哈尔滨城市森林遮荫和降温增湿效应差异及其影响因素

Shading,cooling and humidifying effects of urban forests in Harbin City and possible association with various factors

在哈尔滨市内选取4种不同林型(单位附属林、道路林、风景游憩林和生态公益林)共183块样地,通过实地测量样地内主要树种的测树因子和样地内外环境因子,定量研究了不同林型在遮荫、降温、增湿效应的差异及其与外界环境、树木生长特征之间的关系。结果表明:城市森林遮荫、增湿效应程度分别为77%~90%、3%~6%;水平降温约3℃、土壤降温1~2℃;而垂直降温多表现为冠层温度低于林内温度1℃以内;4种不同林型遮荫、降温、增湿效应差异显著,总效益综合得分显示风景游憩林比其他3种林分平均高19%;城市森林遮荫、降温、增湿等生态服务功能在高温、晴朗和低湿环境下更强;树高、枝下高、冠幅和胸径对树木遮荫、降温增湿效果有显著影响,且多表现为高大树木具有更明显的生态服务功能;不同城市森林类型具有明显的微气候调节相关生态服务功能差异,对于风景游憩林应继续维持其高生态服务功能,对于环境调节能力较低的森林类型应加强管理。

In this paper, a total of 183 plots distributed in Harbin urban region were selected, and 4 different forest types （ affiliated forests, AF; roadside forests, RF; landscape forests, LF and ecological welfare forests, EF） were classified, and tree growth-related parameters and envi- ronmental factors （ inside and outside the forest） were measured simultaneously. The aims of this study were to find differences between the 4 forests types in shading, cooling and humidifying effects and their associations with the environmental and tree growth characteristics. We found that urban forests produced a 77%-90% reduction of sun lights （ shading effect） and a 3%-6% increase in relative humidity （humidifying effect）. The forests had a horizontal cooling effect of around 3 ℃ lower than open sites （outside forests）. Soil cooling effect was 1-2 ℃ lower under canopy than in outside forests. The vertical cooling effect characterized as canopy temperature about 1 ℃ lower than under canopy temperature. Shading, cooling and humidifying effects signif- icantly differed among the four forest types. The comprehensive scores for all these microclimate regulations demonstrated that LF was 19% higher than the other three forest types on average. Ur- ban forests had much stronger regulating functions at high air temperature, low air humidity and sunny days. Moreover, four tree-growth factors （tree height, canopy area, clear bole height and diameter at breast height） had significant influences on temperature reduction and relative humid-tion ability.