| As a spatial carrier of population,industry,economy and other factors,urban agglomerations are more important sources of greenhouse gas production.The escalating expansion of urban agglomerations has led to huge changes in regional land use and exacerbated the problem of high carbon emissions from urban agglomerations.Therefore,it is necessary to analyze the spatial and temporal patterns of carbon sources and sinks at the level of urban agglomerations to further investigate the carbon balance mechanism within urban agglomerations and provide a theoretical basis for promoting regional low-carbon economic development and promoting the formulation of energysaving and low-carbon policies.In the context of territorial spatial planning and low-carbon development,land use and comprehensive improvement have entered a comprehensive and integrated stage.Land use planning needs not only to improve the mechanism of territorial spatial development,resource conservation and ecological environmental protection,but also to build a system of territorial spatial development and protection to achieve the maximum economic and social benefits with the minimum carbon cost.We focus on exploring the optimal ratio of carbon source and sink land and its equivalent conversion,emphasizing the combination of carbon emission and territorial spatial development intensity,and realizing the construction of a territorial spatial organization system of "mountain,water,forest,field,lake,grass and sand" through cross-border integration,so that territorial spatial planning can be organically integrated with sustainable development.In recent years,the impetus for the development of low-carbon eco-cities in China and its background have shown the urgency of developing low-carbon eco-city construction.Therefore,this paper takes the Beibu Gulf urban agglomeration as an empirical study and uses land use,energy consumption and socio-economic data to construct a framework and methodological system for assessing the carbon balance effect of urban agglomerations,accounting for and analyzing the land use,carbon(source)emission,carbon(sink)absorption and net carbon emission changes in the study area in 2000,2010 and 2020,and exploring their spatial and temporal differentiation characteristics and spatial correlation.The spatial and temporal variation characteristics and spatial correlation were investigated.Then,we extracted the landscape pattern indices of 15 cities in the Beibu Gulf urban agglomeration,and analyzed the spatial pattern coupling with carbon income and expenditure by using the geographically weighted regression(GWR)model;we constructed the "carbon source-carbon sink" coordination model to analyze the coupling coordination of carbon sources and sinks.Finally,based on the "dual evaluation" of territorial spatial planning and carbon neutral strategy,a comprehensive evaluation system of carbon balance of urban agglomerations is established,and the carbon balance proximity of 15 cities in Beibu Gulf urban agglomerations in 2020 is measured by combining entropy weight method and TOPSIS method,and the main factors are detected and analyzed by geographic probe.Thus,a carbon balance hierarchy model is further constructed for functional zoning research,and carbon emission reduction spatial optimization measures oriented to low carbon development are proposed to provide reference for implementation strategies at the city cluster level to achieve the carbon neutrality goal.The main research results are as follows:(1)Analysis of the land use structure,change characteristics and carbon emission data measurement of the Beibu Gulf city cluster.Arable land and forest land are the most widely distributed and concentrated land use types,and there is an uneven spatial distribution of various land uses.The most drastic transformation in the whole research sequence is the conversion of arable land and forest land to construction land,followed by the mutual conversion of arable land and forest land;the measured changes in carbon emission,net carbon emission and carbon emission intensity of each city are significant,and the changes in carbon absorption are basically stable.(2)To explore the spatial and temporal characteristics and interactions of carbon income and expenditure in the Beibu Gulf urban agglomeration.Carbon emissions from construction land decreased significantly,while carbon sinks from forest land remained stable.There are significant differences in carbon income and expenditure among cities,with obvious gradient transition characteristics.The carbon sink of cities shows a stable state,while the carbon source shows a significant decrease,and the carbon emission intensity shows an overall decreasing trend,and the divergence pattern between carbon source and carbon sink basically remains stable.The "hot spot" and "cold spot" cities in the Beibu Gulf City Cluster are divided,and the spatial aggregation of carbon income and expenditure in the municipal units of the Beibu Gulf City Cluster is remarkable and the pattern remains stable.The landscape pattern indices of construction land and forest land are mostly positively correlated with the carbon balance,while a few of them are negatively correlated.The overall carbon sources and sinks of the Beibu Gulf city cluster have good coupling and coordination.(3)To construct a carbon balance spatial zoning unit for low-carbon development in the Beibu Gulf city cluster and to build a planning and control guide.On the basis of measuring the closeness of the socio-economic,resource utilization and ecological environment subsystems of the 15 cities in the Beibu Gulf city cluster to the ideal values,factor detection and interaction analysis are conducted to determine the optimal cities in each subsystem,and a threedimensional magic square unit is constructed according to the level of the closeness index to determine the carbon balance zoning guidelines,and then the cities in the carbon intensity control zone,low carbon optimization zone and carbon balance zone are delineated.The carbon intensity control zone,the low carbon optimization zone and the carbon balance zone are determined.We grasp the carbon balance difference factors of urban clusters,construct the underlying logic of planning and control for the carbon balance development of different unit cities,and build specific spatial control elements and optimization methods. |
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