V.T.A symptoms "the chatty trees"

[mrtree]

I think your photos show the difference between relatively safe trees with included bark and those that fail because of reduced cross-sectional area. The interesting thing is that you show many trees where only one side fails. If included bark is the defect why do both sides not fail? I think what we see is something slightly different. We can identify the presence of a defect by a V union with included bark, but the real defect is the stems are essentially an inverted triangle with the point at the base and widen as you move upwards. Thus you have a large weight over a smaller cross-section (caused as the stem cannot grow as a circle) and thus eventually the stem with the lowest safety factor fails at the tearout point that is a fulcrum because it is the point of lowest strength.

 

I have read both works and I think that there are problems, not so much in analysis but rather in approach. I look at a tree with large ears and knitting of the two sides and I see something quite different than a bifurcated tree without ears. I do not look at ears as a (desperate) effort to react to strength loss. (In many cases) There has been no strength loss as you indicate by no decay. They are a reaction to a strain and as such, whether optimally designed or not, are a strength increasing mechanism. They may also be a reaction to movement in the tree.

 

What we certainly agreee upon is that most of these earred trees can be saved with some effort.

[Tony Croft aka hamadryad]

I think your photos show the difference between relatively safe trees with included bark and those that fail because of reduced cross-sectional area. The interesting thing is that you show many trees where only one side fails. If included bark is the defect why do both sides not fail? I think what we see is something slightly different. We can identify the presence of a defect by a V union with included bark, but the real defect is the stems are essentially an inverted triangle with the point at the base and widen as you move upwards. Thus you have a large weight over a smaller cross-section (caused as the stem cannot grow as a circle) and thus eventually the stem with the lowest safety factor fails at the tearout point that is a fulcrum because it is the point of lowest strength.

 

I have read both works and I think that there are problems, not so much in analysis but rather in approach. I look at a tree with large ears and knitting of the two sides and I see something quite different than a bifurcated tree without ears. I do not look at ears as a (desperate) effort to react to strength loss. (In many cases) There has been no strength loss as you indicate by no decay. They are a reaction to a strain and as such, whether optimally designed or not, are a strength increasing mechanism. They may also be a reaction to movement in the tree.

 

What we certainly agreee upon is that most of these earred trees can be saved with some effort.

 

Longitudinal shear is the problem, started by a bark imposed crack at the unions centre, and all these failures are due to overly extended growth in competition, redcution of length would give the tree less stress and a chance to lay annual incriments over the defect. (DEFECT)

 

Trees produce symptoms when they have DEFECTS.

 

Included bark does not always result in failure, but it is more certain than not, and i have walked amoung the old growths for many many years, and I know the cycle particulary on beech, and the multi stemmed ones always fall first.

 

Becasuse of this DEFECT:001_tt2:

 

Whippendell woods is a great place to study the effects of included bark, all ages in all phases.

 

Knowing nothing of trees, ray mears does not recommend camping beneath beech trees, due to their pre disposition to limb failures in the forest!

 

You are going to have to bring something more to this table if you want to convince me that these forks are not dangerous.

[Paul Barton]

Great thread! Included forks and ears have always perplexed me. I am looking forward to hearing more of Duncan Slater's research in to this.

 

I agree that the presence of pronounced ears shows a symptom of an internal defect, usually an internal crack. However, many trees present this symptom for many years before failure occurs and it currently seems hard to predict what the tipping point is.

 

Obviously management of trees with these symptoms depend on the local environment and the presence of targets that could be affected by the potential failure. I personally find it a hard call to make in the scenario where you have a high value tree of overall good vitality located in a moderately high target area showing these symptoms. To do nothing could be perceived as negligence!

 

My gut tells me that imminent failure is unlikely, but given that included unions and 'ears' are indeed a recognised defect it seems very difficult to do nothing.

 

I would think that crown reduction to minimise the stresses on the weak point makes sense, but in the long run if the two opposing stems are incrementally thickening against each other it seems inevitable that at some stage they are going to peel apart.

 

Would value your thoughts on this....

Edited February 23, 2011 by Paul Barton
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[mrtree]

"You are going to have to bring something more to this table if you want to convince me that these forks are not dangerous."

 

It is not a case of these forks being dangerous or not, it is a matter of degrees, all limbs will eventually fail. My belief is that if we always approach a tree and identify the defects during a risk assesment we are destined for the road of removal. Just the mere mention of "risk" assessment puts a negative mark against a tree, then add in the cumulative totals of risks involved and you have decision makers running scared.

 

You must not only assess the location of the tree but perhaps more importantly the severity of the defect found. In the case of a V-crotch you need to look at size, cross-sectional areas, ears, included bark, verticalness of the stems, stems crossing side to side, wind exposure, decay etc.. When you have done this you then need to compare it with your knowledge and any literature you have. This will help to determine the likelihood of failure and perhaps under what conditions.

 

Prescriptions are then able to be formulated. Again experience and knowledge is paramont. In small trees can you remove one side of the bifurcation? Is cabling and bracing needed? Is thinning best? Is topping called for? Is crown-reduction needed, To what degree is a treatment called for?

 

I know that most of my competitors would remove virtually ever tree you have shown, yet these trees have survived decades (or more) with the defect.

 

I believe there is no simple answer to determining the liklihood of failure in these trees but we can certainly make far more informed choices by doing the studing such as you have.

 

I bet the most arborists, let alone tree services, in the world have never looked at ancient or even old trees and studied them. This forum, and a couple others, are populated by a few hundred arborist that are at the forfront of knowledge gathering. Thus I am preaching to the converted but we must learn more about trees if our goal is to save them and we must spread the word. Unless we study trees at all ages it is hard to understand trees.

 

You photos are really quite incredible and a very important learning tool. Studing them (and the trees themselves) is what ever arborist should be doing if they want to do more than removals.

[Tony Croft aka hamadryad]

Firstly before I reply to Mrtree's post (excellent by the way) would a Mod please (as no one picked up on it!) remove the tension fork from the first group of shots which contain mostly compression forks!

[RobArb]

Pardon me for being numb, but what does v.t.a. mean?

 

I am enjoying this thread though!

[mrtree]

VTA is visual tree assessment

 

Discussed in Mattheck's The Body Language of Trees

[RobArb]

a book i have still not managed to read as yet:blushing:

[BenR]

Brilliant thread. Very interesting read so far. Keep it coming Hama!

[Tony Croft aka hamadryad]

a book i have still not managed to read as yet:blushing:

 

any arb that has NOT read this book must get off thier butts and do so, it is without any argument (dare, go on i dare you:001_smile:) essential reading for the modern arb.

 

you simply will never look at trees the same again. I can also thoroughly recommend all the other Claus books, i would loan mine out but they are signed and not leaving my clutches!