DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 1-2/1966 str. 14     <-- 14 -->        PDF

standpoint. His investigations indicated that the most desirable genotype of
Scots pine is the one with a wide crown and horizontal branches.


These investigations indicate that tree breeders should give more
consideration to economic factors in establishing objectives of tree improvement.
We consider it necessary to intensify such investigations, and to extend them
to other species. In this country, forest industries utilizing oak regard the superior-
trees from the standpoint of money yield to be those which do not have a very
long stem, but instead have a large fork at the base of the crown.


It is understandable that such a manner of assessing forest trees has
repercussions in the choice of plus trees. The question is raised whether or
not plus trees are those which have a narrow and small crown with fine and
thin branches.


5. INHERITANCE AND ENVIRONMENT
In the selection of plus trees the factors of environment should also be
taken into consideration. They influence in many ways the habit and growth
rote of the tree. In Norway spruce, the dimensions of mother trees are to a
greater extent than has been assumed the result of environmental factors rather
than inheritance according to Kiellande r (19). The best trees of European
larch were found in England on very good sites. Where a factor is limiting,
trees have a tendency to concentrate on this factor at the expense of others (26).
Wild e (39) stressed that in the selection of plus trees, the productive capacity
of the soil should also be taken into consideration. Matthew s (24) stated
that in selection of plus trees attention should also be paid to the climatic
conditions, age, origin and life history of the tree or of the whole population.


It is also important to pay attention to the silvicultural treatments which
have been caried out. Microclimatic and microedaphic conditions are also
important Jovančevi ć (18) recommends paying attention in the selection
of plus trees to the ground vegetation and to the lowest phytocenological units
(fades) which can serve as an indicator for microecological conditions, because
in such localities it is possible to find local races of forest tree species. Wc
believe that determination of the plant association in natural stands where the
tree occurs will also give us indications about the ecological conditions of the
population. In a general way it is necessary to know well the external conditions
under which the tree is growing in order to evaluate the individual tree as
well as possible.


If we know the external conditions under which a tree has grown and the
biology of the species, we shall be able to assess approximately in what measure
the observed character is the reflection of the inherited factors, and in what
measure the reflection of the environment, even without full knowledge of
heritability of important characters.


6. SELECTION OF TREES IN PLANTATIONS
Selection of plus trees can be made from non-indigenous stands if these
stands represent the progeny of one uniform population (Langne r (21)). If,
however such a culture represents individuals from different populations in
which many various genotypes of unknown origin are included, selection of
plus trees cannot be made. This statement refers, as also Langne r states,