Hi Jerry - that was my point about the individual stems being
non-cylindrical- as compared to a single stem.
I'd agree with you re the remainder!
Atb
Rupert
-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info On Behalf Of Jerry Ross
Sent: 18 January 2022 11:39
To: UK Tree Care <uktc@xxxxxx.tree-care.info>
Subject: Re: stability of surviving stem of a split co-dominant tree.
You say that with a co-dominant stem, there is minimal or zero connectivity
of wood fibres between the two stems. That may be a bit true with some forks,
but unless the division is at ground level (when the contribution of buttress
roots comes in) there is going to be some structural connectivity. It's much
easier to split a tight V-shaped fork as compared to a more open one, but it
still needs /some /force to break it apart, and the force needed to initiate
that split gets greater with larger diameter stems.
I don't think one can disregard that linkage entirely.
There's also the question of the strength of a single stem with a circular
cross section as compared to one that's flattened on one side as a result of
having developed appressed to its do-dominant neighbour; and the section that
actually split is likely to be nearer D-shaped, so the business of "coping
with loadings on cylindrical stems by pre-stressing the wood in cylindrical
section" cannot be assumed to apply. Especially at the tear, where there is
no bark or outer tissues present to hold it all together.
Also, of course, the stem that's left is likely to be leaning with nearly all
the branches on one side. OK as long as it was sheltered by its other half,
but...
Every situation is different but my instinct would be to be rather suspicious
of your imaginary tree.
On 18/01/2022 10:52, "Rupert Baker" (rupert_baker@xxxxxxxx.co.uk) wrote:
Dear Dave et al,
Thanks for the responses so far; the link to treecalc is useful; many
thanks. I do however have reservations about using it in this situation.
As I said in my original post, the x-sectional area supporting the
remaining stem has not changed; on the hypothetical tree -
(and it is hypothetical! - I do not have a particular specimen in
mind at present; it is just something I've come across many times over
the years)
- there were once two stems each connected to the main trunk below; by
definition with a codominant stem, there is minimal or zero connectivity of
wood fibres between the two stems.
Each stem is therefore being supported by its own cross sectional area of
wood. If there is no defect or decay within this wood, what is the
difference between a single stem with the other one broken out and a pair
of such co-dominant stems on a whole, undamaged tree.
I understand the effect of an open cavity on a circular cross section of
wood - one only has to split logs to realise that once one has made the
initial split the others are all easier. Trees have evolved to cope with
loadings on cylindrical stems by pre-stressing the wood in cylindrical
section (Wessolly et al amongst many others).
The key thing I don’t know is: does the presence of the other stem in
a pair of whole co-dominant stems act in any way to assist in the
pre-stressing of its neighbour? Or does each stem behave as -in effect - a
cylinder with a section missing; and thus be prone to failure through
bending stresses.
Rupert
-----Original Message-----
From:uktc-request@xxxxxx.tree-care.info On Behalf Of David Evans
Sent: 17 January 2022 17:10
To: UK Tree Care<uktc@xxxxxx.tree-care.info>
Subject: RE: stability of surviving stem of a split co-dominant tree.
<<I've been musing about this for some time; if one has a tree which
was double-leadered, with a pair of codominant stems and a tight
compression fork between them>>
Hi Rupert
Put your remaining stem through TreeCalc.
https://www.treecalc.com/?lang=2
It'll give you a starting point Safety Factor. You'll then have a
conservative measured assessment, that'll be free of all hidden noise,
bias, and error that are endemic to qualitative opinions about what is
difficult and complicated decision.
Cheers
Acer Ventura
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