Compressive & tension reaction wood

[David Humphries]

I imagine that all trees will add wood where the cambium detects uneven forces - if they are adapted to produce specific types of wood, then they will use those. Trouble is, you need a microscope to see the difference.

 

 

Thanks Tony, good points, but trying to keep it simple here..................no place for microscopes in your average Arb man(s) bag

 

 

Without all of us having access to all of the perceived wisdom from all resources, I think it prudent to probe these thing for discussion (for the benefit of all levels)

in basic terms.

 

Unless of course key facts are omitted.

 

 

I (don't think I'm alone in this) would like to start seeing a wider contribution here, from those that can, for the greater good of the Arb sector.

 

Even if these threads only serve to reiterate the bits and pieces I'm picking up along the way, then that's one Arb who's learnt something

 

 

 

Pdf's, photos, experience, bring it on Tree people

 

 

 

 

 

 

.

[Matthew Corran]

I'm sure I was taught that Conifers will lay down wood on the compression side of a leaning tree to push itself upright.

 

Broadleafs will lay down wood on the tension side of a tree to pull itself upright.

 

But when it comes to lateral limbs they will all lay down extra wood on the compression side against the implied force.

[Rhob the Log]

Any shots?

 

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Sounds like you may be able to explain this beech tree. Forest grown. Not rippled, but bobbled all the way up. I think on the limbs as well.

 

Virus? Genetic?

[Stubby]

Hi David,

 

Similar to your Oak shot above, I think, I have seen pronounced growth striations on the underside of heavily loaded branches on broadleaves indicating reactive growth (?) which I didn't understand.

 

Regarding the general premises of 'push' n 'pull', conifers n broadleaves respectively, in terms of remembering it someone, poss. on the forum, said broadleaves have biceps, i.e. tension pull like a bicep (not mine tho ), n conifers have triceps, i.e. compression pull like a tricep (not mine either )

 

Anyway enough waffle from me, clearly I need to go back to 'arb' school.

 

Thanks as ever for your informative posts, racks up my CPD every time

 

Cheers..

Paul

 

The triceps would be push .....

[Stubby]

Just my opinion but re conifers " pushing " and broad leave " pulling " I think that the saying " for every reaction there is an equal and opposite reaction " so may be they do both . Push were they need to and pull were they need to, displaying it in different ways conifer to broad leaf ?

[David Humphries]

Sounds like you may be able to explain this beech tree. Forest grown. Not rippled, but bobbled all the way up. I think on the limbs as well.

 

Virus? Genetic?

 

 

 

On one face of the trunk or all the way around Rhob?

 

 

 

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[Rhob the Log]

All the way round the trunk David. The ripples you showed made me remember it. I think there's another in the wood that looks similar.

[Paul Jenks]

The triceps would be push .....

 

All muscles pull. They don't have the capacity to push. Triceps are used to straighten the arms by contracting.

 

That beech looks like it has cellulite.

 

I was chopping some ash from a biggish spread out tree the other day. Nice rings 12" thick. One half was a dream to split, the other a right git, being stringy and tough. Trouble is I didn't mark which side was which.

[daltontrees]

Compressive wood = formation of reactive wood to gravity/wind force (made up on the underside of gymnosperm branches & trunks by the laying down of additional lignin in the woody cells to help push the weight against the implied force..

 

Tension wood = formation of reactive wood to gravity/wind force (made up on the upper side of angiosperm branches & trunks by the laying down of additional cellulose in the woody cells to help pull up the weight against the implied force.

 

David, hope you don't mind if I pitch in?

 

I think the use of the words 'reactive wood' could turn out to be unhelpful and confusing. There are the established terms of 'adaptive growth' and 'reaction wood'. The term 'reactive wood' is new to me. If your definitions opened with 'Formation of additional or specialised wood as a reaction by the tree to abnormal external forces....' then I think it would be a reasonable summary.

 

I have always struggled to understand the difference between 'adaptive growth' and 'reaction wood'.

 

The former should probably refer to the general habit of trees of self-optimizing (axiom of uniform stress etc.) by adding to their structure to compensate for forces that would otherwise compromise them. It is, however, also used by many people to mean the extra wood itself. It is further used to describe extra wood, specialised or otherwise, that has grown as a quick response to partial structural failures such as at compression forks or at decaying unions.

 

'Reaction wood' really ought to be saved for describing specially adapted wood. As you have said in your ddescriptions, the wood may be especially rich in lignin or cellulose. But there are other adaptations too in the orientation of fibres and cellulose in cell walls. Cells may be shorter, they may also be rounder. They almost certainly will expand (compression wood) or contract (tension wood) on maturity. That's where the push or pull comes from. All the other specialisations I have taken to be to provide additional strength, not push or pull. As such, I would disagree with the exact wording you have put forward, but only in a pedantic way because the cellulose or lignin does not push it only gives strength to the cells so that when they pull or push by shrinkage or expansion they do not fail.

 

Things get complicated with the terminology in practice. Reaction wood tends to be added with unusually wide annual increments and so can appear just as extra wood. But if you try and put a saw through a branch union of a broadleaf you will soon know that you are encountering extra cellulose. Similarly with a conifer you will sail through the reaction or compression wood relative to the normal wood because it has more lignin that cellulose. It is like a linear resistograph test, you just need to listen to the saw revs to gauge the relative cellulose content. At least, that is how I amuse myself when discing stuff.

 

So in summary my definitions are roughly - adaptive growth is the addition of extra wood (a process, not a substance), reaction wood is specialised wood, compression wood (in conifers) is wood arising from adaptive growth usually including the addition of lignin-rich reaction wood, and tension wood (in broadleaves) is wood arising from adaptive growth usually including the addition of cellulose-rich reaction wood.

 

I am open to any other suggestions or refinements.

Edited November 7, 2013 by daltontrees

[Tony Croft aka hamadryad]

Thanks Tony, good points, but trying to keep it simple here..................no place for microscopes in your average Arb man(s) bag

 

 

Without all of us having access to all of the perceived wisdom from all resources, I think it prudent to probe these thing for discussion (for the benefit of all levels)

in basic terms.

 

Unless of course key facts are omitted.

 

 

I (don't think I'm alone in this) would like to start seeing a wider contribution here, from those that can, for the greater good of the Arb sector.

 

Even if these threads only serve to reiterate the bits and pieces I'm picking up along the way, then that's one Arb who's learnt something

 

 

 

Pdf's, photos, experience, bring it on Tree people

 

 

 

 

 

 

.

 

Liking the way that rolls Mr H:001_cool: