大安森林公園樹木多樣性與健康風險評估調查

An investigation of tree diversity and health risk assessment in Daan Park

王義仲(Yi-Chung Wang) ； 羅翊瑄(Yi-Xuan Lo) ； 林志欽(Chih-Chin Lin)

《華岡農科學報》 44期 (2019/12) Pp. 57-71

摘要

本研究之林木多樣性以10－20－30規則來進行檢測，同時使用目視樹木健康評估法對台灣台北市大安森林公園內胸徑大於15公分樹木進行50%之逢機取樣調查，利用評估表對樹木的根部、冠層狀態、樹冠密度、活冠層比例、樹冠有無梢枯、健康狀態進行健康度評分，依綜合評分將樹木的安全度分為4個等級。調查結果顯示總共有31科54屬75種1,958棵樹。就林木多樣性之評估結果，整體而言大多不符合10－20－30規則，此為單一樹種的數量不應超過總數量的10%，歸於同一屬的數量不應超過總數量的20%，屬於同一科的數量不應超過總數量的30%。研究結果得知數量最多的為黑板樹（Alstonia scholaris）有301棵，佔15.37%，其次為榕樹（Ficus microcarpa）268棵，佔13.69%、垂榕219棵，佔11.18%，這3種樹種即佔了54.24%，數量高於上述標準，代表著雖然林木多樣性豐富，單一樹種的數量卻只集中在3種樹種，其他種類雖多卻每種只有零星幾棵，桑科榕屬的樹木所佔比例過高，未來可補植其他種類較少的樹種來提升生物多樣性。在健康風險評估方面判定為低風險的樹木有778棵佔39.7%，中度風險的樹木有1,148佔58.6%，高風險的樹木有32棵佔1.6%。由於公園生育地土壤固結密實導致林木生長不佳，為解決此問題需要鬆土並適當地增加肥料，且減少人為踩踏導致根部受傷，強度更大的使用規範應被施行，才能提升樹木活力，降低塌壞風險。

關鍵字

大安森林公園 ； 樹木多樣性 ； 樹木健康風險評估 ； 目視樹木評估法

並列摘要

Urban afforestation can be easily seen everywhere in Taiwan. The afforestation sites are located in the scope of human activities. Man-made interference and wrong planting methods can affect the growth and health of trees, which cause destructive trees or falling dead branches. If an unfortunate incident occurs, that the related authorities must take responsibility and provide compensation for the losses human life and properties. Therefore, tree risk assessment should be evaluated for all trees planted in the public areas to find out trees which have potential risks to make early prevention. This investigation is expected to conduct a investigation of more than 50 % tree sampling randomly which diameter of breast height is over 15cm in the Daan Park using the visual tree assessment method (VTA). Meanwhile, 10-20-30 rule was applied to check the tree diversity so as to analyze the replanting tree species. Using the assessment form to investigate the health of the tree roots, canopy status, canopy density, live canopy ratio, crown tip dryness trees, and health status all trees are evaluated were executed in this study. According to the total scores, the safety degree of trees is divided into low risk, moderate risk, high risk and extreme risk. The survey covered 1958 trees in 31 families, 54 genera and 75 species. Results of the survey showed that the greatest number of trees were Blackboard tree (Alstonia scholaris) followed by Chinese banyan (Ficus microcarpa) and Benjamin Tree (Ficus benjamina). Overall, Daan Park now does not conform to the 10-20-30 rule because the proportion of trees in the Moraceae, Ficus is too high. In the future, other species of lesser species should be replanted to enhance tree diversity. Seven hundred and seventy-eight trees (39.7 %) were rated as low risk, 1,148 trees (58.6 %) as moderate risk, and 32 trees (1.6 %) as high risk. According to the survey results, the high-risk tree species is Golden Shower Tree (Cassia fistula) and Blackboard tree, but, the rate was judged to be high risk is low. Due to soil consolidation in the habitat of this area, the trees are not growing well. In order to solve the problem, it is necessary to loosen the soil and reduce Man-made trample which causes root injury. In this way, the vitality of the trees can be improved and the risk of tree failure can be reduced.

並列關鍵字

Daan park ； tree diversity ； health risk assessment ； visual tree assessmen