都市公園樹木之健康度評估與環境因子探討-以大安森林公園為例

Abstract

樹木健康評估一般使用目視樹木評估法以量化都市樹木對人類生命財產帶來的潛在威脅。本研究以大安森林公園為基地，並應用現有樹木健康評估方法，整理出簡易目視樹木評估 (Simplified visual tree assessment, SVTA) 表格作為判斷標準，對大安森林公園內10種常見樹種（n = 214）進行健康度評估，常見樹種包括：垂榕(Ficus benjamina L.)、黑板樹(Alstonia scholaris L. R. Br)、榕樹(Ficus microcarpa L.)、阿勃勒(Cassia fistula L.)、楓香(Liquidambar formosana Hance)、茄苳(Bischofia javanica Bl.)、水黃皮(Pongamia pinnata L.)、台灣欒樹(Koelreuteria elegans Laxm.)、樟樹(Cinnamomum camphora L.)及印度紫檀(Pterocarpus indicus Willd.)。 SVTA評估指標包括樹形、樹冠、主幹、分枝、樹基的生長勢及缺陷類型評分結果。為了驗證SVTA之判視是否具有一致性，本研究將評估人員以具備樹木健康評估經驗分為有和無兩組進行測試。此外，颱風風損為常見之樹木擾動因子，本研究根據風害調查結果分析樹種、SVTA各項指標及SVTA綜合健康度與風害之關係。 根據本研究調查結果，大安森林公園10種常見樹種平均健康度(Mean ± SD)有顯著差異(P < 0.001)，排名由高至低依序為楓香(4.41±0.4)、茄苳(4.31±0.5)、黑板樹(4.01±0.5)、正榕(3.91±0.6)、樟樹(3.73±0.8)、印度紫檀(3.71±0.4)、台灣欒樹(3.71±0.9)、垂榕(3.61±0.4)、阿勃勒(3.58±0.6)及水黃皮(3.53±0.5)。對於人員評估一致性而言，無論評估人員有無經驗，兩組之間評估結果並無顯著差異，但組內之變異數較大，因此證明無法證明經驗是結果具有在一致性。此外樹冠均勻程度會因人員經驗之不同而有顯著差異。 尼莎颱風後樹木風損調查中，受損狀況可分為受損類型為枝條斷裂、半倒、全倒和主幹斷裂。本研究經由卡方檢定我們發現黑板樹、印度紫檀及垂榕較容易發生風損，而茄苳、正榕、阿勃勒及楓香相對於不容易發生風害。此外，SVTA樹木健康度與樹木颱風損傷無顯著相關，而主幹明顯缺陷指標與風害有顯著相關。

Visual Tree Assessment is used as common way to quantify potential threats of urban trees that posed to human life and property. In this study, we established a Simplified Visual Tree Assessment (SVTA) which based on the current tree health assessment and then applied on Da-an Forest park in Taipei. This study selected 10 common tree species (n = 214), including Ficus benjamina L., Alstonia scholaris L. R. Br, Ficus microcarpa L., Cassia fistula L., Liquidambar formosana Hance, Bischofia javanica Bl., Pongamia pinnata L., Koelreuteria elegans Laxm., Cinnamomum camphora L., Pterocarpus indicus Willd. as research subjects. Used indicators of SVTA in this study include growth potential, defect of tree form, tree crown, trunk, branch, and tree base. In this study, evaluators were divided into 2 groups: with experienced group and without experienced group to verify consistency of SVTA’s results. Moreover, we analyzed relations between wind damage and tree species, every single indicator of SVTA, as well as scores of tree health. It was found that, average score of tree health (Mean ± SD) have significant difference (P < 0.001) among 10 common tree species in Da-an Forest Park, which L. formosana(4.41±0.4) has highest score, following were B. javanica (4.31±0.5), A. scholaris (4.01±0.5), F. microcarpa (3.91±0.6), C. camphora (3.73±0.8), P. indicus (3.71±0.4), K. elegans (3.71±0.9), F. benjamina (3.61±0.4), C. fistula (3.58±0.6), and P. pinnata (3.53±0.5). In respect of assessment consistency, with or without experienced has no effect on result of tree health assessment. On the other hand, there is no significant difference between with experienced and without experienced groups, while the number of variations within each group are large. However, significant differences were found between with experienced and without experienced group when evaluating degree of crown balance. Damage conditions such as broken branch, lean trees, uprooted trees, broken stem of 10 tree species in Da-an Forest Park were investigated after Typhoon Nesat. A chi-square test conducted on investigation data, also indicated that A. scholaris, P. indicus, and F. benjamina are more prone to wind damage. It was also found that no significant relationship existed between tree health and wind damage and correlated relationships existed between trunk defect and wind damage.