Harvesting timber is one of the oldest professions in the United States. As soon as the early settlers arrived on the East Coast, standing timber had to be cleared before establishing a settlement. As Americans moved West, vast timberlands awaited to supply them with natural resources to help the country flourish. Harvesting timber has historically been very demanding and very dangerous work. It still has its dangers, but advancements have made the work safer, somewhat easier, and definitely faster. Harvesting includes all operations necessary to remove timber from the forest and deliver it to the mill. These operations are felling, delimbing and bucking, skidding, loading and hauling.
Several methods for accomplishing these operations are available. The correct methods to be used on any particular site depends upon several factors such as: tract size, timber type, volume per acre, type of cut (clearcut, thinning, etc.), terrain, soil types, equipment availability, and the timberland owner's desires.
Felling
Felling is the act of severing standing trees from their stumps. Felling is normally accomplished with a chainsaw or a hydraulic-powered felling head attached to a mobile machine. The chainsaw can be used to fell any tree, however, it is the primary tool used for cutting higher-value products such as poles and veneer sawlogs. There are several types of felling heads in service. Some have either one or two blades that shear the tree from the stump. They can cause damage to the butt log, thus limiting their use to mainly pulpwood. Other heads use cleaner methods to cleanly saw the tree thereby reducing log damage and enabling its use on other products. The felling head can be mounted on a crawler tractor, rubber-tired carrier, excavator, or specialized machine.
Delimbing and Bucking
Delimbing entails removing limbs from the trunk of the tree up to a minimum top diameter while bucking involves cutting the stem into logs or bolts of predetermined lengths. The tree can be delimbed and bucked where felled or the entire tree can be skidded to a clearing called a log landing for delimbing and bucking. Equipment used includes chainsaws and a variety of mechanized methods. In some cases the bucking step is eliminated and the entire tree (minus limbs and top) is transported to the mill. In some pulpwood operations, the entire tree (limbs and all) may be reduced to small chips and blown into trailers for transport to the mill.
Skidding
In the South, most movement of wood from the stump to the landing is done with wheeled or tracked machines. Skidding, or dragging logs, is accomplished with rubber-tired skidders, crawler tractors, or even horses or mules. Skidders and crawlers can be equipped with wire nooses called chokers or grapples to secure the stems for transport.
Forwarding or prehauling involves carrying the wood on a vehicle, from stump to landing. Skidder type machines, equipped with bunks or trailers are commonly used. In mountainous areas, cable logging systems are sometimes used. These have a tower, yarder, and cables to move the logs. Generally, there is less ground disturbance on steep slopes with cable yarding.
Depending on soil properties, terrain slope and rainfall patterns, ground skidding can sometimes cause unacceptable levels of soil disturbance of forestland, resulting in reduced tree growth and lower water quality through erosion. These impacts can be reduced by a combination of minimizing the area in skid trails and limiting logging to dry weather. The location of skid trails should be determined in a harvesting plan.
Loading
Loading is the link between logging and hauling operations. Loading is performed from the log deck located at the landing. Several landings are often used on larger tracts so that skidding distances are minimized. Loading is done with a variety of machinery, rarely by hand. The most common machines are hydraulic knuckle boom loader, front-end loader, and big-stick loader. If the end product is wood chips, chippers are often located at the landing, and the chips are blown into special trailers.
Hauling
The final harvesting operation is the movement of bolts, logs, trees or chips from the deck to a local woodyard or mill. All log decks should be located beside a haul road system developed for the tract. This transportation network, including deck and skid trail locations, should be specified in the harvesting plan to minimize skidding distances, haul-road construction, maintenance costs, and soil disturbances.
