DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 1-2/1966 str. 64     <-- 64 -->        PDF

of a population can be preserved through a proportionally small number of
representatives. This is particularly true with regard to the preservation of
genetic material for sexual reproduction and improvement. However, if one
also has in mind other objectives including genetic studies of the material, use
of it for seed production, etc., he should also consider these needs in a decision
about the minimum of necessary genotypes. In general terms, a small sample
is usually considered to be one containing fewer than 30 units. According to
Wrigh t (1962), statistical theory cost and genetic conditions make small
samples of 1 to 16 trees each in many repetitions preferable to large samples
of 100 individuals or more in few replications.


POSSIBILITIES FOR THE PRESERVATION OF THE GENE POOL IN
NATURAL FORESTS


The gene pool of natural forests can be preserved by maintaining living trees
in nature reserves or in special plantations.


By »nature reserves« we mean large forest complexes and smaller tree
groups, or as a last resort individual trees which are given fullest protection
by law. The size of the reserves and the method of treatment will depend not
only on the basic purpose of preserving of the natural state, but also on other
objectives such as education, tourism, recreation and various types of scientific
study.


Possibilities for the establishment of nature reserves are relatively limited.
It will often be necessary to reproduce the selected sample of the gene pool
and to put it into special plantings in order to preserve it.


Reproduction of the selected material will often require studies.
Special types of plantations for preservation of the gene pool of natural
forests are:


(1) arboreta and living archives
(2) seed orchards
(3) provenance tests
(4) progeny tests
(5) clonal tests
Each of the types of plantations mentioned has a definite objective which
can be harmonized with the need to preserve the gene pool. There are numerous
publications dealing with the problems and methods of their establishment.
These problems will be discussed here only with regard to the possibility of
preserving the gene pool.


The terms arboretum and living archives describe plantings destined for
the preservation of the gene pool. Other purposes of these plantings are
biological studies, use of flower and seed material for hybridization, educational
purposes, and recreation. Plantings of this type are rarely established on the
principles of statistics. They are especially suitable for the preservation of individual
trees representing populations, or for the preservation of the gene pool
with a small number of representatives, and they can rarely be considered
for the preservation of group samples of natural populations.


Seed orchards are plantations for the production of seed of the selected
parents. They can be established by the use of the vegetatively propagated
material of plus trees or elite trees (»clonal seed orchards«), or by the use of
plants of half-sib families as »seedling seed orchards« (Schreine r 1962).
Clonal seed orchards are usually established by use of a fairly large number