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ŠUMARSKI LIST 1-2/2001 str. 20     <-- 20 -->        PDF

M. Božić. .1. Čavlović: ODNOS DOMINANTNE VISINE. DIMENZIJE S.IEČIVE ZRELOSTI 1 NORMALNE DRVNE ... Šumarski list br. 1 2.CXXV (2001 ). 9-18
Osnova gospodarenja za g.j. "Kupjački vrh" od 1. Pravilnik o uređivanju šuma. N. N. broj 52 od 7.


1. 1985. do 31. 12. 1994. godine. Zagreb 1985. g. srpnja 1994. godine.
Program gospodarenja za g.j. "Belevine" od 1. 1. Pravilnik o uređivanju šuma. N. N. broj 11 od 31.
2000. do 31. 12. 2009. godine. Zagreb 2000. g. siječnja 1997. godine


SUMMARY: According to the current Forest Management Act, selection
(variable aged) forests in the Republic of Croatia are managed with the normal
model method, that is, according to the "New system of selection forest
management". Klepac (1961) based "The new system of selection forest
management" on Susmel´s correlation for the fir, Colletés for the beech and
on šurić ´s site quality classes.


In Susmel s and Colette s correlation, the mean height of dominant trees is
the measurable parameter of a concrete forest representing the link between
the forest and its normal model. The normal model could therefore be constructed
for each concrete case on the basis of the measured heights of dominant
trees. However, there is a problem of reducing the mean height of dominant
trees (in relation to those used by Klepac), arising from:
a) different ways of defining the notion of dominant height;
b) lowered dimension of physiological maturity in relation to crop maturity.


The authors studied the extent to which the reduction of the mean height of
dominant trees (resulting from different definitions of dominant height or from
achieving of a certain diameter of crop maturity with management methods)
influences the decrease in the growing stock based on the "New system... ".


The authors have used several parameters in their research:


a) Klepac s original normal model for the II, II//II and III site class corrected
to the German diameter degrees with the physiological maturity and the dimension
of the crop maturity of 70 and 60 cm;


b) four concrete stands, of which two were the managed selection stands from
the Management Unit "Milanov Vrh" (compartments 2b and 13a), in
which the distributions of tree numbers end with diameter degrees of 77.5
and 62.5 cm, and two were transitional stands from the Management Unit
"Crni Lug" (compartments 39c and 61 b), where the distributions of tree
numbers end with the diameter degree of 97.5 cm; and


c) the mean height of dominant trees for the Management Unit "Belevine"
measured for the Management Programme for "Belevine ".
The dominant heights were defined according to Susmel and Weis. The


height of the tallest tree was measured in every hectare of the Management
Unit "Belevine", and the mean height of dominant trees was calculated as
their mean value.


A reduction in the mean height of dominant trees or the dimensions of crop
maturity leads to a decrease in the growing stock of the newly constructed normal
model. The decrease by one meter per height is almost constant and
amounts to about 11 mVhafor the III site class at the maturity dimension of 60
cm, up to 16-17 m3/ha in the IIsite class with physiological maturity, or 17-18
nr´/ha in the compartment 39c located in the II site class, but its tariff is slightly
higher than the Surić-Pranjić tariff. The maximal relative decrease in the
growing stock is 146.31 m´/ha or 37.38 %. The decrease percentage by 1 meter
per height ranges from about 3.1 % for the II site class with the maturity dimension
of 60 cm to 4.1-4.2 %for the III site class with physiological maturity.


In order to avoid the decrease in the growing stock of the normal model
caused by different definitions of dominant heights, the original Klepac s normal
model corrected to the German diameter degree should be used in managing
selection forests.


Key words : normal model, dominant height, maturity dimension, growing
stock