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AAC
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.
Anchor
A stump or tree to which the end of the skyline cable in
a cable yarding system is affixed.
Arch
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.
BA
Basal area. The cross-sectional area of the trees in a
forest unit, usually measured at Dbh and expressed in m² per
hectare. Commonly used as a measure of tree density in a forest.
Block
A large pulley used in cable logging to change the
direction of the cables.
Bole
A tree stem that has grown to substantial thickness,
capable of yielding saw logs, veneer logs or large poles.
Bucking
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.
Buttress
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.
Cable
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.
Cableway
The pathway along which logs are yarded with a cable
yarding system. Also referred to as the cable corridor or skyline
corridor.
Canopy
The part of the forest formed by the crowns of the
dominant trees.
Choker
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.
Choker-setter
A worker employed to attach chokers to logs for
extraction to a landing.
Clear-felling
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.
Climbers
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.
Corridor
See cableway.
Coupe
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.
Crosscutting
See bucking.
Cross-drain
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.
Cutting
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.
Dbh
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.
Debranching
See limbing.
Deck
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.
Dominants
Trees whose crowns are in or above the main part of the
forest canopy.
Drum
A spool around which cable is wound. Compare winch.
Emergents
Trees whose crowns extend above the general level of the
forest canopy.
Erosion
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.
Extraction
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.
Felling
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.
Forwarding
Transporting trees or logs by carrying them completely in
the air rather than pulling or dragging them along the ground.
Grapple
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.
Harvester
A machine that fells trees, delimbs them and crosscuts
them into logs.
Harvesting
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.
Hauler
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.
Landing
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.
Lianas
See climbers.
Limbing
The act or process of severing the branches from the stem
of a felled tree.
Log
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.
Logging
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.
Lumber
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.
NWFP
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.
PFE
Permanent forest estate. The total area of forest land in
a country that has been legally designated for retention as
forest in perpetuity.
Pole
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.
Processor
A machine that delimbs trees and crosscuts them into
logs. Machines that do this and also fell the trees are called
harvesters.
Ramp
See landing.
Rattan
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.
Resource
As used in this paper, any component of the natural
environment that is recognized as having value or usefulness.
Rotation
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.
Roundwood
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.
Sediment
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.
Setting
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.
Skidding
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.
Stem
The principal axis of a plant, from which buds and shoots
develop. The stem of a large tree may also be called the bole.
Stump
The woody base of a tree that remains in the ground after
felling.
Sulky
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.
Timber
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.
Tower
A mast, usually of steel, used with cable extraction
systems. Compare spar tree.
Trimming
See limbing.
Volume
The estimated or measured quantity of wood in a log or
tree, commonly expressed in m³.
Winch
A powered drum used to reel in or pay out cable for
hauling or hoisting.
Winching machine
See yarder.
Wire rope
See cable.
Yarder
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.
Yarding
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.