Analysis Of Urban Spatial Expansion Characteristics And Driving Factors Of Urban Agglomeration In The Yellow River Basin

Ecological protection and high-quality development in the Yellow River basin have become a major national strategy.Urban agglomeration is not only a strategic highland to participate in global competition,but also an important carrier of China’s new urbanization and a growth pole of regional high-quality development.The high intensity of population and economic factors leads to the urban agglomeration and its internal urban spatial expansion intensity and speed significantly faster than that of the general region.It is of great strategic significance to scientifically evaluate the process of urban agglomeration spatial expansion,examine its driving mechanism,and reasonably control the sprawl expansion to promote the high-quality development of urban agglomeration.The paper selects seven major urban agglomerations in the Yellow River basin as the research object,uses the continuous night light data of the integrated time series,and tries to compare and analyze the characteristics of urban spatial expansion intensity,expansion form,expansion and agglomeration degree of urban agglomerations in a panoramic way from the perspective of space and time,and reveals the driving factors of expansion.The results show that:(1)From 2000 to 2020,the expansion,density and continuity of night light in the Yellow River Basin were obvious,and the brightness of night light in urban agglomeration was increasing,and increased from upstream to downstream.High-value clusters and low-value clusters cluster obviously,and high-value clusters mainly appear in the core cities,important node cities and their connecting corridors of urban agglomeration.(2)From 2000 to 2020,the cities in the urban agglomeration of the Yellow River basin experienced the evolution of slow expansion-medium speed expansion-high speed expansion,and after 2011,the expansion speed was significantly accelerated,and the spatial differentiation was obvious.Among the urban agglomeration in the middle and lower reaches,the number of cities with medium speed and high speed expansion continued to increase;However,the urban agglomeration in the upstream region is still dominated by slow and slow expansion,and only in the core cities,there is a lack of high-speed expansion type.(3)From 2000 to 2020,all urban agglomerations were dominated by marginal expansion,supplemented by enclave and infill expansion.Among them,the marginal expansion is manifested in all cities,while the enclave expansion and infill expansion mainly occur in the marginal areas of the core cities(especially the new cities/new areas),as well as the traffic corridors connecting the core cities and important node cities.The number of patches in the built-up area increased significantly,and the patch density increased significantly;At the same time,the patch connectivity was enhanced and the corridor effect was significant;The patches in the built-up area are complicated and the landscape fragmentation is enhanced.(4)The scale of urban spatial expansion conforms to the law of hierarchy,that is,the larger the city size,the more obvious the expansion.The | q | value of each urban agglomeration in 2020 is less than the | q | value in 2000,that is,the scale of urban land use is concentrated in the initial stage,and tends to disperse in the later stage.(5)The urban expansion of urban agglomeration is the result of comprehensive driving of multiple factors.Quantitative analysis shows that the socio-economic factors such as regional gross product,fixed assets investment,primary and secondary industrial output value are highly related to the expansion of built-up areas.