The Distribution Characteristics And Influencing Factors Of Elements In Wuhan

City is a complex dynamic system composed of infrastructure,human activities and social connections.Quantitatively investigating the aggregation patterns of urban elements and their influential factors is beneficial to understand the mechanism of urban development and support urban planning.Different urban elements may exhibit various aggregation patterns,but the bulk of previous studies concentrated on a single urban element.The disparity and the connection among different urban elements is still unknown.Taking Wuhan city,Central China,as a case,we collect five types of urban elements,namely,impervious surface,population density,Point of Interest(POI),floor area ratio,and road network,to explore their spatial distribution and characteristics of aggregation patterns.We first use Kernel Density Estimation(KDE)method to identify the city centers.Then we partition the study area by gradient analysis,and calculate the densities of urban elements in each buffer.We quantitatively describe the spatial distribution of urban elements using the urban density function.The derivative indicator of the function,named Concentration Degree Index(CDI),was used to quantify the aggregation degree of urban elements.The spatial econometric model was used to explore factors that influence the distribution of each urban element.Based on the analysis above,we drew conclusions as follows:(1)There is a major center and seven sub-centers in Wuhan.The density of each urban element decreases outward from the centers,which is fitted well using "Inverse S-shaped" function.(2)The aggregation degree of urban elements are:Commercial POI>population>floor area ratio>road>build-up area.The aggregation patterns of urban elements in Wuhan are point pattern,strip pattern/axial pattern,zonal pattern,ring pattern.(3)Commercial POI and population are highly aggregated in the urban core area,while floor area ratio and road are moderately aggregated in the urban core area.The commercial POI and population are highly aggregated as a combination of point pattern,strip pattern and zonal pattern,while the road network and floor area ratio exhibited a combination of point pattern.ring pattern and axial pattern.The lowly aggregated impervious surface shows a ring pattern and zonal pattern.(4)The spatial econometric model results show that scarce landscape resources like the East Lake and the Yangtze River positively affect the spatial distribution of build-up area and road density,but negatively affect the floor area ratio.The attraction of city centers promotes the spatial aggregation of road density,floor area ratio,and commercial POI.The spatial distribution of commercial POI is consistent with the location of city centers.Transportation(bus and subway stations)positively affects the build-up area and road density.Public service facilities like governments and social organizations have a significant positive influence on the population density.The healthcare organizations have a positive significant influence on the road density and floor area ratio.The building height promotes the floor area ratio and population density,especially for the former.The mixed land use negatively affects the commercial POI density and road density,while positively affects the build-up density.