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ŠUMARSKI LIST 5-6/2009 str. 18     <-- 18 -->        PDF

I. Tikvić, Ž. Zečić, D. Ugarković, D. Posarić: OŠTEĆENOST STABALA I KAKVOĆA DRVNIH ... Šumarski list br. 5–6, CXXXIII (2009), 237-248
planning and management and rising management costs, have made this the
most important management and ecological problem in Croatian forestry.
Tree decline is a gradual, continuous, or in some cases, rapid loss of tree vitality.
In forestry, tree decline is assessed on the basis of the exterior appearance
of a tree, i.e. on the basis of tree damage assessment. Tree damage relates to
crown, stem and root damage. Crown damage assessment is based on crown
defoliation and changes in leaf colour. Tree dieback is sudden death of trees
due to diseases or a complex action of adverse factors. It can often stem from
a continuous decline of trees and a disturbed stability of forest ecosystems. In
Croatia, the most severely affected tree species are the two principal ones: pedunculate
oak and silver fir. Tree decline and dieback incur high financial losses,
amounting to as much as 40 % of the potential market value of forest
assortments. However, a decrease in non-market forest functions is much
more serious. The economic consequences of tree decline are reflected on the
quality and lower value of wood assortments. Dieback of pedunculate oak
trees leads to sapwood degradation and a decrease in assortment diameter,
which may amount to as much as 33 % of the diameter.

The goal of research was to determine the impact of pedunculate oak damage
on the structure and volume of wood assortments. Research was conducted
on tree samples from four management units in Vinkovci ForestAdministration, along the Županja - Lipovac road. Wood volume utilization of
dead and differently damaged trees of pedunculate oak was analyzed.

Tree crowns along the Županja - Lipovac road were found to be more defoliated
compared to those in the “Spačva basin” area. Crown defoliation of pedunculate
oak was about 60 %, which indicates decreased tree vitality.
Severely defoliated and dead trees manifested significantly higher biotic damage
in relation to slightly and moderately defoliated trees. The percentage
share of veneer logs and class I logs, as well as stacked wood, was higher in
trees with the first and second defoliation class. The share of lower class logs
(II and III class), as well as the percentage share of waste was higher in trees
with higher defoliation classes. Of the total wood volume, there were 20 % of
veneer logs in defoliation classes 1 and 2 (slight and moderate defoliation),
and 10 % of veneer logs in defoliation classes 3 and 4 (severe defoliation). According
to the percentage share of assortments in the total technical roundwood,
there were 37 % of veneer logs in trees with defoliation classes 1 and
2, and 18 % of veneer logs in defoliation classes 3 and 4. The proportion of
lower-class technical assortments was higher in higher classes of crown defoliation.
The proportion of second class logs in defoliation classes 1 and 2 was
11 %, and in defoliation classes 3 and 4 it was 19 %. The proportion of third
class logs in defoliation classes 1 and 2 was 15 %, while in defoliation classes
3 and 4 it reached 19%. There was more waste in defoliation classes 3 and 4
(30 %), and slightly less in defoliation classes 1 and 2 (27 %).

Tree damage lowers the quality of logs and lessens the income from pedunculate
oak management. Tree damage assessment may reduce the amount of
snags and increase management yields. Timely and appropriate tree damage
assessments have a positive effect on overall management with pedunculate
oak. The selection of damaged trees for felling is a key factor that ensures the
quality of the wood matter in disturbed and unstable forest ecosystems.

Key words:pedunculate oak, timber quality, damage trees, utilization