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ŠUMARSKI LIST 13/2011 str. 263     <-- 263 -->        PDF

E. Paladinić, D. Štimac, H. Marjanović, I. Balenović, M. Z. Ostrogović: SUŠENJE OBIČNE JELE (Abies alba Mill.) ... Šumarski list – Posebni broj (2011), 248-263


order to get timber assortments, have questionable cost-effectiveness, and in
some cases are fully unprofitable. The key point in process of calculating planned
values according to timber assortments are so called “Assortment tables”,
empirical models for estimation of timber assortments structure, which
are definitely inappropriate for current climatic and disturbed stand conditions.
Hence, the aim of this research is to study existing Assortment tables for
fir, which are used by the Production department of Forest Administration
branch Delnice, in order to satisfy criteria for sufficiently reliable planning in
the production of timber assortments.


Material and methods. In order to ensure quality and uniformity of research
from the be ginning, the detailed plan of field activities was designed and
agreed for implementati on with Production department. On the research area
in target Forest management un i ts, a few forest compartments were chosen for
field data acquisition each year. In each of selected forest compartments it was
required to collect data for around 100 marked fir tr ees, which were felled during
selecting cutting. Diameter distribution of those hundred tr ees should represent
fir diameter distribution of whole compartment. Each of those fir tr ees
got measured diameter at breast height, total height, height of the first branch,
and all bucked timber assortments. From those data we got volumes (per trees
and per timber assortment). Ultimately, assortment structure data were collected
from seven forest co mpartments. Each compartment has two dataset, one
representing produced timber assortments (done by foresters) versus planned
assortment structure (calculated using assortments tables).


Concerning research aim, two hypotheses (H1, H2) were constructed. H1
states: If planned and realised timber assortments production from forest compartment
significantly affected by fir dieback is compared, than statistically significant
differences between planned and realised values according to
assortments classes will be confirmed. H2 states: If timber assortments production
is compared according to three general health categories of fir stands,
than statistically significant differences between same assortment classes will
be confirmed. For testing H1, One-way ANOVA was used together with Test of
Homogeneity of Variances. Analysed variables are veneer logs volume, sawlogs
(1st, 2nd and 3rd class), pulp-wood and firewood, and volume of wood residues
(recovered wood). Pulp-wood and firewood are in the same category,
because only 14 pieces of firewood were measured in whole sample. Wood residue
category refers to timber assortments thicker than 16 cm and left on forest
floor because of its uselessness for technical purposes (damaged, decayed).


Statistical significance of differences between samples of planned and realised
volume according to assortment classes was analysed. Testing homogeneity
of variances between these two samples showed in most cases that
variances of the same assortment classes’ volumes are not homogenous. Considering
this findings, Independent-samples T test was used for analyzing H1.
Analog to H1 testing, the same tests were used for H2 analyzing. Forest compartments
which were compared represented two of three health categories of
fir stands (stands of moderately damaged health condition were missing).
Those two compared groups of data were unequal in size, one consisting of
data acquired from 5 forest compartments, and another of data acquired from
two forest compartments.


This research was partially extended with sampling of fallen fir trees to get
a clue about insect and pest species which could be one of main factors causing
fir dieback. So, in the 2008 woody samples collected from fallen trees in
one forest compartment, were analysed in CFRI laboratory.


Research area. In wider context, research area represents fir-beach stands
of Gorski Kotar region, and narrower area is determined by boundaries of