Forestry Glossary

Acre

A land area of 43,560 square feet (About 209 by 209 feet).

All-aged (or uneven-aged) forest management

Management of a forest by periodically removing some trees from the stand. (See also even-aged forest management.)

Allowable cut

Volume of wood that can be cut during a given period without exceeding the forest's net growth.

Alluvial

Pertaining to material that is transported and deposited by running water.

Anadromous fish

Those species of fish which mature in the sea and migrate into streams to spawn. Salmon, steelhead, and shad are examples.

Aspect

Compass direction towards which a slope faces.

Basal area

A. Cross-sectional area (in square feet) of the trunk of one tree at breast height (4.5 feet above the ground). For example, the basal area of one tree 14 inches in diameter at breast height is approximately 1 square foot. B. The sum of basal area of the individual trees on an acre of forest. For example, a well stocked mixed redwood stand might contain (a total of) 500 square feet of basal area per acre.

Biological diversity or biodiversity

Refers to the variety of life. It encompasses the number and type of plants and animal species in a given area, as well as the interactions among them.

Board foot

A unit of measure for wood volume equaling 144 cubic inches, commonly used to measure and express the amount of wood in a tree, sawlog, veneer log or individual piece of lumber. For example, a piece of wood 1 foot by 1 foot by 1 inch or one measuring 1 foot by 3 inches by 4 inches both contain 1 board of wood.

Bole

Main tree trunk.

Breast height

See DBH.

California Forest Practice Act (Rules)

Also known as the "Z'berg-Nejedly Forest Practice Act of 1973." This legislation initiated the forest practice rules in California that, when followed, will allow maximum sustained production of timber, while giving consideration to values such as recreation, watershed, wildlife, range and forage, fisheries, and aesthetic enjoyment.

Canopy

Layer of tree crowns in a forest.

Clearcut

A harvesting and regeneration system which removes all the trees (regardless of size) on an area in one operation. Clear cutting is mostly used with species that require full sunlight to reproduce and grow well. Produces an even-aged forest stand.

Commercial cut

A cutting on a forested property that yields a net income (when product sale receipts exceed cutting cost).

Competition

The struggle for environmental resources among trees that require the same resources on the same land area, usually at the same time.

Conifer

A tree belonging to the order Coniferales - usually evergreen, cone-bearing, and with needles, awl, or scalelike leaves- for example, pine spruces, firs, cedars, and redwood; often called 'softwoods.'

Conservation

Protection, improvement and wise use of natural resources to assure the attainment of their highest economic and social values in perpetuity.

Cord

A stack of round or split wood containing 128 cubic feet. A standard cord measures 4 feet by 4 feet by 8 feet. A face or short cord is 4 feet by 8 feet of any length wood less than 4 feet.

Crop tree

A tree identified as mature and ready for final harvest cut. Usually selected on the basis of its location to other trees and its quality.

Crown

Branches and foliage of a tree.

Crown class

Any class into which the trees forming a crop or stand may be divided on the basis of both their crown development and crown position relative to the crowns of adjacent trees and the general canopy.

Cruise

A survey of forest land to locate timber and estimate its quantity by species, products, size, and quality, or other characteristics; the estimate obtained in such a survey.

Cubic foot

A unit of measure for wood volume containing 1,728 cubic inches - for example, a piece of wood measuring 1 foot on a side. A cubic foot of wood contains approximately 6 usable board feet of lumber rather than 12 board feet because wood is lost as sawdust and shavings during processing.

Cull

A tree or log of merchantable size useless for all but perhaps firewood because of shape, disease, insect infestation, or injury.

Cutting cycle

Planned time interval between major harvesting operations in the same stand, usually in uneven-aged stands. For example, a cutting cycle of 10 years means a commercial cut every 10 years.

DBH

Tree diameter at breast height (4.5 feet above the ground).

Defect

That portion of a tree or log unusable for the intended product and therefore, not measured. Defects are rot, crookedness, cavities, and excessive limbiness.

Diameter

Tree diameter is usually measured 4.5 feet above the average ground level (see DBH).

Ecosystem

An interacting system of living organism (plants and animals), soil, and climatic factors. A forest is an ecosystem.

Environment

Prevailing conditions reflecting the combined influences of climate, soil, topography, and biology (other plants and animals) in an area. Environmental factors determine how well a particular species will grow in a given area.

Even-aged forest

A forest of trees all essentially the same age (within 10-20 years).

Even-aged forest management

Forest management with periodic harvest of all trees on part of the forest at one time or in several cuttings over a short time to produce stands containing trees all the same or nearly the same age. In California, this type of management is commonly applied to conifers using the clearcut, seed tree, or shelterwood silvicultural systems.

Forest

A plant community with trees and other woody plants dominating.

Forest management

Giving the forest proper care so that it remains healthy and vigorous and provides the products and amenities the landowner desires. Technical: Applying technical forestry principles and practices and business techniques (such as accounting and benefit-cost analysis) to forest management.

Forest type

A group of tree species that, because of shared environmental requirements and tolerances, commonly grow together. Three examples of forest types are the mixed conifer, true fir, redwood and Douglas-fir.

Forestry

The science, art, and practice of managing trees and forests and their associated resources for human benefit.

Habitat

Local environment of a plant of animal.

Harvest

As generally used, to remove all or portions of the trees in an area. Technical definition: To remove trees in an area (1) for financial gain; (2) to develop the environment necessary to regenerate the forest; and, (3) on occasion, to achieve some special objectives, such as the development of special wildlife habitat needs.

Hardwood

A term describing broadleaf (usually deciduous) trees such as oaks, maples, ashes, eucalyptus, and elms. Not necessarily the hardness of the wood.

IHV

(Immediate Harvest Value). Stumpage values determined by the State Board of Equalization from many timber sales in each timber value area and influenced by species, age, logging method, and volume harvest.

Increment borer

A hollow, auger-like instrument used to bore into the tree trunk to remove a cylindrical cross section of the tree's growth rings.

Intermediate cut

Removal of immature trees from the forest sometime between establishment and major harvest to improve quality of the remaining forest stand. An intermediate cut may generate income (commercial cutting), or may cost the forest landowner more than income realized (a pre-commercial cutting).

Log

A piece of woody stem (trunk or limb) of a tree. The trunk portion of a tree.

Log rule

A device, usually in tabular form, that expresses log volume content base on log diameter (inside the bark of the small end) and length. The Scribner Rule is the legal rule in California and is most often used.

Log scaling

Measuring logs to determine their volume.

Lop

To sever and sometimes scatter branches, tops, or small trees after felling, leaving the slash closer to the ground.

Mature tree

A tree that has reached the desired size or age for its intended use. Size or age will vary considerably depending on the species, intended use, and markets.

MBF

Thousand board feet.

Multiple use

Land management for more that one purpose.

Plantation

An artificially reforested or afforested area established by planting or direct seeding. Contrast with a forest stand established naturally.

Pole stand

A stand of trees whose diameters range from 4 inches to approximately 12 inches.

Riparian

Referring to the land bordering a stream, lake or tidewater.

Reforestation

Re-establishing a forest on an area where forest vegetation has been removed.

Reproduction

(A) The growth process whereby young trees become the older trees in the future forest. (B) The process of forest replacement or renewal - either artificially by seeding or planting or naturally, by sprouting or natural seeding.

Roots

That portion of the tree, generally underground, which absorbs nutrients, anchors, and stores food and waste products.

Salvage cut

Harvesting trees that are infected by or highly susceptible to insects or diseases to protect the rest of the forest stand.

Sapling

A small tree, usually between 2 and 4 inches DBH.

Sawlog

A log large enough to produce a sawn product -- usually at least 10 to 12 inches in diameter at breast height.

Scribner's Rule

A diagrammatic log rule developed over 100 years ago to estimate the volume of a log assuming a ¼ inch saw kerf and no definite slab allowance. However, the Rule more accurately estimates product output rather than log volume.

Second growth

A loose term for a young stand, or smaller trees, left after cutting. Also, residual trees available for another logging on the same area.

Seed-tree harvest system

Removal of all trees from the harvest area at one time except for a few scattered trees left to provide seed to establish a new forest stand. California Forest Practice rules specify the number and size to be left per acre.

Seedling

(A) A tree, usually less than 2 inches DBH, that has growth from a seed not a sprout. (B) Nursery-grown trees that have not been lifted and replanted in the nursery.

Selection harvest system

Harvest of individual trees or small groups of trees at periodic intervals (usually 8 to 15 years) based on their physical condition or degree of maturity. Produces an uneven-aged stand.

Seral

A biotic community which is a developmental transitory stage in an ecologic succession.

Shelterwood harvest system

Removal of trees on the harvest area in a series of two or more cuttings so that new seedlings can establish and grow in the partial shade and protection of older trees.

Silvicultural system

A process, following accepted silvicultural principles, whereby the crops constituting forests are tended, harvested, and replaced, resulting in the production of crops of distinctive form. Systems are conveniently classified (for example, clearcut) according to the method of carrying out the fellings that remove the mature crop with a view to regeneration and according to the type of crop produced.

Silviculture

The art, science, and practice of establishing, tending, and reproducing forest stands of desired characteristics based on knowledge of the characteristics and environmental requirements of the tree species.

Site index

An expression of forest site quality based on the height of the dominant trees at a specified age, usually 50 or 100 years.

Site preparation

Preparing an area of land for forest establishment, including mechanical clearing, vegetation control, or burning.

Skid

To pull logs from the stump to the skid trail or landing.

Slash

Residue left on the ground after logging, pruning, or other forest operations. Includes tree tops, branches, or bark.

Softwood

See conifer.

Soil texture

The feel or composition of soil based on the proportion of sand, silt, and clay in the soil.

Sprout

A tree growing from the base, stump, or root of another tree. Coastal redwoods sprout vigorously.

Stand (timber types)

A community of trees of sufficient uniformity, with respect to composition, age spatial arrangement or condition, to be distinguished from adjacent communities, so forming a management entity.

Fully stocked

A forest stand with all growing space effectively occupied but have ample room for crop development.

Mixed

A stand having less than 80 percent of the trees in the main crown canopy of a single species.

Overstocked

Overcrowding in a stand leading to retarded growth.

Pole-timber

A stand with most trees from 4 to 8 or 12 inches in diameter.

Pure

A stand with at least 80 percent of the trees in the main crown canopy of a single species.

Sawtimber

A stand with most trees large enough in diameter (usually 10 to 12 inches DBH or larger) to be sawn into lumber.

Understocked

A stand with the growing space not effectively occupied by potential crop trees.

Stocking level

Number of trees in a forest stand. Often, stocking level is the term used for the desirable number of trees at a given age for best growth and management against which comparisons can be made, such as partially-stocked, well-stocked, or over-stocked.

Stumpage

Value or volume of a tree or group of trees as they stand in the woods uncut (on-the-stump).

Succession

Replacement of one plant community by another until a climax ecosystem is achieved.

Sustained yield

The yield that a forest can produce continuously at a given intensity of management. Sustained yield management implies continuous production so planned as to achieve at the earliest practical time a balance between increment and cutting.

Thinning

Generally, a cutting in an immature forest stand to reduce the tree density and concentrate the growth potential of fewer, higher quality trees resulting in larger trees with faster growth.

Commercial thinning

A thinning that pays for itself and then provides a profit for the owner.

Natural thinning

A natural process whereby a tree's branches or the tree itself dies as a result of root or crown competition.

Pre-commercial thinning

A cutting, which does not yield a net income, usually because the trees cut are too small, poor quality, or not marketable.

Row thinning

A plantation thinning with specified rows removed regardless of size.

Selection thinning

A thinning with individual trees selected for removal.

THP (Timber Harvesting Plan)

As a result of Article 7 of the "Z'berg-Nejedly Forest Practice Act" of 1973, a THP is required for timber operation to take place on land other than federal land within the State of California.

Tolerance

A tree's capacity to develop and grow in the shade of other trees.

TPZ (Timberland Production Zone)

Created by the "California Taxation Reform Act" of 1976, TPZs were established so that forest landowners would not pay property tax on the basis of the land's "highest and best use."

Tree

A woody plant having a well-defined stem, more or less definitely formed crown and usually at least 20 feet tall.

Tree farm

A privately-owned forest in which producing timber crops is a major management goal.

Volume table

A table estimating volume of wood in a standing tree based on measurements of the tree, most commonly DBH and merchantable height.

Windfall, windthrow, (blowdown)

An area or group of trees blown over by high wind.