sensing data in 1980, 1990, 2000, and 2010 and then was used to calculate intensity and speed of urban expansion. Position of cities in the traffic network of the urban agglomeration was analyzed by accessibility to and spatial interaction intensity of core cities. The space syntax model was used to compute accessibility of the road network and the status of a city in the network of the urban agglomeration. The results show that, first, urban expansion intensity displayed a positive correlation with accessibility to core cities, spatial interaction intensity of core cities, and space syntax indicators. Second, there was a positive correlation between urban expansion velocity and indicators identified above in the first (1980-1990) and second (1990-2000) periods. However, it exhibited a negative correlation in the third period (2000-2010). Cities with a relatively poor interconnectivity of traffic network and located in the periphery of the urban agglomeration developed more quickly in the last time period, displaying a trend of spatial convergence. This study shows that spatial linkage played an important but evolving role in urban expansion within the urban agglomeration of the Yangtze River Delta. In addition, it serves as a reference for the planning of the Yangtze River Delta urban agglomeration and the regulation of urban expansion of other urban agglomerations.