Or to put it another way, could I reasonably foresee that the tree might
fail, or if not and then it did, could I then argue that I could not have
reasonably foreseen it?
I'll let Mike answer in his way. I have had similar discussions here.
Forseeability of failure is always held up as an 'acid test' of sorts. Since
all trees always die, probability of failure is always 100%. We just don't
know when. I have a lot of Phaeolus to deal with. The Provincial book makes a
generalisation that conks only appear after extensive decay is present,
therefore see a conk = remove the tree. I have dissected 5 - 6 firs with
Phaeolus. Yes, extensive decay on structural roots, but not all of them,
sometimes only one with the rest being just fine. Of course it's foreseeable
that the tree will fail. But can we retain it another ten yerars? Five years?
Who knows. I can see that time and budgets always constrain how much info we
can gather. But, it is important to appreciate that the job of the risk
assessor is to assess risk, and not be biased by political pressures etc. Let
the risk manager do that, it's his / her job to balance risk issues.
The trees that are flagrantly 'had it' and about to collapse are easy to deal
with. It's the ones with less evidence we need to examine further. If we
always take the safe route, we run the risk of slowly institutionalising a
culture of removal when none is needed. I like the idea that David can quote
citations and say, "see, I have taken contemporary work, and applied it in a
professional manner." That's why we have education - it hgelps to move our
thinking forward.
jd
----- Original Message -----
From: "Daniel Wynn" <Daniel.Wynn@xxxxxx.gov.uk>
To: "UK Tree Care" <uktc@xxxxxx.tree-care.info>
Sent: Wednesday, December 07, 2005 6:23 AM
Subject: RE: Beech + Meripilus = fell ?
Mike
Further discussion; When assessing the condition of a potentially unsound
tree and its position in relation to targets I seem to revert to asking
myself the following questions; Would I be happy standing up in front of a
Judge and/or the grieving relatives to explain why the tree had failed and
(god forbid) killed someone when I knew there was a decay pathogen present
and that the presence of this type of pathogen is widely known to cause
instability? Or to put it another way, could I reasonably foresee that the
tree might fail, or if not and then it did, could I then argue that I could
not have reasonably foreseen it?
It is all well and good quoting alternative assessments of the status of a
fungi, but David Lonsdale's book 'Principles of Tree Hazard Assessment and
Management' is widely used by just about everyone I know in this industry. We
all use a variety of books but this one has a good pedigree which is
difficult to ignore. Can I ask how would you argue in court against
Lonsdale's works if you pronounced a tree 'an acceptable risk' that
subsequently failed?
DW
mike@xxxxx.co.uk 07/12/05 13:08 >>>
Edmund et.al.
I was intending to post in response to the wider issues discussed in and
implications of this thread but your post and those of Chris Wilken, Neil
Edmundson and Chris Hastie prompt a more immediate response.
CW: Bottom line is, if you have a Beech with Meripilus on your hands with a
significant target present, there really is only one outcome, get rid of the
tree pronto, it's going to go sooner rather than later anyway.
ME: This seems to me to be an illogical argument based on the propositions
that M. Giganteus always results in the failure of the tree and that the
tree always has a significant target. As with the whole spectrum of
ecological relationships there are no 'yes or no', 'black or white' answers
in respect of the effects of fungi on tree stability. There are degrees of
just about everything.
CW: You could get all technical I suppose, and argue that the tree has years
in front of it. End of the day, it's only a tree, plant 2 or 3 more in its
place, then, (and here's the difficult part), maintain the trees so they
establish.
ME: That's another sweeping statement, which ignores the value of the tree.
Regarding the Barnsbury beech, a summary of the basic facts as I understand
them:
1) the council identified M. giganteus at the base of the tree adjacent to
the footway.
2) For whatever reason, the council spent hundreds of pounds commissioning
an independent assessment from David Evans who, after what appears to me to
have been an appropriate inspection, concluded in a well reasoned and well
referenced report "In summary, the tree at has a very low risk of harm
(1/200,000). A reasonable level of risk, where the risk is imposed is
considered to be 1 in 10,000." Whether or not you accept the qtra
methodology is irrelevant because the key is the opinion that the tree
represented "a very low risk".
3) For reasons unknown to me, the council decided to spend yet more
taxpayers money on a third opinion and commissioned a third report from ASC
Consulting, the conclusion of which I wanted to cite but have as yet been
unable to obtain consent to reproduce. The recommendation of this report is
to fell the tree on safety grounds.
4) the tree was felled and the stump ground. I then received photographs of
the stump during stump cutting.
It is clear from the council's own website and the local press that the tree
had considerable value and was locally important.
EH: Yes, I always was of that persuasion, depending obviously on the
context, and it has been very instructive to see the increasing
sophistication of tree inspections which enables even well known "villains"
to be weighed up carefully before felling is ordered (or not).
I have felled a succession of beech with Meripilus on highways, and in well
populated parks, and never was there any leeway in the budget whatsoever: in
fact usually we were limited to so called safety work anyway. The notion of
commissioning sophisticated analyses in these contexts is simply fanciful.
Still Chris Wilken has a point, and perhaps its a local authority point,
which is that once the Meripilus has appeared we know that the tree either
has, or will become, hazardous. We then have to justify spending several
large sums of money either to endorse a judgement that cost us nothing when
we made it ourselves, and to receive a report which says its alright now but
you'll have to spend every year on a new report.
ME: These are the kind of sweeping statements that have resulted in the
Meripilus = fell conclusion. In one situation the tree may have such
limited value that resources are best allocated to removal of the perceived
hazard rather than to further assessment. At the other end of the scale,
people are prepared to spend inordinate amounts of money retaining beloved
but unstable trees and between the two is a scale of value. This point is
wasted in the context of the Barnsbury beech because the money had been
spent and spent again before the tree was felled against the advice of a
well considered report written by a respected consultant.
CH: However, Edmund's point about budgets is well made. It seems unlikely
(though perhaps just possible) that a large tree with a moderate - high use
target with M.g. is going to have a significant 'safe' life
expectancy. It's going to have to go eventually, and probably quite soon, so
why delay the inevitable and incur the monitoring costs in the mean time?
ME: Firstly, I disagree with your suggestion of inevitability that M.
giganteus will result in the loss of a tree. Secondly, in the context of
urban tree management, the argument that "why delay the inevitable" seems
illogical. As all trees will die and fail if left in a natural state, your
proposition leads to the conclusion that we should fell all trees rather
than delay their inevitable demise.
CH: It seems to me to be eminently sensible, in the context of LA budgets,
to deck the thing and spend the money you saved on monitoring on
establishing some replacements.
ME: This statement ignores the tree's position on the scale of value from
almost worthless to priceless. As I have stated above, there should quite
rightly be consideration of whether there should be further assessment or
removal/reduction of the hazard.
NE: In respect of this thread I would refer all participants to the final
paragraph on page - 121 - of David Lonsdale's book 'Principles of Tree
Hazard Assessment and Management'
It seems to me that when Meripilus G. is detected any deliberation as to how
long the tree stands should concentrate on the use/population of the target
area and not the condition of the tree.
ME: To rely on the Lonsdale reference seems to me slightly spurious. This
two page reference opens by describing the decay as a 'white rot' citing
work published in 1958, when we are now aware that the fungus has a soft rot
mode. To quote from David Evans's report "The presence of fruiting bodies
of M. giganteus alone does not necessarily mean that the structural
integrity of the host tree is compromised. The fungus can be associated
with the degradation of a long dead tap root (Schwarze et al, 2000), or
relatively small diameter woody roots (Burdekin & Phillips, 1992). Even
where there is colonisation and decay of structural roots, as long as there
is sufficient proportion of sound structural roots (two thirds), or a
residual upper wall thickness on buttress roots greater than 0.15 x DBH,
then stability is not significantly impaired (Fraedrich & Smiley * Smiley &
Coder 2001). In the case of this Beech tree, because it has lean to the
south and it being an angiosperm, the integrity of structural roots on the
tension side (north) are particularly important." (The Meripilus was on the
south side).
Perhaps this is too much information and, for some, to much opinion, but it
needs to be said.
Mike
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