| In the process of continuous urban development,urban environmental problems are gradually prominent,and urban ecological construction has become an indispensable subject for urban development research.With the global warming,carbon emission control has become an important responsibility of the international community and the governments of all countries.Hot words such as"low carbon","low carbon economy"and"low carbon city"gradually come into the public’s vision,and low-carbon development has become the only way for development.At present,the research on"low-carbon"of urban development is divided into two parts:"carbon source"and"carbon sink".At present,studies on urban carbon sink by different experts and scholars in China mainly focus on forest ecosystem and wetland ecosystem,and the site selection scope is concentrated outside the urban area of cities,counties and cities.Urban green space system is the core contributor of urban carbon sink.However,there is no unified and perfect research system and research paradigm for carbon sink evaluation system,value measurement method and evaluation index measurement method.Therefore,further in-depth research is needed.Urban green space system has distinct regional characteristics.Taking a city as a unit and combining regional characteristics,it is imperative to construct a carbon sequestration evaluation index system suitable for local green space.Taking the urban green space system of Chanba ecological district,xi’an city as the research object,this paper estimated the carbon reserve of urban green space through interpretation of remote sensing images and field survey data,and proposed a development strategy of high carbon sink.Will action the Chanba ecological urban green space is divided into the park green space(G1),protective green space(G2),attached green space(XG)and regional green space(EG)four categories,including affiliated green space and residential green space,cultural and educational area,administrative office,green land,commercial,industrial park green space and road green space,after the carbon intensity of different types of green space,carbon modeling estimation respectively.Field survey of urban green space in Chanba ecological district was conducted to make statistics and analysis of vegetation data,and the 12 planting patterns in the study area were summarized according to the regular characteristics of current green space and vegetation.The detailed data in all kinds of green space are investigated by means of sample land inventory,and the sample land is selected according to the space balance sampling method combined with stratified sampling and systematic sampling.Firstly,the sampling box was established,and the research area was finally divided into 50m*50m sampling box by the general random grid stratification algorithm.A total of 236 sampling sites were selected from each layer of green space,and the data in the sample site were checked,counted and analyzed through field investigation.Then,the allometric growth equation of biomass was used to calculate the carbon storage of the sample plot,and the carbon storage of the 12planting modes was calculated with 50m*50m as the unit,and then the carbon sequestration capacity was compared and analyzed.A regression model of carbon reserve and vegetation index was established to estimate the carbon reserve of urban green space system in Chanba ecological district.Finally,based on the estimated results,the strategy of developing high carbon sink in urban green space is put forwardth in Chanba ecological district.The results showed that the final estimated total carbon reserve of urban green space in Chanba ecological district was 348.559*10~6kg.The carbon reserve of park green space is 223.005*10~6kg;The carbon reserve of protected green space is13.715*10~6kg;The carbon reserve of regional greenbelt is 36.150*10~6kg;The carbon reserve of residential green space is 51.457*10~6kg;The carbon storage of greenbelt in cultural and educational area is 10.667*10~6kg;The carbon storage of administrative green space is 1.362*10~6kg;The carbon reserve of commercial green space is1.847*106kg;The greenbelt carbon reserve of the industrial zone is 4.243*106kg;The carbon storage of road greenbelt is 6.113*10~6kg.The influencing factors include:DBH of vegetation,plant height of vegetation,patch area of greenbelt,tree age,canopy density,species composition and planting mode.The mature forests of chanba ecological district have the strongest carbon sink capacity.There are few mature woodlands in chanba ecological district,and most of them are of medium and young ages.Therefore,the carbon sequestration capacity of the greenbelt is still in the stage of rapid development.Of course,the larger the patch area,the higher the carbon sink capacity.How to increase the green area in the limited urban land is the best solution to improve this index.Canopy density is 0.5-0.6,which is the best planting amount of green space,and the carbon sink capacity is the strongest in this range.Under the influence of planting mode of plants,the carbon sink capacity of forest edge planting mode with groove or undulating planting mode was significantly higher than that of the planting mode without change of forest edge,and the carbon sink capacity of planting mode with groove was significantly higher than that of planting mode only with bulge.In Chanba ecological district,the vegetation with high carbon sink capacity per plant includes Cedar,Platanus,Poplar,Locust,Ginkgo,Ligustrum lucidum and other trees,and the carbon sink capacity of Camphor,Ailanthus,Albizzia julibrissn,Metasimeria,Pittosporum tobiraand other vegetation is also high.In mixed forests,the combination of Platanus and Poplar as the dominant species had the highest carbon sink capacity,followed by the combination of Platanus and Ginkgo,with the dominant species accounting for no less than 50%of the total number.Suggestions for the development of Chanba ecological district’s urban green space system:in addition to increasing the area,reasonable allocation of green space can be made to improve the carbon sequestration capacity of Chanba ecological district through connectivity and coupling of green space carbon sink network,vertical extension of green ecological space,and smart guidance and control of green space function services.Strengthen the internal connection between Chanba ecological district and xi’an city as well as the penetration of the external natural environment.Build the green connection corridor inside the ecological district to realize the benign interaction between urban green space and other land,and build the green network of Chanba ecological district.Through optimizing the allocation of natural communities,controlling the planting density of vegetation,selecting high-carbon sink vegetation under appropriate conditions,and strengthening the management of green space in the later period,the carbon density and carbon sequestration capacity of urban green space can be improved.Finally,the high carbon sink development of chanba ecological district’s urban green space will be realized. |
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