DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 1-2/2018 str. 41     <-- 41 -->        PDF

4.6 mm∙year-1 in the representative of the 400 thickest trees per hectare.
Since height and diameter increments of dominant trees retain high values in the period after the culmination, up to the age of 21, the period between the age of 15 (17) and 21 can be taken as the optimum time for thinning in the investigated stand. According to the model, the current height increment had a culmination at the age of 25 (when the dominant trees reached a height of 11 m), so if we apply this biological criterion, the first commercial thinning should be carried out not later than the age of 25 (Graph 6).
Thinning characteristics – Karakteristike prorjeda
Thinning in the study culture was primarily aimed at fostering the development of high-quality trees (candidates and aspirants) that belonged to the category of dominant trees. The first thinning was carried out at the age of 32 (when the aspirants reached an average height of 15.1 m) and the second thinning at the age of 40 (when the aspirants reached an average height of 20.5 m).
In the thinning that was conducted in the 32nd year of age, 1,378 trees were cut per hectare (35.2%). Their volume amounted to 115.1 m3∙ha-1. In the period from the age of 32 to the age of 40, 555 trees per hectare were cut down due to mortality and snow-breaks (14.2%). Their volume was 22.0 m3∙ha-1. It follows that out of the initial number of trees, a total of 1,933 trees per hectare were cut down (49.4%) in the 32nd year of age. Their total volume was 137.1 m3∙ha-1 (35.9%). The trees harvested at the age of 32 had diameters at breast height from 7.0 to 20.0 cm and the mean diameter of 12.7 cm (0.93·dg), while the subsequently harvested trees had diameters of 6.6-10.6 cm and the mean diameter of 9.3 cm (0.68·dg) (Tables 1 and 2, Graph 1).
The thinning that was conducted at the age of 40 included 911 trees per hectare (46.1%) with the volume of 142.3 m3·ha-1 (33.7%). The trees harvested at the age of 40 had diameters at breast height from 10.1 to 23.9 cm and the mean diameter of 15.7 cm (0.88·dg) (Tables 1 and 2, Graph 2).
The two thinnings and the subsequently felled thin trees on the experimental plot in the period from the age of 33 to 40 included 2,844 trees per hectare (72.7%) with the volume of 279.4 m3·ha-1. Based on the ratio between the quadratic mean diameter of the trees harvested in the thinning and the remaining trees at the ages of 32 and 40, the thinnings were low (qd=0.84-0.80) and based on the percentage decrease in basal area (35-37%) and volume (34-36%), they were heavy thinnings (Tables 1 and 2).