Tension and Compression?

[scotspine1]

Ok, in the most simple terms - a conifer puts on extra reaction wood on the underside of the branch which supports and pushes up the branch creating larger growth rings on the lower side when viewed through the cross-section. This is called compression wood.

 

A decidous tree pulls the branch up this is called tension wood, when viewed through the cross section there will be larger growth rings on the topside of the branch.

 

Is this a general rule? or are there some decidous trees that act like conifers and put on compression wood on the underside to force the branch upright?

 

Cheers

 

TC

[John Shutler]

im not sure but could it be tip weight limb weight related

[David Humphries]

Good question Tim.

 

My first hunch was that possibly Ginkgo could be a cross over species in terms of it being a gymnosperm with tension wood.

 

Although slightly different from other gymnos, it does however appear that it has compression wood, as stated in the following link.

 

 

http://www.springerlink.com/content/mu227w0202683uuu/fulltext.pdf?page=1

 

 

If I'm reading it correctly, the links suggests that Gycadales and Gnetales, which appear to be gymnos dont have compression wood.

 

However these aren't technically Trees.

 

http://en.wikipedia.org/wiki/Gnetophyta

 

 

 

Blimey, I must be bored.

 

 

 

 

 

.

[Amelanchier]

I have a slice of E. gunni at home that clearly shows the preferential creation of wood on the underside of the long heavily end weighted limb it was taken from.

 

I also have photos at home of preferential creation of addtional wood on the tension side of a leaning C. macrocarpa.

 

However, actual 'compression wood' is structurally distinct from normal wood and is particular to coniferous trees. (Apparently including ginkos too... ) So to answer your original question I would suggest that a tree acting in line with Matthecks Axiom of Uniform Stress will add wood where the cambium detects uneven forces - if its adapted to produce specific types of wood, then it will use those.

 

Annoyingly most of the literature about compression wood focuses on commercial impacts on the timber quality of crop trees.

[Bundle 2]

I wondered when someone would get there Tony....! It can be misleading as the wood from trees of both conifer and broadleaves will look the same in cross section as the "type" of wood put down by the tree is modified .

Trees can alter the wood ( broadleaves ) usually by the structure and lignin/microfibril matrix & pectin I think, to be up to 4 x stronger when needed!!

The anatomy of conifer wood is significantly different from that of broadleaves....

[Ian Leach]

This is what it says in one of my books and how i understand it, hope it helps and hope you can read it. I'm only a beginner on the techical stuff.

[Khriss]

I am glad someones put this thread up-had nearly forgotten about this.

 

K

[scotspine1]

Reason I asked, was that I recently removed a large lateral branch from a mature Hybrid Black Poplar, and the growth rings were very wide on the underside and only just visible on the topside they were so close together. This is what I'd expect to see on a Lawson's Cypress or Leylandii etc. Its makes me think very little research has been done on this issue.