Adjusting Strength Loss Formula for Woundwood

[Guy Meilleur]

Here is a pic of a cavity. Since research shows that woundwood in red maple is 40% tougher than normal wood, the formula must be adjusted for this type of cavity:

 

[TheTreeSpyder]

Wouldn't the real strength issue be what leveraged positions of compression and tension of regular wood, wound wood, no wood positions addressed the axis of the lean?

So that the sealing over instead of replacing strategy, always places the stronger wound wood in a better leveraged position, compounding it's strength increase; but the final analisys (mechanically) would be the way those leveraged positions addressed the loading(?)

And, perhaps if this wound wood did as well in compression as tension loading(?); it would seem easy to visualize it's strength and flexability superiour on the tension side, does that hold true for compression side? Would that change, if the conifer grew from compression side and oak from tension side (affect how would wood reacted in those positions)?

Great topic, jsut don't know much about it!

 

[NeTree]

Kenny, the tree has already addressed those issues itself.

 

[TheTreeSpyder]

So the open part of the wound will always adjust to not be near the loaded axis?

i have seen failures that seemed to fit that model; as similar comparisons to evaluating hinging on where face inspection shows rot, dead, dry, or this real elastic, tough wound wood.

So i just kinda figured the wound could come anywhere, and could end up with weakness in wrong position to handle loading till sealed, or close radiant to.

 

[glens]

That's a classic, Guy.

Glen

[pruned]

 

[Kneejerk Bombas]

I agree Guy. They may then need to come up with a strength gain formula.

 

[JeffE]

I think Spyder's got a point... is it stronger by tension or compression, or both, or either (depending on the location of the wound)? What does "strength" mean in that context? Of course, if it resists bending too much, it could lead to failure in the "real world."

Guy, got a journal citation?

 

[Guy Meilleur]

Originally posted by JeffE
What does "strength" mean in that context?

Resistance to failure.

Of course, if it resists bending too much, it could lead to failure in the "real world."

Since the woundwood developed in response to real world stresses, I generally think not.

Guy, got a journal citation?

JOurnal of Arboriculture, July 2003, page 209-218.

Strength Gain Formula, thanks Mike, can I use that phrase, please?

I measured this cavity 2 years ago, and again this month. Since I pointed out the defect to him he has been obsessed with the safety aspect.
I'll post the math soon when I get caught up on work.

I reduce the end of this thing each time I'm in it. On one hand I have to stay mindful of the the effect of loss of photosynthesis on the tree's ability to seal. On the other hand needing to reduce strain on defect. Cuts are made where sprawl is excessive, and to relieve competition with better-structured branches that we want to dominate.

Subordination of codominant stem; training the defective stem to be a branch. Client wants whole-tree reduction to lessen windsail, but listens to reasons against that. We'll check it again in December.

 

[Guy Meilleur]

Originally posted by Mike Maas
It's the exposure to movement that strengthens it. By reducing strain, you're signaling the tree not to support itself as much.
This is true, and one more factor that goes into the decision of where to make reduction cuts.

How about tieing ropes to the top of the tree and shaking it real hard once a month? I've seen experiments on small trees that did this exact thing and grew a stronger tree.

I've read the same, and agree. I call this "flexing" and do it regularly. Maybe I'll tie an old rope into the top of this maple and tell the client to pull on it a few times a day. This is one guy who would probably do it, too.

 

[TheTreeSpyder]

once again i think that all growth is a responsive action; as in Mike's illustrative.

In greenhouses etc.; especially when forcing a lot of fruiting or flowering weight; shaking stems; placing fans on plants is known to make stronger and larger parent stems.

i think it would be down to limiting how much movement dynamically; copying the Cobra support strategies into the 'shake line'. Not necessarily any constraint at neutral, so no constant support, jsut a 'red zone' that dynamic support is metered in.

On a full sized injured tree that might be a loose line to top; with tire tied in it at bottom before anchor? Could shake to strengthen, tire weight on line shouldn't be too much on decent tree, at so much movement line would start giving some support, higher loading dynamically stretches tire?

i think it is all about balance again. If we have lost so much strength, do to a leveraged position injury; tree is out of balance of pulls perhaps, and might be lightened, targeting, lower performance if some thin, or heading towards were someone would want to trim off something soon), high leveraged branches. Especially on the sun side, or going to a heavier weight bearing season.

All conjecture, feeling around in the dark, manipulating between fractions of light, trying to see the whole, and make best decision. But, i guess that is why regular doctors have practices; and ya try to get the one that has the best feel and understanding if ya want the ailment to have a higher probability of being neutralized/repaired. As always the best long term solutions considering the whole system, and generarlly going with it; rather than straight against.


Or something like that,
:alien:

 

[Guy Meilleur]

Originally posted by TheTreeSpyder
If we have lost so much strength, do to a leveraged position injury; tree is out of balance of pulls perhaps, and might be lightened,...high leveraged branches. Especially on the sun side, or going to a heavier weight bearing season.

Absolutely. A little reduction of tips yields a great reduction in leverage. And heavy ends on the sunny side are the ones that get the most off, keeping in mind the need to turn light into sugar.

In a middle-aged maple like this one there's some margin for error; in old oaks there is great need for caution with the saw.

 

[Guy Meilleur]

Originally posted by Mike Maas
Just so some fool doesn't come along with a resistograph and start punching holes through those walls.

No worries there. mate. I excavated the cavity so I could measure it with a tape measure.

"Anyone ever try to do some grafting on the callused area on an injury like this?"

No, better to invigorate roots to speed callus formation.

"The strength loss with the injury shown is probably the greatest below or above the injury, where the trunk doesn't have woundwood."

Right again; the cavity extends down 6", and this is right where the defective , included bark fork is. That's why the judicious reduction pruning.

"I would (not) mind you doing a crown reduction if you put the branches back on the tree."

Yessir, first chance I get. O and the umpteenth time for this correction--I made reduction cuts on a small portion of the crown. I did NOT do a crown reduction; my earlier post said "Client wants whole-tree reduction to lessen windsail, but listens to reasons against that." You must have missed that.

 

[Guy Meilleur]

Originally posted by Mike Maas
prolonged exposure to greater movement has strengthened these perimeter trees over the years.
No dobt, because the trees were flexed they are stronger.

If there were a bigger pocket of decay and a target,
The target is the house and the client is hyperconcerned.

then I might consider reduction as a last resort. doing a crown reduction on such a tree seems counter productive.

Making reduction cuts to subordinate the defective limb was necessary. This pruning work was not crown reduction per se because it was a small % of the total crown, and it allowed more stable branches to dominate, and they will fill in the void in short order.

I agree it may seem counterproductive, as much as less photosynthesis beyond the defect slows down the sealing of the defect. But we don't know how much effect that has, or how much that effect can be compensated for by root invigoration. I agree that all we can do is to proceed on informed intuition.