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FENNIA 66, N;o 4
35
If the part of the tree forming the log shows defects caused by rot, the
probable shortening of the log caused by them should be taken into account. Rot
must not occur in the log except to a very limited extent in class II.
Logs of deciduous trees.
I. Plywood logs. The part of the tree forming the log must be fairly straight
and must have few branches. Healthy, living branches are permissible, however,
up to a diameter of about 1", if they do not occur very densely. Only a few
dry branches may occur at suitable intervals from each other (so that logs of
the length of 3.5—4.5 feet are obtained from the portions between them).
Rotten branches are not permitted. Minor surface defects are permissible in
mature stands, if it can be considered probable that they have not yet caused
rot. Cracks caused by frost and defects due to fire are not permissible, and
they must be omitted from the measurements.
II. Saw logs. These consist of logs that do not fulfil the requirements of
plywood logs, but fulfil the requirements for pine logs of class III.
The total volume of logs, as defined above, amounts to 8 623.6
million cubic feet, of which 5 590.2 million cub. ft. represent pine logs,
2 557.0 cub. ft. spruce logs and 476.4 million cub. ft. logs of deciduous
trees (chiefly birch). If the top diameter is fixed at 9", 6 163.1 million
cub. ft. are below it and 2 460.5 million cub. ft. above it. If the lowest
size of logs were fixed at 5", as is often done, their volume would be
increased by at least 2 000 million cub. ft.
It is estimated that 58.8 per cent of the pine logs belong to class II
and 33.8 per cent to class III. Thus the proportion of logs of the best
class, or class I, is only 7.4 per cent, but the requirements of this class
are very high, the logs giving almost entirely u/s sawn timber. The
requirements for spruce and birch logs of class I are very much lower,
and therefore this class exceeds class II in quantity.
A comparison between the southern and northern parts of Finland
shows that both the total volume and the average per hectare are
considerably higher in the former. The quality of logs in North
Finland is also in general somewhat lower than in the southern part of
the country. This is especially the case in regard to spruce logs and,,
above all, in regard to birch logs.
5. The annual growth of the forests.
The calculation of the growth, as of the growing stock, is based
both on the results obtained from the sample plots and on the ocular
estimation carried out, stand by stand, on the survey lines. The
latter were checked and, if necessary, corrected by the methods
provided by the calculation of probability, generally being employed.
Various auxiliary tables were drawn up for the purpose of calculating
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