Differentiated effects of morphological and functional polycentricurban spatial structure on carbon emissions in China: an empiricalanalysis from remotely sensed nighttime light approach

Understanding the relationship between urban development and environmental sustainability to achieve‘double carbon’goals in China can be strengthened by evaluating the environmental effect of urban spatial structure(US).However,there have been few studies that consider the differentiated effects of polycentric US(PUS)on carbon emissions from both functional and morphological perspectives simultaneously.Thus,taking China’s 31 provinces as experimental subjects,our study developed a novel framework with remotely sensed nighttime light(NTL)data to quantify morphological PUS(MPUS)and functional PUS(FPUS)from 2000 to 2019.Then,from these two dimensions,differentiated effects of PUS on carbon emissions were further examined.Results indicated that NTL data presented high potential in quantifying MPUS and FPUS.The effect of FPUS on carbon emission-cutting outperformed that of MPUS.In addition,the spillover effect effectively enhanced the decreasing effect of the FPUS on carbon emissions.Our empiricalfindings can provide guidance for the government in developing strategies for reducing carbon emissions and optimizing USs.

国家行政区划调整下的城市多中心发展——城市空间转型的政策启示

Polycentric urban development has profound impacts on urban development worldwide.Most studies have identified its complex drivers of social economy and natural condition while ignoring the state-led policy factors.In recent years,China has undergone dramatic administrative division adjustment(ADA)during the process of unique state-led urbanization.However,as a crucial government strategy,the impacts of ADA on urban polycentricity remain unclear.This research investigates the relationship between ADA and urban polycentricity through spatial difference-in-differences models.The results reveal that ADA has contributed to the polycentric urban development in China.Specifically,boundary restructuring has more substantial impacts than hierarchy reorganization.In addition,ADA has significantly promoted urban polycentricity in local cities in central China and neighbouring cities in eastern China,while it has no significant effects in western China.Furthermore,ADA reshapes urban polycentricity mainly by the influencing mechanism of construction land and industrial structure.Policymakers should consider the various ADA’s impacts on urban polycentricity with socio-economic conditions.This research provides a deeper insight into urban spatial transformation with state-led drivers.

Understanding spatial structures and organizational patterns of city networks in China: A highway passenger flow perspective

The use of multi-perspective and multi-scalar city networks has gradually developed into a range of critical approaches to understand spatial interactions and linkages. In particular, road linkages represent key characteristics of spatial dependence and distance decay, and are of great significance in depicting spatial relationships at the regional scale. Therefore, based on highway passenger flow data between prefecture-level administrative units, this paper attempted to identify the functional structures and regional impacts of city networks in China, and to further explore the spatial organization patterns of the existing functional regions, aiming to deepen our understanding of city network structures and to provide new cognitive perspectives for ongoing research. The research results lead to four key conclusions. First, city networks that are based on highway flows exhibit strong spatial dependence and hierarchical characteristics, to a large extent spatially coupled with the distributions of major megaregions in China. These phenomena are a reflection of spatial relationships at regional scales as well as core-periphery structure. Second, 19 communities that belong to an important type of spatial configuration are identified through community detection algorithm, and we suggest they are correspondingly urban economic regions within urban China. Their spatial metaphors include the administrative region economy, spatial spillover effects of megaregions, and core-periphery structure. Third, each community possesses a specific city network system and exhibits strong spatial dependence and various spatial organization patterns. Regional patterns have emerged as the result of multi-level, dynamic, and networked characteristics. Fourth, adopting a morphology-based perspective, the regional city network systems can be basically divided into monocentric, dual-nuclei, polycentric, and low-level equilibration spatial structures, while most are developing monocentrically.