Multiple Tree Handling in the Selective Felling and Bunching of Small Trees in Dense Stands
Authors
Jerry Johansson
Dalarna University, Garpenberg, Sweden
Tomas Gullberg
Dalarna University, Garpenberg, Sweden
Abstract
Harvesting very small trees one by one has always been comparatively unproductive. Multiple-tree handling creates opportunities to reduce time per tree and thereby make it profitable to harvest small trees instead of thinning to waste. Multiple tree-handling is achieved by felling more than one tree in one cut or by felling one tree per cut and accumulating trees on the felling head, thereby handling several trees during one crane cycle.
The effect of accumulating trees depends on how much faster each additional tree can be felled (positioning head and cutting off) compared with the previous tree and how much time (per tree) is saved when moving several trees during crane-in (bunching). Felling several trees in one cut reduces time per tree substantially, but is often of limited relevance due to spacing between trees.
Field studies showed significantly lower time consumption when accumulating smaller tree sizes. Reduction of time consumption for crane work was approximately 40 % for the smallest trees. The difference decreased as tree size increased. Time consumption for the first "crane to tree" was a little higher than for the following crane movements to trees to be cut. Time for "crane-in" only slightly increased with the number of trees in the felling head. The time required to fell two or more trees in one cut was not significantly different than for a single tree, giving a substantial reduction in time per tree.
