北京市城区扩展的空间格局与影响因素

2000年以来北京市持续推进产业结构升级,由此引发了经济活动的空间重构,伴随着住宅郊区化、职住分离以及交通基础设施的配套建设,将引起新一轮城市空间扩展。构建顾及综合可达性因素、邻域因素、自然因素、规划因素以及社会经济因素的城市空间扩展模型,分析诊断北京城区扩展进程中的主要影响因素及问题,从而为指导与管治北京市城市空间的有序扩展提供科学支撑。研究表明：① 综合交通静态可达性（单一年份）与城市扩展呈显著负相关;综合交通动态可达性（年份之间的可达性变化）则在引导北京市城市空间发展方面并无显著影响。② 邻域建设用地百分比与城市扩展呈正相关,而农用地、林业用地及水域用地的比例将减少土地开发的概率。③ 城市总体规划在指导城市空间扩展的纲领性地位逐渐受到重视,其对城区扩展的影响程度最为显著。④ 常住人口的分布现状、第二产业企业数量、第三产业企业数量分布现状对土地开发无显著影响。⑤ 认为北京市静态可达性与土地利用变化呈负相关,即可达性条件较差的地区,土地开发的可能性越小,这与北京市“摊大饼式”空间蔓延和居住郊区化的发展现实相符;北京市动态可达性与土地利用变化亦呈负相关,表明可达性提高程度越大的区域并不一定带来更高的土地开发几率,这从侧面传递了沿着既有建成区进行土地扩展的概率远远大于由于诸如轨道交通建设而带来可达性极大改善区域的概率。因此,重视与发挥综合交通动态可达性指标对城市扩展的引导作用,将是有效破解城市蔓延式扩张、优化城市扩展的重要手段。

The spatial pattern and influence factors of urban expansion: A case study of Beijing

Since the year of 2000, Beijing has promoted industrial structure upgrading, which leads to the spatial reconstruction of economic activity. Concurrently, three factors will result in a new round of urban spatial expansion, which are residential suburbanization, mismatch between workplace and residence, and the construction of transport infrastructure. An urban spatial expansion model was put forward in this paper, in which we take natural factors, neighborhood factors, planning factors and socioeconomic factors into account. What's more, the principal factors and issues that occurred in the development process were analyzed in order to provide scientific basis for well-organized urban expansion in Beijing. This research shows that the static accessibility (a single year) has a significant negative correlation with urban expansion; integrated transportation accessibility has no significant positive effect in guiding the urban expansion in Beijing. Percentage of urban construction within neighborhood is positively correlated with land expansion. However, the smaller proportion of agricultural land, forest land and waters land will reduce the probability of land development. The role of overall urban planning in guiding urban expansion has gained attention increasingly, whose impact on urban expansion is of most significant. The spatial distribution of permanent residents, secondary and tertiary industrial enterprises have no significant effect on the land development. This paper argues that the static accessibility has a significant negative correlation with urban expansion, namely the region with poorer accessibility was unlikely to develop the land, which is in line with the urban sprawl structure of blind expansion and residential suburbanization in Beijing; the negative correlation between dynamic accessibility and land use change was also found, indicating that the higher region's degree of accessibility does not necessarily lead to higher probability of land development, which also implicates that the probability of land development around the existing built-up area is far higher than that along the rail transit. Therefore, this paper points out that more attention should be attached to the dynamic transport accessibility and its key role in leading the reasonable urban land use pattern and the rational urban development, which would be effective in avoiding urban sprawl and optimizing urban expansion.