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Forestry Terms - A -

ABNEY LEVEL -Hand-held clinometer used to measure slope in percent.

ACRE - An area of land measuring about 43,560 square feet. A square 1-acre plot measures about 209 feet by 209 feet; a circular acre has a radius of 117.75 feet.

ADMINISTRATIVE UNIT - The basic geographic management area within a Forest Service Region, Station, or Area.

AFFORESTATION - Establishment of forest crops by artificial methods, such as planting or sowing on land where trees have never grown .

AGE -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. -Of a tree: the time elapsed since the germination of the seed, or the budding of the sprout or cutting from which the treedeveloped .

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.

AIR-DRIED - Lumber or other wood products that have been either dried by exposure to natural atmospheric conditions outdoors or in an unheated shed or dried to equilibrium with the surrounding atmosphere. Moisture content of air-dried wood fiber depends on relative humidity, temperature, and length of drying period. Also referred to as air seasoned.

ALL-AGED - Forest or stand containing trees of almost all age classes up to and including trees of harvestable age.

AGRICULTURAL LAND - Areas used primarily for production of food and/or fiber (excludes wood fiber). Examples are cropland, pasture, orchards, vineyards, nurseries, confined feeding areas, farmsteads, and ranch headquarters.

ALKALINITY - A measure of calcium carbonate expressed as mag/l of CaCO3.

ALL-AGED or UNEVEN-AGED MANAGEMENT - The practice of managing a forest by periodically selecting and harvesting individual trees or groups of trees from the stand while preserving its natural appearance. Most common in hardwood forests.

ALL-AGED or UNEVEN-AGED STAND - A forest stand composed of trees of different ages and sizes.

ALLOWABLE CUT - Volume of timber that may be harvested during a given period to maintain sustained production (31).

ALLOWABLE CUT EFFECT - Allocation of anticipated future forest timber yields to the present allowable cut; this is employed to increase current harvest levels (especially when constrained by evenflow) by spreading anticipated future growth over all the years in the rotation.

AMOUNT OF WATER APPROPRIATED OR CLAIMED - An entry in either cubic feet per second or acre-feet per year or gallons per day is required for all current uses.

ANNUAL - A plant that lives or grows for only one year or one growing season.

ANNUAL ALLOWABLE HARVEST - Quantity of timber scheduled to be removed from a particular management unit in 1 year.

ANNUAL GROWTH - Average annual increase in the biomass of growing-stock trees of a specified area.

AQUATIC HABITAT TYPES - The classification of instream habitat based on location within channel, patterns of water flow, and nature of flow controlling structures. Habitat is classified into a number of types according to location within the channel, patterns of water flow, and nature of flow controlling structure. Riffles are divided into three habitat types: low gradient riffles, rapids, and cascades. Pools are divided into seven types: secondary channel pools, backward pools, trench pools, plunge pools, lateral scour pools, dammed pools, and beaver ponds. Glides, the third habitat type are intermediate in many characteristics between riffles and pools. It is recognized that as aquatic habitat types occurs in various parts of the country additional habitat types may have to be described. If that becomes necessary it will be the responsibility of the regional fishery biologist to describe and define the additional habitat types.

AREA REGULATION - Method of controlling the annual or periodic acreage harvested from a forest, despite fluctuations in fiber-yield volumes. Leads to a managed forest.

AREA SALVAGE - Timber sales in which the USDA Forest Service sells dead timber within a given area. Usually covers more than one operating season and requires the operator to return annually to remove any dead timber present.

ARTICULATED - With reference to a vehicle, hinged at the center for turning, as with a wheeled skidder.

ARTIFICIAL REGENERATION - Renewal of the forest by planting or direct seeding; establishing a new stand of trees by planting seeds or seedlings by hand or machine.

ASPECT - Compass direction to which a slope faces. Also called exposure.

AUTHORIZED USE - Specific activity or occupancy, such as ski area, historical marker, or oil and gas lease, for which a special authorization is issued.

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