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ŠUMARSKI LIST 7-8/2020 str. 44     <-- 44 -->        PDF

growing stock and basal area started to decline or stagnate after the stand was approximately 80 years old (Figures 4 and 5). At the start of monitoring of plot 4, at stand age approximately 51, most of the trees in moderately and high intensity thinning fields were in diameter class 6 and 7 (Figure 2). The control field has a slightly higher proportion of trees in diameter classes 4 and 5 compared to the thinning fields; 51 years later, the control field still had a noticeably higher proportion of trees in lower diameter classes. Regardless of thinning model, most trees gained 3–4 diameter classes. On other plots trees gained 3–4 diameter classes as well, despite lower age.
Annual diameter increment of trees in control fields and moderately thinned fields was practically the same, averaging 0.33 cm/year. In high intensity thinning fields it was slightly higher, on average 0.37 cm/year (Figure 6). Using statistical analysis, we determined statistically significant differences among thinning models (χ2 = 29.540; p < 0.001). There were statistically significant differences in annual diameter increments between high intensity and moderate intensity thinning fields (χ2 = 120.744; p < 0.001) and between high intensity thinning and control fields (χ2 = -119.383; p < 0.001). There were no statistically significant differences between moderately thinned and control fields