以簡易目視評估法進行樹木風險評估──以大安森林公園為例

Application of Visual Tree Assessment for Health and Failure Evaluation - A Case Study in Daan Park

樹木在都市環境中能帶來固碳、減緩熱島效應、增進景觀等多重效益，然而若非栽植於適合的環境或是缺乏良好的維護管理，除了無法發揮其效益，更可能影響其健康狀況，甚至存在危害人員及財產損失之風險。而透過目視樹木評估法，能夠以非破壞性的方式進行樹木風險評估，瞭解樹木健康度及危險度，以提供樹木管理單位訂定管理策略及參考。本研究以大安森林公園全區及周圍行道樹胸高直徑大於5公分的樹木，作為本次研究之對象，以目視樹木評估法中的快速評估法檢視其生長狀況及健康度。研究結果顯示，所有受評估樹木中（5,617株），需「專門診斷」者有587株（10.45%）；需「緊急處理」者有119株（2.12%）；需「一般處理」者有407株（1.25%）。使用迴歸分析，發現胸徑越大，專門診斷之比例越高。「專門診斷」及「緊急處理」之樹木，在空間上皆呈現顯著之群聚情形。不同樹種間的異常情形亦有所差異，應採取不同的管理措施。透過本研究瞭解大安森林公園樹木之健康情形，期望作為大安森林公園樹木經營管理策略之參考，提升樹木健康、降低危害之風險。

Trees in the urban environment can produce multiple benefits such as carbon sequestration, reduction of the heat of the island, and enhancement of landscapes. However, if they are not planted in a suitable environment or lack good maintenance and management, they will not be beneficial and might affect their health even putting people and property at risk. Through the visual tree assessment method to do tree risk assessment, health and danger degree of trees can be understood by a non-destructive way, so as to provide a reference for the tree management unit in formulating management strategies. This study takes the trees in Daan Park as research objects. We evaluate the trees with Visual Tree Assessment (VTA) to view their growth and health. The result shows that among all the trees assessed, 587 (10.45%) need“specially diagnosis,”119 (2.12%) need“emergency treatment”and 407 (1.25%) need“general treatment.”Via regression analysis, it was found that the larger the diameter at breast height (DBH), the higher the proportion of specialized diagnoses. The trees in need of“special diagnosis”and“emergency treatment”show significant clustering in space. The abnormal situation between different tree species is also different, and different management measures should be adopted. Through this research to understand the health of trees in Daan Park, hopefully that will be used as a reference for the development of tree management strategies in Daan Park in order to improve tree health and reduce the harm risk.