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ŠUMARSKI LIST 7-8/1972 str. 13     <-- 13 -->        PDF

Since it was found that the bark thickness depends on the diameter of stemwood
we made a numerical smoothing of the double bark thickness of the stemwood of
mean dimeters o.´b. ranging from 7 to 57 cm. by means of a regression equation of
the 2nd degree parabola, viz.: y´ = a+ bx + ex2; where


x = mean diameter of the roundwood o.b. in cm., and


y´ = double bark thickness of the stemwood in mm.


The results of numerical smoothing are given in Tab. 3 and Fig. 3.


The results of numerical smoothing show that with the stemwood diameter
increasing, the bark thickness increases also. The ratio between the double bark
thickness of the thinnest and stoutest roundwocd under discussion was 1:3.


However, the percentage of bark thickness in relation to the roundwood diameter
decreases with the roundwood diameter increasing. In the same manner, with the
roundwood diameter increasing, also the volume of bark decreases in preoortion to
the volume of roundwood over bark and under bark. The percentage of the bark
volume In proportion to the volume of wood and bai´k amounts in the stoutest
roundwood under discussion to 10.3%, and in the thinnest roundwood to 26.3l3/o, so
that these percents stand in a 1:2.0 ratio. Whc r determining the net volume of roundwood
(logs and pitprops), which is sold over bark, it is best to determine the share
of bark by means of the bark percentage.


We ought to refrain from the frequently used method of calculating the bark
by substracting from diameter o.b. the double bark in whole centimetres, because
such a method of determining the share of bark may lead to gross errors.


Considering the relatively small participation of branchwood in the roundwood
(logs and pitorops), as well as the small difference of the bark volume percentage
between stemwood and branchwood, the bark percentage of stemwood can also be
applied to branchwood. The deviation will be negligible, while the procedure is of
practical importance.