Please use this identifier to cite or link to this item:
Studies on Casual Factors and their Management of Tree Falling by Typhoon at Taipei Areas
wind-fallen trees,Causes of tree failure,Tree risk assessment,Wood rot fungi,Post-typhoon treatments,
|Publication Year :||2018|
|Abstract:||一個適合的樹木健康照護(Plant Health Care,PHC)計畫，應該就不同的國家或地區需要就當地氣候環境，以及逆境例如颱風等，並配合其都市樹木的功能加以規劃。臺灣北部為副熱帶季風氣候，每年夏季均受到颱風吹襲影響，故都市樹木之管理必須包含颱風風害預防的考量。
本研究共診斷調查2015-2017三年間3個中度颱風，於臺北地區所造成之樹木風倒狀況。樹木受風倒者共有637筆，共分成四個風倒級別，分別為全倒286筆（44.9%）、莖斷132筆（29.0%）、枝斷146筆（22.9%）以及傾斜20筆（3.1%），當中以榕樹(Ficus microcarpa)最常見，其後依序為垂榕(Ficus benjamina)、台灣欒樹(Koelreuteria elegans)、白千層(Melaleuca leucadendron)、小葉欖仁(Terminalis mantaly H. Perrier)。並嘗試利用3個颱風對樹木造成的風倒級別及最大切風風速與樹木莖斷及枝斷之關聯性作分析，結果皆未能證明颱風強度及最大切風風速對預測樹木風倒災情有指標性作用。後以樹冠寬與風倒級別作分析，發現樹冠寬／胸徑值比值介乎5.00到19.99之間，較容易受風倒影響。同時，樹冠形狀為展開及尖錐形的樹木，立於人行道旁的行道樹，相比其他樹冠形狀及立地位置的樹木，更容易造成風倒。
在臺北地區颱風造成樹木風倒害因的統計及分析中，資料倒分析分成單一害因及複合害因，經3次颱風資訊比較後，害因常見以樹冠過重、受腐朽影響、生長逆境、患有褐根病為主，樹木淺根、處於風場、白蟻蛀食為副。經卡方統計及類別變項交叉分析之勝算比，可知行道樹、樹木淺根、處於生長逆境的樹木遇上風害時傾向發生全倒。在災後三個月及生長季後進行災後調查，有經災後處理的樹木之生長勢恢復能力明顯比沒有經災後處理的樹木為高。同時，目前的災後處理方法使樹木生長勢恢復能力，無論在四個立地位置之中，皆比期望值高。唯盾柱木(Peltophorum pterocarpum)、鐵刀木(Senna siamea)、豔紫荊(Bauhinia x blakeana Dunn.)需要進行災後的結構性修剪。
經研究發現菲克利10%乳劑80 ppm、撲克拉25%水基乳劑40 ppm及普克利25%乳劑90 ppm效果最佳，在田間試驗中即利用上述三種配方在每200平方毫米的木材面積下以50mL藥劑處理腐朽菌，於預防及治療測試上都達到90%以上之防治成效。
A flexible Plant Health Care program, PHC, has to consider the difference and extreme climates in countries and cities, such as typhoons, in order to manage the urban trees and maintain their functional contributions. Because of the subtropics monsoon and humid climate, five to six typhoons usually attacked the northern Taiwan every summer. Therefore, typhoon is an essential consideration for urban trees management program in Taipei
A 3-year study was from 2015 to 2017, to diagnose and survey the wind-fallen trees caused by three typhoons with intensities not lower than moderate at Taipei areas. A total of 637 cases of wind-fallen trees were diagnosed and recorded. The fallen trees were separated into 4 tree falling levels, including 286 fully fallen cases (44.90%), 132 trunk broken cases (29.04%), 146 twig broken cases (22.91%), and 20 leaning cases (3.13%). Among 637 cases, the dominant tree species in decreasing series, are Chinese banyan (Ficus microcarpa), Benjamin tree (Ficus benjamina), Taiwan golden-rain tree (Koelreuteria elegans), Cajeput tree(Melaleuca leucadendron) and Madagascar almond (Terminalis mantaly H. Perrier).
The study tried to reveal the relationship between trees falling levels as well as numbers of trunk broken or twig broken and the maximum wind speed. Results showed that the maximum wind speed played no significant effect on tree falling level or numbers of trunk broken or twig broken. This study, however, discovered that those trees with canopy-width/DBH ratio between 5.00-19.99, or trees with either open shape or sharp canopy shape, are more easily suffered by typhoons.
The study also determined the major and minor causal factors of tree falling. The main causal factors usually are trees with too heavy crowns, infected by wood rot fungi, with environmental stress, or with brown root rot disease. The second causal factors are trees with shallow root systems, growing within strong wind field, or attacked by termites.
According to the results of Chi-square test and odd ratio analysis, road side trees, trees with shallow root systems, and trees growing with environmental stress, have higher potential for fully falling during typhoons, other than trunk broken or leaning. The survey of efficacy for post-typhoon tree treatment after 3-months or after the next growth season revealed that the present post-typhoon treatment for wind-fallen trees were effective and beneficial for tree vigor recovering. The observed recovered numbers of trees are more than the expected ones, wherever they are growing in one of 4 planting sites. The survey finally suggested that a structural pruning is necessary for yellow flame tree (Peltophorum pterocarpum), Kassod tree (Cassia siamea), Hong Kong orchid tree (Bauhinia x blakeana Dunn.) after typhoons.
The study also focused on the issue of wood rot fungi. After isolating 35 common rot fungi from 52 wind-fallen tree samples, 6 stronger fungi were screened from them by comparing their enzymes activities for lignin and cellulose degradation. Those wood rot fungi were inoculated onto wood chips from 3 tree species for 30 days to determine the weight loss rate caused by the fungi. Results showed that the wood chips showed different level of dry weight loss and different color change. The six selected wood rot fungi can be reisolated and thus fulfilled the rules of Koch’s postulates. In order to find out the most suitable fungicides for wood rot control, a series of experiments were done.
Nine fungicides with different action mode or mechanism were chosen and tested each at dilution of 10,000X, to find their mycelium inhibition rates. Then five of them were determined for their half maximum inhibitory and half lethal concentration when each is diluted into 12 serial concentrations in PDA medium, and to test their mycelium inhibition rates against the six wood rot fungi.
The study results showed that hexaconazole (10% EC) at 80 ppm, prochloraz (25% EW) at 40 ppm, and propiconazole (25% EC) at 90ppm, are the most effective fungicide formulations for field application. A 50 mL of them were used to spray on maple wood block each for a 200 cm2 wood surface. Results showed that for preventing or curing the wood rot fungi, all three fungicides performed at least a 90% control rate in the field tests.
|Appears in Collections:||植物醫學碩士學位學程|
Files in This Item:
|50.8 MB||Adobe PDF|
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.