Stempski, W. and Jabłoński, K. 2018. Damage to Trees from Wood Extraction in Motor-Manual Wood Harvesting Technologies in Thinnings of Pine Stands. Baltic Forestry 24(2): 313-320.

   The purpose of this research was to assess the damage caused by the extraction of wood harvested with chain-saws in thinnings in pine tree-stands, 35, 52 and 69 years old. Two methods of wood extraction were applied, in one case the wood was dragged with an agricultural tractor or a horse, and in the other case wood was extracted with a 10-ton forwarder. The investigations were conducted in Oborniki Forest District in western Poland. The horse and tractor skidding were carried out in variants with strip-roads or without them, while the extraction of wood with the forwarder was on strip-roads only. The distance between the strip-roads was 30 m, while their widths were about 1.5 m for the horse, 2.5 m for the agricultural tractor and 3.5 m for the forwarder. The analysis presented in the paper focused on the shares of the damaged trees and differences in the numbers and frequencies of wounds in damage classes, related to the technology applied. The damage was divided into classes according to three criteria: depth (1-bark, 2-phloem, 3-wood), the wound place (stem, root crown, roots), and the damage causing factor (machine/horse, the wood/payload). The damage on trees in all the damage classes was statistically more significant in technologies with wood skidding than in technologies with wood forwarding, whereas the damage to the phloem was more frequent in the technology with the forwarder (no class 3 damage to the wood was observed). When the wood was skidded with the horse or the tractor, the wounds to the root crowns were statistically more frequent, while during the forwarding the damage to the stems dominated. As to the factor causing the damage, in the case of the forwarding operation, the machine was the main cause; while in the case of wood skidding the damage was usually caused by the wood (payload).

Keywords: thinning, skidding, damage, horse, agricultural tractor, forwarder.