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FENNIA 66, N;o 4
23
the sake of comparison. In the forests dominated by pine in the
southern half of Finland medium-aged and mature forests have increased to
some extent and seedling stands possibly slightly, but fairly young
and over-mature forests have decreased slightly. In forests dominated
by spruce it is noticeable that the proportion of young and medium
age-classes has increased and the proportion of fully mature
age-classes has fallen off. In forests dominated by deciduous trees there
has been an increase in the classes above 40 years, especially in the
class 41—60 years, and a contraction of the area of the classes below
40 years, and especially below 20 years.
In the northern part of the country forests dominated by pine have
secured an increase up to the age of 160 years and forests dominated
by spruce up to the age of 120 years, while the proportionate area of
older forests has been reduced very much. These changes in the
age-classes are also partly due to the felling of the older and larger trees
of uneven-aged stands, partly, too, they cannot be actual, especially
as regards spruce stands, but are due to differences in estimating the
age of poorly developed spruce stands. The so-called over-mature
forests have decreased to far smaller areas than formerly. In the
forests dominated by deciduous trees growing on comparatively small
areas in North Finland an increase in the older age-classes is visible,
and an absence of change in fully mature age-classes and classes
approaching maturity, while the large percentage of medium
age-classes has fallen off to some extent.
8. The growing stock of the forests.
The volume or the growing stock of the forests has been calculated
both with and without bark and measured in cubic metres of solid
measure, which are indicated in the following pages by the sign: in3.
The calculation of the volume is based on the results obtained both
from the sample plots and by ocular estimates. As a basis for
calculating the volume of the sample plots volume tables were used that had
been prepared for the survey on the basis of extensive materials,
collected from about 10 000 accurate measurements of stems made
during 15 years. All the results of the ocular estimates were checked
before being employed and, if necessary, corrected by means of the
sample plots and of the methods of the calculation of probability.
The volume figures are limited to growing, living stock, the volume
of dried trees and windfalls being dealt with separately.
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