Timber Harvesting Systems Flashcards
What are some characteristics of high lead cable yarding systems?
In high lead, chokers are attached directly to the mainline
- provides no more than partial suspension of logs as a consequence of tower height and topography.
- No lateral yarding capability beyond the length of the chokers
- Limited to yarding distances of 200-300m depending on log lift
- Production rate decreases significantly with distance
- Requires 5-6 crew members to operate
What is the typical production rate of a high lead system?
Depends on lift and distance
- ~100m3 per shift if lift is poor and distance is long
- ~220m3 per shift with good lift and short distances
What are the two main types of cable logging?
- High lead - Chokers attached directly to the mainline
2. Skyline - separated into true skylines and running skylines
What differentiates true skylines from running skylines?
True skylines include both live and standing skylines that use a stationary cable called a skyline to increase lift.
Running skylines are like highlead in that they have a mainline and a haulback line. In the running skyline, the haulback doubles as a skyline to provide additional lift.
Both can yard op to 1000m or more given appropriate topography.
Where is grapple yarding best suited to?
Clearcuts with short logging distances of 150-200m
Roads cannot be constrained since this system requires the most roads.
When would you use a “live” skyline?
Where road access is constrained and long yarding distances of over 300m are required. Capable of full suspension in favourable topography.
When would you use a standing skyline?
Where full suspension of logs is desired or for long distances up to 1500m.
Lateral yarding is possible if chokers are attached to a dropline.
What are some factors that affect our choice of harvesting system?
- topography (%slope and variability)
- soils (composition/sensitivity)
- silvicultural system (level of retention, number of harvest entries)
- Timber characteristics (log size, volume per hectare)
- Potential road access and building constraints
- Yarding direction and distance
Which cable yarding systems are best suited to clearcutting?
High lead and Grapple yarding since they are suited to short distances and typically do not have lateral yarding capabilities.
What is a detriment of adopting harvesting plans that incorporate smaller, dispersed cutblocks?
Small dispersed blocks lead to a higher density of active roads which inevitably lead to sedimentation of streams and increase the chances of mass wasting events in steep topo.
What is the cable yarding system that is best suited to retention? Why?Which type of retention is it better suited to?
Skyline systems, particularly with dispersed retention, since they have full suspension capabilities as well as lateral yarding capabilities with a minimal requirement for roads.
What are the limitations of ground based yarding?
topography and soil conditions.
What are the limitations of highlead cable yarding?
- Limited by lack of lateral yarding capability.
- Future use limited to small clearcuts and aggregated retention cuts.
What are the limitations of a grapple yarder?
- No lateral yarding
- short logging distances
- potential for narrow strip cuts between retention strips due to its mobility.
What are the limitations of the yarding crane?
- Limited to medium distance
- Rarely able to achieve full suspension due to machine and line wear.
- Good for relatively uniform valleysides.
