区域尺度城镇扩张的情景模拟与生态效应——以广西西江经济带为例

以快速城镇化的广西西江经济带为案例区,以生态重要性和开发建设适宜性为情景、利用最小累积阻力模型对城镇扩张进行模拟,进而从区域生态系统服务功能变化角度定量分析两种情景的生态效应差异。结果表明,经济带东西两翼地区生态重要性较高,中部地区开发建设适宜性较高。中小城镇在生态重要性情景中获得了较大的发展机遇,而大城市在开发建设适宜性情景下扩张更快。相同扩张强度下,生态重要性情景的区域生态系统服务功能总量下降较少,除食物生产功能外的其他各项服务功能呈现类似格局。随着扩张强度增加,两种情景下生态系统服务功能下降量之间的差异逐渐增大,从0.5%强度下的1.09亿元增大到10.0%强度下的4.05亿元。基于生态重要性的扩张情景对于保护生态环境、维持开发与保护之间的平衡更加有利,是一种相对合理的扩张方式。为开展区域层面城镇扩张情景模拟分析提供了参考,也为未来调控城镇扩展格局提供了优化情景和科学依据。

Regioanl-level scenario simulation of urban expansion and the ecological effects: the case of Guangxi Xijiang River Economic Belt, Southwest China

Urban expansion has been the focus of researchers from various research fields for a long time, and the process, affecting factors, effects and simulation of urban expansion are the most interested aspects. Aim at enriching research on multi-scenarios simulations of urban expansion at the regional level, taking Guangxi Xijiang River Economic Belt (GXEB for short) as the case area, we carried out ecological importance (EI for short) and development suitability (DS for short) assessment and the results were used to design resistance surfaces of the minimum cumulative resistance model (MCR model for short) for simulating urban expansion of major cities and towns of GXEB. The current urban lands were regarded as the sources of MCR model for modelling urban expansion. In addidation, the effects on regional ecosystem service were analyzed accordingly. Results of EI assessment indicated that the western and eastern parts were relatively more important than the middle parts, and formed the ecological barrier of GXEB with higher significance for biodiversity protection, water & soil conservation, gas & climate regulation, etc. However, the middle part of GXEB was relatively more suitable than two wings from the aspect of DS assessment. The results of urban expansion modelling indicated that the surrounding areas were facing the destination of being occupied by urban expansion firstly. With the increasing of MCR, the amount of cumulative construction lands increased accordingly. Expansion of urban lands and related ecological space occupation caused the decrease of regional ecosystem service and changes of its structure, and the amount became bigger and bigger with the increasing of expanding intensities. However, the reductions of total amount of DS scenario were higher because of the differences of two scenarios in terms of urban expanding intensity and style. EI scenario gave more expanding opportunities to medium-sized cities and towns, while bigger cities were the priority of DS scenario. Moreover, DS scenario made more "pie-type" cities and towns, while EI scenario provided cities and towns sprawl along certain development directions or axis. Therefore, the decreasing of ecosystem services of EI scenario were smaller than that of DS scenario for the occupation on ecological spaces of more importance at DS scenario. With the increasing intensity of urban expansion, the difference between two expanding scenarios increased from 1.09×10⁸ yuan at 0.5% intensity to 4.05×10⁸ yuan at 10.0% intensity gradually. Considering the sub-items of ecosystem services, most showed similar trends with the regional ecosystem service except food production function. With the increase of urban expansion, the difference between EI and DS scenarios trended to be more significant. It was concluded that EI scenario limited the uncontrolled expansion of big cities, gave more opportunities to medium-sized and small cities and towns, and reduced the occupation on important ecological spaces and the degradation of regional ecosystem service. From above aspects, EI scenario lightened the contradiction between urban expansion and ecological protection, was of higher advantages for protecting environment and keeping the balance of development and protection, and was of significance for regional sustainable development.