樹木目視評估危險度及健康度－以台中縣市老樹為例

Application of Tree Visual Assessment for Failure and Health Evaluation-A Case Study of Aged Trees in Taichung City and County

詹明勳(Ming-Hsun Chan) ； 王亞男(Ya-Nan Wang) ； 高毓謙(Yu-Chien Kao) ； 陳勁豪(Jin-Hau Chen) ； 林金樹(Chin-Su Lin) ； 蕭文偉(Wen-Wei Hsiao)

《國立臺灣大學生物資源暨農學院實驗林研究報告》 20卷2期 (2006/06) Pp. 99-116

https://doi.org/10.6542/EFNTU.200606_20(2).0003

摘要

老樹或行道樹若屬於公共設施，其設置及管理與人民生命、身體、財產息息相關，現場樹木管理人員有義務確保行人的安全，然而老樹或行道樹崩壞傾倒產生危險衍生法律責任，管理人員卻無法理解判決所依據之技術基準，而砍伐了不需砍伐的樹木，並胡亂對樹木進行修剪或外科手術。本研究應用樹木目視評估台中縣市老樹，提供老樹或行道樹危險度及健康度評估技術基準。樹木目視評估法主要由生物力學的角度由「外觀評估」及「精密檢查」程序，屬於非破壞性檢測。
外觀評估依據樹勢、樹形、枝的伸長量、枝梢端枯損、枝葉密度、樹皮的狀態進行衰退度的評價，並將衰退度分成5級，良＜0.6、稍微不良0.6-1.2、不良1.2-1.8、明顯不良1.8-2.4、快要枯死2.4以上；精密檢查以腐朽率評估健康度分成4級，1級腐朽率0-25%，2級朽率26-50%，3級腐朽率51-75%，4級腐朽率76-100%。藉由衰退度與健康度評估平均值為總合評價分成健全、需注意、要注意、危險4級。
本研究以台中縣市老樹共16棵，進行樹木非破壞檢測評估危險度及健康度，結果顯示外觀評估衰退度4級有2株屬於明顯不良，3級有4株屬於不良，2級有10株屬於稍微不良。精密檢查樹幹腐朽健康度3級有1株，2級有1株，1級14株，2株芒果樹幹腐朽率，健全半徑及腐朽半徑比超過30%門檻值分別為42.04%和64.45%，有折斷的危險。。藉由樹木目視評估法檢測總評價沒有達到危險第4級，2級需注意的有13株，3級要注意的有1株芒果及2株樟樹。

關鍵字

樹木目視評估 ； 危險度 ； 健康度 ； 老樹 ； 司法判決 ； 非破壞評估

並列摘要

Aged or shaded trees belong to public facilities. Management of these trees is closely related to the people's life, health and property. Managers of these trees are responsible to ensure the safety of pedestrians, since these trees pose a potential risk for the pedestrians. In addition, possible damages to properties of the third party by the falling of aged or shaded trees compose liability for those tree managers. However, those taking care of shaded trees don't understand technical standards and thereby log and trim trees arbitrarily. This paper employs tree visual assessment to evaluate aged or shaded trees in Taichung city and country and offers technical standards for judging the danger and health of aged or shaded trees. This technique is a non-destructive evaluation and is composed of two procedures: surface assessment and accurate examination.
Surface assessment includes the gesture and shape of trees, the extending length of branches, the damage of the edge of braches, thickness of leaves and the degree of aging of the barks. The degree of aging can be classified into five types: better ＜0.8, slightly worse ＜0.8-1.6, worse ＜1.6-2.4, significantly worse ＜2.4-3.2 and immediately dying ＜3.2. According to the degree of decay, accurate examination is ranked into four levels: the first level ＜25%, the second level ＜26-50%, the third level ＜51-75%, the fourth level ＜76-100%. A comprehensive evaluation based on the degree of decay and health is divided into four levels: healthy, noticeable, significantly noticeable and dangerous.
According to the surface assessment, four are significantly worse of the third level of decay; nine are worse of the second level of decay and three are slightly worse of the first level of decay. As far as the accurate examination of truck decay is concerned, one is in the second and third level and 14 are in the first level. Judging from the comprehensive evaluation of tree visual assessment, three aged trees are in healthy condition, two are in noticeable condition, and two mangoes are in substantial condition. None is in the dangerous condition. It is notable that the two mangoes might break because of the decayed trunk over the threshold (30%).

並列關鍵字

Tree visual assessment ； Failure ； Health ； Aged tree ； Legal judgments ； Nondestructive evaluation