山地城市建设用地增长的坡度梯度效应——以贵阳市为例

山地城市快速扩张致使其建设用地爬坡现象日趋普遍,深入认识该现象将有助提高山区国土空间管控科学性。以中国西南典型山地城市贵阳为例,利用数字高程模型和2000—2020年五期建设用地数据,构建建设用地密度、建设用地爬坡热度等指标,基于网格单元和坡度区段单元开展统计分析,探究该市建设用地增长的坡度梯度效应。结果表明：（1）建设用地面积的增长总体伴随着建设用地平均坡度的趋陡,各相邻时段新增建设用地面积先增大后减小,但新增建设用地平均坡度却一直在变陡;（2）各时期建设用地的现状密度和新增密度均随坡度上升而减小,在坡度梯度上体现出强烈的“择平而建”效应;（3）建设用地密度对建设用地爬坡热度有显著线性影响,且该影响随着背景地面平均坡度上升而增强。研究认为,建设用地爬坡现象通常更多出现在建设用地加密时期,这有利于促进山地城市实现更为集约紧凑的空间增长。

Relationship between construction land and slope in rapidly expanding mountain cities: A case study in Guiyang,China

With the rapid urbanization, the land utilization rate in the mountainous areas has been increasing. Therefore, we should deepen our understanding of the construction land expansion in mountain cities, so as to carry out more scientific management of land use in mountainous areas. This paper studied the slope gradient effect of construction land growth in Guiyang, a typical mountain city in Southwest China, using digital elevation model (DEM) and construction land datasets of 2000, 2005, 2010, 2015 and 2020, which was integrated with zonal statistics approaches based on spatial statistics unit of kilometer grid and slope section with one degree interval. Combined with the information of construction land density and slope, we propose a novel method to quantify the spatial pattern of construction land climbing. The research was designed to address three research questions: Is there a synergistic relationship between the area of construction land and the average slope of construction land? What are the distribution and change characteristics of construction land density on the slope gradient? What is the relationship between the density of construction land and the heat of construction land climbing? The results showed that: (1) The total area of construction land is positively correlated with the average slope of construction land, both of which increase gradually across the entire study period. However, the average slope of new construction land gradually becomes steeper among four neighboring periods, while the area of new construction land turns from increasing to decreasing, implying that they are not synchronous. (2) The density of construction land in each period decreased with the increase of slope, no matter in one period or in the other four periods. (3) The density of construction land has a significant impact on the heat of construction land climbing, and this influence increases as the average slope of the background ground rises. This paper suggests that the phenomenon of construction land climbing would promote the intensification and compactness of construction land in mountain cities.