Wednesday, May 21, 2008

ISA HK/China --- 2008 Wind Loading Analysis (WLA) research for Tree Assessment

Please note this Station Mail is split in transmission in two parts to facilitate printing by Station Members to read the attachment.

Dear Station Members,

ISA has recently published the latest Wind Load Analysis (WLA) protocol in Arborist News April 2008 edition for yet another method to carry out Tree Assessment & Pruning currently practised in some parts of Europe. The mathematical formulae & calculations contained may please the engineers in our Station in which we have dozens.

The information given in this article is well beyond the knowledge required for the current Certified Arborist (CA) exam & it is really targeted for serious Tree Assessors with adequate scientific background to understand how to use mathematical tools for detailed analysis. On the other hand, this WLA process has stated very clearly that it can only be used for single, open-grown trees with a single trunk. Most of the ' flowering species' in our territory would fall outside this category & any expert would hesitate to use this method for a lot of decurrent ' flowering' trees planted like dense forest in our territory. This system is also based on the European Standard of Beaufort 12 windspeed, for which most typhoons in our territory would exceed the required windspeed easily in a most situation. The wood property values of a lot of our ' flowering species' are also unknown & not published anywhere at present, & this will leave ground of speculation when this WLA model is to be used.

Internationally speaking, any CA wishing to become a competent Tree Assessor would have to seriously educate himself/herself with profound Tree Biology & Tree Biomechanics before going into this area of practice. The former consists of mostly Tree Pathology & the later Wood Science & Mathematical Models. There are currently very few competent Tree Assessors willing to stand up in Court to testify a Tree Dispute with legal liabilities in our territory. There is indeed much more to learn & develop for a CA to enter into this specialist area of Tree Inspection & Risk Assessment, after obtaining the CA credential which is viewed upon as an entrance ticket to Professional Arboriculture around the world.

It may be perhaps true that over 90% of our Station Members & most of our current CA's reading the attached article may not understand what is going on in there, since not too many of them have been trained with such relevant scientific background. However, this Station wishes to show our territory that Modern Arboriculture is not just all about simple pruning & climbing like some have anticipated. Arboriculture is vast, profound & deep, well worth a life time of studying to not be able to master it all. The attitude of forever learning must persist if an Arborist wishes to stay & do well in this specialist profession, especially if wanting to go into practice. Becoming a CA should be considered a beginning, & not an end to learning.

Arboriculture has been developed as a practical need in western countries over the years & not out of hobby like some sectors of greenery industry. Practising arboriculture as a profession involves legal liabilities much more easily than a lot of landscape disciplines. Facts & reports in arboriculture are frequently challenged in Court & Practicing Arborists must arm themselves for legal challenge at all times. Continuous education appears to be the best defense.

May our territory now respect the Arborist Profession as an unique discipline to serve our society, & would regard Arborists as more than just 'Tree Men' pruning & climbing trees after seeing some of our research.

best regards,

Sammy Au
Station Manager

The ISA Mission - Through research, technology, and education, promote the professional practice of arboriculture and foster a greater public awareness of the benefits of trees. (


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