Very frequently - Notwithstanding Jon's, and Tim's, dismissal of it!
It may be unreliable but it's all that's readily available to give some
weight when some weight is required over and above the results of simple
beard-stroking.
(Also, with all those figures and equations, it'll be bound to impress
Counsellors, planning inspectors and magistrates)
And as I wrote previously, you can omit all the calculations by using
the bristoltrees.space webpage
On 12/01/2022 12:22, elsteadbysea@xxxxxxxxxxx.com wrote:
Has anyone used this document from the FC?
https://www.forestresearch.gov.uk/documents/6765/FCIN012.pdf
Phillip
-----Original Message-----
From:uktc-request@xxxxxx.tree-care.info <uktc-request@xxxxxx.tree-care.info>
On Behalf Of Tim Moya
Sent: 12 January 2022 12:16
To: UK Tree Care<uktc@xxxxxx.tree-care.info>
Subject: RE: Estimating tree ages based on trunk diameter/girth
Yes - What Grumpy said
Tim Moya
-----Original Message-----
From:uktc-request@xxxxxx.tree-care.info <uktc-request@xxxxxx.tree-care.info>
On Behalf Ofgrumpy@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.co.uk
Sent: 12 January 2022 11:50
To: UK Tree Care<uktc@xxxxxx.tree-care.info>
Subject: RE: Estimating tree ages based on trunk diameter/girth
Paul
You already have a reference to "Mitchell". No doubt someone will point out
"White" shortly. Neither were mensurationists or statisticians, although clearly both
collected loads of data. I frankly am appalled by what I read and hear about tree age and
diameter.
I realise most of us need a good old beard to stroke (sorry, ladies) when we
are asked how old a tree is. We stroke our beard (I don't have one) to
impress on our listeners how much thinking we are doing and how much
experience we are recollecting when we examine the size of a tree and come up
with a number. Ooooo this one must be at least 200 years old, I say. Gasps of
adulation arrive and we all go off happy, respectful of this ancient tree.
It's frankly nonsense:
Trees vary considerably in their diameter growth. Partially determined by
species, partly determined by site, partly determined by density. The latter
simply acknowledges that competition from nearby vegetation and trees alters
growth rates - closely growing trees will fatten less quickly than free
growing trees. Yes obvious in a spacing trial in early years, but less
obvious with widely grown trees when they are large.
The situation was acknowledged in Forestry Commission Bulletin No 1 dated
1919 Collection of Data as to the Rate of Growth of Timber.
We all know that weather and climate alter growth, so attempting to have a
figure for all species in all conditions is well.......an average. It's of
very little use in determining age of individual stands, and in particular
individual trees. If someone were to bring this into a court room, I would
have a field day.
Yes, it would be nice to have a simple solution to a complex problem. The
solution is to kick councils up the backside and say 50 year old, or even 20
year old Area orders are unworkable......and if you want to prosecute people
for tree works to marginally aged trees you may have a problem. I realise you
have a practical problem in front of you, but there is no easy answer. You
are better off trying to find old aerial photos from the second world war (or
more recent if that is the age of the TPO)
Before someone does mention "White" look at his FC Information Note dated 1998. Table 1a sort of
acknowledges the significant variation in growth rates possible. But without some sight of the data on
which this table is based or any analysis arising from it you could get seriously misled. All of the
figures are averages. Thus expectation that growth might be greater on a "good" site than on an
"average" site doesn't help much. Poorly growing trees on a good site are likely to grow less
than fast growing trees on an average site. Using these to estimate the age of trees using these averages
is as good as stroking my beard......
A good source of tree growth data? The only source is Forest Research but clearly their data is
almost entirely for plantations & forest species. I doubt they have much data on widely
spaced trees and even less on open grown trees. I wonder whether they hold Mitchell's and
White's data and whether it was approved for professional use (i.e. anecdotal data doesn't
stand up to much scrutiny), or just binned?. Zero data on the wider range of trees used in
arboriculture? I approached them a little while ago to see if they have any data on yew growth.
Zero was the reply. You can find a synopsis, but no growth data in a paper in the RFS QJF in
early 2021 or late 2020. I am afraid I don't have the specific reference to hand but I think it
contains "Permanent Sample Plots" in the title. Richard Baden came back to me with a
very long email & you could explore what data they have, but Richard's remit may be limited
to the plots:
Richard Baden (email using @forestresearch.gov.uk)
Assistant Sample Plot Officer
Forest Mensuration, Modelling and Forecasting Forest Research Alice Holt
Lodge Farnham GU10 4LH
They may have a dusty cabinet of growth data that no-one has looked at for a
while. That's always the impression I get when I go to Alice Holt.
Jon
-----Original Message-----
From:uktc-request@xxxxxx.tree-care.info <uktc-request@xxxxxx.tree-care.info>
On Behalf Of Paul Barton
Sent: 12 January 2022 08:56
To: UK Tree Care<uktc@xxxxxx.tree-care.info>
Subject: Estimating tree ages based on trunk diameter/girth
Dear collective,
I wonder if you can help me? I am looking for a simple method to estimate
tree ages as part of a preliminary review of some area TPOs - i.e. to assess
whether trees that are present now were most likely present (or not) on the
year the area TPO was served.
I have come across various apps that claim to give an age based on trunk
girth but after a brief test they seem to overestimate age (based on my
experience only) as I suspect they are based on forestry plantation trees
which tend to be more slender over time than open grown trees.
I came across this document from Newport council
(https://www.newport.gov.uk/documents/Leisure-and-Tourism/Countryside/Measuring-Trees.pdf)
which suggests that tree growth rates could be split out in to slow, moderate and fast -
each with a corresponding ‘average’ annual girth increase. These are given
as:
• Slow - 1.88 cm per year
• Average - 2.5 cm per year
• Fast - 3.13 cm per year
Using such values would allow me to classify species by growth rate category
and therefore have a ready reckoner to estimate tree ages based on their
girth. It can never be claimed to be very accurate but for the purpose of
quickly assessing hundreds of trees a repeatable documented method would be
useful.
BUT I don’t know if the above growth rate values are based on good data,
ideally in the UK.
Finally to the point (congratulations if you lasted this long)…can anyone
point me to a reliable source of UK tree growth rate data so that I could verify or
amend the above suggested rates of growth?
Kind regards,
Paul Barton
www.barton-hyett.co.uk | Barton Hyett Associates Ltd | Arboricultural Experts
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