DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 1-2/2018 str. 44     <-- 44 -->        PDF

of the aspirant trees at the age of 40 and 90% at the age of 50 (Graph 8 right).
According to the non-parametric Kolmogorov-Smirnov test, the cumulative curves of slenderness for all trees show significant differences between the three measurements of growth elements, which is ascribed to the reactions of trees to the conducted thinning and to the reduction in the number of trees due to thinning. However, with the same number of aspirant trees, significant differences were found only in the period between the ages of 32 and 40, i.e. after the first thinning (Table 8).
Discussion and conclusions
Rasprava i zaključci
A comparison of the growth elements of the investigated culture with the elements of growth in other young to middle-aged spruce cultures in Serbia (Stojanović and Banković,1981; Stojanović and Krstić, 1984; Vučković et al., 1990; Tomanić, 1990; Dražić, 1994; Koprivica and Ratknić, 1996; Koprivica et al., 1998; Krstić, 1998; Ratknić, 1994; Ratknić and Vučković, 1999; Ratknić et al., 2001) shows that the  investigated culture is in the category of the best cultures in Serbia. Another conclusion we can make from the comparison of the elements of growth of the investigated culture and the spruce cultures in other areas is that the investigated culture has high productivity (Assmann,1970; Maunaga, 1999; Pretzsch, 2005; Orlić, 1987; 1994; 1999; Orlić et al., 1997, Oršanić, 1995; Slodičak and Novak, 2003) or good site quality (Halaj et al., 1987, Maunaga, 2001).
The first thinning at the age of 32 and the height of  dominant trees of 15 m was  low (qd <0.85) and heavy (36% of the volume) selective thinning. The age at which the thinning was carried out does not significantly deviate from the age at which the first “commercial” thinnings are performed in Europe (Slodičák and Novak, 2003). However, the flows of the current diameter increment determined by the detailed analysis of dominant trees (D100 and D400) show that the thinning at the age of 32 was performed late, while the height growth (increment) model shows that the culmination was reached at the age of 25 (when the dominant trees reached the height of 11 m), which means that the first commercial thinning should not be performed later than the age of 25. The adoption of this biological criterion for the determination of the optimum timing for thinning would, according to (Vučković, 1991; Kotar, 2005), produce the best effects of thinning on the increment and stability of trees and stands. Following the recommendations of Assmann (1970), it has been stated that when applying selective thinning after Schädelin (1934),