This letter informs you of the forestery reference in Rev Ciencia
en México 19 (76) 1994: 141-152 by Bertil Matérn of the Dept of Forest
Biometry, University of Agricultural Sciences, Umea, Sweden. The Poisson
forest (Keuls et al., 1963), the angle count method (Bitterlich, 1984)
the central satellite model (Warren, 1991) are emphasized. Basal area at
breast height going to square meters per hectare is the main target.
Using Goodlands (1971, J Ecol) work on the Brazilian Cerrado quite
from Matérns brilliant review, the writer calculated these relations
4 niches1) grassland, 2) matorral (short open woods), 3) light forest &
4) forest. The relation of the 4 sites (X) to basal area (Y) is
site by number of tree species fits: Species = a + b(Site)3 + c
and Site by tree height fits: Height = a + b(Site) + c(Site)2. The
coefficients of determination are at unity, and these relations are
As the X and Y axes have only 4 points, perfect curves must result.
relations may help in the statistical management of new data from
When the foliar morphometric averages in 4 mezquitales (mesquite woods)
are so compared, logistic equations explain site by leaflet length and
site by rachis length, because the curve that runs through any 4 points
likely to be logistic, sine, exponential, extreme value, rational, etc.
Also, using (or overusing!) averages is just not the same as running a
through the many original data points. Bias must arrive, because the
experiential judgement of the researcher is called upon for expression
reasonable caution in the use of such models since many work as well as
another. When several thousand raw data points are run, the results
be DF Adj r2 = 0.25 or less, leaving one to wonder what happened.
More, of course. See Means, JE et al, Software for computing plant
biomassBIOPAK users guide, USDA, Forest Serv, Gen Tech Rep
which refers to a DOS program on Internet that has a library of
Go to http://www.fsl.orst.edu/lter/data/software/biopak.htm
Best Regards, Paul R. Earl
PS See Software at http://www.fs.fed.us/links/software.shtml
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