Studies On Spatial Patterns And Ecosystem Services Of City Functional Components

A city is a complex system where people and facilities（city functional components）are coupled.City functional components provide people with most goods and services,and are an important guarantee for urban operation.The spatial distribution of city functional components at each stage is a state of dynamic equilibrium between supply and demand in that period,and it also shapes the functional spatial structure of the city.Understanding the spatial distribution characteristics and formation mechanism of city functional components is the basis for optimizing urban layout.However,the current researches on the distribution of city functional components still have been limited to the use of traditional geographical methods for spatial statistics,the research object is relatively single,and there has been a lack of the researches on the overall distribution and relative position relationships of various types of city functional components.The researches on the formation mechanisms of the spatial pattern of city functional components have mostly focused on social and economic factors,and there has been a lack of the researches on ecological factors as variables affecting the distribution of functional components.In addition,there also has been a lack of the mechanism models that can integrate multiple driving factors to simulate the formation of the spatial pattern of city functional components.In this study,different types of city functional components were compared to"species"in biological communities,and with the help of niche theory and gradient analysis methods in ecology,the distribution of 22 types of city functional components in 15 case cities in China on the urban-rural gradient was quantitatively analyzed through the density distribution curves.This study explored the distribution dynamics of various types of city functional components with urban development and developed a"gradient model"based on ecosystem services that integrated driving factors such as population and land rent to simulate the spatial distribution of city functional components.The mechanism that affects the formation of the spatial pattern of city functional components was analyzed.The main results are as follows.（1）This study quantifies the niche characteristics of city functional components on the urban-rural gradient,and verified the applicability of the ecological gradient analysis method in the study of component distribution.Statistical results showed that the density distribution curve of city functional components on the urban-rural gradient was similar to the density distribution curve of species on the environmental gradient,and both show a unimodal or monotonic form.There was a significant correlation between the characteristic values（peak position,peak value,niche width,skewness,kurtosis）of the density distribution curves of 22 functional components in the same city.The peak value,skewness,and kurtosis were negatively correlated with the peak position,while the niche width showed a significant positive correlation with the peak position.That is,the closer the peak position is to the city center,the higher the peak value,the narrower the niche,the greater the degree of skewness of the curve towards the city center,and the greater the kurtosis.These were similar to the distribution law of species in natural ecosystems.That is,the higher the resource level,the greater the density of species and the narrower the niche.The niche width of the same functional components in different cities had a significant positive correlation with the total urban population,and the niche width of retail stores and express outlets also had a significant positive correlation with the urban per capital GDP.In addition,the degree of niche overlaps between functional components of the same category（such as KFC and Mc Donald’s shops in the category of Western fast food restaurants）were greater than that between different categories of components（such as Western fast food restaurants and express outlets）.（2）This study revealed that the spatiotemporal dynamic changes of city functional components were related to the types of components and the size of the city.The statistical results showed that from 2012 to 2018,some city functional components had different spatiotemporal dynamics in cities of different sizes.The peak positions of the density distribution curves of Western fast food restaurants in large cities（Beijing and Shanghai）had moved about 1 to 2 kilometers away from the city center,while the peak positions of the density distribution curves of Western fast food restaurants in the other case cities remained almost unchanged.The peak positions of the density distribution curves of express outlets were constantly moving towards the suburbs in large cities（Beijing and Shanghai）,but the peak positions of the density distribution curves of express outlets were moving towards the city center in smaller cities（Changzhou and Jiaxing）.There were also some functional components that showed the same spatiotemporal dynamic trends in cities of different sizes.In the case cities,the peak positions of the dairy farm density distribution curves tended to move away from the city center;the peak positions of banks had hardly changed,and they were always in the city center.In addition,the statistical results of the case cities showed that the peak value and niche width of the density distribution curves of special sports venues,Chinese fast food restaurants,express outlets,and general hospitals increased significantly;the peak value of the density distribution curve of comprehensive sports venues decreased,but the niche width increased significantly;the overlap of the two types of functional components（Western fast food restaurants and express outlets）with other types of functional components increased over time.（3）Based on the basic information of 13 types of city functional components surveyed in the field,this study calculated their ecosystem services,and explored the relationship between the distribution of city functional components and their ecosystem services.The statistical results showed that the stronger the net ecosystem service capacity of the city functional components,the closer the peak position of the density distribution curve was to the city center.For example,Agricultural Bank of China had the highest net ecosystem service per unit area(99,100 yuan m^-2 yr^-1),and the peak position of the density distribution curve was located in the city center;while the greenhouse had the lowest net ecosystem service per unit area(22 yuan m^-2 yr^-1),the peak position was located at the edge of the built-up area.In addition,the ecological index（the ratio of target service intensity to dis-services intensity）of city functional components also affected the peak position of the density distribution curve of the component.For example,the net ecosystem service intensity of the swimming pools were lower than that of Chinese fast food restaurants,but due to their high ecological index,the peak position of the density distribution curve was closer to the city center;the net ecosystem service intensity of the dairy farms were higher than that of the greenhouses,but due to their low ecological index,the peak position was distributed further from the city center.（4）This study is based on the principle that city functional components are in a specific position due to the balance of gravitational force and repulsive force in the city center on the urban-rural gradient,a gradient model for simulating the spatial pattern of functional components was developed.The model revealed the general laws of urban development,expansion and renewal.The model relies on 4 key parameters:two component attributes（net ecosystem service m,environmental indexγ）and two urban attributes（population decay exponentβand land rent decay exponentσ）.Using this model,the density distribution curves of 4 types of functional components on the urban-rural gradient,such as Western fast food KFC shops,ZTO express outlets,greenhouses and dairy farms,were well simulated in 13 case cities in China,and their coexistence on the urban-rural gradient was simulated.This study also used the model to further predict the spatial pattern changes of functional components in Hangzhou and Ningbo in different periods.This means that the model can predict the change of density distribution curve of various city functional components with urban development according to city and component attributes.The model can also quantitatively analyze the spatial pattern of the coexistence of multiple functional components in an urban system that is in equilibrium due to the interaction of various elements at any period of time.This study applies the theories and methods of ecology,economics and physics to conduct interdisciplinary research.On the basis of traditional location factors,ecological factors are added to explore the spatial distribution dynamics of city functional components and their formation mechanisms,and the key regulatory variables that can adjust the distribution of city functional components are found.This work provides a new perspective for the rational planning of city functional components,and provides technical support for evaluating urban policies,weighing the suitability of planning,and analyzing the future evolution of urban spatial structure.This study will further stimulate interdisciplinary research in the field of urban studies by majors such as ecology,economics,urban planning and management.