Research On Ecological Benefits Survey And Construction Management Countermeasures Of Shanghai Typical Urban Green Streets

As an important part of the urban green space system, urban greenstreets plays an important role in solving urban environmental problems,improving the urban ecological environment. One key to betterconstruction and management of urban green streets is to understand therelationship between spatial structure and ecological benefits.In this study, the typical urban green street of Shanghai was selectedas an object, based on the analysis of investigation and analysis of thepresent situation overview of Shanghai urban green street, six typicalurban green streets in different street trees and different coverage ratewere selected, carbon-fixing and oxygen-releasing, light shading,temperature decreasing and humidification, negative air ionsconcentration was choosed as an indicator, through the measurement andanalysis of the ecological benefits, to explore the relationship between thestructural characteristics and ecological benefits of urban green streets. Meanwhile, it also could propose construction and managementcountermeasures of Shanghai urban green streets. The main conclusionsare as follows:1. The four benefits, carbon-fixing and oxygen-releasing, lightshading, temperature decreasing and humidification, and negative air ionsconcentration, were mainly controlled by leaf area index (LAI) andcanopy closure. The two and the above four benefits were significantlypositively correlated. They were the important structural parameters thatindicated the ecological benefits of urban green streets.2. As typical urban street trees, the net photosynthesis rate ofPlatanus acerifolia was significantly lower than Cinnamomum camphorain summer, the diurnal variation of net photosynthesis rate ofCinnamomum camphora showed a single peak curve, while Platanusacerifolia showed a bimodal curve, the diurnal variation because thetemperature is too high that stomatal closure enter "lunch break" state.The mean fixed carbondioxide and release oxygen per unit land areashowed positive correlation with coverage rate, that the green street withhigher coverage rate and LAI, would perform greater ablity ofcarbon-fixing and oxygen-releasing. During the planning andconstruction of urban green streets, the plant materials with strongcarbon-fixing and oxygen-releasing capacity should be choosedaccording to activity places around. 3. Urban green streets show significant light shading effect, the lightintensity decreases with the increasing coverage. In the hot summerweather, light intensity so strong during11:00to15:00that people’soutdoor activities are affected. Through the absorption and reflection ofsolar radiation by tree crown, light intensity together with the ambienttemperature are reduced and thus activity time in the shade of the trees iscreated.The light shading effect is mainly determined by the spatial structurecharacteristics of of typical urban green streets. LAI and canopy densityshowed significantly positive correlation with the light shadingpercentage, while plant spacing was significantly negative correlated.When AI=2.4, CC=82.85%, AS=6m, the light shading percentage ofthe samples reached80%. Bigger and denser canopy of arbors should beused during the greenway construction. Reasonable configuration,scientific management of plant space, and increase the tree-lined spacecanopy density in the premise of uninfluence of plant growth, then thelight shading effect of the urban green streets and the microclimateenvironment of the summer are improved.4. In summer, green streets present significant temperaturedecreasing and humidification effect. The daily average maximumtemperature difference inside and outside the green streets was2.8℃,humidity difference was5.7%. The urban green street with higher coverage rate performs greater temperature decreasing and humidification,human comfort index is lower, the body feels more comfortable. Thecritical coverage rate of urban green streets for the obvious effect ontemperature decreasing and humidification is from70%to90%. Underthe same conditions, Cinnamomum camphora acts stronger capabilitiesthan Platanus acerifolia on temperature decreasing and humidification.5. Negative air ions concentration of urban green streets showedcertain negative correlation with traffic flow. Compared with forests andpark green space, negative air ion concentration of urban green streets islower, and air quality is poorer. CI value is mainly affected by the impactof the external environment, vehicle exhaust, dust and anthropogenicinterference, reduce the capacity of the air purifier, resulting in poor airenvironment quality of the green street. CI value was less than0.29,classified to be slight pollution. LAI, canopy density, spacing and CIvalues has some correlation, but the impact is limited.Urban green streets play a variety of ecological functions,considering the influence of spatial structure on ecological benefits, highcoverage, high canopy density of spatial structure is better, to helpenhance the eco-efficiency, and improve the urban environment.