Simulation Study of a Single-grip Harvester in Thinning from Below and Thinning from Above
The time consumption and productivity of a single-grip harvester were studied, using a simulation model, when thinning from below and above in eight randomly selected stands. The model estimated the time required for each work element, given machine and tree positions, and tree size. A 2×5 factorial design was used with factors thinning type [from below (Tb) and above (Ta)] and tree size. Trees were subjectively selected for harvest according to thinning type. Total basal area removal was 30% plot-1. Approximately 50% more trees were harvested in Tb than in Ta. Time consumption tree-1 was higher for Ta than Tb. Time consumption for machine and boom movements decreased with increasing number of harvested trees, and time for felling and processing of trees increased with harvested mean stem volume. Harvester productivity was 36% higher for Ta, since the increase in harvested mean stem volume was higher than the increase in time consumption tree-1.