Annual ring -
The growth layer of 1 year, as viewed on the cross section of a stem, branch, or root. One year's growth consists of a layer of lighter-colored wood (springwood) and a layer of darker-colored wood (summerwood).

Biological control - Control of plants, diseases, and animal pests by the use of natural enemies.

Blaze - A mark placed on a standing tree to call special attention to the tree.

Blowdown - Trees that have been knocked over by wind.

Blue stain - A fungus discoloration, predominantly bluish, but sometimes grayish, blackish, or brownish in appearance; confined almost exclusively to sapwood; common in pines.

Bole - The main trunk of a tree.

Browse - Small bushes, sprouts, herbaceous plants, small trees, etc., that wildlife feed on.

Burn, controlled - Any burning that a landowner starts intentionally to accomplish a particular purpose, and over which he or she exercises some surveillance or control.

Burn, prescribed - The application of fire to land under conditions of weather, soil moisture, and time of day, that will accomplish specific silvicultural, wildlife, grazing, or fire hazard reduction purposes.

Canopy - A collective term for the layer formed by the crowns of the taller trees in a forest.The canopy is the highest layer of the forest--the intertwined branches of mature trees that shade and protect lower forest layers and provide a habitat for insects, birds and small mammals.

Crotch - The fork of a tree or branch.

Crown - The branches and foliage of a tree.

Deciduous - Term applied to trees (commonly broadleaf) that drop all their leaves sometime during the year.

Dendrology - The identification and systematic classification of trees and shrubs.

Duff - Forest litter and other organic debris in various stages of decomposition on top of the mineral soil; typical of coniferous forests in cool climates, where rate of decomposition is slow and where litter accumulation exceeds decay.

Habitat -The environment in which the plant or animal lives.

Field layer - The field layer is the first layer of growth on the forest floor--a soft carpet of mosses, ferns, wildflowers, grasses and other low plants. It is a habitat for many insects, mammals, reptiles and amphibians.

Latitude - distance north or south from the earth's equator measured through 90 degrees

Litter layer - The litter layer is the floor of the forest, where decaying plant matter and fungi undergo the transformation into soil. Bacteria, insects and worms in the litter help break down the plant matter.

Old growth - A forest that has never been changed by management or harvesting. This term is misapplied by many to describe any forest that appears to be old. Individual trees in this type of forest are usually over 200 years old, and there are large standing and fallen dead trees throughout the stand.

Riparian zone -That area adjacent to rivers and streams identified by vegetation, wildlife, and other qualities unique to these locations.

Sapling - A young tree of small diameter

Silviculture - The art and science of producing and tending a forest; the theory and practice of controlling forest establishment, composition, growth, and quality of forests to achieve the objectives of management.

Snag - A standing, dead tree or a standing section of the stem of a tree broken off at the height of 20 ft or more. If less than 20 ft, it is properly termed a "stub.

Softwood - One of the botanical group of trees that generally have needle or scalelike leaves-the conifers. Also the wood produced by such trees, regardless of texture or density

Soil layer - The soil layer is the foundation of the forest, supporting and providing moisture and nutrients to plant and tree roots. It consists of decomposed plant matter and inorganic material, such as rocks, minerals and clay.

Timber - A term loosely applied to forest stands or their products; often applied to wood in forms suitable for heavy construction (houses, ships, bridges).

Understory - The understory is made up of bushes, shrubs, woody plants and young trees reaching up to the forest canopy; it provides a habitat for birds and insects.

Virgin forest - A mature or overmature forest essentially uninfluenced by human activity.


Alluvial Fan
- A large, fan-shaped pile of sediment forming at the base of narrow canyons onto a flat plain at the foot of a mountain range.

Alluviam - Loose material deposited by running water, typically streams. Usually a mixture of clay, silt, sand, and gravel.

Arroyo - A dry desert gully cut by an intermittant stream.

Artesian Spring - A flowing spring, where the water table is higher than the surrounding topography. Also called spring, hotspring, oasis.

Badlands - A region of barren land characterized by roughly eroded ridges, peaks, and mesas with sparse vegetation.

Butte - A tall, steeply-walled, isolated erosion resistant rock with very steep sides, generally higher than wide.

Canyon - A deep gully, caused by extensive persistent erosion relating to that typically of a river.

Desert - Receiving less than 10 inches of precipitation annually.

Dunes - Mounds of loose sand grains shaped up by the wind

Flash Flood - A sudden flood event through a valley, canyon or wash, following a short duration, high intensity rainfall.

Mesa - Broad, flat-topped hill surrounded by cliffs and capped with a resistant rock layer.

Mirage - A phenomenon that creates the optical illusion of water, often with inverted reflections, resulting from the distortion of light by air rising from the ground.

Playa - A very flat, dry lake bed of hard, mud-cracked clay.

Salt Lake or Sink - A shallow body of salt water, where, in the cycle of water flowing in and then evaporating, salty minerals are left behind, causing the lake to become increasingly salty. Also see PAN

Semiarid - Receiving between 10 and 20 inches of precipitation annually


Anaerobic - Without oxygen, as in wetlands soils that are starved of oxygen.

Contaminant - Harmful substance deposited in the air or water or land.

Detritus - Dead and dying plants; can also be bits of animal remains; forms base of nutrient web in wetlands.

Habitat - Food, water, shelter, and space that an animal requires.

Hydrology - (as in wetlands) Amount and period of time that water is present.

Hydric soils - Soils low or absent in oxygen due to their saturation in water.

Hydrophytic vegetation - Plants adapted to wet soil.

Load - Amount of contaminant/pollutant/ sediment being carried by a stream, river, or other waterway.

Pollutant - See "contaminant."

*Runoff - Water that drains or flows off the surface of the land.

Sediment - Silt washed from the land and into the water. Soil, mineral Contains few decomposing plants; usually comprised of materials such as clay, sand, or silt. Soil, organic Contains large amount of decomposing plants.

*Water cycle - The continuous circulation of water in systems throughout the planet, involving condensation, precipitation, runoff, evaporation, and transpiration.

Wetland - As defined by the U.S. Army Corps of Engineers: An area inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances does support, a prevalence of vegetation typically adapted for life in saturated soil conditions.

*Indicates definitions adapted from Project WILD or Project WILD Aquatic Education Activity Guide, 1992.

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