Changes in the configuration of a tree stern result insignificant
differences in its total volume and in the proportion
of that volume that is merchantable timber. Tree allometry, as
represented by stem-fo~, is the result of the vertical force of
gravity and the horizontal force of wind. The effect of wind force
is demonstrated in the relationship between stem-form, standclosure
and site-conditions. An increase in wind force on the
individual tree due to a decrease in stand density should produce
a more tapered tree. The density of the stand is determined by the
conditions that the trees are growing under. The ability of the
tree to respond to increased wind force may also be a function of
these conditions . This stem-form/stand-closure/site-conditions
relationship was examined using a pre-existing database from westcentral
Alberta. This database consisted of environmental,
vegetation, soils and timber data covering a wide range of sites.
There were 653 sample trees with 82 variables that formed the basis
of the analysis. There were eight tree species consisting of Pinus
contorta, Picea mariana, Picea engelmannii x glauca, Abies
lasiocarpa, Larix laricina, Populus tremuloides, Betula papyrifera
and Populus balsamifera plus a comprehensive all-species data set.
As the actual conformation of the stern is very individual,
stem-fo~was represented by the diameter at breast height to total
height r~tio. The four stand-closure variables, crown closure,
total basal area, total volume and total number of stems were
reduced to total basal area and total number of stems utilizing a
bivariate correlation matrix by species. Site-conditions were subdivided
into macro, meso and micro variables and reduced in number
3
using cross-tabulations, bivariate correlation and principal components
analysis as screening tools. The stem-fo~/stand-closure
relationship was examined using bivariate correlation coefficients
for stem-fo~ with total number of stems and stem-fo~ with total
basal area. The stem-fo~/site-conditions and the stand-closure/site-
conditions relationships were examined using multiple correlation
coefficients. The stem-form/stand-closure/site-conditions
relationship was examined using multiple correlation coefficients
in separate analyses for both total number of stems and total basal
area.
An increase in stand-closure produced a decrease in stem-form
for both total number of stems and total basal area for most
species. There was a significant relationship between stem-form
and site-conditions and between stand-closure and site-conditions
for both total number of stems and total basal area for most
species. There was a significant relationship between the stemform
and site-conditions, including the stand-closure, for most
species; total number of stems was involved independently of the
site-conditions in the prediction of stem-form and total basal area
was not. Larix laricina and Betula papyrifera were the exceptions
to the trends observed with most species.
The influence of both stand-closure (total number of stems in
particular) and site-conditions (elevation in particular) suggest
that forest management practices should include these- ecological
parameters in determining appropriate restocking levels.