旱区城市扩展过程区位因素研究——以中国呼包鄂榆城市群为例

认识城市扩展过程的区位因素特征对旱区城市可持续发展具有重要意义。为此,以中国呼包鄂榆城市群为例,利用随机森林方法量化区位因素对城市扩展过程的影响。研究发现:随机森林方法能够有效地量化旱区城市扩展过程区位因素的基本特征,模型的AUC(area under curve)值达到0.97。同时,到城市中心距离对区域1980—2017年城市扩展过程影响最大,重要性达到42.62%。国道、高速公路和铁路等交通因素也有重要的影响,重要性均大于10%。此外,所有区位因素对区域城市扩展过程的影响均存在尺度效应,其中地形、气候和河流对城市扩展过程影响的尺度效应相对比较明显。地形、气候和河流对大城市影响的重要性分别为27.17%、20.23%和8.12%,分别是其对小城市影响的4.02倍、3.91倍和2.36倍。因此,建议在旱区城市建设中,应该高度重视地形、气候和河流等自然要素的约束作用,因地制宜地进行城市规划和建设。

Study on the location factors of urban expansion in the drylands: A case study in the Hohhot-Baotou-Ordos-Yulin Urban Agglomeration,China

Understanding the characteristics of location factors of urban expansion is important to urban sustainable development in the drylands. Taking the Hohhot-Baotou-Ordos-Yulin Urban Agglomeration in China as an example, this study assessed the impacts of location factors on urban expansion using the random forest model. The results indicated that the random forest model can effectively quantify the basic characteristics of location factors of urban expansion in the drylands, with the area under curve (AUC) index of 0.97. The distance to the urban centers had the greatest influence on urban expansion from 1980 to 2017, with the importance of 42.62%. The traffic factors such as highways, national roads, and railways also played an important role with the importance above 10%. All location factors had scaling effects on regional urban expansion, among which the topographic, the climate and the river factors had the most obvious effects. The importance of topography, climate and rivers to large cities was 27.17%, 20.23% and 8.12%, respectively, 4.02 times, 3.91 times and 2.36 times that of small cities. Thus, we suggest that the local governments should pay close attention to the constraint effects of the natural factors (e.g., topography, climate and rivers) on the urban construction in the drylands, and perform urban planning and construction according to local conditions.