The Scale Effects And Influencing Factors Of Carbon Sink Capacity In Urban Green Space

A growing number of studies have demonstrated that urban green spaces play a crucial role in regulating the carbon cycle of terrestrial ecosystems and slowing down the increase of atmospheric CO₂ concentration.However,previous studies on carbon sequestration potential have mainly focused on natural or semi-natural ecosystems such as forests,grasslands,or farmlands,while research on the carbon sequestration capacity and carbon sequestration of urban green spaces is limited.The role of urban green space in promoting the construction of urban green space and serving the national"carbon-neutral"strategy will become more and more significant with the progress of urbanization,the increase of people’s ecological awareness,and the rise of demand for urban green space ecosystem services.Therefore,this study will concentrate on the urban green space,which needs to be researched and take the China Green Expo in Zhengzhou City as the research site.Based on the data from multiple sources,such as field surveys,Li DAR point clouds,remote sensing,and literature,we will use Li DAR scanning and point cloud data processing techniques,spatial data analysis,and processing techniques,as well as correlation analysis,full-subset regression,HP analysis,structural equation modeling,and cluster analysis.The spatial quantification and influence mechanisms of carbon storage and sequestration in urban green spaces at different scales are systematically studied in terms of vegetation configuration,green space structure,remote sensing information,and multiple scales.The main research results are as follows:1)In 2021,the carbon storage and carbon sequestration in Zhengzhou-China Green Expo were 48.58 Gg and 3.26 Gg,while the carbon density and carbon sequestration density were30.72 kg m-2 and 2.06 kg m-2 yr-1,respectively.Among them,the carbon storage of trees,shrubs,and herbs were 43.17 Gg,5.31 Gg,and 0.1 Gg,while the carbon sequestration was2.57 Gg,0.64 Gg,and 0.05 Gg,respectively.2)The trees in Zhengzhou-China Green Expo Park consist of 108,241 trees of 54 families,97 genera,and 169 species,with an average height and diameter at breast height of 6.3m and0.32m.3)For the first time,"dbh-age"relationships were established for 169 tree species during the rapid growth period.Then we calculated growth factors for landscape trees in the Zhengzhou area.4)The carbon sequestration capacity of trees varies widely among different species.Based on the cluster analysis,169 tree species were classified into nine categories.Considering the planning and design scenarios and the characteristics of each type of species,we proposed suitable planting recommendations.It offers a theoretical basis for planting design with the goal of carbon sink enhancement.5)The optimal sample size for investigating carbon storage and sequestration in urban green space parks is 100 m.The traditional sample size for forest ecosystems is inaccurate when applied to urban green space.6)Carbon sequestration is significantly influenced by biodiversity,while the stand structure mainly influences carbon stock.This driving relationship varies with scale,for example,the proportion of water bodies has a more significant effect on carbon density in large-scale samples.In urban green space planning,carbon density can be enhanced by increasing the area of water bodies in large green spaces;urban green spaces of all scales can get greater carbon density by optimizing Planting configuration.7)Compared with the vegetation index,the texture characteristics can better explain the variation of vegetation carbon density.Meanwhile,RVI can replace NDVI better to predict carbon sequestration density in urban green space.Future studies on the carbon density of urban green space can improve the accuracy of the results by applying RVI and texture features.The above findings improved our systematic understanding of the carbon sink in the urban green area,provided an essential reference for the study of the carbon cycle in urban green space,and provided a theoretical basis for planning and designing urban green space with the goal of carbon sink enhancement.