Research On Optimizing Street Trees Of Harbin Pedestrian Street Based On Thermal Comfort

High-speed urbanization led to urban environmental problems such as “Urban Heat Island Effect”, and the effect of micro climate regulation, one of the landscape elements, gradually aroused researcher’s attention. Urban pedestrian streets not only function as traffic, but also as an important place for recreation activities, and it’s thermal comfort of the environment for outdoor public space of city development is of great significance. Based on four typical pedestrian streets of Harbin, this paper adopts the method of field measurement and comparative analysis, and explores the thermal comfort which influences by pedestrian street trees species and planting methods, in order to providing the basic qualitative and quantitative data for optimization street trees of Chinese cold areas.First, relative basic research. Clarifying the characteristic of seasonal pattern in Harbin; analysing the factors that affect microclimate thermal comfort like the layout of urban pedestrian streets, space geometry, the materials of underlying surface, greening patterns; exploring the principles of how street trees modulate microclimate thermal comfort. Second, field measurement. Based on the typicality of the layout of urban pedestrian streets, space geometry, the materials of underlying surface, greening patterns, four test sites: Wuming Street, Fuhua Street, Fuxing Street, and the Central Street, were measured. Five kinds of commonly representative street trees in Harbin, Populusalba×Populusberolinensis; Salix matsudana; Ulmus pumila; Acer Saccharum; Picea koraiensis were chosen as samples. It’s measured in summer(August) and winter(November), 1 minute per 3 days from 8:00 to 17:00 as a period. In summer, the daily changes of microclimate conditions in which 5 kinds of trees and street trees located in the 4 pedestrian streets were measured respectively. In winter, the daily change of microclimate condition of every single evergreen tree species were measured. In the aim of fitting out the thermal comfort index of PET, the test content mainly includes four climate factors: air temperature, humidity, wind speed, and solar radiation intensity. Finally, data analysis. On the basis of the testing data, this paper(1) analyses adjustment of different street single-tree in Harbin during winter and summer modulating the microclimate factors, such as temperature, humidity, wind speed, solar radiation and the microclimate of thermal comfort(PET), and provides the corresponding tree species selections for heat comfort optimization.(2) using SPSS software, analyses biological factors of street trees- height, crown breadth, canopy density, ramification points- and the correlation of the above four kinds of microclimate elements, interpretating the the relevance of biological characteristics of street trees and the influence of thermal comfort.(3) analyses the adjustment of different street determinant-trees in Harbin during summer modulating the microclimate factors, such as temperature, humidity, wind speed, solar radiation and the microclimate of thermal comfort(PET); compares the different ways of planting which have different impacts on thermal comfort of microclimate, explores the best way of planting.