Abstract:
Commercial thinning young growth forests is an increasingly
important silvicultural technique for improving second growth
management of Douglas-fir stands. Research aimed at advancing the
efficiency of skyline logging operations in small wood timber stands
is essential in order to make thinning these young stands economical.
The purpose of this study was to evaluate one case of prebunching
small logs to a skyline corridor with a portable winch and swinging
the logs to a haul road with a conventional mobile yarder. Prebunching
involves lateral yarding of logs from both sides of a skyline corridor
and decking the logs along the corridor.
The multiinoinent time study method was used for obtaining data
that was analyzed with multiple linear regression procedures. Predicted
hourly and daily production rates were determined from the
regression equations. The yarding system involving prebunching was
compared to a similar system without prebunching on a cost basis.
This study showed that prebunching logs to a skyline corridor
reduced the conventional mobile yarder's yarding time 65 percent and
more than doubled log and volume production per day. The results
favored the prebunching and swinging yarding technique. Several
suggestions, that require additional research, were made for
modification in the system that may improve the overall operation.
