USDA Forest Service

Pacific Northwest Research Station

Pacific Northwest Research Station
1220 SW 3rd Ave.
Portland, OR 97204

(503) 808-2100

US Forest Service





Airborne laser scanning—A remote sensing technology that uses a scanning laser mounted on an aircraft to survey the shape and structure of terrain, buildings, and vegetation.
Amphibian—A cold-blooded species that spends some portion of its life in water.
Anadromous—A fish species that is born in freshwater, matures in marine (saltwater) ecosystems, and then returns to freshwater to reproduce.



Benthic—An aquatic organism living on, or very close to, the floor (or bed) of a body of water.
Biodiversity—Variation in species or life forms within a landscape or ecosystem. Promoting biodiversity is often an objective of ecosystem management.
Biogeography—Study of the geographical distributions of species and the factors that control them.
Biomass—Broadly defined, refers to the entire collection of living organisms and dead organic material an ecosystem supports; can include grasses, trees, insects, fish, birds, and mammals. More typically, is used in reference to the amount of living and dead vegetative material an ecosystem is capable of supporting.
Biophysical—The physical processes that affect organisms, populations, or communities.
Boreal—Species or ecosystems of the far north, such as of interior Alaska.
Buffer—A strip of land surrounding or bordering a body of water (stream or lake) that is meant to protect it from the effects of land management activities.



Carnivore—A meat-eating species.
Coarse woody debris—Large woody material from trees that have fallen to the forest floor; includes the trunk and large branches. Is an important habitat component for numerous wildlife species, although excessive amounts can be a concern for fire managers trying to manage for reduced fire fuel loads.
Conifer—A tree, usually evergreen, whose reproductive bodies (seeds) are contained within a cone.
Crown—The upper portion of a tree or plant; ultimately forms the canopy.



Deciduous—Perennial plants that lose their foliage for some time of the year.
Dendrochronology—The study of the process of estimating a tree’s age by counting its yearly growth rings.
Digital elevation model—Digital files that consist of points of ground surface elevations that are sampled systematically at equally spaced intervals over an area. Used to represent the terrain surface shape in a form that can be read and displayed by a computer.
Disturbance—Broad term referring to any event that disrupts an ecosystem and its components; includes fire, insect and disease outbreaks, and thinning.


Ecology—A field of study concerned with the interactions of organisms and their environment.
Emissions—In fire science, refers to the byproducts of fire that are put into the air; includes soot, carbon dioxide, water, and other compounds that are found in smoke.



Fuel—In fire science, refers to organic matter that can burn in a fire; includes live and dead standing trees; dead and downed logs and branches; pine needles; leaves; grasses; and shrubs.
Fuel consumption—In fire science, the process by which fire converts fuels to energy (heat) and combustion byproducts, such as ash, charcoal, and smoke or emissions. Knowledge of the amount and rate of fuel consumption can help predict fire effects, intensity, and severity.
Fuel reduction (fuel treatment)—Management activity in which fuels are removed or altered to reduce the likelihood, intensity, or severity of fire.



Geographic information system (GIS)—A computer system for capturing, storing, analyzing, managing, and displaying data and associated attributes that are spatially referenced to the Earth.
Geomorphology—The study of the processes that shape the physical features of the Earth.



Habitat—The place where a species lives and where it finds the specific kinds of food, shelter, and other components necessary for its survival and successful reproduction.
Hardwood—A deciduous, nonconiferous tree, such as maple, alder, and willow.
Headwater—The upper portion of a body of water that is nearest to the source.
Herbivory—Grazing of vegetation.


Indicator species—A species that is intimately associated with one or more of an ecosystem’s components. The presence and abundance of an indicator species in an ecosystem can be an indication of ecosystem health as well as the presence or abundance of other species in the ecosystem.
Integrated resource management—The management of various resource values so that they are utilized in the combination that best meets present and future needs.
Invasive species—Species that occur outside of their native range and that are detrimental to the new ecosystems they inhabit; includes plants, animals, and pathogens.
Inventory—A research activity in which the quantity and quality of ecosystem components (such as trees) are assessed.



Land cover—The observed (bio)physicalcover on the Earth’s surface, such as Douglas-fir forest.
Land use—The use (purpose) to which land is put by people; includes protected areas, plantations, pastures, and human settlements.
Landscape ecology—Study of how ecological patterns and processes interact across space (landscapes).
Legacy trees—Trees that are retained while most of the surrounding trees are harvested, or trees that survive catastrophic events that kill most of the surrounding trees; also known as residual trees. Can promote biodiversity by providing important habitat components for some organisms while the new forest grows.
Long-term ecosystem productivity—Managing ecosystems to provide goods and services without reducing the land’s capability to provide that rate of production in the future.



Mycorrhizal fungi—A special group of soil fungi that form symbiotic associations with plant roots called mycorrhizae. In these associations, the fungi receive their primary energy source from the host plant in the form of simple sugars; in return, the plant receives soil nutrients from the fungus. Mycorrhizal fungi and their resulting plant symbioses are critical to the health of Pacific Northwest ecosystems.



Old growth—Refers to ecosystems characterized by old trees and other structural attributes that represent the later stages of stand development, such as coarse woody debris and multiple canopy layers.



Pathogen—A disease-causing agent; includes bacteria, viruses, and fungi.
Pioneer plants—Plants that are adapted to colonize and grow in a site following a disturbance.



Reduced-impact logging—Technologies and practices designed to minimize damage to residual trees, soils, and other resources in and around a harvesting site.
Remote sensing—Broad term referring to techniques that measure conditions of forests and landscapes from the air or space; includes Landsat, light detection and ranging (LiDAR), radar, and aerial photography.
Riparian—An ecosystem bordering a stream, river, or lake that is strongly influenced by the adjacent body of water.
Rotation age—The age at which trees are suitable for final harvest and regeneration.
Ruminants—Hoofed herbivores (plant eaters), such as deer, elk, and cattle, that chew their cud and possess four specially divided stomachs, the first part of which is called a rumen (which contains microbes that digest the foods eaten).



Salmonids—A group of fish that includes salmon, trout, and char.
Seral—Refers to a stage of forest development. Early seral (also known as early successional) refers to relatively young forests with simple attributes; late seral (also known as late successional) refers to mature forests with complex attributes, such as coarse woody debris, snags, and spatial heterogeneity.
Silviculture—The science of controlling the vegetation, growth, composition, and health of forests to meet the objectives of landowners.
Snag—Standing dead tree.
Spatial data—Data arranging and displaying information across space; often presented in the form of maps.
Spatial heterogeneity—Typically refers to variation in the amount and diversity of trees, shrubs, and understory plants at various vertical and horizontal areas within a forest. High levels of spatial heterogeneity are believed important for healthy, resilient forests.
Spatial scale—The resolution of the scale of reference; includes individual tree, stand, and landscape scale.
Special forest product—A harvestable nontimber forest product that has commercial, medicinal, and/or craft value; includes mushrooms and floral greens.
Stand—In forestry and silviculture, refers to a contiguous group of trees of relatively similar age, composition, and structure, so as to be a distinguishable unit.
Stressor—A physical or biological component that reduces the vigor of organisms or ecosystems and potentially reduces their resistance to other stressors; includes invasive species, contaminants, drought, and fungal pathogens.
Succession—The growth and change of a forest over time and the replacement of an earlier stage of development with a newer phase (as in early seral to late seral).
Symbiotic—A type of biological or ecological relationship in which two organisms associate, often to the benefit of one or both; see mycorrhizal fungi.



Temperate rain forest—Forest type characterized by abundant rainfall and mild seasonal temperatures; distinct from tropical rain forest.
Temporal scale—The scale of reference that refers to the distribution of a variable across time; includes daily, monthly, and annual resolution of data.
Thinning—The removal of some, but not all, trees in a forest.
Tree grading—Process in which the value of a tree as lumber or other solid wood products is assessed.
Tributary—A smaller stream that flows into a larger stream, river, or lake.



Understory—The lower, or ground, portion of a forest; often consists of grasses, shrubs, or immature trees.
Ungulate—Hoofed herbivores (plant eaters), such as deer or elk.
Urbanization—A land use change involving the conversion of rural lands (such as agricultural land) to developed areas (such as residential areas or commercial sites). Urban and developed areas consist of residential, industrial, commercial, and institutional lands.



Variable-density thinning—Ecosilvicultural practice in which a forest is thinned in a way that creates variation in the space between the trees that are left.



Watershed—The part of a landscape where precipitation flows into a single river system.
Weathering—Physical or chemical process that breaks down rocks, develops soil profiles, and makes nutrients available to plants.
Wildland-urban interface—Area at which a wildland (such as a forest, range, or woodland) intersects with a developed area, such as a residential community; also known as the WUI. As urbanization continues and expands into wildlands, the WUI grows, often translating into an increased  risk of severe wildfires, as human lives and structures become involved.
Windthrow—The uprooting of trees and other vegetation by wind.


US Forest Service - Pacific Northwest Research Station
Last Modified: Wednesday,02July2014 at11:44:27CDT

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