Work systems
A work system is the chosen chain of jobs, people and machines from the standing tree to the truck. Two common ones:
- Cut-to-length system: the tree is felled and cut into logs right at the stump. A small machine called a forwarder then carries the logs out. It leaves branches in the forest.
- Full-tree system: the whole tree is dragged (skidded) to the roadside and cut up at the landing.
The choice depends on the slope, soil, tree size and money. On gentle slopes machines can drive. On steep slopes logs are lifted on cables (cable yarding) because heavy vehicles would damage the soil. Hand work with a chainsaw is used for small or difficult sites.
Forest roads and operation roads
Roads decide how cheap and safe harvesting is.
- Forest road: a permanent, wider road (about 4 m or more) built to a plan, with gravel and drains. Trucks use it. It also helps fire fighting and forest care.
- Operation road: a narrow (about 2.5 to 3 m), simpler road that branches off the forest road into the stand for forwarders and small trucks. It can be rough and is used for years.
Good roads keep a gentle gradient, have drains so rain does not cut channels, and avoid streams. Road density = road length ÷ forest area, for example 30 m per hectare. More roads make work easier but cost more and disturb the soil.
Felling, bucking and yarding
Felling means cutting down the standing tree. The cutter first looks at the lean of the tree, wind and obstacles, and picks a falling direction and an escape path. Then makes a notch (a wedge cut) on the side where the tree should fall, and a back cut on the opposite side a little higher. A strip of wood between them, the hinge, steers the fall.
Limbing removes the branches. Bucking cuts the trunk into logs of the length buyers want, such as 3 m or 4 m, avoiding bends and rot. Yarding moves the logs from the stump to the landing, a flat yard beside the road. Methods: skidding (dragging), forwarding (carrying on a machine) and cable yarding (hanging on a wire). At the landing logs are sorted, stacked and loaded on trucks.
Occupational safety
Logging is among the most dangerous jobs, so safety is part of every step.
- Protective gear: helmet with face guard, ear protection, cut-resistant trousers, safety boots, gloves, bright clothes.
- Safety distance: keep at least 2 tree-lengths from a tree being felled. Only the cutter stays near.
- Plan two escape paths at about 45 degrees behind the fall line. Shout a warning before the tree falls.
- Check for a hung tree (caught in another tree). Never walk under it.
- Handle the chainsaw with both hands and watch for kickback. Keep it sharp and well tuned.
- Never work alone, stop in strong wind or rain, take training and rest breaks, and keep a first-aid kit.
Key formulas and definitions
- Safety distance = 2 × tree height
- Road density (m/ha) = road length (m) / forest area (ha)
- Log volume ≈ π × (diameter/2)² × length
- Order of harvest: road → fell → limb → buck → yard → load
Worked examples
1. A tree is 25 m tall. What is the safety distance when felling it?
Safety distance = 2 × 25 = 50 m.
2. 600 m of operation road serve a 20 ha stand. Find the road density.
Density = 600 / 20 = 30 m per hectare.
3. A usable trunk is 12 m long. It is bucked into 4 m logs. How many logs?
12 / 4 = 3 logs.
4. A log is 0.3 m across and 4 m long. Estimate its volume (π = 3.14).
Radius = 0.15 m. Volume = 3.14 × 0.15 × 0.15 × 4 = 0.28 m³ (about).
Common mistakes
- Standing close to watch a tree fall. Stay 2 tree-lengths away.
- Mixing up the two roads: the forest road is permanent and wide, the operation road is narrow and simple.
- Mixing up bucking (cutting the fallen trunk into logs) with felling (cutting the standing tree).
- Thinking cable yarding is for flat land. It is for steep slopes.