DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 1-2/1966 str. 167     <-- 167 -->        PDF

In Table 4 is given a survey of the selected plus trees of the mentioned species
acording to the Republics. The selection started with Black Poplar. It plus trees
were used first for the production of clone material and later as the parent trees
for controlled hybridization. The selection of plus trees of white Poplar, Aspen and
Willows is in progress. The selection was carried out chiefly in the plains. In the
mountain regions selection has only started.


A great number of plus trees have already been transferred into living archives,
viz. populeta and saliceta. The value of the plus trees of Poplars and Willovs
is being checked by testing their vegetative and generative offsprings.


3. Investigation of the lower taxonomic categories
The basis and the most important method for the improvement of forest trees
is represented by the selection of individuals in natural forests, which from the genetic
standpoint are promising for the further work on inprovement. Such individuals
still exist in natural forests and we have only to find out and describe them,
and to study the hereditary stability of their biological and commercially useful
characters. In this country a sysstematic study of the natural variability of forest —
tree species has practically commenced with the selection of plus trees. Initial investigations
in this field are to be assigned to the Institute for Dendrology and Genetics
of the Forestry Faculty in Zagreb (1, 2, 3, 4) and the Forest Institute, Skopje
(73, 74, 76, 77). Such investigations are given more and more place also in the programmes
of other research institutes.


Previous investigations of Socts Pine (Pinus silvestris L.) were indicative of the
existence of a lowland type and a mountain type. In the mountain type were found
and studied the following forms: the first displaying platelike bark (and high percentage
of heartwood), the second with long-scale bark (and small percentage of
heartwood), and a third form with small — scale bark and a strongly pronounced
pyramidal crown (elite form) which does not suffer from snow (Macedonia, Slovenia).


In Austrian Pine (Pinus nigra Arn.) was proved the occurrence of the subspecies
Pallasiana, dalmatica, gočensis, ssp. gočensis var. illyrica, as well as of the ecotypes
on limeston and silicate substrata, and of the biotypes with different crown forms
and differences in the rhythm of the growing seasons (Croatia, Macedonia, Serbia).


In Silver Fir (Abies alba Mill.) were used also transitional forms between Greek
Fir and European Fir, as well as forms with rough and smooth bark. Investigated
were concurrently the couses of the dieback of European Fir, and the occurrence
of its natural ecotypes and mutans. On the territory of the SIR of Slovenia has been
established a catastrophic dying back of this species over an area of 30,000 ha. In
progress are investigations to explain this phenomenon genetically, and attempts
have been made for the selection of disease — resistant individuals. Found was an
ecotype which, for the time being, manifests a resistance to dieback. This ecotype
exhibits a greater increment which exceeds considerably the normal mean increment
of Fir in this area.


In Norway Spruce (Picea abies (L.) Karst) are studied forms which distinguish
themselves with respect to the type of branching, then forms displaying uniform
growth rings (resonance wood), and forms with a rough and smooth bark, as well as
the occurrence of natural mutants (Slovenia, Bosnia and Hercegovina, Croatia, Macedonia).


In European Larch (Larix decidua Mill.), whose natural range is confined to a
smaller area (alpine portion of Slovenia), are performed compass investigations
with the aim to establish the specific morphological and physiological characteristics
of its geographical race called »Bloody Larch«.


In Macedonian Pine (Pinus peuce Griseb.) were noted special ecotypes occurring
on limestone and silicate parent material, as well as early and late phenotypes (Macedonia).


In the broadleaved species too, more and more the phenomenon of natural variability
has been noted. In this sense the study of Beech, Oaks, Lime-trees, Birch,
Walnut, Locust-tree, etc. has been initiated.


In Beech (Fagus silvatica L., Fagus moesiaca Maly (Czech), it was established
that to a greater extent it belongs to the species of Balkan Beech. Its subdivision