Bunching with a self-levelling feller-buncher on steep terrain for efficient yarder extraction

A research trial was conducted in Victoria, Australia, to evaluate a self-levelling feller-buncher on steep terrain and its potential to improve the overall productivity of steep terrain cable logging. The production study was conducted for a mechanized harvesting system using a Valmet 445 EXL self-levelling tracked feller-buncher and a Madill 124 swing yarder while operating in a clear fell plantation. This study quantified the equipment productivity of steep slope harvesting in a 33 year-old Pinus radiata D. Don (radiata pine) plantation. Mechanized felling was an integral part of this operation, although there were areas of motor-manually felled trees due to terrain and stream restrictions. Thus the difference in productivity of the yarder for bunched and unbunched trees was quantified. For an average piece size of 0.8 m³, a productivity of 138 m³/PMH was predicted for the feller-buncher. Bunching substantially improved the productivity of the swing yarder. Mean volume per cycle for the swing yarder was 1.9 m³ for bunched trees versus 1.3 m³ for unbunched trees. For a yarding distance range between 150 and 240 metres, bunching increased the productivity by 25%. These results show the potential of self-levelling feller-bunchers in cable logging operations and suggest that research into mechanised felling be directed towards acquiring more information on the performance of steep terrain feller-bunchers in larger trees sizes, and under other slope and soil conditions in Australia.