Hi Tim and all,
How about ten times the diameter as in the 2005 version?
Over the last few years we've used a combination of both methods adopting
what appears to be the most appropriate.
Regards
Luke Steer
Chartered Arboriculturist
Treescapes Consultancy Ltd.
Tel: 015394 34698
Mobile: 07734 113964
www.treescapesconsultancy.co.uk
-----Original Message-----
From: Tim Moya <Tim.Moya@xxxxxxxxxxxxxxxx.co.uk>
Date: Thu, 24 May 2012 21:29:59
To: UK Tree Care<uktc@xxxxxx.tree-care.info>
Reply-To: uktc@xxxxxx.tree-care.info
Subject: RE: BS5837-2012 - Combined Stem Diameter
I think Paul has a point
My maths is not as good as it once was but it seems to me that there are some
scenarios where the BS formula for more than 5 stems will give a result that
makes no sense.
If you have a tree with one stem of 400mm and 4 stems of 100mm the first
calculation will give a root protection radius (RPR) which represents the
combined cross sectional area of the stem
If you add another stem of 100mm to the same tree and use calculation 2 you
get an RPR of about 80% of the smaller tree
The resulting root protection area for calculation 2 will be about 65% of the
smaller tree's RPA
If you increase the size of the larger stem to 600mm the result is that the
RPA for calculation 2 is about half of that for calculation 1 (even though
it’s a bigger tree)
For both the examples of calculation 2 above you would get a larger RPA by
taking the largest stem and treating the tree as single stemmed - although
this can't be the answer either.
One possibility would be to simply use the largest 5 stems and calculation 1
where there is a one large and several small stems. It would give a better
result
While not getting hung up on the maths is fair enough, the calculation in the
BS surely has to work as a reliable guide.
TIM MOYA
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