Research on The Girdling Roots of Three Street Trees in Taichung

• Main Authors: Jheng-Syun Jhong, 鍾政勳
• Other Authors: Chin-Yu Chang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/08359120062927062121

碩士 === 東海大學 === 景觀學系 === 97 === Girdling roots refers to the ones growing around the tree trunk, with time, both the roots and the trunk would grow thicker, to the point when they pressure each other, causing the tree to grow weak and even wither. On the other hand, the area that is restrained by the girdling root, cannot grow thicker and ends up shrinking, under strong wind the tree may bend at the point of shrinkage, causing threat of potential damage towards the surrounding people, cars and buildings. This study focuses on three common shade trees in Taichung: corel tree (Erythrina indica), white barkfig (Ficus benjamina) and green maple (Alstonia scholaris), respectively. The study focuses on the forming condition of girdling roots and its influence variables. The results of the study could be used for reference in planting designs and methods to reduce girdling roots, and an early solution for the maintenance personnel of the shade trees that have already developed girdling roots to handle such condition, in order not to affect the growth of trees and cause potential threat. Methods used is to first do a field observation on all common shade trees in Taichung City, then focusing on the corel tree, white barkfig and green maple due to the more common condition of girdling roots for an actual examination. The study shows that the ratio of girdling root forming on corel tree, white barkfig and green maple are 64.2%, 75.9% and 57.08%, respectively. There is a high positive relation between the formation of girdling roots and the tree types trunk diameter, which indicates the older the tree, the larger the trunk diameter, and thus the higher the rate of girdling roots forming. As for the relation between different plug areas of same trunk diameter’s girdling root ratio, as well as that of between same plugging area, different trunk diameter and girdling root ration, only shows small portions of significant relation; one plausible reason could be the insufficient sample numbers. A prediction model was in the end established of the amount of girdling roots forming on white barkfigs’ plugging, the prediction accuracy was 39.8%, the base area of the trunk was a higher influence variable, trunk diameter followed; as for the prediction rate of girdling root’ volume proportion within plug area, had an accuracy rate of 53.3%, the top two variables were trunk base area, and plug length. The prediction model of girdling roots volume of green maples, all variables had an below standard influence and therefore the model did not stand. While the prediction model of girdling roots’ ratio amongst plug area, has a prediction rate of 18%; amongst which the plantation in the plug area was the variable with the highest influence, followed by the trunk circumference.