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Dear Station Members,
The news cutting below has described the effect of the first no. 3 typhoon in HK in the period of June 2, 2011.
By this time, many of the public trees in HK have already undergone Tree Risk Assessment (TRA) as required by the Govt & housing management. It would be interesting to measure the accuracy of these TRA as a feedback on the work of our local Arborists.
Were obvious structural defects spotted? Were recommendations genuine & accurate? Were those trees that can be saved simply cut down to achieve "zero risk"? Were potential dangers addressed in the TRA?
Research in North America has shown that even healthy branches can break when wind speed exceeds 70 kmh for temperate trees under experimental conditions. Australia has also conducted vast amount of research on Tree Biomechanics to study Tree Failure in wind. A lot of such research can be found in ISA public education programs. Tree Biomechanics is a very complicated subject & the mathematical modeling there can lose anyone without a scientific background. Arborist Profession on its own is scientifically based with little inclination in art. Arboriculture is also completely different from most other greenery subjects especially those with design inclination. They cannot replace us.
If anyone asks a seasoned Arborist for his technical opinion on TRA, one might get an answer on uncertainties on absolute basis. The seasoned Arborist may not be able to "define" a critical time period for branch failure, or under what wind condition that a leaning tree may topple. All he can say may be his knowledge to advise guidelines & speculations. His experience & years of practice may count more than scientific quotations. Therefore, when we talk about Arboriculture as a scientific subject, we also need to understand that we are dealing with a living organism which changes its conditions in time, & would react to the environment. Arboriculture is not an absolute science.
Tree Failures invite insurance claims & maybe law suits. Prevention is always better than cure. Designing & installing the trees right are the first step. We always recommend any Tree planting is to be reviewed independently by a qualified Arborist. Removing every tree with the slightest harm is an escape for the incompetent to avoid professional liabilities. The balance of keeping a tree against risk depends on the tolerance of risk itself.
Therefore, this is Arboriculture, a mixture of science, law & love of trees.
best regards,
Sammy Au
President (Station Manager)
"Providing treatment without in-depth diagnosis & research support is professional misconduct. "
"Casual tree assessor delivers wanton tree assessment. Mother Nature makes the rules."
各位会员,下列剪报搜集之新闻稿件描述了今年首个在6月2日悬挂之三号台风于香港造成的影响。
而此刻，很多市树都已接受了政府管理部门之树木风险之评估(TRA）。如以衡量这些TRA之准确性来反映本地树艺师之工作将会是很有趣。
有否仔细查出明显的结构性缺陷？提出之建议是否符合实情？有否为了实现“零风险”而将那些可以拯救的树干脆砍掉？潜在的危险有否注于TRA上？
北美的研究显示即使在那里温带树木的健康树枝也可以于实验情况下被超过每小时70公里的风速折断。澳大利亚亦从事了大量树生物力学研究树于风速下的受害情况。很多这些研究可以在ISA公共教育环节中看到。树生物力学是一门非常复杂的学问, 对没有科学背景的人来说, 其数学模拟只有使人迷惑。树艺专业本身是以科学为基准, 少于倾向艺术。树艺与大多数之绿化专题也完全不同，特别是那些强调以设计为主的。
如果有人问一位精炼树艺师对TRA的技术意见，他将会获得一个基于绝对科学而又充满很多不确定的答案。精炼树艺师未必能“定义”一支树干折断的关键时刻，又或一棵斜树会在什么情况下倒地。所有他能做到的只是以他的知识提供指导和推测。他的经验和多年的实践比他的评论来得更重要。因此，当我们谈论有关树艺为一个科学题材时，我们还须要明白，我们是处理着一个生物体, 它能随时间和环境的改变而改变它的生存状况。树艺并不是一门绝对科学。
折树会招致保险索赔及诉讼。预防总是胜于治疗。移除每棵只有丝毫损害的树是那些不胜职不愿承担专业责任的人的逃避方法。保持一棵树对风险的平衡取决于风险本身的承担能力。
这就是树艺，是一门集科学，法律和树爱于一身的学术修养。
敬祝安康
国际树木学会 中国地区分会 会长
欧永森
“不深入诊断和参照研究来批出处方，是专业失当。”
“速成出来的树木评估员，只会作出胡乱的树木评估。大自然会决定成败。”
(以上由罗叶明 注册树艺师号 HK-0538A 翻绎。一切内容以英文版本为准。)
今年首發三號波 百宗塌樹
【本報訊】熱帶風暴「海馬」為本港帶來今年首個三號強風信號。受「海馬」外 圍雨帶影響，本港昨整日橫風橫雨，全日逾百宗塌樹意外，其中慈雲山一株大樹被強風吹至連根拔起，樹枝擊傷一男子。天文台表示，「海馬」今 早最接近本港，預 料在本港西南掠過後，會在廣東台山一帶登陸，天文台預計不會改發更高信號。
天文台昨晨五時四十五分發出三號強風信號，各區竟日狂風大雨，市民上班上學狼狽。天文台昨錄得橫瀾島及長洲最高持續風速為每小時五十五及五 十八公里，長洲最高陣風則達每小時七十七公里。幼稚園、肢體傷殘兒童學校及智障兒童學校須停課。
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