Research On The Ecological Function And Optimization Countermeasures Of Street Trees On Urban Main Roads

The rapid development of the city has led to the rapid development of motor vehicle road traffic.The emission of exhaust gases from cars not only aggravates the greenhouse effect,but also brings other environmental pollution problems.Street trees are an important part of greening the entire urban road space,they block strong direct sunlight in summer,effectively improve the microclimate of the entire city,and also have good shading and effective temperature adjustment.Not only that,it can also absorb toxic substances in the air,fix carbon and release oxygen,retain dust,reduce airborne bacteria,and reduce noise.However,through the analysis of the urban road green status quo of street trees in Licheng District,Jinan,it is found that urban road landscape planning pursues the appreciation and growth speed,and not enough attention is paid to the ecological functions of street trees.The research is applicable to the characteristics of the local situation and provides guidance and optimization for the selection of trees in the streets,which is an important central theme of road greening today.Therefore,a quantitative study on the ecological functions of street trees was carried out in Licheng district,and on this basis relevant strategies for road greening were proposed.This paper selects 6 main urban roads(Jingshi East Road,Century Avenue,Gongye South Road,Gongye North Road,Fenghuang North Road,Tourism Road)in Licheng District of Jinan City as the basic research objects,and selects the street trees in the green belt of the road for investigation.The research content of this article includes:the tree species and configuration of street trees,their growth status and the quantitative analysis of their ecological functions.Analyze and summarize the tree species selection to meet the requirements of different ecological functions.The main research results are as follows:1.Determination of the amount of greenness of different sidewalk trees in the road:the differences in the canopy structure,tree height,and crown width of different sidewalk tree species lead to different leaf area indexes.The order of the leaf area index of 13 street tree species is Platanus acerifolia>Ginkgo biloba L>Fraxinus chinensis>Catalpa bungei>Populus tomentosa>Ligustrum lucidum>Cedrus deodara>Acer mono Maxim>Sophora japonica>Koelreuteria bipinnata Franch>Prunus Cerasifera>Pinus bungeana>Sabina chinensis.By sorting the green quantity of 13 kinds of street trees,the green quantity is as follows:Phyllanthus vulgaris>White wax>Sophora japonicus>Cedrus>Pentatum quinquefolia>Huangshan Luan>Ligustrum lucidum>Calpa tree>Populus tomentosa>White bark pine>Ginkgo>Purple leaf plum>Juniper cypress.According to the analysis results,the ranking of green quantity and the ranking of leaf area index between different tree species are different.Analyzed from the leaf area,the dominant tree species,such as Fatong,Ginkgo and Catalpa,have high landscape and ecological value.Analyzing from the perspective of the green quantity of plants,the green quantity per plant of Fatong and Chinese Sophora japonica is relatively high,and the green quantity of different tree species is very different.2.Through field investigation regression analysis was carried out on the various parameters of street tree species and the leaf area index in Licheng District,and a functional relationship between each index and the leaf area index(LAI)was established.Result:The crown width,diameter at breast height,height of tree species and green quantity of different tree species are correlated.3.Determination of the amount of dust retention of tree species(1)The dust retention capacity of tree species will reach the peak after a period of accumulation.Jinan is rainy in summer,and the particles stay on the leaves for up to a week.Among the tested tree species,and the results were as follows:Phyllostachys vulgaris>Populus tomentosa>Ginkgo biloba>Catalpa tree>Pentagonal maple>Sophora tree>Ash;the cycle of a single evergreen tree The order of the dust retention in the house is:juniper>L.lucidum>cedar>white bark pine.Among the tested deciduous trees,the single tree with the highest amount of dust retention was the Chinese Sophora japonicus,and the smallest was the White wax.The amount of change in the amount of dust retention increases with time.The amount of dust retention of these tree species does not increase linearly every week,but gradually decreases.When the amount of dust retention reaches a certain saturation state,the amount of dust retention will not change until the next rainfall.(2)Tree species such as Populus tomentosa and Platanus vulgaris have strong dust retention capacity per unit area.Because of their larger leaf area,the plant's dust retention capacity increases;although the dust retention capacity per unit leaf area of pewter is less,the total plant leaves after adulthood.The area is large,so the dust retention capacity of the whole plant is larger.The difference in the ability of adsorbing and retaining particulate matter between tree species has an obvious relationship with the biological characteristics of the tree species and the structure of the leaf surface.(3)The dust-retaining ability of the same plant at different times in the same day does not have a certain rule.(4)The amount of dust held by the same plant on different roads,and some roadside trees in Licheng District have a single tree species,resulting in the same tree species in the sample plots only Fatong.Therefore,a number of determinations were made on Farton,and the average value was used for determination.The same plant has different dust retention capacity per unit leaf area on different roads.4.Measurement of cooling and humidification functionDifferent trees have different cooling effects.Among them,Populus tomentosa>Platanus vulgaris>Luan tree with the most obvious cooling effect.Ginkgo,purple leaf plum,Ligustrum lucidum and juniper,cedar,white bark pine and other tree species have poor cooling effect.Both Phyllostachys vulgaris and white wax have higher density of branches and leaves,higher and relatively large crowns,which are easy to block sunlight and have an obvious cooling effect.Conversely,plants with poor cooling effect have high crowns but less crown layers,smaller crown widths,and smaller leaf areas,so the cooling effect is not obvious.5.As the research objects of noise reduction function,such as white poplar,platanus,luan tree,white bark pine,cedar,purple leaf plum,catalpa tree,etc.,the measurement results are analyzed and compared.The results show that the larger the crown of the tree crown,the height of the tree species.The lower the value,the stronger the noise reduction function of the tree species,which can effectively reduce the noise pollution of urban roads.Reduce the direct impact of traffic noise on peoples daily production and living.Comparing the noise attenuation changes of green belts with different widths and different structures,the noise reduction effect of arbor,shrub and grass plants is the best.6.The leaves of 13 greening tree species from 6 roads were sampled,and their ability to absorb SO₂ was studied by spectrophotometer-barium sulfate turbidimetric method.It was found that the sulfur content of leaves of various tree species at different sampling points differed greatly.The sulfur content in the leaves of the plant and Jinan Iron and Steel Plant is high in high pollution areas,and the sulfur content in the leaves in the school area(control group)is relatively low.The sulfur content measured in the leaves of Populus tomentosa and Platanus vulgaris is relatively high.The sulfur content of the same tree species varies with the degree of pollution.The higher the pollution degree,the higher the sulfur content in the leaves is positively correlated.The specific performance is severely polluted area>moderately polluted area>lightly polluted area>control group.An optimization strategy is proposed for the selection of street trees in Licheng District and the construction of street trees and green spaces.7.Through a comprehensive analysis of the ecological functions of urban street trees,it is determined that the dominant tree species in Licheng District is Phyllostachys vulgaris,which has the best ecological benefits;tree species with better ecological benefits include white poplar,cedar,juniper,locust,and white wax;the ecological benefits are average The tree species are five-cornered maple,Ligustrum lucidum,Catalpa tree,and Luan tree.An optimization strategy is proposed for the selection of street trees in Licheng District,and the construction of street trees and green spaces.