剔除县域人口密度极端值对地形因子与人口密度关系的影响

Effect of Excluding Counties with Population Density Extremes on the Relationship Between Topographic Factors and Population Density in China

人口密度随地形梯度升高而减小的规律性仅适用于一定的人口密度范围,若在相关研究中注意该特性,将有利于更科学地开展解释和建模。通过对比地形因子(海拔、起伏度及坡度)与人口密度的关系在剔除人口极端分布县域前后的差别,并在人口适度密集县域范围内分析了各类地形因子对人口密度的影响特征,提出区分人口极端分布县域与人口适度密集县域的方法。结果表明:(1)剔除人口极端分布县域后,人口密度与三类地形因子的关系均更趋简单,其中坡度和起伏度对人口密度的拟合能力明显增强,尤其坡度的解释力从相对最弱转变为相对最强;(2)在人口适度密集县域,沿地形因子梯度上升方向看,人口密度在低海拔区段和小起伏区段有规律地剧烈减小,在较大起伏区段和几乎全部坡度区段有规律地缓慢减小,在中等海拔区段波动较大,且这些特征在2000-2020年间保持稳定。

The regularity of population density decreasing with increasing terrain gradient only applies to a certain range of population density.If this characteristic is taken into account in relevant research,it will be beneficial for a more scientific understanding of the relationship between population and terrain.A method to distinguish between counties with extreme population density and counties with moderate population density is proposed at the county-level scale in China.Using the census population data of China in 2000 and 2020 and a 30m DEM(Digital Elevation Model),this paper compares the differences in relationship between topographic factors(elevation,ruggedness,slope)and population density of before and after excluding counties with extreme population density which bases on classification of population density at the county-level scale.Furthermore,this research quantifies the relationship between population density and topographic factors based on the exclusion of population density extremes.The results show that:(1)After excluding the extreme effects of population density at the county-level scale,the relationship between population density and topographic factors is relatively simple,and the fitting ability of slope and ruggedness to population density is obviously enhanced,especially the explainability of slope has changed from the weakest to relatively strongest.(2)Based on counties with moderate population density and a perspective of rising topographic gradient,the population density shows a regular and sharp decrease in the low elevation section and the small ruggedness section,a regular and relatively gentle decrease in the larger ruggedness section and almost the whole slope section,and a large fluctuation in the medium elevation section.These characteristics of the change between population density and topographic factors remains stable during 2000-2020.