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ŠUMARSKI LIST 1-2/1966 str. 75     <-- 75 -->        PDF

mother trees were well scattered throughout the population, but not scattered
too sparsely, we could then transfer nearly completely the gene pool of the
population into the seed lot.

The new platnations should include a large number of individuals. Since
some of the useful genes may show very low frequencies such as 10~2 per cent
or less, it is evident that a large number of individuals is desirable. But the
productivity of such stands are not as large as those of the stands established
with the seeds of elite seed orchards, because the former have not passed
through selections as intensive as the latter. Therefore, the establishment of
too large plantations of such purpose is not desirable from the viewpoint of
commercial forestry. Ten to twenty hectares must be the maximum on which
several ten thousand individuals can be grown. The plantations should be
divided into two or three plots and be located apart from each other, to avoid
total destruction by accidents.

Individual plots should be no smaller than two or three hectares. If the
preservation of specific genes is the objective in the plantation, smaller size
plots may be acceptable, but, on the other hand, the conservation of the total
gene pool requires larger plots because the peripheral members of the stands
cannot be used as seed trees for the next generation because of contamination
from foreign pollen.

In Kyusyu, the south-western most major island of Japan, we have been
making efforts to establish gene preservation stands since 1958. The efforts have
been concentrated on the four main conifers, Cryptomeria japonica, Chamaecyparis
obtusa, Pinus thunbergii and Pinus densiflora, which constitute the bulk
of all plantations in this area. Cryptomeria and Chamaecyparis are not naturally
distributed in Kyusyu, with rare exceptions. Populations were selected, such
as (1) ones exhibiting very good performance, (2) fairly old plantations, (3)
plantations famous for some special characteristic, and (4) undisturbed natural
stands. As for the two pines, on the other hand, there are many natural stands
and naturally regenerated second growth, so the effort was concentrated in
natural populations of nice growth and gcod tree from. However, nice plantations
were also sampled as well.

Seeds have been harvested from six stands of Cryptomeria, two of
Chamaecyparis, five of P. thunbergii and two of P. densiflora. These seeds
were sown in the nursery of Kyusyu Forest Tree Breeding Station at Kumamoto.
The seedlings were divided into two lots for each population, one being sent
back to the original Forest Districts and the second to some other Districts.
They were planted by the State Forest agents in a manner similar to usual
commercial plantations. Unfortunately, the total area for each population has
been too small, five to eight hectares. Sometimes, mistakes occurred, for
instance, when two lots of seedlings of different origin were sent to one District,
they were planted together in the same plot, making it impossible to get second
generation seeds of the characteristic gene pool for the two populations
separately. These plantings are not yet enough for Kyusyu and must be
expanded. In the other parts of Japan, similar work has been started more

The »gene pool« plantations are registered and their development is observed
periodically. The stands will be harvested when they have reached
commercial maturity. The time for collecting second generation seeds needs
special considerations. In general, young stands do not supply suitable seed,