Shade Trees Studied for Cooling Effects

TAIPEI, Taiwan, April 22 (UPI) — National Taiwan University researchers say they have determined which shade trees provide the best cooling in tropical and subtropical regions.

The scientists said shade trees are known to reduce air and noise pollution and offer cooling, but most studies focused on temperate urban areas, while studies for tropical and subtropical regions are limited since climate conditions and tree species in the tropics or subtropics differ from those in more temperate regions.

Researchers Bau-Show Li and Yann-Jou Lin said they evaluated the differences in cooling effects of 10 species of trees and two species of bamboo in a park in Taipei, Taiwan.

When analyzed for their cooling effect, the scientists said Chinese elm (Ulmus parvifolia) and Rose wood (Pterocarpus indicus) were the most effective, while Golden shower tree (Cassia fitula), Autumn maple (Bischofia javanica) and Swollen bamboo (Bambusa ventricosa) were the least effective.

“The shading of U. parvifolia reduced air temperature by 2.52 degrees C but that of C. fitula only by 0.64 degrees C; the difference was almost fourfold”, the scientists said.

“This research could help maximize the cooling effect of shade trees by careful selection of species based on their canopy and leaf characteristics,” the researchers said, noting although the studies were carried out in a park, the results can be applied to shade trees in subtropical urban environments.

The study is available in the early online edition of the journal HortScience.

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