Microclimate regulating functions of urban forests in Changchun City (north-east China) and their associations with different factors

Abstract

Microclimate regulating functions of urban trees and their associations with environmental factors and tree-growth characteristics are important for management and ecological evaluations. In this study, a total of 637 trees distributed in the Changchun urban region (ca. 400 km2, northeastern China) were sampled in four different types of urban forests (AF: affiliated forests; RF: roadside forests; LF: landscape and relaxation forests; EF: ecological welfare forests). Tree growth-related parameters and environmental factors (inside and outside the forest) were simultaneously measured, and location-dependent differences in shading, cooling and humidifying effects were assessed, along with their associations with the measured variables. We found that urban forests in Changchun reduced the incident sunlight by 74-86% and increased air relative humidity by 3-7%, on average. Air, soil, and upper-canopy temperatures were decreased approximately by 3 °C, <1 °C and 1 °C, respectively, showing a 3-dimensional cooling effect of urban forests on both air and soil. Shading, cooling and humidifying effects significantly differed among the four forest types, with AF stands showing the highest comprehensive scores for all the microclimate regulation functions. Regression analyses and redundancy analysis revealed that urban forests had much stronger effect in terms of microclimate regulation at sunny days with high temperature, and low air humidity. In general, stands with larger trees showed the higher regulating functions, regardless of the stand structure and composition. The results of this study may help urban forest management and planning aimed at maximizing their ecological services.

Keywords

• Urban Forest Types
• Shading Effect
• Cooling Effect
• Humidifying Effect