| With the development of urbanisation,the dramatic increase in hard paved urban areas and motor vehicle ownership,as well as the frequent occurrence of climate extremes,have led to prominent environmental problems on urban roads.Urban road green belts are an important part of urban forests,which are dominated by trees and have ecological benefit functions such as regulating runoff,reducing air pollution,sequestering carbon and releasing oxygen,and weakening noise.This study uses the i-Tree model to predict the current and future characteristics and ecological benefits of urban road green belts in the city of Qingdao,with a view to providing theoretical and practical references for the current road green belt structure adjustment and future road tree planting transformation.Firstly,a specific analysis is conducted on the tree structure characteristics and ecological benefits of the urban road green belt in Shinan District.The analysis shows that the current road green belts in Shinan District are poorly continuous;they are dominated by young deciduous species and are rich in species,but the health of the trees is not ideal;the road canopy coverage is good,but there are significant differences between the areas.Among them,the central coastal area,eastern area,and historical and cultural area have higher road crown coverage and ecological benefits.In addition,tree species with higher ecological benefits per plant include Salix matsudana,Quercus robur,Acer pictum,Acer truncatum,Eucommia ulmoides.Secondly,a specific analysis of the structural characteristics and ecological benefits of road green belts in Shinan District over the next ten years was carried out based on the optimal tree planting capacity,including 12 scenarios with different tree planting times and quantities.The analysis shows that the road green belt is more continuous after the transformation.Under the no-tree planting scenario,the number of trees declines significantly in all zones,while the road canopy coverage and ecological benefits show a declining trend but little overall change.Under the tree planting scenario,the tree canopy coverage and ecological benefits are increased to varying degrees under each scenario,but the best scenario to adopt is based on annual replanting after the first year of compliance under the optimal tree planting capacity of the road.Finally,based on the results of the above analysis,the following conclusions are summarised: Firstly,in terms of road greening patterns,their transformation and enhancement rates are mainly determined by the roadside conditions and the surrounding environment.Secondly,in terms of the structural characteristics and ecological benefits of the current road green belt,different structural characteristics of the road green belt will bring about different ecological benefits,and the ecological benefits are proportional to the growth of the number of trees;in the different ecological benefits of the individual tree species with higher value,and the total ecological benefits of the tree species with high individual value is not necessarily high.Thirdly,with regard to the prediction of future road green belt structural characteristics and ecological benefits,different timing of tree planting will lead to slight differences in road canopy coverage and ecological benefits,and post-disaster replanting is as important as early planting;different road green belt structural characteristics will lead to different time points for future changes in tree mortality and road canopy coverage;and there are large differences in ecological benefits brought about by different tree planting schemes.Based on the above summary of the research on the structural characteristics and ecological benefits of urban road green belt in Shinan District,the optimization and quantitative management of urban road green belt construction can be further optimized,and more scientific judgment and prediction can be provided. |
