UKTC Archive

RE: {SPAM?}RE: Ben's Red Oak photo 1

Subject: RE: {SPAM?}RE: Ben's Red Oak photo 1
From: Jim Quaife
Date: Dec 19 2018 08:37:07
As ever David, thank you.
Following the '87 blow there were numerous mature trees that were dislodged 
but settled at an angle.  Several years on the top part of the main stem 
(where there was a persistent main stem) had curved to be upright.  This 
curve was not just the new growth but from a point some way down the stem 
which was present at the time.   This was more noticeable with conifers 
(obviously), but the correction adaptation is clear.
Having dealt with sweet chestnut timber, the spiral bark formation on old 
mature trees tends to start from (very approximately) 60 - 80 years.
Where an established branch "creeps" round to fill a gap, for the want of any 
investigation on my part, I have just assumed that this may be something to 
do with asymmetric leaf development toward the light with a consequent weight 
asymmetry, and maybe the linear vascular function has produced bias growth 
where the sap flow has increased - I don't know!
Clearly physical stress upon a cell produces thickening but the branches on 
the red oak in question ascend, and maybe (just maybe) the angle is 
sufficient for this type of adaptive growth to occur.
Perhaps a bit early in the day now, but this is the sort of thing that needs 
the brain enhancement of a pint!
Jim 

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info 
[mailto:uktc-request@xxxxxx.tree-care.info] On Behalf Of "David Lonsdale"
Sent: 19 December 2018 00:37
To: UK Tree Care
Subject: Re: {SPAM?}RE: Ben's Red Oak photo 1

I doubt whether I am qualified to give the definitive response, Paul, but I 
agree with most of what you say.  Experiments have shown that reaction wood 
(i.e. tension wood in angiosperms or compression wood in gymnosperms) is 
formed by cambial cells that are at an angle to the gravitational field (i.e. 
not vertical).  I think that there is evidence that reaction wood can also 
form in upright stems that are swaying in the wind and thus not always 
exactly vertical.  I am not, however, aware of evidence showing an effect of 
sunlight but I admit that I have not kept up with recent research.

As far as the 'purpose' (or perhaps, I should say 'effect' or 'function') of 
reaction wood is concerned, I am sure that it helps to resist downward 
bending, acting like a taut rope on the upper side in a angiosperm, or like a 
rigid buttress on the lower side in a gymnosperm.  Also, as you have 
mentioned, Claus Mattheck has stated that reaction wood can also reduce, or 
even reverse, a downward bend or a lean of a relatively slender stem or 
branch.  I am not sure whether there is 'before and after' evidence of this 
but again I ought to be keeping up with research on the subject.

Although reaction wood resists stresses induced by gravity or by swaying, I 
think that similar functions are sometimes performed by adaptive growth 
which, as you have pointed out, occurs in response to mechanical stress; i.e. 
by regulating the amount of wood being laid down in a particular part of the 
tree.  For example, extra-wide wood increments (presumably ordinary wood, 
rather than reaction wood) can be laid down on the underside of the base of 
an angiosperm branch, as can sometimes be seen in pruning wounds.

Given that reaction wood is laid down by non-vertical cambial cells, I am not 
sure how it could play a role in the lateral re-orientation that seems to 
have occurred in Ben's red oak.  I think however, that this re-orientation 
might have involved adaptive growth (i.e. extra wood), in response to changes 
in the distribution of weight of branches that have been growing into the 
space released by the removal of the adjacent ash tree. 
Anyway, I assume that the apparent re-orientation has involved bending of 
branches rather than rotation of branch-sockets.   Claus Mattheck has, 
however, stated that some trees acquire helical grain by gradually twisting 
as they grow, perhaps because of torsional stress from the wind.   If so, 
their branch attachments would rotate in unison with the increasing twist of 
the stem.   I do not, however, know of any 'before and after' evidence to 
support this explanation of helical grain.  In any case, I assume that 
helical grain can have (or perhaps always has) a genetic origin.

Also, I've seen Ian Brewster's very interesting comments about summer branch 
drop (SBD).   I agree that SBD probably involves changes in the natural 
pre-stressing of branches that contain a downwardly bent core of older wood. 
I mentioned pre-stressing in relation to reaction wood and SBD  in 
"Principles of Tree Hazard Assessment and Management", Sections 2.1.2.1 and
2.1.2.2 (sorry for the plug but I don't make any money from sales!).

DL



-----Original Message-----
From: Paul Muir
Sent: Tuesday, December 18, 2018 4:40 PM
To: UK Tree Care
Subject: RE: {SPAM?}RE: Ben's Red Oak photo 1

Adaptive growth is not the same as reaction wood. I believe that the 
production of reaction wood is a response to gravity in a leaning stem, and a 
response to gravity/preferred (genetic) branch angle and also to light in a 
branch. Compression wood and tension wood are terms used to describe which 
side of a stem or branch gymnosperms and angiosperms produce reaction wood in 
relation to gravity. The purpose of reaction wood is to re-orientate a stem 
or limb. It seems we've started to confuse adaptive growth, in response to 
stress, with a very different mechanism. And the terms tension wood and 
compression wood don't help.

I'd expect David Lonsdale to jump in here to give the definitive response. 
:-)


Paul Muir
Principal Arboricultural Consultant
Treework Environmental Practice
Tree Experts Across the UK
Winner of Trees & Development Award 2018

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