Structural Characteristics and Influencing Factors of Carbon Emission Spatial Association Network:A Case Study of Yangtze River Delta City Cluster,China

City cluster is an effective platform for encouraging regionally coordinated development.Coordinated reduction of carbon emissions within city cluster via the spatial association network between cities can help coordinate the regional carbon emission management,realize sustainable development,and assist China in achieving the carbon peaking and carbon neutrality goals.This paper applies the improved gravity model and social network analysis(SNA)to the study of spatial correlation of carbon emissions in city clusters and analyzes the structural characteristics of the spatial correlation network of carbon emissions in the Yangtze River Delta(YRD)city cluster in China and its influencing factors.The results demonstrate that:1)the spatial association of carbon emissions in the YRD city cluster exhibits a typical and complex multi-threaded network structure.The network association number and density show an upward trend,indicating closer spatial association between cities,but their values remain generally low.Meanwhile,the network hierarchy and network efficiency show a downward trend but remain high.2)The spatial association network of carbon emissions in the YRD city cluster shows an obvious‘core-edge’distribution pattern.The network is centered around Shanghai,Suzhou and Wuxi,all of which play the role of‘bridges’,while cities such as Zhoushan,Ma'anshan,Tongling and other cities characterized by the remote location,single transportation mode or lower economic level are positioned at the edge of the network.3)Geographic proximity,varying levels of economic development,different industrial structures,degrees of urbanization,levels of technological innovation,energy intensities and environmental regulation are important influencing factors on the spatial association of within the YRD city cluster.Finally,policy implications are provided from four aspects:government macro-control and market mechanism guidance,structural characteristics of the‘core-edge’network,reconfiguration and optimization of the spatial layout of the YRD city cluster,and the application of advanced technologies.

Structural characteristics and influencing factors of spatial correlation network for regional high-quality development in China

On the basis of measuring the regional high-quality development in China from 2011 to 2020,this study uses gravity model to build spatial correlation network,and uses social network analysis method to analyze the structural characteristics and influencing factors of correlation network.The results are shown as follows.First,from 2011 to 2020,the level of regional high-quality development in China is rising gradually,and the discrete characteristics between regions are gradually obvious,showing a step-like distribution structure decreasing from east to west.Second,the network density of regional high-quality development is generally low and tends to decline,but it has strong stability and correlation strength.Third,the spatial correlation network has an obvious core-edge structure.Shanghai is always at the center of the network and plays a significant intermediary role,while Qinghai and Xinjiang are always at the edge of the network.Fourth,the regional high-quality development association network can be divided into four major sectors:main benefit,net benefit,net spillover,and broker,showing the spatial correlation characteristics of inter-plate contact and intra-plate agglomeration.Fifth,the level of economic development,the level of urbanization and geographical proximity have a significant impact on the formation of regional high-quality development correlation network.

Interspecific association of sika deer in terrestrial animal communities of Liancheng National Nature Reserve, China

The prevention and control of invasive of alien species is an important work for nature reserves.This study analyzes the development trend of the alien species sika deer in Liancheng National Nature Reserve.From October 2019 to June 2020,3523 valid photos and videos of terrestrial animals were acquired from 130 camera traps,and sika deer were recorded in 21 photos from 13 traps.The survival of the sika deer population was investigated by means of morphological identification,population structure analysis,species relative abundance indices,and species spatial association analysis.A total of 13 sika deer individuals were identified by camera trapping,including two kids and three subadults representing the reproductive capacity of the population.Spatially,sika deer is not associated with any local species and was outside the spatial association network of terrestrial animals in Liancheng National Nature Reserve,indicating that the sika deer population has not been integrated into the local community and has failed to perform its ecological function.It is worth noting that the reserve provides habitat suitable for sika deer and that the population has adequate reproductive capacity.Due to the lack of large apex predators in the reserve,the population size of ungulates such as sika deer,red deer,and Siberian roe deer may expand and lead to population outbreaks and the associated problems for the ecosystem.To restore large-and medium-sized carnivores and avoid the population outbreak of the species,the present challenges require immediate attention in Liancheng National Nature Reserve.