DIGITALNA ARHIVA ŠUMARSKOG LISTA
prilagođeno pretraživanje po punom tekstu



ŠUMARSKI LIST 1-2/1966 str. 166     <-- 166 -->        PDF

penological, orographical and hydrographical conditions in this country are so varying
and rich in transitions that even at a distance of only one hundred metres
the conditions for growth and development of forest trees may differ considerably.
This occurs especially in the areas of a labile climate where in time intervals of
only 10 years the sequences of years with the elements of the Mediterranean or
continental climate are alternating. The consequence of all this is a great genetic
variability of our forest - tree species, i. e. their richness in ecotypes and biotypes.
The natural variability of our forest trees has not yet been enough studied and it
appeared more and more as a problem at the occasion of selection of seed stands
and plus trees. However, all the mentioned difficulties could not be an obstacle to
the selection of plus trees because in the further work in this field there will be
effected the necessary amendments and corrections thanks to the new knowledge
and the findings in the nature.


a) Plus trees of coniferous species


Bearing in mind the objective of tree improvement and the small occurrence
of conifers in our forests we started first with the selection of plus trees of these
species. This work was done by the internal and external collaborators of the Institute
for Conifers at Jastrebarsko (Croatia), the Institutes for Forestry and Timber
Industry in Ljubljana, Sarajevo, and Beograd (Slovenia, Bosnia and Hercegovina,
and Serbia), and of the Forest Institute in Skopje (Macedonia). These plus trees are
phenotypcs selected mainly on the basis of biological characters. A smaller number
was selected on the basis of a superior growth rate (in Slovenia: 26 trees of Larix
decidua, 7 trees of Pinus nigra, 2 trees of Picea abies). On the basis of the technological
characters the selection was performed before all in the species of Picea abies
(growth-ring uniformity — resonance timber), Larix decidua (quality of wood), Pinus
silvestris (with small and high proportion of heartwood), etc. Selected were
also trees of Pinus nigra, P. peuce, and P. silvestris with an above-average resin
production (in Serbia and Macedonia). The latter trees are not given in the enclosed
Tab. 3.


In Table 3 can be seen the number of selected plus trees of the principal species
of autochthonous and allochthonous conifers according to the individual Republics.
Their total number is 1,061. The selection of plus trees is not finished because all
forests of coniferous species were not yet surveyed.


b) Plus trees of broadleaved species


To the selection of plus trees of broadleaved species was paid by the researcn
institutions a sufficient attention, in conformity with the general and economic significance
of these species in the individual Republics. This selection was carried
out by the collaborators of the Institutes in Beograd, Sarajevo, and Skopje, as well
as by the Institute for Dendrology and Genetics of the Forestry Faculty Zagreb.
The plus trees were selected on the basis of phenotype and biological characters
In Table 3 is visible the number of plus trees according to the Republics and species.
Their total number is 476 which is less than the corresponding number of coniferous
trees. Also the selection of plus trees of broadleaved species has not yet
been finished.


c) Plus trees of Poplars and Willows


The selection of plus trees of Poplars and Willows was carried out by the collaborators
of the Poplar Institute, Novi Sad (Serbia), the Institute for Dendrology and
Genetics of the Forestry Faculty, Zagreb (Croatia), and the Institutes in Ljubljana
and Skopje. Although the foreign selected clones of Poplars and Willows contributed
considerably to the increase of the wood production of these species in this
country, we started to study the native species of these two genera and to select
their plus trees, which are already used and will further be used as an initial material
for improvement. In this work conspicious results have been achieved by investigators
of the Poplar Institute in Novi Sad and of the Forestry Faculties in Beograd
and Zagreb.