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M. Božić, J. Čavlović, M. Vedriš, M. Jazbec: MODELIRANJE DEBLJINE KORE STABALA OBIČNE JELE ... Šumarski list br. 1–2, CXXXI (2007), 3-12
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waldinventur – Konzeption, Verfahrenstest, Er-Düsseldorf.

gebnisse. Heft 5 Schriftenreihe der Landesfor-

SUMMARY: Basic aim of research was to make correlation models that
explain bark thickness of silver fir in dinaric beech – fir forests as a function
of ecological and stand factors. Modeling was made by using spatial variables
(altitude, terrain slope and orientation) and individual tree characteristics
(diameter at breast height, tree height and age). Sample was taken by measuring
given parameters of 531 fir trees in dinaric region of Republic of Croatia
(Forest Administrations: Delnice, Gospić, Ogulin i Senj). Bark thickness
was measured on increment cores taken at breast height by using Pressler’s
increment bore. Calculating was made by MS Excel application, and modeling
bark thickness by Statistica 7.1 software. Diameter at breast height
(DBH), tree height, tree age and altitude were variables with highest correlation
coefficients to bark thickness that proved to be statistically significant,
and were therefore used in model building. Models were made using partial
linear correlation method, with variables calculated both in original and logarithmic
form, considering p = 0,05 as a limit of statistical significance. Determination
coefficients of 8 models ranged from 62,5 % to 70,4 %, with logarithmic
form variables showing on average 4 % higher values. Diameter at
breast height proved to be basic variable for models, with determination coef

ficient of 63 %, while additional variables increased it at most to 70 %. Therefore
it is suggested to use simple model for predicting bark thickness, with
DBH in logarithmic form as the only independent variable. Impact of site
quality on bark thickness was also studied, emphasizing that trees in lower
quality stands have thicker bark. Models obtained by this research give lower
values of bark thickness compared to former studies of Bojanin (1966a,
1966b) and Klepac (1972). Calculating percentage in tree dimensions, accor

5 cding to our model 1.2, bark make 4,1 % (diameter class 97,
97,97,5 cm) to 8,1 % (diameter
class 12,5 cm) of tree diameter, which i
ss abou
tt 2,
33 %
%% lower to 1,7 %
higher compared to their research. According to this study silviculture and
management proved to influence bark thickness: trees in intensively managed
stands have thinner bark. However this may be the result of difference in site
quality of intensively managed and non-managed stands. Bark increment can
also be predicted based on obtained models. According to model 1.2, bark
contributes from 2,8 % (diameter class 92,5 cm). to 5,6 % (diameter class
12,5 cm) in tree diameter increment

er incre ent.
K e y wo rd s : bark thickness
thicknessthickness, silver fir, modeling, linear correlation

, silver