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ŠUMARSKI LIST 1-2/1966 str. 29     <-- 29 -->        PDF

1958 a and b and 1959). A genotypic variation in, among other things, branch
thickness and branch angle, and in the number of branches per whorl in clones
of Scots pine, has been demonstrated by Nylsso n (1956), and in branch
angle and growth rate, by Arnborg and Hadders (1957). Points are
assigned also for the number of branches per whorl. This character seems to


Density class Score


Extremely high 115.5 . 1«

Very high 107. 5-111.´« a.i

Hleh io% 5-107.U . i

Ave rage 96.5-103.<« 0

Low 92. 5-96.1« -i

Very low 88. 5-92.1« -2.5

Extremely low 88.1« - I«

1 Relative basic wood density =s density observed for »lus
trees In oer cent of density calculated on the basis Bf mean
annual ring´ width tor « number of sample trees of the same
trep species at the same latitude anil altitude.

be dependent on genetic factors to a higher degree than is the thickness of the
branches. With regard to branch angles (see Table 1) in Scots pine, the
heritability values, for this character in ten-year-old progenies, which were
estimated in two field experiments (Eklundh Ehrenberg, 1963) in
Sweden, varied between 14 and 96 per cent. There are, however, wide variations
in heritability estimates of this character between experiments and even
between branch whorls. Johnsso n (1965) has shown in clonal experiments
on Scots pine in various environments, that the branch angle is quite strictly
controlled genetically. He even found that the genotype »is the sole determinant
of the branch angle«.

»The proposed plus trees of Scots pine and Norway spruce were investigated,
as previously stated, with regard to basic density, which gives the dry
substance content of the wood in g per cm3 or in kg per m3 of raw wood. The
basic density varies within wide limits. In the stand, the standard deviation for
the trees is between 7—8 per cent. The mean standard deviation for Scots pine
and Norway spruce for the whole Sweden is about 10 per cent of the mean
basic density (see Eriscon , 1961, Table 2). In one and the same stand we
can find, in certain cases, one stem with a mean basic density of 320 kg/m:!f,
and another stem with a basic density of 480 kg/m3f, when the mean basic
density of the stems in the stand is 400: kg/m3f. From the wood of the stem
first mentioned we can obtain 160 kg dry pulp per m3f of raw wood; from the
other stem the corresponding figure is 240 kg when the same cocking process