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(1) Mean age of the trees comprising a forest, crop, or stand. In forests, the mean age of dominant (and sometimes codominant) trees is taken. The plantation age is generally taken from the year the plantation was begun, without adding the age of the nursery stock. (2) Of a tree: the time elapsed since the germination of the seed, or the budding of the sprout or cutting from which the tree developed.
Age class:
One of the intervals, commonly 10 or 20 years, into which the age range of tree crops is divided for classification or use. Also pertains to the trees included in such an interval. For example, trees ranging in age from 21 to 40 years fall into a 30-year age class; 30 designates the midpoint of the 20-year interval from 21 to 40 years.
Forest or stand containing trees of almost all age classes up to and including trees of harvestable age.
Annual growth:
Average annual increase in the biomass of growing-stock trees of a specified area.


Bark Thickness:
A measure of the thickness of the bark at breast-height, unless otherwise specified. It is measured from the inside of the cambium layer to the outside of the exterior bark. 
Raised mound on which seedlings are planted. Site preparation method used most extensively in the Southeastern United States.
(1) Total woody material in a forest referring to both merchantable material and material left following a conventional logging operation. (2) All of the organic material on a given area or the burnable vegetation to be used for fuel in a combustion system.
Board foot:
(1) Unit of measurement represented by a 12- by 12- by 1-inch board. (2) Unit of measurement for lumber and saw logs referring to a 12- by 12- by 1- inch board or a segment of a log that will produce boards with these dimensions.
Bone-dry ton:
Wood pulp or residue that weighs 2,000 pounds at zero percent moisture content. Also known as an ovendry ton.
Bone-dry unit:
Wood residue that weighs 2,400 pounds at zero percent moisture content.
(1) To saw a felled tree into short cuts. (2) To saw felled trees into shorter lengths.
Buffer strip or buffer zone: (1) Strip of uncut timber left between cutting units or adjacent to another resource. Also known as a green strip, leave strip, or streamside management zone. (2) Strip of land varying in size and shape, preserving or enhancing aesthetic values around recreation sites and along roads, trails, or water.


Cable yarding:
Taking logs from the stump area to a landing using an overhead system of winch-driven cables to which logs are attached with chokers.
(1) Instrument for determining tree and log diameters by measuring their rectangular projection on a straight graduated rule via two arms at right angles to (and one of them sliding along) the rule itself. (2) The optical caliper determines upper, out-of-reach tree diameters through an optical system incorporating two parallel lines of sight separated by a variable baseline.
Layer of living cells between the wood and the innermost bark of a tree. Each growing season the cambium adds a new layer of cells (by cell division) on the wood already formed, as well as a layer of inner bark on the cambium's outer face.
(1) More or less continuous cover of branches and foliage formed collectively by adjacent tree crowns. (2) Protective covering over an operator's cab.
Canopy cover:
The percent of a fixed area covered by the crown of an individual plant species or delimited by the vertical projection of its outermost perimeter; small openings in the crown are included. Used to express the relative importance of individual species within a vegetation community or to express the canopy cover of woody species. Canopy cover may be used as a measure of LAND COVER change or trend and is often used for wildlife habitat evaluations.
Channel depth: The average depth of a stream channel from mean high water mark to mean high water mark. Categorization of the entrenchment and confinement is accomplished by visual analysis or by aerial photos.
Channel gradient:
The slope of the stream channel expressed on a percent of rise per unit length. A measure of the drop in water surface elevation per unit length of channel. Channel gradient is a parameter used in model building, channel hydraulics and flow response water yield, water use, instream and flood hazard.
Small piece of wood used to make pulp. Chips are made either from wood waste in a sawmill or pulpwood operation, or from pulpwood specifically cut for this purpose. Chips are larger and coarser than sawdust.
Registered trade name for a machine that makes small logs into cants, converting part of the outside of the log directly into chips without producing any sawdust. Cants are then sawn into lumber as part of the same operation.
Commercial thinning:
Partial harvesting of a stand of trees for economic gains from the harvested trees and to accelerate the growth of the trees left standing.
Tree that is a gymnosperm, usually evergreen, with cones and needle-shaped or scalelike leaves, producing wood known commercially as softwood.
Cover type:
Category of forest defined primarily by its vegetative composition and/or locality factors.
Crop tree:
Any tree forming or selected to form a component of the final crop. The tree is usually selected when the stand or plantation is young.
Upper part of a tree, including the branches and foliage.
(1) Survey of forest land that includes the location, volume, species, size, and quality of timber stands. (2) Estimate obtained in such a survey.
Land that has previously been logged.


A harvest function referring to removing the outer protective layer (bark) from trees or parts of trees.
Crook, conk, decay, split, sweep, or other injury that decreases the amount of usable wood that can be obtained from a log.
Direct seeding:
(1) Spreading seeds over the forest seedbed by hand or machine. (2) Practice used to assist or supplement natural seed fall and to achieve regeneration.
Dominant trees:
Trees or shrubs with crowns receiving full light from above and partly from the side; usually larger than the average trees or shrubs in the stand, with crowns that extend above the general level of the canopy and that are well developed but possibly somewhat crowded on the sides. A dominant tree is one which generally stands head and shoulders above all other trees in its vicinity. However, there may be a young, vigorous tree nearby, but not overtopped by a dominant tree. This smaller tree may be considerably shorter than the dominant, but still be receiving full light from above and partly from the sides. In its own immediate environment, it is dominant and should be recorded as such. Only understory trees immediately adjacent to the overstory tree will be assigned subordinate crown classes.


Economic rotation:
Rotation of tree crops determined solely by economic considerations (which are related to biological production potential) in order to obtain the highest monetary values over time, in terms of optimum net present value or return on investment.
Complex ecological community and environment forming a functional whole in nature.
Stand of trees in which there are only small differences in age among the individual trees.
Even-aged management:
Silvicultural system in which the individual trees originate at about the same time and are removed in one or more harvest cuts, after which a new stand is established.


A harvest function referring to cutting or uprooting standing trees, causing them to fall as a result of the cutting or uprooting.
Forest management:
Generally, the practical application of scientific, economic, and social principles to the administration and working of a specific forest area for specified objectives.
Forest residuals:
(1) Sum of wasted and unused wood in the forest, including logging residues; rough, rotten, and dead trees; and annual mortality. (2) Unmerchantable material normally left following conventional logging operations other than whole-tree harvesting.


(1) Established quality or use classification of timber. (2) Slope of a surface, such as a roadway. (3) Completed base for a road. (4) To reduce ground to a level or sloped surface.
Growing stock:
Sum (by number or volume) of all the trees in a forest or in a specified part of the forest.
Increase in diameter, basal area, height, and volume of individual trees or stands during a given period of time. Also known as increment.


Height growth:
The increase in height over 5 years or the period between measurements (measured for coniferous trees).


Intermediate trees:
Trees with small, crowded crowns below (but extending into) the general canopy level; these trees receive a little light from above and none from the side.
Tree relatively incapable of developing and growing normally in the shade of, and in competition with, other trees.


  • Cleared area in the woods to which logs are yarded for loading onto trucks for shipment to a processing plant. Also known as brow, deck, dock, or ramp.
  • Usually flat ground to which logs are yarded, where they will be loaded on railroad cars or trucks; a collection point for logs. Center of operations on a logging operation.
  • Landing gear-Dollies or portion of a trailer that holds the trailer upright when it is not being supported by the truck tractor.
  • Block or roller attached to a stationary object that guides the pull of a cable.


Thousand board feet.
Mean annual increment ("MAI"): Total increment growth up to a given age divided by that age.
-Average growth per year.
Moisture content:
Amount of water present in a material such as wood or soil. Generally expressed as a percentage of the material's ovendry weight.
-Amount of water in a material, expressed as a percentage of the material's total weight; used in the pulp and paper industry.
Multiple-use forestry:
Concept of forest management that combines two or more objectives, such as production of wood or wood-derivative products, forage and browse for domestic livestock, proper environmental conditions for wildlife, landscape effects, protection against floods and erosion, recreation, and protection of water supplies.
Multiple-use management:
Management of land resources with the objective of achieving optimum yields of products and services from a given area without impairing the productive capacity of the site.


Natural regeneration:
Renewal of the forest achieved either by natural seeding or from the vegetative reproduction of plants on the site.
Net annual growth:
Increase in volume of trees during a specified year. Components of net annual growth include the increment of net volume of trees at the beginning of the specified year that survive to the year's end, plus the net volume of trees reaching the minimum size class during the year, minus the volume of trees that died during the year, and minus the net volume of trees that become rough or rotten trees during the year.


Old growth:
Layer of foliage in a forest canopy including the trees in a timber stand. Tall mature trees that rise above the shorter immature understory trees.


Partial cut:
Logging area in which only part of the trees are felled and bucked, as opposed to clearcut.
Periodic annual increment ("PAI"):
Mean annual growth or increase in volume during a specific period of time.
Precommercial thinning:
Cutting trees from a young stand so that the remaining trees will have more room to grow to marketable size. Trees cut in a precommercial thinning have no commercial value and normally none of the felled trees are removed for utilization. The primary intent is to improve growth potential for the trees left after thinning.
Removal of live or dead branches from standing trees-usually the lower branches of young trees and of multiple leaders or shoots in plantation trees- for the improvement of the tree or its timber. Cutting away of superfluous growth, including roots, from any plant to improve its development.
(1) Roundwood used as a source of wood fiber in a pulp mill. (2) Wood cut or prepared primarily for wood pulp and subsequent manufacture into paper, fiberboard, or other products, depending largely on the species cut and the pulping process.


(1) Renewal of a tree crop, either by natural or artificial means. (2) Young tree crop.
Trees remaining after an intermediate or partial cutting of tree crops or stands. In general, residuals are byproducts of some operation. Also known as waste. Examples are chips from lumber production and hog fuel from any wood processing operation.
(1) Period of years between establishment of a stand of timber and the time when it is considered ready for final harvest and regeneration. (2) Planned number of years between the regeneration of a timber stand and its final cutting.


Young tree less than 4 inches in dbh. The minimum diameter of saplings is usually, although not always, placed at 2 inches.
Saw logs (sawlogs):
Logs meeting minimum regional standards of diameter, length, and defect. Logs must be at least 8 feet long, have a minimum diameter inside bark of 6 inches for softwoods and 8 inches for hardwoods, and maximum defect as specified by regional standards.
Sealed bid sale:
Sale in which interested parties submit written bids at the time and place specified.
Second growth:
Trees that come up naturally after the first growth of timber has been cut or destroyed by fire. Also known as young timber.
(1) Young tree grown from seed, from the time of germination until it reaches sapling size. (2) In nursery practices, a young tree that has not been transplanted.
Seedling and sapling stands:
Where 10 percent of the stand consists of growing-stock trees, and saplings and/or seedlings constitute more than half this stocking.
Seed tree:
Tree that produces seeds; usually a superior tree left standing at the time of cutting to produce seeds for reforestation.
Selective cut:
Type of timber harvesting that removes only certain species above a certain size or value.
Silvicultural system:
Process of tending, harvesting, and replacing forest trees, which results in the production of forests with distinct compositions. Systems are classified according to the method of harvest cutting used for stand reproduction.
Generally, the science and art of cultivating (such as with growing and tending) forest crops, based on the knowledge of silvics. More explicitly, the theory and practice of controlling the establishment, composition, constitution, and growth of forests.
Site class:
(1) Classification based on ecological factors and the potential production capacity of an area; a measure of the relative production capacity of a site. (2) Measure of forest productivity generally expressed as the height in feet of dominant and codominant tree species at a specific index age such as 25, 50, or 100 years. Site indexes are normally grouped by site classes.
Site index:
Height of a tree at a specified index or base age. Used as an indicator of site quality.
Site preparation:
Removal or deadening of unwanted vegetation prior to planting trees; includes prescribed burning, use of herbicides, disking, and other mechanical means of removing vegetative cover.
(1) Botanical grouping of trees that are usually evergreen and have needlelike or scalelike leaves. Also known as conifers and coniferous trees. (2) Also the wood produced from such trees. The term softwood does not refer to the hardness of the wood.
Spacing control:
Act of creating, within the limits of the existing stand, a uniform distribution of trees that provides optimum growing space for each tree by eliminating overcrowding. As a result, tree diameter growth is increased and the time required for the forest to reach harvestable size is decreased.
Group of similar individuals having a number of correlated characteristics and sharing a common gene pool. The species is the basic unit of taxonomy on which the binomial system has been established. The scientific name of a plant or animal gives the genus first and then the species as in Abies (genus) grandis (species). Species is both the singular and plural form of the word.
In silviculture and management, a tree community that possesses sufficient uniformity in composition, constitution, age, spatial arrangement, or condition to be distinguishable from adjacent communities. This tree community forms a silvicultural or management entity; for example, a subcompartment. Both natural and artificial crops are included, and there is no connotation of a particular age.
Stand age:
The mean age of the dominant and co-dominant trees in the stand.
Stand condition:
General health of a stand of trees reflected by its development relative to the site potential. A good stand condition refers to a fully stocked stand that is producing fiber at a high rate based on specific site conditions such as moisture, soil quality, and other biological variables.
Stand condition classification:
Stand characterization based upon the age of maturity and structure of the overstory and understory.
1. Old-Growth Stands: Ecosystems distinguished by old trees and related structural attributes. Old growth encompasses the later stages of stand development which typically differ from earlier stages in a variety of characteristics that may include tree size, accumulations of large dead woody material, number of canopy layers, species composition, and ecosystem function. The age at which old growth develops and the specific structural attributes that characterize old growth will vary widely according to forest type, climate, site conditions and disturbance regime. For example, old growth in fire-dependent forest types may not differ from younger forests in the number of canopy layers or accumulation of down woody material. However, old growth is typically distinguished from younger growth by several of the following structural attributes:
A. Large trees for species and site.
B. Wide variation in tree sizes and spacing.
C. Accumulations of large-size dead standing and fallen trees that are high relative to earlier stages.
D. Decadence in the form of broken or deformed tops or bole and root decay.
E. Multiple canopy layers.
F. Canopy gaps and understory patchiness.
2. Young-Growth Stand: Any forested stand not meeting the definition of old growth.
Stand density: Number of merchantable trees per acre - Quantitative measure of tree stocking frequently expressed in terms of number of trees, basal area, or volume per unit area.
Stand improvement: Measures such as thinning, release cutting, girdling, weeding, or poisoning of unwanted trees to improve growing conditions.
Stand size class: A classification of land based on the stocking of all live vegetation of various sizes.
1. Non-stocked with vegetation.
2. Land less than 10-percent stocked with trees, but having vegetation.
A. Grass-Forb Stands: Stands less than 10 percent stocked with trees. Shrubs less than 40 percent crown canopy.
B. Shrub Stands: Stands less than 10 percent stocked with trees. Shrubs greater than 40 percent crown canopy.
3. Stocked with trees.
A. Seedling-Sapling Stands: Stands at least 10 percent stocked with live trees of all sizes, of which half or more of the stocking consists of seedling and/or saplings (trees < 5.0" d.b.h.).
B. Poletimber Stands: Stands at least 10 percent stocked with live trees of which half or more of the stocking is in trees, 5.0 inches dbh and larger, and in which the stocking of poletimber (softwoods-5.0 to 8.9 inches dbh, hardwoods-5.0 to 10.9 inches dbh) exceeds the stocking of sawtimber (trees larger than poletimber).
C. Sawtimber Stands: Stands at least 10-percent stocked with live trees of which half or more of the stocking is in trees 5.0 inches dbh and larger, in which the stocking of sawtimber trees is at least equal to the stocking of poletimber trees.
Stand table:
Table showing the number of trees by species and diameter classes, generally per unit area of a stand. Such data may be presented in the form of a frequency distribution of diameter classes.
Degree of utilization of land by trees. Measured in terms of basal area and/or the number of trees in a stand compared to the basal area and/or number of trees required to fully utilize the growth potential of the land. A stocking percent of 100 indicates full utilization of the site and is equivalent to 80 square feet of basal area per acre in trees 5 inches in dbh and larger. A stocking percent of 100 in a stand of trees less than 5 inches in dbh would indicate that the present number of trees is sufficient to produce 80 square feet of basal area per acre when the trees reach 5 inches dbh. A stocking percent of over 100 is fully utilizing the site.
Stocking classes -
Fully stocked stands -Stands in which the stocking of trees is from 100 to 133 percent.
Medium stocked stands -Stands in which the stocking of trees is from 60 to 100 percent.
Nonstocked areas -Commercial forestland on which the stocking of trees is less than 16.7 percent.
Overstocked stands -Stands in which the stocking of trees is 133 percent or more.
Poorly stocked stands -Stands in which the stocking of trees is from 16.7 to 60 percent.
Measure of the volume of water passing a given point in a stream channel at a given point in time. Streamflow is a function of depth, width, and velocity of water in a channel. Changes in streamflow affect the available habitat for fish spawning or rearing. Streamflow can be determined using a number of methods. Expressed in cubic feet/sec. or cubic meters/sec.
Value of timber as it stands uncut in the woods.
-Standing timber itself.
Sustained yield:
Timber yield that a forest can produce continuously at a given intensity of management. Sustained yield management therefore implies continuous production planned to achieve a balance between growth (increment) and harvest at the earliest practical time.


Cuttings made in immature stands in order to stimulate the growth of the trees that remain and to increase the total yield of useful material from the stand.
Timber volume - 
Volume of growing stock -Volume of sound wood in the bole of sawtimber and poletimber from a stump to a 4-inch minimum top diameter outside bark or to the point where the central stem breaks into limbs.
Volume of sawtimber -Net volume of the sawlog portion of live sawtimber in board feet.
Tree volume:
The amount of wood in a tree. This may be expressed in board feet or cubic feet. It may be gross volume or net volume (gross less defects).


(1) Foliage layer beneath the forest canopy. (2) Young trees that are growing beneath the tall mature trees in a timber stand.
Unmerchantable wood:
Material that is unsuitable for conversion to industrial wood products due to size, form, or quality. May include rough, rotten, and dead trees; the tops, limbs, and cull sections from harvested trees; or small and noncommercial trees.


Those areas that are inundated by surface or ground water with a frequency sufficient to support, and under normal circumstances do or would support, a prevalence of vegetation or aquatic life that requires saturated soil conditions for growth and reproduction. Wetlands generally include swamps, marshes, bogs, and similar areas such as sloughs, potholes, wet meadows, river overflows, mud flats, and natural ponds.


Amount of product output recovered from a quantity of raw material input in forest product industries. -Estimate in forest mensuration of the amount of wood that may be harvested from a particular type of forest stand by species, site, stocking, and management regime at various ages.