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ŠUMARSKI LIST 9-10/2009 str. 64     <-- 64 -->        PDF

M. Bobinac, S.Andrašev: UČINCI UZGOJNIH MJERA U DEVITALIZIRANOJ SREDNJEDOBNOJ ... Šumarski list br. 9–10, CXXXIII (2009), 513-526

tree age 42. At the age of 52, the status was retained by 124 trees. The primary measure in
P.P.-1 involved removing the strongest competition against future trees from the stand, so
the treatment also had the character of selective thinning. Using similar silvicultural principles,
156 dominant trees aged 42 were selected for comparison in P.P.-2. Of these, 148
trees retained the status of future trees at age 52, while P.P.-2 was left to natural tree selection.
During measurements in the year 42, a crown class (CC) and the degree of crown
freedom position (CF) was determined for each tree. To assess crown damage intensity
(defoliation), classification with degrees 0–4 was used.

Data processing consisted of determining the numerical parameters of diameter structure,
while the non-parametric Kolmogorov-Smirnov test (|D| statistics) was used to compare
diameter distribution with the distribution of diameter increment. The .2test for
independence was used to define dependence of the degree of crown freedom position and
the degree of crown defoliation, as well as the crown class and the degree of crown defoliation
in sample plots at stand age 42. The effects of different stand treatments were analyzed
in the age period 43–52. The current (average periodical) diameter increments (id)
obtained with the control method was compared for all the trees in the sample plots and
separately for the future trees in P.P.-1, and the comparison trees in P.P.-2. The statistical
t-test was used to assess the impact of silvicultural treatments on the increment size.

Growth elements of all the trees and future trees in the sample plots at age 42 and 52,
as well as the trees cut at ages 42 and 48, are given in Table 1. Table 2 contains numerical
indicators of their diameter distribution. Cumulative curves of diameter distribution of all
the trees show that at age 42 the trees in P.P.-2 have a somewhat bigger breast diameter.
Due to differential silvicultural treatments and different increment tree reactions, diameter
distribution of all the trees and future trees were approximated at age 52, which was
also confirmed by the Kolmogorov-Smirnov test (Graph 1, Table 2).

Based on the test for independence applied at age 42, high dependence was found in the
monoculture of the degree of crown defoliation on the crown class and the degree of crown
freedom position. This indicates that the devitalization process in directly linked with stand
structure, i.e. silvicultural treatments in the previous period (Table 3 and 4, Figure 1).

The Kolmogorov-Smirnov test confirmed the difference in diameter distribution of selected
trees in the sample plots in the 42ndand 48thyear (Graph 2, Table 2). The thinning indicator
(qd) shows that tree selection in the sample plots had the character of low thinning. In
the age period between 43 and 52, a more intensive treatment of silvicultural-sanitary cuts
(P.P.-1) showed that the current diameter increment was on average higher by 37 % in all
the other trees and by 35 % in future trees, in relation to the sanitary cut (Graph 3). Cumulative
curves of diameter increment in P.P.-1, for all the trees and for future trees, are shifted
rightwards towards higher increment values, in relation to P.P.-2. There are also differences
in the shape of the curve, which implies a difference in the variability of diameter increment
(Graph 4). The Kolmogorov-Smirnov test confirmed considerable differences in the distribution
of diameter increment, both for the entire group of trees and for future trees (Table
5). Dependence of diameter increment on diameters at breast height (Graph 5 and Table 6)
in all the trees shows moderate correlation ((R = 0.52-0.54), whereas correlation is less distinct
(R = 0.28-0.32) for the collective of futures. For all the remaining trees, the importance
of a regression coefficient of diameter increment dependence on diameters at breast
height confirms that at this developmental stage the recovery from stressful impacts depends
on the intensity and character of silvicultural measures and on the tree´s increment
potential. For the collective of future trees in P.P.-1 (and potentially for the group of dominant
comparison trees in P.P.-2), which are the first object of tending, recovery from adverse
impacts primarily depends on the nature and intensity of silvicultural measures.

Key words:pedunculate oak, permanent experiments, devitalisation, impacts of silvicultural
measures, diameter increment