Tuesday, April 14, 2009

ISA HK/China --- 2009 ISA Research on 'Tools and Techniques for Detecting Decay'


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Dear Station Members,

Attached is a recent research published by ISA in Feb 2009 giving an insight on the knowledge of Tools & Techniques for Detecting Decay.

In recent seminars & tender requirement in our territory of HK, Macau, Taiwan & China, there appeared to be a lob-sided reliance on the use of Resistance Drilling & Sonic Equipment for detecting Decay, & the results were waved around to be the only viable conclusion to determine a Tree Failure. As seen in the attached article, Resistance Drilling is invasive & will break the Natural Protection Zones of a tree & Mature Trees are not known to compartmentalize well after injury. The photos of the Tomograph results were also clear to show an approximate situation of a decay & the result would need expert analysis to draw any conclusion. All these would mean that machines can not replace the experience, observation & knowledge of a well trained Tree Assessor.

In HK where an 'Independent Tree Specialist' is preferred to be someone with horticultural background, ISA HK/China does not agree with that at all. A Tree is an engineered structure & its biggest enemy is wind. It is wind that can kill a tree in seconds by toppling it. A Tree is also a porous structure (with vessels in it) & it constantly changes shape in wind in order to dissipate breaking stresses on its parts. Without basic knowledge in Wind Mechanics, it would be difficult to predict Wind Failure & to prescribe Treatment such as Pruning & Cabling, & Pruning is not just cutting from Branch Bark Ridge to Branch Collar only but why, where, how much & with what to cut. A proper Tree Assessment would be the first step before prescribing Pruning.


In prescribing Tree Work, the Practicing Arborist should be familiar with the practical side of Arboriculture such as Tree Climbing & Chainsaw Uses. Without such knowledge & skills, this 'Independent Tree Specialist' would be just another expert gardener, & would need to rely on paper work (photos & reports?) to supervise site work. This method does not appear to work out well internationally.

It is the opinion of ISA HK/China that The Arborist Profession in our territory should not rely too heavily on credential only, but more on skills & experience. ISA HK/China would like to see an Apprentice System among our fresh Certified Arborists (CA) to follow Senior Arborists like the Independent Practicing Arborist (IPA) (http://isahkchina.blogspot.com/2008/09/isa-hkchina-reply-on-tree-transplanting.html) or someone similar, to learn & advance their skills & knowledge before going into self-practice. The HK Legal & Medical System would require juniors to follow seniors for apprenticeship for a number of years & they have a Practicing Certificate to ensure quality. Then why not in the Arborist System were Arborists are Tree Doctors & Tree Detectives? However in doing that, the Senior Arborist must have enough work to sustain himself & apparently at present, it is not the case.

For any of our CA wanting to perform Tree Risk Assessment, it would be the advice of ISA HK/China for them to first go & master Tree Biology & Tree Bio-mechanics before attempting to enter this sophisticated area of practice. Both Dr. Alex Shigo & Prof. Claus Mattheck offer great publication in this area to provide important information. The literature can be purchased on ISA website of www.isa-arbor.com . They are difficult to read & understand, & the later part is full of engineering & mathematics. However, there appears to be little alternative if an CA wishes to enter into this area of practice.

It is important to remember that any Tree Inspection & Risk Assessment may bear legal consequences since Arborists are held to a higher degree of 'Duty of Care' in law to provide technical advice. Negligence or foul play can easily be detected by another Arborist & Arboriculture is a discipline based on science & research. There are many Court cases challenging Tree Inspection & Risk Assessment in western countries, & it will not take long for our territory to begin to have precedents. Therefore, our CA's should take great care in their work in order to stay dry & clean.

Trees would become liabilities if not designed, planted & maintained well. Poor quality trees & trees planted in the wrong places are difficult to maintain with the only option to be replaced with new one later. If trees in our territory now are to be compared with those of the western world or even with Singapore in terms of safety & amenity, we may have a long way to go indeed.

May the Arborist Profession in our territory develop well to turn our trees into assets, with HK possible taking the lead in its drive after the tragic Stanley Tree Failure.

best regards,

Sammy Au
Station Manager

"If a tree is not designed, installed, maintained & inspected properly, it is likely to become a liability rather than an asset."

"Trees are good for the community. Trees need care like human beings. Arborists are the Tree Care Professionals."


1 comment:

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