Study On The Pattern Optimization Of Regional Green Space In Mega-cities Based On Increasing Carbon Sink

Regional green areas are green areas located outside of urban construction land,except for arable land,with functions of urban and rural ecological environment and natural and cultural resources protection,recreation and fitness,security and protection isolation,species protection,garden seedling production,etc.They are the main source of carbon sinks within the city municipal area.The contradiction between carbon emissions caused by urban development and carbon sinks generated by regional green areas seriously threatens the low-carbon development of cities.Studies show that the regional green space area in China decreased by 16.4×103km2 from 2010 to 2015,of which 35.2% was caused by the expansion of construction land.Under the goal of "peak carbon by 2030 and carbon neutral by 2060",the low-carbon development strategy of megacities,as geographically superior and core economic pattern,is more complicated than that of ordinary cities,and improving carbon sinks through scientific and reasonable planning of regional green space layout has become an important part of the low-carbon development strategy of megacities.This paper takes the regional green areas of megacities as the research object,and aims at increasing carbon sink,based on "the current problem--optimization target--optimization principle--optimization method--optimization path".Based on the "current problem-optimization objective-optimization principle-optimization method-optimization path",this paper constructs a technical path for optimizing the layout of regional green areas in megacities from macroscopic and microscopic scales,and provides methodological support for low-carbon urban development from the perspective of carbon sink.This paper is divided into four parts: analysis of regional green space layout characteristics of megacities,data analysis,indexes and models of existing regional green space and carbon sinks,construction of technical paths for optimizing regional green space layout under the goal of carbon sink enhancement and empirical study of case cities.Firstly,we analyze the land use characteristics,carbon sink characteristics and regional green space layout characteristics of 14 megacities based on the north-south zoning of the Qinling and Huaihe line,and put forward the existing problems-the lack of regional green space layout integrity,insufficient use of water bodies,and the decline of mountain green space.Secondly,the objectives of carbon sink optimization of regional green areas-to increase the area of regional green areas,to improve the carbon sink capacity of regional green areas and the corresponding optimization principles-the principle of network layout,the principle of localization,the principle of land use coordination and symbiosis,and the principle of functionality-are constructed from macroscopic scale and microscopic scale respectively.and functional principles.The technical path is then constructed: the method of green space suitability analysis is proposed at the macroscopic scale,the frequency ratio model and logistic regression model are integrated to determine the optimal zoning of regional green space in megacities within the city limits,and the schematic diagram of regional green space layout optimization is proposed based on the green space layout model of "green heart,green wedge,green corridor and green ring".CASA model is used to calculate NPP to measure the carbon sink capacity of regional green areas,and the landscape pattern index method is used to quantify the layout structure of regional green areas,and it is proposed to conduct scale effect analysis and correlation analysis based on gridding at the microscopic scale to explore the spatial relationship between the layout structure of regional green areas and the carbon sink function,and to determine the appropriate scale for optimization,based on the "patch,corridor,substrate Based on the "patch,corridor,substrate" landscape ecology theory,we propose the optimization model of land use carbon sink layout at microscopic scale.Finally,north of the Qinling-Huaihe line-Xi’an city and south of the Qinling-Huaihe line-Wuhan city were selected respectively for the empirical study of the optimization method.Through the suitability analysis,4457.69km~2 of regional greenland core protection zone and 1287.3km~2 of regional greenland core development zone in Xi’an,640.1km~2 of regional greenland core protection and development zone and 1687.51km~2 of regional greenland development zone in Wuhan were identified respectively,and the optimization paths were proposed in combination with other related planning and optimization zoning of the city;at the microscopic scale,4km×4km of regional greenland core protection and development zone in Xi’an and 1687.51km~2 of regional greenland core protection and development zone in Wuhan were identified.In the microscopic scale,the suitable grid scales of 4km×4km in Xi’an and 2km×2km in Wuhan were identified,and the optimization models of land use carbon sink layout for arable land substrate and forest land substrate were constructed quantitatively and qualitatively,respectively,to provide new ideas for regional greenland carbon sink.The main results of this study are three:(1)to determine the objectives and principles of regional green space optimization in megacities and to point out the direction for constructing optimization methods and optimization paths;(2)to construct a technical path for optimizing the layout of dual-scale regional green space in megacities from the perspective of carbon enhancement;and(3)to conduct an empirical study of the technical path with the objective of improving the carbon sink of regional green space,using Xi’an and Wuhan as case cities.