Conventional Ground-Based: Steep Terrain

The conventional ground-based logging system for steep, mountainous terrain typically utilizes the chainsaw, cable skidder, and trailer-mounted loader for harvesting timber. A small or medium-sized bulldozer is also often found on site to construct the landing as well as skid roads. These machines allow for the effective removal of timber with minimal impact to the residual stand and site when employed by a skilled operator.

Small ground-based harvesting system, at the landing (photo Brian Rodgers)

Felling the trees with a chainsaw requires great skill to fell the trees without harm to the cutter, and with limited damage to the stem or the surrounding trees.

Chainsaw felling in steep terrain (photo Brian Rodgers)

 

Furthermore, directional felling can expedite the work of skidder extraction. When necessary, wedges or hydraulic jacks can be used to fell a tree that is leaning in the opposite direction of the intended drop zone. The chainsaw is also used to delimb and top the trees before skidding. The trees are then either bucked, which means cut to the desired log lengths, at the stump or skidded whole tree and then bucked at the landing 1 .

The extraction or skidding of timber takes place with use of either a steel tracked crawler or rubber-tired skidder .

Tracked skidder (photo R. Visser)

 

The best skidder type depends on the steepness of the terrain and whether the condition of the site is dry or wet. For example, the crawler is better able to maneuver on steep or wet ground with less soil damage. This machine can safely work on slopes as high as 50-60 percent. Rubber tires offer the advantage of faster travel speeds along skid trails and greater operator comfort, and when equipped with chains can adequately perform in damp conditions. The recommended maximum slope for rubber-tired skidders is no greater than 30 percent 2 .

Most steep terrain skidders are equipped with a cable winch (instead of a grapple). The cable is pulled from the winch by either the skidder operator or another crew member to the intended turn of logs. These logs are attached by a series of 3 to 5 chokers and pulled to the skidder by the winch. This system is particularly advantageous in rough terrain since the cable can be pulled to retrieve logs from deep gullies or wet areas by simply winching the logs back to the vehicle which can remain on the skid road 3 .

Skidder operator winches logs up to the skidder (photo R. Visser)

 

Once the trees have been brought to the landing, processing takes place. In hardwoods, this typically includes cutting the trees into log lengths and sorting them according to species and which mill they will go to. In softwoods, processing typically includes cutting the trees into logs or into the proper pulpwood length. All of this is typically done with a trailer-mounted loader . The skidders drag the trees within reach of the loader, the chokers are released and the logs dropped off. The loader picks up the trees and lays them into a sawbuck to cut them to the appropriate length.

Sawbuck processing hardwood logs
(from http://www.luckyhydraulics.com/pageimages/Images-shadows/1020d-sawbuck.jpg )