Forestry machines: harvesters, forwarders and how cut-to-length logging works

Forestry machines fell, process and transport trees. Two main logging systems dominate:

• Cut-to-length (CTL): a harvester fells the tree, delimbs it and cuts it into logs in the forest; a forwarder then carries the logs to the roadside. CTL is standard in Scandinavia and Europe and growing worldwide because it is gentle on the forest floor.
• Full-tree / whole-tree: a feller buncher cuts trees, a skidder drags them to a landing, and a processor delimbs and cuts them. Common in North America and the southern hemisphere.

Harvesters

A harvester has a long hydraulic crane with a harvester head that grips the tree, cuts it with a chainsaw bar, feeds it through delimbing knives with rollers, measures its length and diameter and cuts logs to optimised lengths. On-board computers optimise each log for value using the StanForD standard.

Forwarders

Forwarders have a loading crane and a bunk that carries 8–20 tonnes of logs. Large wheels with bogie axles and optional tracks spread the load on soft ground.

6-wheel vs 8-wheel

Eight-wheel harvesters and forwarders have better stability and lower ground pressure on steep slopes and soft soils, while six-wheel machines are lighter and more agile.