From standing tree to log
Logging turns standing trees into products that can be transported: logs for sawmills, pulpwood for paper and biomass for energy. The work breaks into a few steps. The tree is felled, the branches are removed, the stem is cut to lengths, and the pieces are moved to a landing or roadside for loading. Which machines do each step depends on the terrain, the size of the trees and the system the crew uses.
Forestry is regulated in most places, with rules for harvest planning, stream protection, road construction and worker safety. Those rules differ by region, so this article describes general practice only.
Manual felling
Chainsaws are still used where machines cannot go: steep slopes, small woodlots, selective harvests, trees with awkward lean or size, and cleanup after storms. A trained feller reads the tree’s lean, the wind, the surroundings and the escape route before cutting, and cuts a notch and a back cut to guide the fall. It is skilled and hazardous work, and personal protective gear and training are not optional.
Even on mechanized sites a person with a chainsaw often handles the trees that machines cannot, so manual felling and machines complement each other.
Feller-bunchers
A feller-buncher is a tracked or wheeled machine with a cutting head on a boom. The head grips the tree, cuts it near the base with a saw disc or a shear and holds it while the machine swings and sets it down in a pile, or bunch, with others. The bunches are later picked up and dragged to a landing.
This approach is commonly associated with whole-tree harvesting, where the full tree is taken to a landing and processed there. It is efficient on flatter ground and where trees are moderately sized. A feller-buncher may be a tracked machine with a leveling cab for slopes, or a wheeled one for flatter sites.
Harvesters and processors
A harvester combines felling with processing. The head, mounted on a long crane, grips the tree and cuts it, then feeds the stem through rollers and delimbing knives that strip the branches. A measuring system tracks length and diameter, and a saw cuts the stem to lengths set by the buyer’s needs. The logs are dropped in neat piles beside the machine, and branches stay on the forest floor, forming a mat that the machines can drive on.
This system, known as cut-to-length, is common in many regions. It leaves the tops and branches in the forest, and it handles processing at the stump. A computer on the harvester stores the products and can report volumes cut, which is an everyday example of how process control sensors appear in forestry.
A stationary processor does similar work at a landing instead of in the forest. It takes whole trees brought in by skidders and delimbs and cuts them to length there.
The base machine and head
Many harvesters use an excavator-type carrier with a specialized head. The head is powered by hydraulics, so the carrier’s pumps, hoses and cylinders carry large loads in a tough environment. The system relies on the same hydraulic cylinders and valves as other heavy equipment, and it is subject to branches, dirt and impact. Hose protection and routine inspection are standard practice.
A typical crew in a mechanized operation
Roles differ between crews, but a typical mechanized crew may include:
- Felling machine. A feller-buncher or harvester that cuts the trees.
- Processing. The harvester itself in cut-to-length systems, or a processor at the landing in whole-tree systems.
- Primary transport. Skidders or forwarders that carry wood from the stump area to the roadside or landing, the subject of the companion review on log hauling equipment.
- Loader. A knuckleboom or front-end loader that places logs on trucks at the landing.
- Trucks. Log trucks that carry the load to a mill. Some mills use sawmill equipment to cut logs into lumber.
- Support. Bulldozers or excavators building and maintaining roads, a mechanic or service vehicle, and often a supervisor or forester who plans the harvest.
Crew size and composition change a great deal. A small operation may have one harvester, one forwarder and a truck. A large one may be a coordinated production line.
Choosing a system
Whole-tree and cut-to-length systems are two broad approaches. Which one suits a site depends on the slope, soil, tree size, local rules, the mill’s needs and what happens to the tops and branches. Steep slopes may call for cable-based systems or specialized equipment, and wet or sensitive soils may call for lower-impact machines or frozen-ground seasons. Any simple rule is a starting point, not a decision.
Operating in a harsh setting
Logging is unforgiving on machines. Debris, mud, rock, vibration and large temperature swings are all normal. Careful harsh environment protection of hoses, cables and electronics, along with regular greasing and cleaning, helps equipment hold up. Fire is a risk, since hot surfaces and dry debris sit together, so many machines carry fire suppression systems or extinguishers, and operators clean debris from engine areas.
Safety
Falling trees, rolling logs, steep slopes, overhead hazards and machine rollovers make forestry dangerous. In general terms, safe work depends on trained and certified operators, protective cabs with guarding against strikes, clear exclusion zones around felling machines, communication between machine and ground crews, and attention to machine safety features and local rules. Manufacturer manuals and safe machinery operation practices apply, and operator training matters, because experience on the job is hard to replace.