Adiabatic. Of or denoting change in volume or pressure, with no heat gain or loss with the surrounding air.

Allogenic succession. Change in plant communities produced by alterations of the environment or community members by factors outside of the system (such as sediment filling a pond, disturbance, etc.)

Aspect. The direction a slope faces.

Autogenic succession. Change in plant communities produced by alterations of the environment caused by the resident organisms.

Avoider. A life-history strategy of plants that have little adaptation to fire.

Basal area. The area of a given unit of land, such as a ha or ac, that is occupied by the cross-sectional area of tree boles measured at breast height. Usually expressed as square feet per ac or square meters per ha.

Biodiversity. The variety of species and habitats within an ecosystem and the genetic variability within a species or population.

Biome. A set of plant communities that have similar life-forms, generally expressed at a continental scale (e.g., the coniferous biome).

Broadcast burning. Burning forest fuels as they are; no piling or windrowing.

Canopy. The part of any stand of trees represented by the tree crowns; canopies may occur in layers.

Clearcut. A unit of forest where all the trees are removed. It is intended to produce a new even-aged forest stand.

Climax species or communities. Represents the stage of a sere dominated by shade tollerant species that are able to perpetuate under the shade of the canopy. Historically considered the final stage of a successional sequence in the absence of disturbance.

Coarse filter. Conservation of land areas and representatives habitats, and the processes associated with them, with the intent that the needs of all associated species and communities will be met (see fine filter).

Coarse woody debris. Large dead wood in the forest, that may be either snags or down logs usually greater than 10 cm or 4 inches in diameter.

Conduction. Transfer of energy from one molecule to another, such as through the soil or through bark.

Convection. Transfer of energy by movement of liquid or gas, such as the movement of hot air into tree canopies.

Crown fire. A fire that burns into the crowns of the vegetation, often dependent on intense understory fire.

Disturbance. Any event that alters the structure, composition, or function of terrestrial or aquatic habitats.

Ecosystem. All of the organisms in any system of interest, and the environments that encompass their interactions.

Endurer. A life-history strategy of plants to fire where the plant resprouts or endures the effects of fire.

Epidemic or outbreak. Pertaining to pathogen or insect populations that expand to an extreme level, often disturbing processes and interactions within forested stands and landscapes to the point of causing economic or habitat loss.

Evader. A life-history strategy of plants to fire where long-lived propagules are stored in the soil or canopy and evade elimination for the site after fire.

Fine filter. Specific management for a single species or group of species rather than community or ecosystem-level strategies (see coarse filter).

Fire danger rating. The rating of relative fire danger for a given period of time, usually based on daily and cumulative indexes to fire weather.

Fire frequency. The return interval of fire.

Fire hazard. The amount, conditions, and structure of fuels that will burn if a fire enters an area.

Fire predictability. A measure of variation in fire frequency.

Fire regime. The combination of fire frequency, predictability, intensity, seasonality, and extent characteristic of fire in an ecosystem.

Fire return interval. The average time between fires in a given area (see fire frequency).

Fire risk. The chance of a fire starting.

Fire severity. The effect of fire on plant communities. For trees, usually measured as a proportion of the basal area removed.

Fireline intensity. The rate of heat release along a unit length of fireline, measured in kW m-1 or BTU sec-1 ft-1.

Flagging. A tree crown that looks similar to a flag due to persistent mortality of needles on one side of the tree caused by abrasion or desiccation.

Foehn wind. A dry wind associated with windflow down the lee side of a plateau or mountain range and with adiabatic warming.

Fuel load. the dry weight of combustible materials per unit area.

Fuel moisture. The percentage of water in a fuel particle, measured on a dry weight basis.

Fuelbreak. A zone of reduced fuel, generally linear, designed to reduce fire behavior as fires enter the treated area.

Habitat type. The land area capable of supporting a single plant association.

Indicator species. A species that by its presence indicates a particular set of environmental conditions (wet, dry, cold, warm, etc.).

Initial floristics. A process of succession where seeds or plants of later successional stages are present from the outset but are subordinate to other species (see relay floristics).

Invader. A life history strategy of plants to fire where the plant, through highly dispersive propagules, invades the site after fire.

Managed wildland fire (pnf). The new term for a naturally-ignited fire that occurs within an approved management zone and meets prescription criteria (see prescribed natural fire).

Natural fire rotation. A fire return interval calculated as the quotient of a time period and the proportion of a study area burned in that time period.

Overstory. Those plants that are dominant on a site, usually a tall tree layer.

Plant association. The distinctive combination of trees, shrubs, and herbs occurring in a theoretical terminal or climax community, identified by indicator species.

Plant community. An assemblage of plant species that occur widely enough across the landscape to be recognized as a unit. This assemblage can be a pioneer group of species, a late successional group, or a combination of both.

Plant series. Aggregations of plant associations having the same overstory dominant.

Prescribed fire. A fire ignited under predetermined conditions of fuels, weather, and topography to meet specific management objectives.

Prescribed natural fire.  A fire ignited by natural processes (usually lightning) and allowed to burn within specified parameters of fuels, weather, and topography to achieve specified objectives (now called managed wildland fire).

Pruning. The removal of branches from a tree stem, usually from the bottom up, in order to improve wood quality or reduce the chance of fire moving into the tree crown.

Radiation. Transfer of energy through electromagnetic wave motion, such as being warmed by a campfire.

Rate of spread. The movement of fire across a landscape, often measured as m sec-1 or ft sec-1.

Relay floristics. A process of succession where one set of species prepares the site and is replaced by a new set of species (see initial floristics).

Resister. A life-history strategy of plants in which the plants, through adaptation like thick bark, survive low intensity fire relatively unscathed.

Restoration. The maintenance or recovery of original elements, structures, processes, and interactions of an ecosystem.

Riparian. Pertaining to land that is next to water, where plant communities dependent on a permanent water source are found.

Seral. A plant species or community which will be replaced by another plant community if protected from disturbance.

Sere. The product of succession: the entire sequence of plant communities that successively occupy and replace one another in a particular environment over time.

Serotinous cones. Conifer cones whose scales are sealed with a thin coat of resin. Intense heat melts the resin and allows the cone to open.

Slope. The amount of pitch on a hill or mountain, usually measured as a percentage: the vertical gain divided by the unit horizontal length times 100. A 100% slope is equal to a 45o slope.

Snag. A standing dead tree.

Spotting. The convective movement of firebrands carried over the main perimeter of a fire.

Stability. The degree to which an ecosystem can resist change or rebound from change.

Stand. A vegetation group occupying a specific area and sufficiently uniform in composition, size, arrangement, structure, and condition to be distinguished from adjacent vegetation units.

Stream buffer. Strips of trees either left uncut, or selectively cut, in the vicinity of streams.

Succession. The process of change in plant communities.

Surface fire. A fire that moves above the ground in fuels that have contact with the surface, without moving into the shrub or tree layer. Usually a flame length < 1 m.

Thinning. The planned removal of trees during the development of a forest, used to regulate characteristics of tree growth through adjustments in tree spacing and density without creating a new age class.

Timelag class. A method of categorizing fuels by the rate at which they are capable of moisture gain or loss, indexed by size class of fuel.

Underburn. A low-intensity surface fire burning under a forest canopy, with a flame length < 1 m.

Understory fire. A fire that burns surface fuels and torches into the understory, often with flame lengths of 1-3 m.

Understory. Those plants beneath the overstory.

Values. The net change in resource condition when a fire occurs.

Vegetation zone. Aland area with a single overstory dominant as the primary climax dominant. Occasionally zones are named after major seral species. Other climax types may exist in the zone.

Wildfire. An unwanted wildland fire.

Wildland fire. Any non-structure fire, other than a prescribed fire, that occurs in a wildland.

Windsnap. Trees that have broken boles due to wind.

Windthrow. Trees blown over by the wind.