Skogsbränsledrivare i klen förstagallring med contorta

Abstract: The aim for the study was to examine a harwarder´s (combined harvester-forwarder) productivity when harvesting forest fuel in first thinning stands that contains Lodgepole pine and calculate the economy of the harvesting work and estimate the quality of the thinning . The field study area where located near Arvån, about 15 kilometres south –east from the city of Lycksele. The field studies were taken place in three different stands. All tree stands had the same tree age, but the tree species combination and the density varied. The harwarder in the study was a Valmet 801 combi modified for whole tree harvesting. Ten study units were created in the tree stands, each study unit was 1250 m2. The average density before thinning was 3809 trees/ha, the average stem size was 0.031 m3. In average were 2135 trees/ha harvested, corresponding to 26.2 oven dry tons (ODt)/ha. After thinning was the average stand density 1647 trees/ha. Twenty percent of the total surface of the stand were strip roads, and the average width of the strip road was 4.3 m. The number of damaged residual trees correspond to 2% of the total number of residual trees. The total time consumption including harvest and forwarding work (100 m forwarding distance) was 13.9 E0-hour/ha. The average productivity was 1.87 ODt/ E0-hour at 100 meter forwarding distance. The net yield was -1935 SEK/ha given that the forwarding distance was 100 meter, the cost per hour was 835 SEK/ E0-hour, the price for the forest fuel was 80 SEK/MWh and the average harvested stem size was 0.022 m3. The net yield per hectare is highly affected by the harvested stem size but also the price for the forest fuel SEK/MWh affected the net yield.