FACTORS AFFECTING PRODUCTIVITY OF MACHINED LOGGING IN THINNING USING SMALL SIZE FOREST MACHINES

The aim of the research is to find out changes in productivity depending on the diameter of the tree to be cut as well as the most important factor influencing the reduction of productivity using small size forest machines in thinning in Latvia. The equipment used in the study - both the harvester and the forwarder is Vimek. The results of the research confirm the appropriateness of the exact technique in thinning if diameter of the harvested trees is 3 to 30 cm. The average productivity of the harvester achieved with a harvester head Keto Forest Eco (option 2) in Norway spruce stands with 8 cm weighted average tree reached 9.59 m(3) h(-1), in deciduous tree stands with 9 cm weighted average was 10.17 m(3) h(-1), but in Scots pine stands with 12 cm average weighted tree diameter reached 10.19 m(3) h(-1). By using the Keto Forest Eco Harvester head according to the thinning productivity figures, no significant difference among the tree species was detected. For the forest owner to predict the theoretical productivity of the harvester, it is possible to apply the equation R = K + KD * D, that is statistically significant, R-2=0.85. This equation is applicable to thinnings when the diameter of thinned trees is between 4 and 25 cm. Forwarder's average productivity in thinned stands is 8.63 m(3) h(-1).