  In the research scope of forest stand self-thinning, the analysis reveals a
broad picture in which the -3/2 rule takes a definite and special place. The
application of the simple geometrical model to the Douglas-fir and Scots pine
data suggests that the slope of the self-thinning curve will not remain
constant during the course of growth and self-thinning of a single forest
stand. Most probable, at the initial stages of stand growth the slope will be
less than -3/2 and at old ages of the stand the slope will be higher than -3/2.
Inevitably, a time will come when the slope is exactly equals -3/2. In other
words, the slope -3/2 is an obligatory state in the course of self-thinning of
a forest stand. At the very time of -3/2 slope two particular features coincide
with it. One is that the total bole surface area remains constant. The length
of the constancy stage would probably vary with species, initial stand
densities, their spatial arrangements, conditions of growth, and other specific
factors. Another feature of the time is that a geometric similarity in the
growth of the forest stand takes place, which is not in a contradiction with
the -3/2 rule as it had been formulated by its authors. To put it shortly, the
slope -3/2: i) is a very specific and obligatory state in the process of forest
stand growth and ii) is not an asymptote but rather a transitional point (span)
in the time of growth. These two assertions may be called a transitional status
of the -3/2 rule. The geometric model of a forest stand (Gavrikov, 2014) has
proved to be rather helpful at analyzing of real forest stand structure and
dynamics. Despite of its extreme simplicity (it uses cones as representations
of trees) the model looks like having enough similarity with real even-aged
forests since the model's predictions are often reasonably close to measured
values of power exponents.
