Effect of Tree Size on Productivity and Time Required for Work Elements in Selective Thinning by a Harvester

Abstract The effect of diameter at breast height (DBH) on the time required for work elements in felling, delimbing, and bunching by a harvester was studied. Move and boom, position, felling and tree fall, and cross cutting were not affected by the DBH of the harvested tree. On the other hand, the greater the DBH of the harvested tree, the significantly longer the time required to delimb because of increasing tree height and decreasing delimbing speed. Nonetheless, the total time required to fell, delimb, and bunch one tree was not affected by its DBH, because the proportion of time for delimbing was only 16 percent of the total time. As a result, the productivity of the harvester was 9.2 m3 per productive machine hour, about 33.4 times the piece volume of the harvested tree. This study demonstrated that harvester productivity varied in a roughly linear manner with the piece volume of the harvested tree in a single tree selective thinning that removed only a small percentage of the stand volume.