Glossary

This is a list of forestry-related terms and definitions.

Glossary A - L

Access Road - A temporary or permanent access route.
Acidic soil - A soil with a pH below 6.6 as determined by a soil test.
Active crown fire - A fire in which a solid flame develops in the crowns of trees, but the surface and crown phases advance as a linked unit dependent on each other.
Acre - An area of land measuring 43,560 square feet. A square 1-acre plot measures 209 feet by 209 feet; a circular acre has a radius of 117.75 feet.
Aeration - The exchange of air in the soil. Compaction reduces and cultivation improves soil aeration. Determined by a soil test.
Aerial detection - A system for or the act of discovering, locating and reporting fires by monitoring with aircraft.
Aerial fuels - Standing and supported live and dead combustibles not in direct contact with the ground and consisting mainly of foliage, twigs, branches, stems, cones, bark and vines.
Aerial observer - A person specifically assigned to discover, locate and report wildland fires from an aircraft and to observe and describe conditions at the fire scene.
Aerial reconnaissance - Use of aircraft for observing fire behavior, property threatened, suppression activity and other critical factors to facilitate command decisions on tactics needed for fire suppression.
Aesthetics - (1) Sensitivity to or appreciation of the forest's beauty through recognition of its unique and varied components. (2) Beauty through an orderly appearance.
Air attack - The direct use of aircraft in the suppression of wildfires.
Air tanker - Fixed-wing aircraft certified by the FAA as being capable of transport and delivery of fire retardant solutions.
Alidade - A sighting apparatus used by lookouts to determine the horizontal bearing and sometimes the vertical angle of a fire.
Alkaline soil - A soil with a pH above 7.3 as determined by a soil test.
Annual ring - Shows the growth layers of each year of wood production throughout the tree's life. Can be seen on the cross-section of a branch or stem.
Arson fire - Fire willfully ignited by anyone to burn or spread to vegetation or property not owned or controlled by the person and without consent of the owner or his/her agent.
Aspect - Direction toward which a slope is facing.
Attack a fire - Limit the spread of fire by any appropriate means.

Backfill - Soil used to fill in the excavated area around the newly planted tree or shrub.
Backfire - A fire set along the inner edge of a fire line to consume the fuel in the path of a wildfire and/or change the direction of force of the fire's convection column.
Backfire torch - A flame-generating device (e.g., a fount containing diesel oil or kerosene and wick or a backpack pump serving a flame-jet).
Backfiring - A tactic associated with indirect attack; intentionally setting fire to fuels inside the control line to slow, knock down or contain a rapidly spreading fire. Backfiring provides a wide defense perimeter and may be further utilized to change the force of the convection column. Backfiring makes possible a strategy of locating control lines at places where the lines can be fought on the firefighter's terms.
Backing fire - Fire spreading or ignited to spread into (against) the wind or downslope. A fire spreading on level ground in the absence of wind is a backing fire.
Balled and burlapped (B&B) - Shrubs and trees dug from fields with a ball of dirt around the roots; the ball is wrapped in burlap and set in a wire basket to hold it together. Usually dug from late fall to early spring.
Bare root (BR) - Trees and shrubs dug from the field without soil around the roots. Plants are dug while they are dormant and stored in very humid, cold storage lockers until spring.
Barrier - Obstructions to pedestrian, horse and/or vehicular traffic, intended to restrict such traffic to a specific location.
Basal area - The area of the cross-section of a tree stem near its base, generally at breast height, inclusive of bark. Expressed in square feet per acre.
Best management practices (BMPs) - A method or combination of methods that is an effective and practical way (technologically and economically) to prevent or reduce pollution.
Blackline - Preburning of fuels adjacent to control line before igniting a prescribed burn. Blacklining is usually done in heavy fuels adjacent to a control line during periods of low fire danger to reduce heat on holding crews and lessen changes for spotting across control line. In fire suppression, a blackline denotes a condition where there is an unburned material between the fire line and the fire edge.
Blowup - Sudden increase in fire line intensity sufficient to preclude direct control or to upset existing suppression plans. Often accompanied by violent convection and may have other characteristics of a firestorm.
Branch bark ridge - The raised area of bark in a strong branch crotch that marks where the branch wood and the trunk wood meet.
Branch collar - Trunk tissue that forms around the base of a branch between the main stem and the branch or a branch and a lateral (side branch). Swollen area between trunk and branch.
Breakover - A fire edge that crosses a control line or natural barrier intended to confine the fire.
Broad base dip - A surface drainage structure built into the roadway to remove storm water from an access road.
Brush fire - A fire burning in vegetation that is predominantly shrubs, brush and scrub growth.
Burn out - Setting fire inside a control line to consume fuel between the edge of the fire and the control line.
Burning ban - A declared ban on open air burning within a specified area, usually due to sustained high fire danger.

Caliper - Diameter of a young tree measured at 6" (for trees up to and including 4" caliper) or 12" (for trees over 4" caliper) above the groundline.
Callus - Tissue formed by the cambium layer of tree that covers around a wound.
Canopy - Upper part of a tree. It includes branches and leaves.
Cambium - The layer of cells between the inner bark and wood tree. This is where growth takes place. The cambium forms sapwood (xylem) to the inside and bark (phloem) to the outside.
Cat line - A fire line constructed with a bulldozer.
Certified arborist - Professional arborists tested by the International Society of Arboriculture (ISA). A certified arborist must possess the technical competence to manage trees in the residential, commercial and private landscape. They must also earn the continuing education units (C.E.U) required by ISA.
Channel - A natural water-carrying trough cut vertically into low areas, caused by concentrated flowing water eroding the land. Also, a ditch or canal excavated for the flow of water.
Clear-cutting - A silviculture system where all trees in a specified area are harvested in one operation. Clear-cut areas in Kentucky begin to regenerate quickly.
Climate - The prevalent or characteristic meteorological conditions of any place or region and their extremes.
Closure - Commonly refers to a complete covering of callus over a pruning cut or other tree wound.
Cold trailing - Usually a part of the "mop-up" process of making sure a fire is completely out. Firefighters feel the fire area with gloved hands to find any remaining hot spots and then put them out.
Community - A collection of living organisms functioning together in an organized system through which energy, nutrients and water cycle.
Coniferous - Woody plant that produces seeds in cones. Most coniferous trees are termed "evergreen" since they keep their needles for two or more years before they die and drop off the plant.
Conservation - The protection, improvement and use of natural resources according to principles that will ensure their highest economic and social service.
Contain a fire - An effort to prevent further spread of fire.
Containerized tree - A tree or shrub placed in a container by the nursery. A good quality containerized plant grows in the container long enough that the roots and soil ball hold their shape and stay together when removed from the container.
Container-grown - A plant that grew in a container from the time it was small.
Contour - An imaginary line on the surface of the earth or a line on a map connecting points of the same elevation.
Controlled fire - A term used when a fire is completely out.
Control line - Also called a fire line, includes line constructed by firefighters using shovels, rakes, pulaskis and chainsaws to clear a line of vegetation so that the fire will not have anything to burn when it reaches this point. Natural barriers to fire include rock outcroppings, roads, streams and other bodies of water.
Cover type - The designation of a vegetation complex described by dominant species, age and form.
Crotch - The angle formed at the place where a branch is attached to another branch or to the trunk of a woody plant.
Crown - Technically, the point where the tree trunk meets the roots of a tree. Commonly, it refers to the leaves and branches in the uppermost part of the tree.
Crown fire - A fire that advances from the top of trees or shrubs more or less independent of a surface fire. Crown fires are sometimes classed as "running."
Crown out - Where a fire has a "ladder" of fuels to climb (grass to shrubs to small trees to large trees). It may rise from ground level to canopy level and begin to advance from treetop to treetop.
Cultivar - A cultivated variety that has noticeable differences from the species, but these differences can only be retained through propagation by vegetative means such as cuttings or grafting.
Culvert - A metal, plastic or concrete pipe that surface water can flow through under roads and trails.
Cut - The wood exposed on a tree when a branch is removed.

Debris fire - A fire spreading from any fire originally set for the purpose of clearing land, meadow burning or waste disposal.
Decay - Deterioration of plant tissue, including wood, by biological organisms. Wood decay can reduce the strength of a tree or branch.
Deciduous - A woody plant that has leaves for one growing season, sheds those leaves, then grows new ones.
Defoliation - The loss of leaves or foliage on a plant or tree.
Den tree - A living or dead tree with a cavity suitable for animals to use for shelter, escape or as a nursery.
Direct attack - Putting out a fire by applying water, smothering or chemically quenching the fire or by physically separating burning from unburned fuel.
Dispersion, soil - Breaking down soil aggregate into individual particles, resulting in a single-grain structure. More easily dispersed soil is more erodible.
Diversion - A drainage depression or ditch built across a slope to intercept surface or subsurface runoff or to divert surface water from the slope.
Dormant - A period of inactivity for a tree. Trees are dormant from the time the leaves fall until new ones appear.
Dozer line - Fireline constructed by a bulldozer.
Drift smoke - Smoke that has drifted from its point of origin and has lost its original billowing form. Drift smoke sometimes gives the false impression of a fire in the general area to which it has drifted.
Drip torch - A small fuel tank with a handle, nozzle and igniter used to drip a burning mixture of oil and gasoline to ignite a prescribed fire or a backfire.
Drought index - A number representing the moisture level in duff or upper soil layers. It measures the evaporation, transpiration and precipitation that has occurred.
Dry lighting - A lightning storm with only a trace of precipitation.
Duff - The partially decomposed organic material of the forest floor beneath the litter of freshly fallen twigs, needles and leaves.

Ecosystem - An interacting system of living organisms, soil and climatic factors. Forests, wetlands, watersheds, ponds, prairies and communities are ecosystems.
Entrapment - A situation where personnel are unexpectedly caught in a fire behavior-related, life-threatening position where planned escape routes or safety zones are absent. An entrapment may or may not include deployment of a fire shelter for its intended purpose. These situations may or may not result in injury.
Environment - The complex surroundings of an item or area of interest, such as air, water, natural resources and their physical conditions (temperature and humidity).
Ephemeral stream - See "Stream."
Erodibility - The susceptibility of soil to being transported away by wind, water and gravity.
Erosion - The wearing away of the land surface by water, wind, ice or other geologic agents and by such processes as gravitational creep.
Escape route - The way out to safety, either to an already burned area, previously constructed safety area, a meadow that won't burn, natural rocky area or other areas that are large enough for firefighters to take refuge without being burned. When escape routes deviate from a defined physical path, they should be clearly marked (flagged).
Evergreen - A plant that retains living leaves or needles year-round or longer or until new ones appear.

False alarm - A report of smoke or fire requiring no suppression; for example, brush burning under control, mill smoke, or false smoke.
Felling - The process of severing trees from stumps.
Fertility, soil - The quality that enables a soil to provide plant nutrients, in adequate amounts and in proper balance, for growth of specified plants when light, moisture, temperature, tilth and other growth factors are favorable.
Fertilizers - Any substance or combination of substances used as a source of plant food or soil amendment.
Fill slope - The surface area formed where soil is deposited to build a road or trail.
Fine fuel moisture - The moisture content of fast-drying fuels such as grass, leaves, ferns, tree moss, fallen pine needles and small twigs.
Fire behavior - The manner in which a fire reacts to the influences of fuel, weather and topography.
Firebreaks - Naturally occurring or man-made barriers to prevent the spread of fire.
Fire danger index - A relative number indicating the severity of forest fire danger as determined from burning conditions and other variable factors of fire danger.
Fire occurrence - The average number of fires in a specified area during a specified time period.
Fire prevention - All activities concerned with minimizing the incidence of wildfires.
Fire retardant - A substance that uses chemical or physical action to reduce flammability of fuels and slow the rate of combustion.
Fire shelter - An aluminized tent offering protection by means of reflecting radiant heat and providing a volume of breathable air in a fire entrapment situation. Shelters may be used for protection against falling embers or smoke inhalation in nonlife threatening situations or as radiant heat shields during escape.
Fire weather - Weather conditions that influence fire ignition, behavior and suppression.
Flame height - The average height of flames at the leading edge of the fire front.
Flanking - Attacking a fire by working around its edges. Flanking fire lines move toward the fire front, where they are linked to stop the fire.
Flareup - Any sudden acceleration in rate of spread or intensification of the fire. Unlike a blowup, a flareup is relatively short in duration and does not radically change existing control plans.
Flash/fine fuels - Grass, leaves, pine needles and other fuels that ignite easily and burn rapidly when dry.
Flowing water - Surface water movement due to the influence of gravity or tides.
FMO - A fire management officer has primary responsibility for directing how fires are managed in his area.
Foam - A chemical fire extinguishing mixture. It adheres to fuels, cooling and moistening them. It also excludes oxygen from them, eliminating one component fire needs to burn.
Ford - A submerged stream crossing that will bear intended traffic.
Forest floor - A layer of accumulated dead organic material, consisting of partially or fully decomposed leaves, needles or twigs, at the surface of forest soil.
Forestland - All land that is capable of supporting a merchantable stand of timber and whose current use is not incompatible with timber growing.
Forest management practice - Any activity conducted on or directly pertaining to forestland and relating to growing, harvesting or processing timber.
Fuel - Combustible plant material, both living and dead, that is capable of burning in a wildland fire situation.
Fuel break - A wide strip or block of land on which the native vegetation has been permanently modified so that fires burning into it can be easier to extinguish. In areas where grass is widespread, landowners or managers may install fuel breaks of some other, less fire-prone vegetation to reduce fire spread.
Furrowing - Site preparation work done by V-blade or fire plow, pushing aside debris and vegetation and/or cutting a trench into the mineral soil to enhance tree planting.

Girdling root - A root that has grown so that it encircles and constricts other roots or the main stem of a tree. May result in the decline or death of the tree.
Grade - Slope of a road or trail, the change in elevation compared to horizontal distance traveled. Usually expressed as a percentage.
Graft union - The place where the bud of one tree is grafted to the trunk of another tree, called the root stock. Usually located a few inches above the roots. Young trees often have a crook at the graft union, but it disappears as the tree gets older.
Ground cover - Any vegetative growth or natural or man-made material that renders the soil surface stable against accelerated erosion.
Ground Fire - A fire that consumes organic material on or beneath the surface litter of the forest floor.
Groundwater - Phreatic water or subsurface water in the zone of saturation.

Hand crew - A group of eight to 25 firefighters organized and trained to clear brush, cut trees and make fire lines with hand tools.
Hardiness - The ability of a plant to withstand cold temperatures without death of woody tissue and/or flower buds.
Hardiness zones - Areas divided by the temperature extremes experienced during a typical year. Most of Kentucky is in the cold hardiness zone 6 (average annual minimum temperature: minus 5 F to 5 F).
Hardpan - A hardened or cemented soil layer. Hardpans occur naturally or are created artificially.
Harvesting - Felling, loading and transporting forest products, roundwood or logs.
Head of fire - The most rapidly spreading portion of a fire's perimeter.
Heading - Cutting a currently growing or one-year-old shoot back to a bud, or cutting an older branch or stem back to a stub or lateral branch not large enough to become the leader. Heading should rarely be used on mature trees.
Heartwood - The inactive, nonconducting tissue of the center of a tree trunk or branch.
Heavy fuels - Fuels of large diameter such as snags, logs and large limbwood that ignite and are consumed more slowly than flash fuels. Also called course fuels.
Helibase - The area where helicopters are parked, fueled, maintained and loaded.
Helispot - A temporary landing spot for helicopters. Often these must be constructed by firefighters who remove all tall vegetation that might prevent the helicopter from landing.
Helitack crew - They are the firefighters that work from the helicopter. Though they assist in actual firefighting, their primary responsibilities include making sure firefighters and equipment are safely loaded and assisting the pilot in takeoff and landing.
Herbicide - Any substance or mixture of substances intended to prevent the growth of or destroy terrestrial or aquatic weeds (wood or nonwoody undesirable vegetation).
Holdover fire - A fire that remains dormant for a day or two before flaring up. Dry lightning storms often cause holdover fires.
Hotshot Crew - An extensively trained firefighting crew. Hotshot crews remain together for an entire season and often for years at a time. They are transported to fires across the country as needed.
Humidity - General term referring to the moisture content of the atmosphere.

Incendiary fire (arson) - Wildfire willfully ignited by anyone to burn or spread to vegetation or property not owned or controlled by that person and without consent of the owner or his/her agent.
Incident command post (ICP) - For very large fires, a command post is set up to manage all fire operations.
Incident command system (ICS) - This system was designed to assist firefighters in doing their job. It provides direction for increasing the size and types of teams fighting fires to respond to the size and type of fire being suppressed.
Incident commander (IC) - When a team is called to assist with fire suppression on a large fire, it is led by an IC.
Indirect attack - A method of suppressing fires by building lines along natural firebreaks and using topography while staying some distance from the head of the fire.
Initial Attack - The first effort to contain a fire. If initial attack is not successful in stopping the fire, additional teams are called to assist.
Insecticide - Any substance or mixture of substances intended to prevent, destroy, repel or control any insect or other arthropods.

Jump spot - A landing spot for smoke jumpers.

Keetch-Byram Drought Index - Commonly used drought index developed specifically for fire management applications, with a numerical range from 0 (no moisture deficiency) to 800 (maximum drought).

Ladder fuels - Fuels that allow a fire to travel from the surface into the crowns of trees or shrubs.
Landing - Place where logs are gathered in or near the forest for further transport. Sometimes called a "deck."
Lateral - A branch or twig growing from a parent branch or from the tree trunk.
Lead plane - An aircraft that directs air tankers to the fire. It also assists in judging air currents and in dropping retardant on the correct spot on the fire.
Leader - A dominant upright stem, usually the main trunk.
Lightning fire - Wildfire caused directly or indirectly by lightning.
Light unit - A fire truck equipped with a generator, flood lights and electrical tools for use in firefighting and rescue work.
Lightning activity level (LAL) - A number on a scale of one to six that describes the relative frequency and character of cloud-to-ground lightning in an area. A rating of six is assigned when little or no rain is expected to reach the ground. "Red Flag" warnings may be issued when level six conditions exist.
Line clearance - Pruning and removing trees for safe, uninterrupted electrical service.
Line holding - Ensuring that the established fire line has completely stopped fire progress.
Live fuel moisture - A description by percent of the moisture in brush and trees.
Logging deck - Place where logs are gathered in or near the forest for further transport. Sometimes called a "landing."
Logging debris - Unwanted, unutilized and unmarketable accumulation of woody material in the forest (large limbs, tops, cull logs and stumps) that remain after harvesting.
Lookout - (1) A person assigned to detect and report fires from a vantage point. (2) A location from which fires can be detected and reported. (3) A fire crew member assigned to observe the fire and warn crews when there is danger of becoming trapped.

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