Economic efficiency of fully mechanized timber har-vesting in coniferous stands of the 2nd age class

The aim of the study was to determine the unit costs of mechanized timber harvesting in pine stands where early thinning was being performed, and to determine the relationship between the cost level and the volume of harvested trees, the harvester model and field conditions. Analysis focused on timber harvesting with the use of small- and mid-sized harvesters. The tested harvesters were specialized forestry machines (Vimek, Sampo, Profi-Pro, Ponsse) and a construction machine (Fao-Far). Terrain accessibility variants were distinguished in relation to furrows between which trees had been planted in the past: flat terrain with the depth of unevenness up to 20 cm, up to 40 cm, and over 40 cm. The operating costs of the analyzed harvesters varied significantly, an hour of operation of the machine that was the cheapest to use (Fao-Far) cost nearly 2.5 times less (37.3 E) than the Profi-Pro harvester, which was the most expensive in operation (89.1 E). In stands without furrows, the lowest unit costs were noted for the Sampo harvester: 8.4 E center dot m-3. The other small harvesters, Vimek and Fao-Far, were slightly more expensive to use: 10.3 E center dot m-3 and 9.1 E center dot m-3, respectively. In areas where furrows were up to 20 cm deep, the cheapest solution was timber harvesting with the Fao-Far harvester (9.9 E center dot m-3). In areas where furrows were up to 40 cm deep, timber harvesting was the cheapest with the Sampo harvester (10.7 E center dot m-3), while harvesters Vimek and Fao-Far were characterized by a similar cost intensity, amounting to just over 12 E center dot m-3. In stands with furrows deeper than 40 cm, it was cheapest to use the Ponsse harvester (10.4 E center dot m-3). The cost of operation of the Profi-Pro harvester was higher by approx. 25% (14.0 E center dot m-3). With the current level of the financing of mechanized timber harvesting in Poland (about 11 E center dot m-3), small harvesters Vimek, Sampo and Fao-Far are cost-effective when single tree volume exceeds 0.05-0.06 m3. Medium harvesters, Profi-Pro and Ponsse, are cost-effective when unit volumes of harvested trees reach 0.08 and 0.11 m3 respectively. The cost-effectiveness of the tested harvesters increased when working shifts were extended.