On Tue, 5 Nov 1996, Oscar Garcia wrote:
> Now, despite what my New Zealand friends said, I believe that this
> kind of approach will give you distribution estimates as good as you
> have the right to expect. The real problem is that talking about
> tree diameter distributions in general does not make much sense. To
> repeat it one more time, usually TREE SIZES ARE NOT RANDOMLY
> DISTRIBUTED ON THE GROUND. Competition induces short-range negative
> spatial correlations (the neighbor of a large tree is likely to be
> small).
I agree with this. However, the effect of using distribution models is
usually to underestimate stand variation for planning purposes. On the
one hand you have spatial correlations of the type mentioned by Oscar,
but on the other hand you have conservative estimates of the extremes of
the distribution, as a natural consequence of sampling. According to
Richard Woollons, experience suggests that the latter effect may
predominate. I would add that underestimates of stand variation are
likely in stand diameter distributions obtained from inventory plots as
well.
Regards,
Euan
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Dr Euan G. Mason Silviculture, Modelling and
Senior Lecturer Decision-support systems
School of Forestry
University of Canterbury New Zealand's professional
Christchurch, New Zealand Forestry School
Home page: http://www.canterbury.ac.nz/fore/EUAN.HTM
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