Compression vs Tension Wood

D Mc

We have been taught that angiosperms put on tension wood in response to stress stimuli and conifers put on compression wood in response to stress.

The demonstration graph in some books is of a leaning trunk of the angiosperm being "pulled" vertical and the conifer being "pushed" up.

How is this determined?

S and D Mc

newguy18

i'm not sure i understand your question.

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old schooler

Eric Frei

I think he means how do they come to that conclusion.

Plenty of info on these SERP's

tension wood - Google Search

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newguy18

ekka.

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old schooler

mdvaden

I think I might understand your question, but don't have the answer. You are wondering how they could figure out that there was a pull, or a push, right?

My guess, is that the wood would appear differently from the rest of what's in the trunk. And that difference would be on one side or the other.

I think that the compression wood or tension wood concept sometimes causes people to ignore something else which I find more interesting, and that's how trees self-correct via the new growth. The new growth orients itself toward light, but just behind it, is an area of cell elongation, which elongates more on the dark side of the stem, and steers the stem as well.

From my reading, I recall Auxin to be involved with that cell elongation up closer to the top.

(Man, what a pain posting this one. A new reply gets entered while typing, and I have to wait 30 seconds even though I didn't post: technically. It's worse if if happens back to back too - and sure enough, a second reply pops in causing repeat delay. You hear that Ekka? A minute or more delay. The end of the world is upon us.)

Eric Frei

When that happens to me I just keep posting but am mentally prepared to edit my post if need be.

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D Mc

Thanks guys for the responses.

This whole question came about as I (SMc) was working on an assignment re Constant Strain Hypothesis. So we got into a big discussion about if a conifer puts on "compression" wood in response to stress and it has an injury on the "compressive" (underneath) side of its trunk, is that far worse than if it had the injury on the tensile (upper) side? (Thinking that it would have put compression wood on in response to stress and was not able to because of the injury.) We are supposing the opposite then would be true for an angiosperm.

This discussion then progressed to upper and lower sections of limbs. We have not seen a large, lateral limb that does not have more wood on the bottom. The tree's response to the "stress" of trying to hold this heavy limb being to put more wood on the bottom. This holds true (I believe) no matter whether it is a conifer or angiosperm. But we still call the upper wood "tension" wood and the bottom wood "compression" wood, right?

When a limb on a conifer dies it droops down, when a limb on an angiosperm dies it tends to bend up (not necessarily as dramatically).

We realize there is a cellular difference between conifers and angiosperms. However, the underside of a branch is going to be shaded no matter which it is. So the auxins causing the elongation of xylem cells (correct Mario) would seem to have to react the same. But the text is telling us they achieve the same results (straightening the trunk, or holding the limb) in a different manner.

That's what we want to know. How did they determine this.

So off we go to Ekka's links on tension wood.

S Mc

Eric Frei

Hey, little off topic but relevant anyway.

Have you ever been cutting a tree down and it has a large limb going off but for some reason or other you are cutting the leader it's growing from. As you work your way down the leader you cut off everything above that big branch.

This happens a lot in eucs when I work out of buckets. Every now and then the thought passes that the large limb could just bust off now as the upper part is now gone.

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D Mc

Eric, The real question here is What is it about working on a euc tree from a bucket truck that causes you to make these kinds of cuts?

Seriously, I know what you mean by it looking weak and actually, I think it is. Not because the attachment wood has been removed but the loading response wave length would be severely altered at the union.

I could go into the Latin on this, but I don't know any.

D Mc

Also want to say that we are still delving through the google material. And other than the information on tension wood from angiosperms being comprised of mostly cellulose and conifers' reaction wood being rich in lignen we still want to research more to see how this relates to hazard assessment. (Is an injury on a conifer much worse if it is on the compression side of the tree?)

S Mc

treeseer

It depends. If the tree has high vitality then perhaps not so much. Other factors are end weight, exposure, pests, all of which can be mitigated, which also should factor into your risk assessment. The term "hazard assessment" assumes a "hazard", and is needlessly negative; Matheny and Clark agree on this point so it ain't just me sayin it.

Eric, I'm with S Mc on your euc cut--reducing to a long lateral like that leaves a long lever that is open to rot at the base. It may be a textbook reduction cut, but by itself it may be wrong. Better imo to cut to a small lateral further up if there is one, angled away from sun and sky, or at least to shorten the lever arm (and experiment with sealant?) if you must make the bigger more horizontal cut.

D Mc

Sorry about the "hazard" wording - my bad. We certainly don't want to be needlessly negative.

Vitality and everything else aside, we are questioning that an injury on the compression side that would require reaction wood to compensate (since it's a conifer in our scenario) is it incapable of other means of reactionary growth; thereby making that injury more significant than if it had occurred on its other side using standard Risk Assessment Values.

S Mc

treeseer

Ohhh, that's what you are after. No, I think the tree would still be capable of forming reaction wood. How could it not? Callus grows, regardless of the books.

The whole conifer-tension/hardwood-compression concept is way overstated. We can go on magical mythical tours to unreality if we take these relatively valid observations and absolutize them to invalidity.

Does that 2.5 cents make sense?

arborjockey

Now that 2.5 cent makes sense. I worrry about tension and compression only when the tree has an awkward growing pattern. Strange lean or weird canapy position. I was taught that the inside of the lean was under compression and backside was under tension. When blocking down big wood on a trees that had exsesive lean(mostly conifers), I notice that the trunk will sometimes pop and make noise. One tree actually started to split and seperate so bad I had to get out of it. Is that from compression and tension?

D Mc

Treeseer, thank you for your 2.5 cents. Actually I do think that answers my question (at least enough).

In understanding the Constant Strain Hypothesis that trees react to stress by putting on wood unevenly to distribute the stress evenly it becomes relative to our daily work in that it is important to know how a tree will respond when cut (as Arborjockey pointed out). This actually is extremely important as those reactions can be huge.

In a risk assessment situation, I feel it is also important to understand the biology of what is going on because it helps to predict those forces (and possible consequences). So it becomes one more aspect of our evaluation and observations, adding accuracy in determining just how much (or little) of a risk any individual tree poses.

When someone is researching anything it becomes easy to focus on just one aspect of an equation, but then we need to plug it back in to the bigger picture to assess its relevance in any given situation.

Thank you.

S Mc