Mark -
As a major fan of the Helliwell System, I would like to offer a couple of
thoughts on yours:
* Future amenity value
This might be something of a red herring, as the small crown size of a young
but ultimately large tree is offset by a greater longevity. In my view this
is how Helliwell factors in 'future amenity value'
* Tree influence (to nearby structure etc)
Surely this could be said to be covered by 'relation to setting'?
We are also looking to changing the Form factor as it seems to be the most
subjective
I think that this is deliberate on the part of Rodney H., but where people
come unglued is trying to relate 'average' for a species to 'good'. Again
this is deliberate: if its a pretty run-of-the-mill oak, it may have what
you consider to be a good form, whilst still actually being average for the
species. If you think about it, this makes sense: higher score for special
trees not just any old examples of their kind.
Hopefully we have come up with a factor that will consider the
trees structural integrity as well as just its shape or appearance.
I would humbly suggest that if the thing is going to fall to bits then its
life expectancy would be somewhat lower than if not. If this could be
corrected by, say, crown reduction, then consider the loss in crown size
reducing the value and possibly a lower 'form' score too.
It has been field tested and changed over a period of 4 years,
With all possible respect, I would gently point out that Mr H's system has
been around for, oh, dunno, a helluva long time. It might even predate Bill
Anderson's first job :-)
One other point, I have heard people, usually from over-staffed consultancy
offices in Essex, complain that Helliwell is too visual and what about
conservation value? Given the illusive 'special factor' score allows for
effectively doubling the result of an ordinary assessment, I suggest that
'great rarity' could be used systematically to cover trees of a high
conservation value.
The main thing I find helpful about Helliwell, is that, by cross-referencing
your thinking, it is possible to consider factors that it might appear to
ignore. I hope that the above few examples help to show how this works.
Despite what might appear to be a critique Mark, I hope that your system
works out and look forward to seeing something published in the future. If
its based on Helliwell, have you thought about running it past him for his
view?
Regards,
Julian.
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