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ŠUMARSKI LIST 11-12/2006 str. 47     <-- 47 -->        PDF

M. Prka: VISINA I ČISTOĆA DEBLA BUKOVIH STABALA PO VRSTI SIJEKA I POSTOTAK ... Šumarski list br. 11–12, CXXX (2006), 511-522
SUMMARY: The subject of research were purity and height of beech trees,
as well as the participation of technical roundwood in trunks and tree tops in
relation to breast diameter and the type of felling.


Research was carried out in the economic unit „Bjelovarska Bilogora“ of
Forest Office Bjelovar, Forest Administration Bjelovar. Data gathering, i.e.
measurement of exemplary beech trees was carried out in 36 areas on 46
occasions (fellings). All the areas belong to ecological-economical type II-D11
and structural class BEECH, with the rotation of 100 years, which participates
in the area of the economic unit with 76.1 %, and with 80.6 % in its timber
stock.


Measurements of exemplary trees were made in relation to diameter class
and the type of felling. Trunk purity was measured on 693 exemplary trees, of
which 237 mere measured in the felling areas of preparatory felling, 139 in
the areas of thinning felling, while 317 were measured in the areas of final felling.
Trunk height was measured on samples including 787 trees in the areas
of thinning felling, 788 trees in the areas of preparatory felling, 467 trees in
the areas of seeding felling and 266 trees in the areas of final felling – a total
of 2,308 trees. Altogether, the research included 3,001 exemplary trees.


Trunk purity is defined as the length of trunk from the butt-end to the first
live or ingrown branch, and other flaws which are not superficial, and take up
more than 15 % of the breast diameter. Trunk height is defined as the length of
trunk from the butt-end to the place where the single longitudinal axis of the
tree disappears, or as the length of trunk from the butt-end to the first thicker
live branch which coherently forms the top of the tree.


Bucking and sorting (classification) of timber assortment of technical roundwood
was carried out according to two standards: Croatian Standards of
Forest Exploitation Products from 1995 (HRN), and European Standards EN
1316-1:1997 (HRN-EN).


Occurrence of flaws has crucial influence on trunk purity. Occurrence of
faults is random in character and isn’t in correlation with any measurable
tree parameter. For that reason we couldn’t establish a closer connection between
trunk purity and breast diameter of tree.


Average values of trunk height according to diameter class increase from
thinning felling towards final felling. Thinning felling has an extremely falling
(almost linear) trend of trunk height average with the increase of diameter
class. The average values of trunk height of final felling show the highest values
of all the diameter classes.


Such distribution of average trunk height according to diameter class and
the type of felling is not accidental. Trunk height of trees in the stand depends
on a range of factors, from hereditary (genetic) predisposition of trees, over
conditions of growth, to the position of trees in the stand. The distribution of
average trunk heights in the felling areas of a certain type of felling is to a
great extend a consequence of the decisions that we make during the selection
of trees for felling in a particular type of felling. Because of their poor technical,
(but not evolutionary) quality, forked trees are the first choice for assignation
in thinning felling and preparatory felling.


According to the European Standards, the participation of technical roundwood
in the net tree volume is greater for trees of all diameter classes. The
difference decreases with the increase of breast diameter of tree, and it ranges
from over 20 % for the thinnest diameter classes to almost 5% in the thickest
diameter classes.


Upon implementation of the two standards (HRN and HRN-EN), a difference
was established between the participation of technical roundwood in