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Annual allowable cut. The volume of timber that may be harvested from a particular area of forest in any one year. From the industrial forestry perspective, the AAC should be set at a level that provides the maximum harvest volume while ensuring that the prospects for future harvests do not deteriorate. When the impact of timber harvest on NWFP is considered, the AAC will be reduced in most cases, in comparison with a situation in which timber production is the sole consideration. This will depend upon the degree to which the timber harvest complements or competes with the production of NWFP, however. Similarly, consideration of the value of the forest's environmental and service functions will tend to reduce the AAC.

Advance regeneration
Small trees (seedlings and saplings) that are already present in the forest at the time a timber harvesting operation is being conducted. Also called advance growth.

A stump or tree to which the end of the skyline cable in a cable yarding system is affixed.

A supporting device towed behind or mounted on a skidding vehicle and used to lift one end of a load of logs in order to reduce sliding resistance.

Basal area. The cross-sectional area of the trees in a forest unit, usually measured at Dbh and expressed in m per hectare. Commonly used as a measure of tree density in a forest.

A large pulley used in cable logging to change the direction of the cables.

A tree stem that has grown to substantial thickness, capable of yielding saw logs, veneer logs or large poles.

The act or process of transversely cutting the stem or branches of a felled tree into logs. Also called crosscutting.

Buffer strip
An area of forest, usually around streams, lakes, parks, major highways or other protected areas, from which all harvesting equipment and operations are excluded. Also called filter strip.

A ridge of wood that develops in the angle between a lateral root and the base of a tree stem to provide lateral stability to the stem. Buttresses develop on many tree species in lowland evergreen rain forest, but occur less commonly in lower montane rain forest and semi-evergreen rain forest; they are comparatively rare in wet deciduous forest.

A flexible steel rope made up of numerous wire strands that are twisted helically together around a core of wire, wire rope, fibre, plastic or other material.

Cable yarding system
Any of a variety of terrain transport systems in which suspended cables are used to convey logs to the landing.

The pathway along which logs are yarded with a cable yarding system. Also referred to as the cable corridor or skyline corridor.

The part of the forest formed by the crowns of the dominant trees.

A noose of wire rope or chain that is wrapped around a log and then attached to a means of conveyance in order to bring the log to a landing.

A worker employed to attach chokers to logs for extraction to a landing.

A harvesting system in which all merchantable trees within a specified physical area of land are felled and no significant tree cover remains. Use is generally limited to plantations. See also monocyclic harvesting systems.

Vines that either hang freely, are suspended from the forest canopy or adhere to the stems of trees by specialized roots. Free-hanging climbers with woody stems are often called big woody climbers or lianas (also spelled lianes). As they often bridge across several tree crowns, severe damage may result when one of the trees is felled. Climbers may represent important sources of food and habitat for animal species, however, and so should be cut only where necessary to reduce felling damage.

See cableway.

In English this term is sometimes used to refer to the AAC and sometimes to a specific area of land that is scheduled to be harvested within a specified period of time (often, but not always, one year). May also be referred to as a felling coupe or annual coupe.

See bucking.

A culvert, pipe or shallow channel laid diagonally across the surface of a road, skid trail or cableway in order to divert water from the cleared surface or from the roadside ditch.

In timber harvesting, a compound term referring to the operations of felling, limbing, debarking and bucking.

Cutting cycle
See felling cycle.

Cutting unit
The area of forest from which timber is removed to a single landing. Also referred to as a setting or set-up.

Diameter at breast height. The diameter of a tree measured at a standard reference point, usually 1.3 m above ground level on the uphill side of the tree after accumulated ground litter has been removed. For trees with large buttresses, a point above the main flare of the buttresses is often used to measure diameter; its abbreviation is Dab.

See limbing.

See log deck.

Designated skid trails
A ground-skidding system in which skid trails are pre-planned and marked clearly on the ground, usually before felling commences. During the skidding operation, skidders are required to stay on the skid trails at all times. This means that each skidder must be equipped with a winch and sufficient cable to reach the logs that have been prepared for skidding.

Trees whose crowns are in or above the main part of the forest canopy.

A spool around which cable is wound. Compare winch.

Trees whose crowns extend above the general level of the forest canopy.

The action of natural atmospheric conditions on any material exposed to them. In this paper, the term refers principally to the wearing away of soil by the physical and chemical action of water. See also sediment.

The act or process of transporting logs from the felling site to a landing. Also referred to as terrain transport. Most extraction is done either by skidding or by yarding.

The act or process of severing a standing tree. Compare cutting.

Felling cycle
In selection (polycyclic) harvesting systems, the planned, recurring number of years between successive harvests on a specific, physical area of land. Compare with rotation. The harvesting activity that occurs at the end of the felling cycle is often referred to as a felling entry.

Filter strip
See buffer strip.

Forest fallow
See shifting cultivation.

Forest harvesting
See harvesting.

Transporting trees or logs by carrying them completely in the air rather than pulling or dragging them along the ground.

A hinged mechanism capable of being opened and closed mechanically, which is used to grip logs during extraction or loading. Also referred to as a grapple hook in helicopter logging.

Ground skidding
See skidding.

A machine that fells trees, delimbs them and crosscuts them into logs.

The aggregation of all operations, including pre-harvest planning and postharvest assessment, related to the felling of trees and the extraction of their stems or other usable parts from the forest for subsequent processing into industrial products. Also called timber harvesting.

Harvesting technology
The study or use of scientific and engineering principles in harvesting. In this model code of forest harvesting practices, the term refers broadly to the equipment and techniques, planning and control methodologies, scientific knowledge and engineering principles, education and training, and practices that contribute directly or indirectly to the success of harvesting operations.

See yarder.

Industrial roundwood
Roundwood that is used for industrial purposes, either in its round form (e.g. as transmission poles or piling) or as raw material to be processed into industrial products such as sawn wood, panel products or pulp. See also roundwood.

Integrated arch
An arch that is securely mounted to the frame of a skidding vehicle.

A cleared area where logs are collected during extraction in preparation for transport to the processing facility or other final destination. Also called a ramp.

See climbers.

The act or process of severing the branches from the stem of a felled tree.

Any section of the bole, or of the thicker branches, of a felled tree after limbing and bucking.

Log deck
A pile of logs, usually on a landing.

The act or process of felling and extracting timber from forests, especially in the form of logs.

Logging truck
A vehicle used to transport logs on roadways. Also referred to as a log truck.

Log transport
Conveyance of logs from the landing to the processing facility or other final destination.

See sawn wood.

Manual felling
Felling of trees with non-motorized tools, such as axes and saws.

Mechanized felling
Felling of trees with specialized machines, such as feller-bunchers and harvesters.

Mixed broad-leaved forest
A forest with many different species of broad-leaved trees. Many tropical forests are of this type.

Monocyclic harvesting systems
Harvesting systems in which the crop trees are harvested all at once, at the end of the rotation. Intermediate entries (thinnings) may be made to remove trees that are not intended for the final crop, so that the crop trees will have access to more light and nutrients, and may thus grow to a larger size. Compare polycyclic harvesting systems.

Motor-manual felling
Felling of trees with motorized hand tools, usually chainsaws.

Non-wood forest products. Defined in this paper as all biological material, other than industrial roundwood, that may be extracted from natural ecosystems, either for commercial purposes, for use within the household or for social, cultural or religious uses. Also referred to as non-timber forest products (NTFP).

Partial cutting

Any harvesting system in which not all merchantable crop trees are harvested. Compare clear-felling.

Permanent forest estate. The total area of forest land in a country that has been legally designated for retention as forest in perpetuity.

Roundwood of a diameter smaller than saw-log size, suitable - without further conversion - for supporting transmission lines or for rough construction.

Polycyclic harvesting systems
Harvesting systems in which crop trees are removed on a cycle of felling entries that occur more frequently than the rotation. In such systems, not all crop trees are removed during a particular felling entry; selection of those to be harvested and those to be retained may be based on Dbh (e.g. only those crop trees larger than 60 cm Dbh are to be removed) or other criteria. For this reason polycyclic systems are often referred to as selection systems. Compare monocyclic harvesting systems.

A machine that delimbs trees and crosscuts them into logs. Machines that do this and also fell the trees are called harvesters.

See landing.

A climbing palm of the subfamily Calamoideae. The stems are commonly used in the construction of furniture. Rattans occur both in Africa and in the Asia and the Pacific region and are of major economic importance as NWFP in Southeast Asia.

Residual tree
A tree of a commercial or potentially commercial species that remains after the harvest has been completed. Of particular significance in polycyclic harvesting systems. Also referred to as a remaining tree.

As used in this paper, any component of the natural environment that is recognized as having value or usefulness.

The planned number of years between the formation or regeneration of a crop of trees and the time when the same crop is felled for final harvest. The age at the time of harvest is referred to as the rotation age when it coincides with the rotation and as the removal age when it does not. In selection harvesting systems, the terms mean exploitable age or mean harvesting age are sometimes used in place of rotation age.

Wood in its natural state as felled, with or without bark. It may be round, split, roughly squared or in other forms.

Saw log
A log considered suitable in size and quality for producing sawn wood.

Sawn wood
Sawn products produced from logs. Also called lumber.

The material products of erosion (soil, sand, clay, gravel and rocks) brought down watercourses and suspended in the water or deposited in outwash fans or on flood plains.

Selection harvesting
See polycyclic harvesting systems.

See cutting unit.

Shifting cultivation
A method of cultivation in which a forest area is cleared of trees, burned to release mineral nutrients, farmed for a few years until the soils become too poor to sustain crops, and then abandoned.

Skid trail
The pathway over which logs are skidded in a ground-skidding extraction system. Referred to in some countries as a snig track.

Terrain transport in which logs are dragged to the landing, rather than suspended in the air or carried on a vehicle. Also referred to as ground skidding or, in some countries, as snigging.

Skidding pan
A plate of metal, usually rounded in front, which is placed under the front end of logs being skidded to prevent them from digging into the ground.

Skyline carriage
A wheeled device that rides along a skyline and is used to support a load of logs in skyline yarding.

Skyline corridor
See cableway.

Skyline yarding system
A cable yarding system that makes use of a heavy wire rope (the skyline) that is stretched between two spar trees and used as a track for a skyline carriage.

Soil erosion
See erosion.

Spar tree
A tower, mast or tree used to elevate the cables in cable yarding systems.

The principal axis of a plant, from which buds and shoots develop. The stem of a large tree may also be called the bole.

The woody base of a tree that remains in the ground after felling.

An open framework, mounted on wheels, which is used to suspend the leading ends of logs being extracted manually, with a ground-skidding system or with draught animals.

Tail tree
A spar tree located at the opposite end of the cableway from the yarder.

Terrain transport
See extraction.

Tether line
In helicopter logging, the line that is suspended beneath the helicopter to reach the load of logs. Also referred to as a tag line. Similar terms are used also in balloon logging.

Trees suitable for conversion into industrial forest products. Sometimes this term is used as a synonym for industrial roundwood, and it may also be used to refer to certain large sawn wood products (e.g. bridge timbers).

Timber harvesting
See harvesting.

A mast, usually of steel, used with cable extraction systems. Compare spar tree.

See limbing.

The estimated or measured quantity of wood in a log or tree, commonly expressed in m.

A powered drum used to reel in or pay out cable for hauling or hoisting.

Winching machine
See yarder.

Wire rope
See cable.

A machine on which is mounted a system of winches that are used to convey logs from the felling area to the landing in a cable yarding system. Also referred to as a hauler or a winching machine.

Terrain transport in which logs are conveyed to the landing by cable or aerial systems that have the capability of fully or partially suspending logs in the air during transit to the landing. An essential characteristic of yarding systems, as opposed to skidding systems, is that the yarding power source does not travel along the ground as is the case with ground skidding.

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