DIGITALNA ARHIVA ŠUMARSKOG LISTA

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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 Tabic 2 CLASSES USf.D HHI KtLATIVE BASIC WOOD DENSITY´ Density class Score Percent 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 |