Thermal Environmental Characteristics of the Shaded Area of Dense and Sparse Red Pine Canopies

Abstract

We investigated the thermal environmental characteristics within and above red pine canopies of varying plant densities in order to examine the amenity of the inside spaces of these canopies in parks.
In dense canopies, the air temperature in the canopy decreases by about 15% compared to that over the canopy, and wind speed decreases to 8-15 % of that at outside, due to thick foliage in the upper part of the crown and bush trees at the bottom of the canopy. Most of the solar radiation is absorbed at the upper layer of red pine foliage and its energy is not distributed uniformly inside the canopy, which makes a vertical temperature profile which is high at the upper part and low at the under part of the foliage. This deviated distribution of thermal storage seems to act as an insulation for heat transfer between the atmosphere and inside the canopy, which can provide amenity spaces under canopies in parks.
In the sparse canopies, there is a relatively high speed air flow which contributes to the turbulent mixing of mass and heat transfer in the canopy, and the temperature difference between the lower level of the canopy and the upper part of the foliage was slight.
As a result, in order to obtain amenity spaces in parks, i.e., to create comfortable spaces under the canopy, there is a need to consider the effects of plant density and canopy structre on the inside disributions of air flow and temperature, and then the scale of the canopy, as well as type of trees, and vegetation density must be thoroughly examined when plant distribution in parks are being designed.