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ŠUMARSKI LIST 7-8/2015 str. 55     <-- 55 -->        PDF

processing (when harvester head is in direct contact with tree) excluding the DBH as covariate effect.
In order to test productivity on the basis of tree characteristics we made separated comparisons inside feasible unique thickness of the trees from 15 to 20 cm DBH (both types of tree characteristics were available), classifying the trees into two classes:
a. single-trunked, short crown and thin branches,
b. multi-trunked, long crown, thick branches.
The results showed that by the average tree 0.21 m3 (DBH 17,5 cm) in stands of privilege class (a class) for mechanized cutting has a 25 % higher productivity than in stands where there are multi-trunked trees with deep crown (b class). Consequently, we conclude that the felling and processing costs of mechanized felling and processing are 25 % lower in younger stands with average DBH 17,5 cm.
In order to test the same influence of tree morphological characteristics on productivity we executed the time study for MM cutting and tractor skidding. The analysis according to the morphological tree characteristics showed minor differences in productivity. When processing tall trees (class a) with the average volume of 0.21 m3 the average productivity was 2.77 m3/hour. It amounted 16 % more than productivity of multi-trunked trees with long crown (class b).
Efficiency analysis – Analiza učinkovitosti
For the purpose of comparing the efficiency of both technologies, we conducted the analysis of the Main work time. The reason of using Main work time as a dependant variable was an objective to find a direct impact of the tree size on the efficiency (Table 10). In case of mechanized cutting we analyzed all the working elements where the harvesting head was in direct contact with a tree (it includes following working elements: felling, delimbing, bucking and crosscutting). In MM cutting we also took into consideration all working elements that were directly related to the processing of tree (felling cut, undercut, wedge driving at felling, root collar processing,