Current issue: 55(2)
Under compilation: 55(3)
In Germany, management restrictions for Norway spruce (Picea abies (L.) H. Karst.) due to climate change lead to increasing interest in Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) as a potential substituting species. However, Douglas fir requires cost-intensive silvicultural treatments, such as periodic thinnings and, in particular, pruning. In order to improve the efficiency of such treatments, a new tending system with an adapted two-step work system was analyzed. The new system, using electric pruning shears and the backpack clearing saw Husqvarna 535FBX ‘Spacer’, was compared to the conventional three-step work system, using handsaw and chainsaw and characterized by tree selection previously conducted as an independent work step. Time and motion studies to determine productivity and costs, as well as ergonomic analysis through heart rate measurements and posture analysis were conducted. Overall, the new system was found to be more productive and to have lower costs, with 8.9 trees per scheduled system hour (4.17 € tree–1), compared to the conventional system with 8.1 trees per scheduled system hour (4.44 € tree–1). Ergonomic improvements with the new system could be mainly observed during the felling of competing trees, when the level of heart rate reserve was reduced by 9.3 percent points, compared to the conventional system. However, significant advantages in reducing unfavorable body postures expected for the ‘Spacer’ could not be confirmed. Since time savings within the new system were mainly attributed to the adaptation of workflow and the use of the electric shears during pruning, it should be considered to replace the ‘Spacer’ within the new system by light chainsaws for best results under the conditions investigated.
The physical strain put on forest workers and work time consumption during pulpwood cutting were compared when the bolts were stacked at the side of strip road, the strip road spacings being 15–25 m and 26–35 m, and when stacked at scattered points along the cutting strip.
When stacking at scattered points along cutting strip work time consumption was 17–21% and the heart rate 9–12% less than when stacking at the side of the strip road, strip road spacing being 15–25 m. When the strip road spacing was increased to 26–35 m, the time consumption increased by 18–30%, but the heart rate appeared unchanged. This result suggests that the forest worker compensates for increased physical strain caused by an increased stacking distance by changing his working technique and rate and by increasing the number of his breaks.
The PDF includes a summary in English.