Ecological Niche-based Competition And Cooperation Relationships Among Cities In Xiangjiang River Basin

City is the main carrier of social and economic activities.With the acceleration of urbanization,it has become the basic unit of regional competition.When facing the imperfect socialist market economy system,there will be corresponding competition between cities,which will have a negative impact on regional economic integration.Therefore,it must accurately locate the development direction,define the development environment,advantages and disadvantages,and select the development strategy suitable for the city resources.This paper takes nine cities in Xiangjiang River Basin as research objects,including Changsha,Xiangtan,Zhuzhou,Hengyang,Chenzhou,Yongzhou,Loudi,Shaoyang and Yueyang.Evaluate the niche intensity and niche overlap in 9 cities from 2007 to 2017 based on niche "state-potential" theoretical model and niche overlap theory model and analyze the niche intensity and the level of competition pressure in each city by Cluster Analysis,and propose a competition and cooperation strategy consistent with the coordinated development of the cities.The conclusions of this paper are the followings:(1)The largest urban niche in the Xiangjiang River Basin is Changsha,with a value of 0.2504,followed by Zhuzhou,Xiangtan,Yueyang,Xiangtan,Yinzhou,Hengyang,Yongzhou,Loudi,Shaoyang.The niche of most cities is below the average level,and the two-level differentiation isobvious,with an extreme value ratio of 5.35.And it shows an unbalanced pattern of "low upstream and high downstream".(2)According to the cluster analysis,Changsha is the first city with obvious niche advantage.Zhuzhou,Yueyang,Xiangtan are the second class cities and have relative competitive advantage.Chenzhou and Hengyangare are the third type cities with weak niche advantage;Shaoyang City,Yongzhou City,and Loudi City are the fourth type of cities,which have the weakest niche advantages in the region.(3)The results show that the overlap degree of other cities in Changsha is the largest,which is greater than 1,and has the least competitive pressure.Shaoyang received the highest degree of overlap from other cities,with an average value of 1.0364,and has the greatest development pressure.The overlap index between some cities is higher than 0.7,and they are competitors.Through the degree of urban niche and niche overlap,there is a high degree of overlap between the four types of cities and within each type of city.(4)Combined with the niche size and niche overlap of each city,the network of urban competition and cooperation system in Xiangjiang River Basin is constructed,forming a hierarchical circle structure with Changsha as the core,Zhuzhou,Yueyang and Xiangtan as the nodes,and the other five cities as the network.And according to the theory of niche,construct the competition and cooperation mode of optimizing urban niche.(5)From the aspects of niche separation,niche expansion,niche generalization and specialization,and coordinated development,put forward the support system to promote the overall coordinated development of the region,and propose specific development measures according to the actual situation of each city's niche.