Thursday, November 15, 2007

ISA HK/China --- Review of Prof. Mattheck's 'Tree Bio-Mechanics' series

*** Our weekly Station Mail is for the information of Station Members only, but Station Mail has given up copyright & can be freely circulated. For administrative reasons, comments from outsiders are usually not entertained & may be circulated within our system locally & overseas. Please note Station Mail is sometimes given in Blog at , although images are usually not attached due to size. ***

Dear Station Members,

It has been an enormous task for this Station to research into the lecture materials, websites & literature of this equally giant Tree Specialist of Professor Claus Mattheck of Germany. We have spent months actually. Profile of Prof Mattheck is given in the attachment for general information.

Despite some may think Prof Mattheck would behave eccentrically especially in his delivery of lectures (He enjoyed shouting 'Ha !!' to wake up the class), this Station has found his teaching is primarily based on years of observation on the behaviour of trees under various conditions with a lot of experimental work. In his books & lectures, Prof Mattheck has given hundreds of photos showing tree defects & responses under wind loading & this evidence serves to back up his claims. In a way, Prof Mattheck was speaking with details of his research, & its up to the audience to reply otherwise.

The 3 books & website besides the lectures notes of Prof Mattheck that this Station has reviewed are:

1. Stupsi Explains the Tree 3rd edition --- 115 pages (1999)

2. Updated Field Guide for Visual Tree Assessment (VTA) --- 170 pages (2007)

3. The Face of Failure in Nature & Engineering --- 208 pages (2004)


Whereas the first two books written in children's language can still be understood in most parts by an experienced Arborist, the 3rd book would definitely require knowledge of Physics & Engineering to apprehend all the equations & mathematics. The written language has been extraordinary in the sense that it was translated from German into English with a heavy European ascent. If anyone in our territory finds Dr. Shigo's Tree Biology with American colloquial English would be difficult enough to read, Prof Mattheck's literature might be even harder. To this Station, reading Dr. Shigo's work was like an uphill battle in every page, whereas for Prof Mattheck's would be for every sentence. There were times that this Station had to go back to Physics & Engineering textbooks to try to figure out the meaning of certain Tree Bio-mechanics terms so described. Arborist without such knowledge may be completely lost in a whirl.

If this Station is asked to compare Dr. Shigo's education with Prof Mattheck's, this Station would reply that Dr.Shigo's work was more on the microscopic side of arboriculture, whereas Prof Mattheck would focus on the macroscopic side. Dr. Shigo would dissect & go deep into the tissue response of a tree after wounding, & Prof Mattheck would focus on the Reaction Wood Development of a tree in wind. This Station felt the work of these two giants complimented each other, & each has filled in the void by the other.

The European attitude of Prof Mattheck in sustaining Mature Trees by constant Crown Reduction to minimize wind loading, would tend to counteract the American attitude of pruning only dead tissues to encourage healthy growth. The two philosophy seems to go in a completely opposite direction, & can anyone say keeping a shortened Mature Tree a crime against humanity while its life can be extended? It may really depend upon how one would take the preference. On the other hand, Prof Mattheck has stood up in Court many times to provide Expert Witness in law cases with his mechanical theories on Tree Failures, & his observation of the development of Fungal Growth in assessing failure time can be educational in our territory. Some of his ideas were completely brand new to many of us indeed.

This Station generally felt that Prof Mattheck's teaching was to incorporate Physics & Engineering into explaining how trees stand & fall. This Station would agree with the proposition of Prof Mattheck in that everything does eventually fail, be it material or organism. It's just that it should not fail prematurely in its designed life, be dead or alive. The ability to predict failure may rest on the knowledge of Failure Mechanics . Since Failure Mechanics are largely studied on objects rather than on living organisms, it may be appropriate that such engineering theories can be borrowed to begin the study on organisms as a start. For living trees, this would mean to combine Tree Biology & Tree Structure for predicting Tree Failures. Prof Mattheck's knowledge seemed to have supplemented the structural side of Tree Physiology in many ways.

Prof Mattheck's education on Tree Mechanics began with forces, vectors, moments, stresses, strains & then progressed to Failure Mechanics, & would even go as far as Mohr-Coulomb's Law of Soil Mechanics. Some may have gone far beyond the domains of our local landscapers & designers. Some would actually take an Engineer to understand what is going on. Yet to carry out Tree Risk Assessment & Tree Failure Analysis to any advanced extent, the knowledge of Bio-mechanics seems inevitable, especially if Expert Witness is to be provided in Court. However, this Station would be bewildered to ask our landscapers & designers to learn Engineering from ground zero to carry out such kind of work, unless we would like to imitate what Singapore has already gone ahead.

There were 5 of our Station Members including the Station Manager attended the 3 day Workshop on Tree Mechanics by Prof Mattheck in August 2007 in Singapore. Pretty much we were all lost during his seminars, because we did not study his information in advance & perhaps thought it could be easily apprehended. We were wrong. Now as this Station has returned to diagnosis this great man's teaching, the knowledge did not seem coming out from nowhere but rather from years of observation & hundreds of experimental research. It is our Station's principles to be fact-finding & truth-telling to be an Arborist in our territory, & Prof Mattheck's information appeared to go along with our belief.

This Station has so far reviewed in our limited capacity of the work of two Arboricultural giants Dr. Alex Shigo on Tree Biology & Prof Claus Mattheck on Tree Mechanics, one being expert on the microscopic side & the other on the macroscopic. Both are necessary to complete our knowledge on Risk Assessment & Failure Analysis. Both are necessary to serve our community with so many Mature Trees nowadays.

Prof Mattheck has expressed the last time he was in Singapore that the Tree Mechanics Workshop there may be his last to tour Asia due to the distance & efforts. May we hope he can change his mind some time in future if we can gather enough money to invite this giant to come over to our territory to share his expertise with us.

May Prof Mattheck live long, healthy & keep shouting 'Ha!!' to us in his lectures.

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. (

Sunday, November 11, 2007

ISA HK/China --- HK Tree News (Pruning public trees)

Our weekly Station Mail is for the information of Station Members only, but Station Mail has given up copyright & can be freely circulated. For administrative reasons, comments from outsiders are usually not entertained & may be circulated within our system locally & overseas. Please note Station Mail is sometimes given in Blog at , although images are usually not attached due to size. ***

Dear Station Members,

It is all familiar that our public frequently complained about the so-called 'incorrect pruning' in our territory. When the attached newspaper cuttings were sent in, this Station decided to respond with an Arborist's viewpoint on events described as such.

In the first set of news, two Bauhinas were pruned for safety reason after branch breakage in strong wind in Ap Lei Chau. Someone wrote in to accuse ' wanton chopping' by a Govt Dept to disturb the greenery development in our city. The second news suggested planting trees in Tsim Sha Tsui created more liability than asset due to Tree Selection.

Before saying anything as such, an Arborist would need to look into the evidence presented for analysis. First, we would need to study the Design & Tree Selection in both cases as a beginning. In the Ap Lei Chau case, the trees selected were Bauhinias which are known not to develop a good Central Leader naturally, but would rather give crooked bends along the stem to branch out in unpredictable manner, which would pose a nightmare for anyone trying to structurally prune. If the Nursery Stocks were not initially selected to have good Central Leader, 60% Live Crown Ratio, Strong Branch Attachment, Balanced Canopy & Taper before installation, even the best pruning operator in the world would have a hard time to correct them back to good Structure & Health afterwards. Poor Nursery Stocks are a bad start & correction will take time & efforts. In reality, some trees may never be able to be pruned back to requirement at all.

Next, we shall need to understand who were doing the pruning? It was said to be the contractor. While it may be easy to teach a contractor to prune at the correct angle from Branch Bark Ridge to Branch Collar in a branch, it would be much harder to teach them what parts to remove & how much to remove. Pruning will lead to responsive growth in a tree. Incorrect pruning will lead to incorrect future growth. To be expert in pruning, the operator will need to understand Tree Biology for tissue response, & also Tree Biomechanics for wind stability. Would it not be too much to ask for a contractor to understand in such details of what they were asked to do? After all, they were only a contractor. It should really be the responsibility of an experienced Arborist to design & supervise the work, & to instruct the contractor on where & how much to cut, & for what objectives.

If an experienced Arborist is to be brought in to design & supervise the pruning, cost will be involved. According to the current Professional Fees Guidelines for CA to provide this kind of supervision for a day, the cost will be HK$6,000.00 each time. Can the tree owner provide this cost? Even if such cost can be provided to employ the right person to carry out the Structural Pruning, there may not be that many qualified Arborists available in our territory to perform the required work at present, because it is rather difficult to teach Crown Thinning, Crown Reduction & Crown Restoration in a classroom. For tall trees, Tree Climbing may also be required to get up inside the canopy to select the branches. Bucket Truck can not penetrate inside tree canopy safely but rather stay on the outside, & usually can not get on top to perform Crown Reduction. Then how many of our CA in HK can climb at present to do this kind of work?

The case in Tsim Sha Tsui followed similar principle of apparently selecting fast growing & wide spreading species without adequate room for future growth, which then led to continuous trimming back to reduce size. This appears to be a classic case of 'tree liability' upon improper Tree Selection in our territory.

The problems with our urban trees appear to be historical. The public also seem to have a lack of understanding of trees. To blame on the maintenance party alone would be like asking Cinderella to dance with an oversized shoe. Would that be fair? On the other hand, if it is the design & tree selection which are causing the problem, there is usually not much that the maintenance party can do to correct it afterwards. Sometimes, a complete renovation may be the only solution. Then the public may outcry for ' tree murder'. Isn't it easy to throw out criticism, but what about finding a workable solution?

Tree Pruning can be compared to human surgery on a person in many ways. No sane person would like his/her body to be operated upon by a meat butcher. Then why should thing happened to our trees ?? Time may be required to train our Arborists to perform quality pruning (with Tree Biology, Tree Biomechanics & perhaps Tree Climbing on real trees), & the road ahead will be long & winding. Maybe an immediate solution is to employ experienced Arborist to design & supervise pruning for certain categories of trees (OVT's, Mature Trees over a certain height/girth, Rare & Endangered Species, Champion Species, etc), & then train up the interested Arborists soonest (Join TCHK?). There appears to be no quick fix on it right away.

Has anybody any better solution?

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. (