USDA Forest Service

Bitterroot Ecosystem Management Research Project

Local Weather
Bitterroot NF
Evaluate Our Service

Mailing Address:

Forestry Sciences Lab
800 E. Beckwith Ave
Missoula, Montana 59801

(406) 542-4150

United States Department of Agriculture Forest Service.

BEMRP logo


Clip art: Colonial man reading a book

"What Do You Mean By That?

Ever wonder about the meaning of Ecosystem Management (EM) and all the unfamiliar terms associated with it? If so, this is the page for you. We provide you with a dynamic list of EM terms and intend to add terms to it as appropriate and upon request. You can help us with our glossary construction by letting us know what terms you'd like defined. Please submit your suggestions to Sherry Ritter (see the Staff page for contact information). (Disclaimer - Definitional terms sometimes vary slightly, depending on who is using them and for what purpose. Terms defined here are intended for the general interest reader and will usually suffice for most EM uses.)

ADAPTIVE MANAGEMENT A type of natural resource management that implies making decisions as part of an on-going process.  Monitoring the results of actions will provide a flow of information that may indicate the need to change a course of action.  Scientific findings and the needs of society may also indicate the need to adapt resource management to new information.
ALLUVIAL FAN A fan-shaped sediment deposit at the bottom of a drainage.
AQUATIC ZONE The aquatic zone of a natural watercourse (as a river) or sometimes of a lake or a tidewater that remains under water the entire year.  Plants in this zone have special adaptations that enable them to survive being partially or totally under water.
BEMRP Bitterroot Ecosystem Management Research Project
BIOCONTROL The use of living organisms, such as predators, parasites, and pathogens, to control weeds, pest insects, or diseases.
BIOMASS The amount of all living or dead plant material in an area. In terms of forest biomass utilization, it is often used to refer to the woody material (resulting from forest treatments) that is unsuitable for traditional forest products such as pulp wood or lumber.
BIOMASS BOILER Boiler fired by biomass used to produce thermal heat and/or electricity.
BIOTA The plant and animal life of a particular region.
BREEDING PRODUCTIVITY The number of young successfully produced per pair of birds in a season.
BROADCAST BURN Using fire over an entire unit to reduce natural fuels or logging residue or to restore ecosystem function.
BROAD-LEAFED COVER Cover composed predominantly of forbs, which are nongrass, nonwoody plants.
BURNED AREA EMERGENCY REHABILITATION (BAER) The treatment of an ecosystem following disturbance to minimize subsequent effects.
BURNING CONDITIONS The state of the combined factors of the environment that affect fire behavior in a specified fuel type.
CANOPY The part of any stand of trees represented by the tree crowns.  It usually refers to the uppermost layer of foliage, but it can be used to describe lower layers in a multi-storied forest.
CANOPY CLOSURE A synonym for "crown cover." 
CANOPY COVER The proportion of ground or water covered by a vertical projection of the outermost perimeter of the natural spread of foliage or plants, including small openings within the canopy.  Note that total canopy coverage may exceed 100 percent because of layering of different vegetative strata such as grass, shrubs, and trees.
CARBON BALANCE The concentration of carbon released into the atmosphere compared to the amounts stored in the oceans, soil, and vegetation.
CARBON OR GREENHOUSE GAS OFFSETS A greenhouse gas offset is generated by the reduction, avoidance, or sequestration of greenhouse gas emissions from a specific project. Offsets counteract or offset greenhouse gases that would have been emitted into the atmosphere; they are a compensating equivalent for reductions made at a specific source of emissions.
CARBON SEQUESTRATION The provision of long-term storage of carbon in the terrestrial biosphere, underground, or the oceans so that the buildup of carbon dioxide (the principal greenhouse gas) concentration in the atmosphere will reduce or slow.
CATEGORICAL EXCLUSION (CE) A category of actions that do not individually or cumulatively have a significant effect on the human environment and that have been found to have no such effect in procedures adopted by a Federal agency in implementation of NEPA regulations and for which, therefore, neither an environmental assessment nor an environmental impact statement is required.
COARSE FILTER MANAGEMENT Land management that addresses the needs of all associated species, communities, environments, and ecological processes in a land area.
COARSE WOODY DEBRIS Large-diameter, dead, woody material. Usually logs (generally greater than about 3 inches diameter) or snags.
COLLABORATION A coalition of diverse people with diverse values and expectations working together at the community level to solve problems.
COST PLUS NET VALUE CHANGE (C + NVC) Cost includes both the fixed annual cost for the protection organization (annual fire program budget) and the variable suppression (emergency fire fighting) costs; NVC is the difference in value of planned resource outputs (such as timber harvest) on an area before and after a fire.
COVER An area occupied by vegetation or foliage.
CRITICAL HABITAT A specific geographic area(s) that is essential for the conservation of a threatened or endangered species and that may require special management and protection.
CROWN The part of a tree or woody plant bearing live branches and foliage.
CROWN COVER The ground area covered by the crowns of trees or woody vegetation. It is delimited by the vertical projection of crown perimeters and commonly expressed as a percent of total ground area. Crown cover measures the extent to which the crowns of trees are nearing general contact with each other.
CROWN FIRE A fire burning into the crowns of vegetation, generally associated with an intense understory fire.
CUT-TO-LENGTH YARDING A method of harvesting trees by removing branches and tops and cutting logs to specific lengths before moving them to the "landing" prior to transport.
DISTURBANCE PROCESS MODEL A computer model-for example, SIMPPLLE-of processes, typically at landscape scales, that includes 1) natural disturbances such as fire, insects, and diseases that affect distribution of vegetation and 2) human-caused disturbances such as vegetation treatment and cattle grazing.
DUFF The layer of decomposing organic materials lying below the litter layer of freshly fallen twigs, needles, and leaves and immediately above the mineral soil.
ECOLOGICAL DIVERSITY The variety, richness, and viability of life forms (the BIOTA) and the processes which occur in a specific location.
ECOSYSTEM An arrangement of living and non-living things and the forces that move among them.  Living things include plants and animals.  Non-living parts of ecosystems may be rocks and minerals.  Weather and wildfire are two of the forces that act within ecosystems.
ECOSYSTEM-BASED PLANNING Planning for ecosystem management.
ECOSYSTEM COMPOSITION The numbers and kinds of plants and animals in an area.
ECOSYSTEM FUNCTION All the processes within an ecosystem through which the elements interact, such as succession, the food chain, fire, weather, and the hydrologic cycle.
ECOSYSTEM MANAGEMENT The careful, skillful use of ecological, economic, social, and managerial principles  in managing ecosystems to produce, restore, or sustain ecosystem integrity and desired conditions, uses, products, and services over the long term.
ECOSYSTEM PROCESS Something going on in the ecosystem.  A natural phenomenon in an ecosystem that leads toward a particular result.
ECOSYSTEM STRUCTURE The sizes, shapes, and/or ages of the plants and animals in an area.
ELEMENT (OF ECOSYSTEMS) An identifiable component, process, or condition of an ecosystem.
ENVIRONMENTAL ASSESSMENT (EA) EAs were authorized by the National Environmental Policy Act (NEPA) of 1969. They are concise, analytical documents prepared with public participation that determine if an Environmental Impact Statement (EIS) is needed for a particular project or action. If an EA determines an EIS is not needed, the EA becomes the document allowing agency compliance with NEPA requirements.
ENVIRONMENTAL IMPACT STATEMENT (EIS) EISs were authorized by the National Environmental Policy Act (NEPA) of 1969. Prepared with public participation, they assist decision makers by providing information, analysis and an array of action alternatives, allowing managers to see the probable effects of decisions on the environment. Generally, EISs are written for large-scale actions or geographical areas.
ESCAPED FIRE A fire that has exceeded or is expected to exceed initial attack capabilities or prescription.
FARSITE MODEL FARSITE is a fire growth simulation model. It uses spatial information on topography and fuels along with weather and wind files to simulate the spread of wildfires and wildland fire use across the landscape.
FINE (LIGHT) FUELS Fast-drying fuels, generally with a comparatively high surface area-to-volume ratio, which are less than 1/4-inch in diameter and have a timelag of one hour or less. These fuels readily ignite and are rapidly consumed by fire when dry.
FIRE BEHAVIOR The manner in which a fire reacts to the influences of fuel, weather, and topography.
FIRE BEHAVIOR MODEL A model that predicts the rate and direction of fire spread and fire intensity. FLAMMAP, MTT, and TOM are examples of fire behavior models..
FIRE INTENSITY A general term relating to the heat energy released by a fire.
FIRE MANAGEMENT ANALYSIS ZONE (FMAZ) Basic geographic area on which the National Fire Management Analysis is performed within a planning unit. A FMAZ is represented by a single set of fire behavior characteristics based on fuels, topography, and local weather.
FIRE PRESCRIPTION Measurable criteria that define conditions under which a prescribed fire may be ignited, guide selection of appropriate management responses, and indicate other required actions. Prescription criteria may include safety, economic, public health, environmental, geographic, administrative, social, or legal considerations.
FIRE REGIME The combination of fire frequency, extent, predictability, intensity, and seasonality in an ecosystem.
FIRE SEVERITY Fire severity denotes the scale at which vegetation and a site are altered or disrupted by fire, from low to high severity. It is a combination of the degree of fire effects on vegetation and on soil properties.
FIRE USE The combination of wildland fire use and prescribed fire application to meet resource objectives.
FIRE WEATHER Weather conditions that influence fire ignition, behavior, and suppression.
FLAME HEIGHT The average maximum vertical extension of flames at the leading edge of the fire front. Occasional flashes that rise above the general level of flames are not considered. This distance is less than the flame length if flames are tilted due to wind or slope.
FLAME LENGTH The distance between the flame tip and the midpoint of the flame depth at the base of the flame (generally the ground surface); an indicator of fire intensity.
FLASH FUELS Fuels such as grass, leaves, draped pine needles, fern, tree moss, and some kinds of slash that ignite readily and are consumed rapidly when dry. Also called fine fuels.
FLUME A flume is an instream structure used to measure the rate and quantity of streamflow.
FOREST VEGETATION SIMULATOR (FVS) The Forest Vegetation Simulator (FVS) is a family of forest growth simulation models. It is an individual-tree, distance-independent growth and yield model that will simulate growth and yield for most major forest tree species, forest types, and stand conditions.
FUEL Combustible material. Includes vegetation such as grass, leaves, ground litter, plants, shrubs, and trees that feed a fire. (See Surface Fuels).
FUEL LOADING The amount of burnable (living or dead) material on the ground.  It is measured in tons per acre.
FUEL MANAGEMENT The practice of evaluating, planning, and executing the treatment of wildland fuel to control flammability and reduce the resistance to control through mechanical, chemical, biological, or manual means, or by prescribed and wildland fire, in support of land management objectives.
FUEL MODEL Simulated fuel complex (or combination of vegetation types) for which all fuel descriptors required for the solution of a mathematical rate of spread model have been specified.
FUEL MOISTURE (FUEL MOISTURE CONTENT) The quantity of moisture in fuel expressed as a percentage of the weight when thoroughly dried at 212 degrees Fahrenheit.
FUEL REDUCTION Manipulation, including combustion, or removal of fuels to reduce the likelihood of ignition and/or to lessen potential damage and resistance to control.
FUEL TYPE An identifiable association of fuel elements of a distinctive plant species, form, size, arrangement, or other characteristics that will cause a predictable rate of fire spread or difficulty of control under specified weather conditions.
GIS (GEOGRAPHIC INFORMATION SYSTEM) A computer system for capturing, storing, checking, integrating, manipulating, analyzing, and displaying data related to positions on the Earth's surface. Typically, a GIS is used for handling maps of one kind or another. These might be represented as several different layers where each layer holds data about a particular kind of feature. Each feature is linked to a position on the graphical image of a map.
HAZARD REDUCTION Any treatment of a hazard that reduces the threat of ignition and fire intensity or rate of spread.
HEAVY FUELS Fuels of large diameter such as snags, logs, large limb wood, that ignite and are consumed more slowly than flash fuels.
HIDING AREA/COVER Vegetation capable of hiding 90 percent of an adult elk or deer from human's view at a distance of 200 feet or less.
HISTORIC RANGE OF VARIABILITY The variation in spatial, structural, compositional, and temporal characteristics of ecosystem elements as affected by minor climatic fluctuations and disturbances within the current climatic period. This range is measured during a reference period prior to intensive resource use and management. The range of historic variability is used as a baseline for comparison with current conditions to assess the degree of past change.
INCREMENT CORE A quarter- to third-inch diameter column of wood taken from a tree trunk, usually for examining growth rings and sometimes age.
INITIAL ATTACK The actions taken by the first resources to arrive at a wildfire to protect lives and property, and prevent further extension of the fire.
INITIAL ATTACK ASSESSMENT (IAA) Mathematical model within National Fire Management Analysis System (NFMAS) that considers resource values, predicted fire effects, probable fire and weather activity, and fire organization alternatives to yield an efficient fire program. IAA evaluates planned suppression action effectiveness for a given set of fire occurrence and fire behavior inputs and calculates resultant Cost Plus Net Value Change (C + NVC) for each Fire Management Analysis Zone (FMAZ).
LADDER FUELS Fuels such as brush, dead limbs, low-hanging limbs, that allow fire to travel vertically from ground level into taller fuels.
LANDSCAPE A large land area composed of interacting ecosystems that are repeated due to factors such as geology, soils, climate, and human impacts.  Landscapes are often used for coarse grain analysis.
LANDSCAPE PROCESSES Physical and biological systems that work together at a moderately large scale (a "landscape" can encompass most of a major watershed, like the Bitterroot River, or a subset of that major watershed). Landscape processes determine patterns of vegetation and stream networks in a watershed. They include things like fire, insects, and diseases that change vegetation, vegetative succession, and physical variables like climate (affected by slope, aspect, and elevation).
LATENCY TO DETECTION The average time it takes before photographic evidence of wildlife is obtained from remote-sensing cameras.
LETHAL UNDERBURN A fire that, although it consumes only surface and understory fuels, kills the overstory through crown scorch, cambium damage, or both.
LIGHT (FINE) FUELS Fast-drying fuels, generally with a comparatively high surface area-to-volume ratio, that are less than 1/4-inch in diameter and have a timelag of one hour or less. These fuels readily ignite and are rapidly consumed by fire when dry.
LITTER (FOREST LITTER) The freshly fallen or only slightly decomposed plant material on the forest floor.  This layer includes foliage, bark fragments, twigs, flowers, and fruit.
MAGIS COMPUTER MODEL A model that enables managers to plan activities on a landscape. It develops optimal schedules for management actions on that landscape, taking into account the multiple goals and constraints of land management.
MICRO-SITES VERY small areas in the environment that may have special characteristics different from the general landscape, such as more moisture.
MODEL A simplified representation of an aspect of the real world that contains the important features of real "life" for making predictions.
MOST EFFICIENT LEVEL (MEL) The optimum pre-suppression (preparedness) organization for the planning unit (usually the national forest).
NATIONAL ENVIRONMENTAL POLICY ACT (NEPA) NEPA is the basic national law for protection of the environment, passed by Congress in 1969. It sets policy and procedures for environmental protection, and authorizes Environmental Impact Statements and Environmental Assessments to be used as analytical tools to help federal managers make decisions.
NATIONAL FIRE MANAGEMENT ANALYSIS SYSTEM (NFMAS) Formal process that provides consistent methods for estimating the effectiveness of alternative fire programs using an economic efficiency criterion.
NATURAL DISTURBANCES Any event, such as forest fire or insect infestations, that alters the structure, composition, or functions of an ecosystem.
NET VALUE CHANGE (NVC) The present value of a loss in resources or property minus any off-setting benefits resulting from the effects of wildland fire.
OVERSTORY The upper canopy layer; the plants below comprise the understory.
PARTICULATE MATTER A complex mixture of extremely small particles and liquid droplets. Particulate matter may be in the form of fly ash, soot, dust, fumes, etc. Small particulate matter, or PM-10, is less than 10 microns in size and can pass through the throat and nose and enter the lungs.
PARTNERSHIP A voluntary, mutually beneficial and desired relationship entered into by two or more person(s) or group(s) to accomplish mutual objectives.
PEER REVIEW A publication is considered peer reviewed if it has been reviewed independently and approved by other experts in the author's field before it is published.
PRESCRIBED BURNING Controlled application of fire to wildland fuels in either their natural or modified state, under specified environmental conditions, that allows the fire to be confined to a predetermined area, and produces the fire behavior and fire characteristics required to attain planned fire treatment and resource management objectives.
PRESCRIBED FIRE Any fire ignited by management actions to meet specific objectives. (Previously defined as a fire ignited under predetermined, known conditions of fuel, weather, and topography to achieve specific management objectives.)
PRESCRIBED NATURAL FIRE A fire ignited by natural processes (usually lightning) that is allowed to burn within specified, predetermined parameters of fuels, weather, and topography to achieve specific objectives. (Note:  This term has been replaced by "wildland fire use.")
PREVENTION Activities directed at reducing the incidence of fires, including public education, law enforcement, personal contact, and reduction of fuel hazards (fuels management).
PROTOCOLS Recommended ways to gather and store data, analyze data, interpret and sue results, and set consistent definitions and terminology.
RESOURCE ADVISORY COMMITTEE Resource Advisory Committees were formed under the Secure Rural Schools and Community Self-Determination Act of 2000 (Public Law 106-393) to improve collaborative relationships and provide advice and recommendations to the land management agencies.
RHIZOME An underground stem that produces leaves on the upper side and roots on the lower side.
RIPARIAN ZONE Relating to or living or located on the bank of a natural watercourse (as a river) or sometimes of a lake or a tidewater.
SALVAGE LOGGING The harvesting of trees that are dead, dying, or deteriorating (e.g., because they are over mature or materially damaged by fire, wind, insects, fungi, or other injurious agencies) before their timber becomes economically worthless.
SCALE In ecosystem management, scale refers to the degree of resolution at which ecosystems are observed and measured.
SEVERE WILDLAND FIRE (CATASTROPHIC WILDFIRE) Fire that burns more intensely than the natural or historical range of variability, thereby fundamentally changing the ecosystem, destroying communities and/ or rare or threatened species/ habitat, or causing unacceptable erosion.
SIMPPLLE COMPUTER MODEL A model that simulates likely patterns of vegetation change over time resulting from various disturbance processes such as insect infestation and wildfire-- with or without fire suppression and management activities.
SLASH Debris left after logging, pruning, thinning, or brush cutting; includes logs, chips, bark, branches, stumps, and broken understory trees or brush.
SLASH BUNDLER A relatively new piece of equipment developed in Scandinavia that collects and bundles forest residue in the forest for utilization in biomass burning industry.
SNAG A standing dead tree or part of a dead tree from which at least the smaller branches have fallen.
SNOTEL The acronym stands for SNOw TELemetry. A SNOTEL site is an automated station that collects information on snowpack and climate. SNOTEL data includes snow water content, precipitation, temperature, and sometimes other climate data such as snow depth, humidity, wind speed, wind direction, and solar radiation. Anyone with internet access can get readouts from SNOTEL sites at
SOIL PRODUCTIVITY The inherent capacity of a soil to support the growth of specified plants, plant communities, or a sequence of plant communities. Soil productivity may be expressed in terms of volume or weight/unit/year, percent plant cover, or other measures of biomass accumulation.
SPATIAL DATA An electronic map of environmental or demographic information.
SPATIAL LANDSCAPE MODEL A computer model—for example, SIMPPLLE—of landscape processes that includes spatially explicit data.
SPATIAL OPTIMIZATION MODEL A computer model—for example, MAGIS—that uses mathematical optimization to find the ‘best’ solution based on objectives entered by the user and quantities calculated by the model (these quantities could include vegetation parameters, economics, and resource benefits).
STEWARDSHIP CONTRACTS The FY-1999 Appropriations Bill (Section 347) authorized the Forest Service to enter into 28 service contracts to achieve land management goals for national forests that meet local and rural community needs. These contracts focus on post-treatment conditions of forest resources rather than commodity outputs. Generally, the contracts differ from conventional timber contracts in four ways: 1) they will be awarded based on best-value to the government instead of the high bid, 2) value of timber and other forest products removed may be applied to offset the cost of services provided, 3) value of services received and resources provided are not considered in calculating the 25% Fund payments to states, and 4) the Forest Service shall establish a multiparty monitoring and evaluation process that assesses each stewardship contract. For FY-2001, Congress authorized 28 additional stewardship contracts.
STRUCTURE How the parts of ecosystems are arranged, both horizontally and vertically. Structure might reveal a pattern, or mosaic, or total randomness of vegetation.
SUPPRESSION All the work of extinguishing or confining a fire beginning with its discovery.
SURFACE FIRE A fire burning in ground surface fuels without significant involvement of the understory or overstory, with flame lengths usually below 1 meter.
SURFACE FUELS Loose surface litter on the soil surface, normally consisting of fallen leaves or needles, twigs, bark, cones, and small branches that have not yet decayed enough to lose their identity; also grasses, forbs, low and medium shrubs, tree seedlings, heavier branchwood, downed logs, and stumps interspersed with or partially replacing the litter.
SUSTAINABILITY The ability of an ecosystem to maintain ecological processes and functions, biological diversity, and productivity over time.
THERMAL COVER Cover used by animals against weather. For elk, thermal cover can be found in a stand of coniferous trees at least 40 feet tall with a crown closure of at least 70 percent.
THINNING A cultural treatment made to reduce stand density of trees primarily to improve growth, enhance forest health, recover potential mortality, or reduce the probability of active crown fires. Thinning from above particularly favors the most promising and not necessarily the dominant stems with due regard to even distribution over the stand by removing from any canopy class those trees that are interfering with them. Also called high thinning or crown thinning. Thinning from below favors dominants, or in the heavier thinning grades selected dominants, more or less evenly distributed over the stand by removing a varying proportion of other trees. Thinning from below includes mechanical cutting of the small tree strata within a stand to reduce competition, direct species dominance, reduce potential insect and disease problems, and reduce the potential for crown fire.
TRACK PLATES Aluminum sheets that are used at bait stations to obtain prints (tracks) of target species such as forest carnivores.
TRAJECTORY A trajectory is a path that a moving object follows. In forest ecology terms, it is the developmental pathway of the forest ecosystem over time.
TRANSECT A straight line of a given length containing study points located at specified distances.
UNDERBURN A fire that consumes surface fuels but not trees or shrubs (See Surface Fuels).
UNDERSTORY The layer formed by the crowns of smaller vegetation in a forest.
UNDERSTORY FIRE A fire burning in a layer formed by the crowns of smaller vegetation in a forest, which is typically more intense than a surface fire and has flame lengths of 1 to 3 meters.
VEGETATIVE STATE Vegetation type, density, size, and structural classes.
V - MAP A project to map current vegetation west of the Continental Divide in the Forest Service's Northern Region and designed to address several needs. The result of this project is a geo-spatial database that produces four primary map products: Dominance Type, Tree Canopy Cover Class, Life Form, and Tree Diameter Class.
WATERSHED The entire region drained by a waterway (or into a lake or reservoir).  More specifically, a watershed is an area of land above a given point on a stream that contributes water to the streamflow at that point.
WEIGHT OF THE EVIDENCE Considering all available research and weighing its relevance and reliability in an integrated manner.
WHOLE-TREE YARDING A method of harvesting trees by cutting and moving the entire tree to a “landing” where its branches and tops are removed in preparation for transport.
WILDFIRE A fire of either natural or human ignition, not meeting land management objectives, and requiring suppression.  (Note:  Recently, the use of the term "wildfire" has been discontinued.  Its replacement term is "wildland fire.")
WILDLAND FIRE Any nonstructure fire, other than prescribed fire, that occurs in the wildland.  This term encompasses fires previously called both wildfires and prescribed natural fires.
WILDLAND FIRE SITUATION ANALYSIS (WFSA) (OR ESCAPED FIRE SITUATION ANALYSIS) A decision-making process that evaluates alternative suppression strategies against selected environmental, social, political, and economic criteria. Provides a record of decisions.
WILDLAND FIRE USE The management of naturally ignited wildland fires to accomplish specific pre-stated resource objectives in predefined geographic areas outlined in fire management plans.
WILDLAND URBAN INTERFACE The line, area, or zone where structures and other human development meet or intermingle with undeveloped wildland or vegetative fuels.

USDA Forest Service - Rocky Mountain Research Station
Webmaster:Janet Sullivan
Original Web Design: Susan Tolliver

USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.