关键词: 城市绿地, 群落结构, 降温增湿, 郁闭度, 三维绿量, 北京市

Abstract:

With rapid urbanization in China,large areas of vegetated surfaces have been replaced by impervious built surfaces. The development of urban heat islands （UHIs）has recently become a critical environmental issue in many cities. Fortunately,trees and vegetation in an urban environment can greatly improve microclimates and mitigate UHI development by reducing summer air temperature. Although many recent studies have observed such ecosystem services as temperature reduction and humidity increase by urban green spaces,the relationship between community structure of urban green space and air temperature reduction and humidity increase remains unknown. This study investigated 24 typical green space communities and observed their role in temperature reduction and humidity increases,and the relationship between these roles and canopy density and green biomass. The results showed that green areas in Beijing reduce summer air temperature by 0.2~2.0\begin{array}{c}℃\end{array},and increase humidity 0.20%~8.26%. The urban green space with a Tree-Shrub-Grass structure can reduce temperature the most,followed by Tree-Grass and Tree. However,the urban green space with Tree structure increases humidity more than Tree-Shrub-Grass. There were clear relationships between canopy density and green biomass of urban green space and such roles as air temperature reduction and humidity increase. At the community scale,the canopy crown closure of green spaces had greater effects on urban temperature and humidity than green biomass. This study suggests that only when the canopy crown closure ranges from 0.60 to 0.85 and 3D green biomass density is larger 5m³/m² can urban green spaces provide maximal microclimatic benefits.

Key words: urban green space, community structure, temperature reduction and humidity increase, canopy density, three-dimension green quantity, Beijing City