Abiotic: Pertaining to nonliving components of the environment (e.g., climate, ice, soil, and water).


Abundance: The number of organisms in a population, combining density within inhabited areas with number and size of inhabited areas.


Acidic deposition: The process by which acids are deposited, either as wet deposition in the form of rain, snow, sleet, hail, or fog; or as dry deposition in the form of particulates such as fly ash, sulphates, nitrates; or as gases like sulphur dioxide and nitric oxide.  Dry particles and gases, deposited onto or adsorbed into surfaces, can be converted into acids after deposition or adsorption when they come in contact with water.


Advance regeneration: Young trees that survive logging to form the initial part of a new stand.


Afforestation: The establishment of a forest in an area where there has not been a forest for at least 50 years. See also deforestation and reforestation.


Age class: A category into which the average age or age range of trees or other vegetation is classified. Age class is usually used in reference to even-aged stands of trees. It represents the dominant age of the main body of trees in a stand. In mixed-aged stands, age class can be used to describe the average age of specific cohorts of trees.


Alien species: Any species not native to a particular ecosystem.


Ambient: Surrounding, as in “ambient air temperature”; the quality of physical parameters in the surrounding, external, or unconfined conditions.


Bequest value: The external benefit that accrues to individuals through the assurance that future generations will also have access to forests.


Biofuel: Fuel made from biomassnonfossil, recently living organisms or their by-products (e.g., ethanol, biodiesel, and methanol).


Biogeochemical cycles: Any of the natural pathways through which a chemical element essential for living matter (e.g., carbon, nitrogen, oxygen, and sulphur) circulates back and forth between the abiotic components of the environment (i.e., air, soil, and water) and organisms; human activities (e.g., the burning of fossil fuels) can alter the rates of at which these elements cycle.


Biological productivity: The capacity to produce biomass; the production of biomass.


Biomass: The mass of organic matter per unit of area or volume of habitat.


Biosphere: That part of the planet that supports life; consisting of the hydrosphere (the earth’s water in all forms), the lithosphere (the earth’s crust and upper mantle), and the lower atmosphere.


Biota: All of the living organisms in a given ecosystem or area, including microorganisms, plants, and animals.


Biotic: Pertaining to any living aspect of the environment, especially population or community characteristics.


Buffer zone: A strip of land maintained along a stream, lake, road, recreation site, or different vegetative zone to mitigate the impacts of actions on adjacent lands, to enhance aesthetic values, or to ensure best management practices.


Catalyst: A substance that changes the speed or yield of a chemical reaction without being consumed or chemically changed by it.


Census subdivision: A geographic designation used by Statistics Canada to approximate the municipal boundaries of a community.  Census subdivisions are located outside of metropolitan areas.


Chlorofluorocarbons (CFCs): Industrial synthetic chemicals used in air conditioning, foam, and cleaning solvents.  CFCs can damage the ozone layer.


Clearcutting: In the Canadian context, a silvicultural system in which most merchantable trees in a stand are harvested simultaneously; often some mature trees are retained to act as a seed source; clearcutting can be implemented in blocks, strips, or patches.


Coarse woody debris: Typically, logs, stumps, or large branches that have fallen or been cut and left in the woods, or trees and branches that have died but remain standing or leaning.


Compaction: A reduction in soil volume leading to poor soil aeration, reduced drainage, and root deformation.


Conifers: Trees in the division Pinophyta (the gymnosperms); cone-bearing, usually evergreen, with needle-shaped or scale-like leaves. Conifers are termed softwoods in the forest industry, although  Douglas-fir and certain pines have harder wood than some broadleaf trees.


Connectivity: Refers to the structural links between habitat patches in a landscape.


Convention on Biological Diversity: A global agreement to address all aspects of biological diversity: genetic resources, species, and ecosystems. The objectives are "the conservation of biological diversity, the sustainable use of its components and the fair and equitable sharing of the benefits arising out of the utilization of genetic resources."


COSEWIC: An acronym for the Committee on the Status of Endangered Wildlife in Canada.  COSEWIC lists and designates plants and animals in Canada according to their relative abundance at the national level.


Cover type: See Forest type.


Critical load: The highest deposition of acidifying compounds or other pollutants that will not cause chemical changes leading to long-term harmful effects on the overall structure or function of an ecosystem.


Crown: The part of a tree or woody plant bearing live branches and foliage.


Crown transparency: The amount of skylight visible through the foliated portion of a tree crown.


Cutover: An area of forest from which some or all of the timber has recently been cut.


Deciduous trees: Trees in the class Magnoliopsida of the division Magnoliophyta (angiosperms); characterized by having flowers  with pistils and stamens (sometimes in separate flowers), fruit-borne seeds containing two cotyledons (seed leaves), and  broad leaves that are usually shed annually. See also Hardwoods.


Decomposition: The breakdown or decay of organic materials by the action of bacteria, fungi, and other microorganisms.


Defoliation: An unseasonable reduction in the foliage cover of a plant due to attacks by insects or fungal disease, or as a result of other factors such as drought, storms, or chemicals in the atmosphere.


Deforestation: The direct human-induced conversion of forested land to nonforested land. See also afforestation and reforestation.


Disturbance: A significant change in the structure and/or composition of ecosystems, communities, or populations through natural or human-induced events.


Ecoclimatic regions: Ecologically based regions in which plant succession and rate of growth are similar on similar sites.


Ecosystem: A dynamic system of plants, animals, and other organisms, together with the nonliving components of the environment, functioning as an interdependent unit.


Ecosystem-based management: Management systems that attempt to simulate ecological processes with the goal of maintaining a satisfactory level of diversity in natural landscapes and their pattern of distribution in order to ensure the sustainability of forest ecosystem processes.


Ecozone: A broad, ecologically distinctive area delineated at a subcontinental level and defined by its interaction of human, vegetative, wildlife, climatic, geologic and physiographic factors.   Canada’s ecological land classification framework comprises 15 terrestrial ecozones; these are subdivided into 53 ecoprovinces, the ecoprovinces into194 ecoregions, and the ecogregions into1020 ecodistricts.


Environmental service value: Values related to the ability of forest ecosystems to assimilate waste and respond to human disturbances while continuing to provide environmental goods and services, such as clean air and water, soil retention, and wildlife habitat.


Erosion: The wearing away of the land surface by running water, wind, ice, or gravity.


Even-Aged: Of a forest stand or forest type in which relatively small age differences (usually less than 10–20 years) exist between individual trees.


Existence value: The benefit that accrues to an individual from the knowledge that an area or feature exists in a particular condition even though that individual may never visit or use the area or feature.


Extinction: The termination of a species caused by the death of all the members of that species.


Extirpation: The elimination of a species or subspecies from a particular area, but not from its entire range. A wildlife species no longer existing in the wild in Canada, but occurring elsewhere (COSEWIC).


Even-aged: Of a forest stand or forest type in which relatively small age differences (usually less than 1020 years) exist between individual trees.


Fauna: The animal life found in a particular region or habitat or at a particular time.


Fire activity: Ignition, flame development, spread, and intensity of a forest or wildland fire.


Fire load: In Canada, the number and magnitude of all fires requiring suppression action during a given period within a specified area.


Fire management: Activities to protect people, property, and forest areas from wildfire; as well, the intentional burning of areas to attain forest management and other land-use objectives.


Fire regime: The characteristic frequency, extent, intensity, severity, and seasonality of fires within an ecosystem.


Fire suppression: All activities concerned with controlling and extinguishing a fire following its detection.


Flora: The life found in a particular region or habitat or at a particular time.


Forest-dependent community: A community or census subdivision that derives at least 50% of employment income from the forest sector.


Forest type: A forested area that can be differentiated from other such areas by its species composition, particularly by its dominant species, and often also by height and crown-closure classes.


Full suppression fire: A forest or wildland fire that because of the social, environmental, or economic threat it poses is controlled as quickly as possible.


Gap analysis: An analytical technique in which the extent of existing protected areas is overlaid with maps of species and ecosystem distribution to identify gaps in the protective network. 


Geographic information system (GIS): An information system that uses a spatial database to provide answers to queries of a geographical nature through a variety of manipulations, such as sorting, selective retrieval, calculation, spatial analysis, and modeling.


Global warming: A real and projected trend in the warming of the earth’s surface caused by natural changes in the global climate system and by human activities such as the release into the atmosphere of the gaseous by-products (principally carbon dioxide) of fossil-fuel consumption, which trap long-wavelength radiant energy.


Greenhouse gases: Molecules in the earth’s atmosphere such as carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons, which warm the atmosphere because they absorb some of the thermal radiation from the surface of the earth.


Greenhouse gas sink: A pool or reservoir that absorbs a greenhouse gas or its precursors at a greater rate than it releases them. A forest is a carbon sink when its uptake of carbon dioxide from the atmosphere, principally through photosynthesis, exceeds its release through processes such as decomposition and burning. See also biogeochemical cycles.


Greenhouse gas source: A point or source that releases a greenhouse gas or its precursors at a greater rate than it absorbs them. A forest is a carbon source when its release of carbon dioxide into the atmosphere, principally through decomposition and burning, exceeds its uptake during photosynthesis. See also biogeochemical cycles.


Habitat generalist: A species capable of exploiting a broad range of habitats or niches.


Hardwoods: Another term for deciduous or broadleaf trees; mostly applied by the forest industry in reference to the hard quality of the wood of most of these trees compared with the softer wood of conifers.


Heritage legislation: Legislation addressing the protection of sites that have cultural, historical, or spiritual significance for present and future generations.


High grading: A partial harvest removing only the most valuable tree species, or trees of desirable size and quality, without regard for the condition of the residual stand.


Humus: A brown or black complex material resulting from the partial decomposition of plant or animal matter and forming the organic portion of the soil.


Intergovernmental Panel on Climate Change (IPCC): A panel open to all members of the United Nations Environment Programme and the World Meteorological Organization. The IPCC assesses the scientific, technical, and socioeconomic information relevant to the understanding of the risk of human-induced climate change.


Invasive species: Any species not native to a particular ecosystem whose introduction does or is likely to cause economic or environmental harm or harm to human health.


Joule: Unit of energy and work. (A petajoule is 1015 joules.)


Kyoto Protocol: (To the United Nations Framework Convention on Climate Change); strengthens the Convention by committing major industrial countries to legally binding targets to limit or reduce their greenhouse gas emissions; the Protocol was adopted at a Conference of Parties to the Convention in Kyoto, Japan, in December 1997.


Landscape: A spatial mosaic of several interacting ecosystems, landforms, and plant communities ranging in size from several hectares to many square kilometres.


Microorganism: An organism too small to be seen with the unaided eye (e.g., a virus, bacterium, protozoan, yeast cell, and fungal hypha).


Mixedwood: Stands of trees having a well-mixed composition of deciduous or broadleaf trees (angiosperms) and conifers (gymnosperms).


Modified fire response: Response to a forest or wildland fire at less than full suppression; normally employed in areas where the fire does not pose a threat to human life or property.


Mycorrhiza: The symbiotic association between higher plant roots and specific fungi that aid plants in the uptake of water and certain nutrients.


Native species: A species known to have existed on a site before the influence of humans.


Nitrous oxide (N2O): A greenhouse gas of increasing significance; although it occurs naturally in the environment, nitrous oxide is mainly released through human activities such as the application of natural and synthetic fertilizers and the burning of fossil fuels.


Nonmarket consumptive goods:  Products (e.g., berries, mushrooms, craft products, firewood, fiddleheads, Christmas and ornamental trees) that individuals harvest from forest lands free of charge.


Nutrient cycle: See biogeochemical cycles.


Option value: The amount an individual would be willing to pay to preserve (or would have to be paid to agree to sell) the option to participate in some activity or to use some resource in the future, whether or not that individual ever actually participated in the activity or used the resource.


Ozone (O3):  A gas formed naturally in the upper atmosphere (stratosphere) when oxygen (O2) is split by ultraviolet (UV) radiation into its component atoms, which then bind individually to other intact oxygen molecules; stratospheric ozone protects the earth’s surface from UV radiation. At ground (or tropospheric) levels, ozone is formed from reactions between human-induced airborne pollutants and sunlight; tropospheric ozone is a major agent in the formation of smog.


Particulate: Of or relating to minute separate particles.


Photosynthesis: The process by which plants transform carbon dioxide and water into carbohydrates using solar energy captured by chlorophyll in the plant. Oxygen is a byproduct of the process.


Phytotoxic: Poisonous to plants.


PPB or ppb: Parts per billion (109).


PPM or ppm: Parts per million (106).


Preservation value: The external benefit derived from existence, option, and/or bequest values.


Reforestation: The reestablishment of a forest in an area that used to be forested but that did not have forest as of 1989; does not include regeneration after harvest. See also afforestation and deforestation.


Remote sensing: The science and art of obtaining information about an object, area, or phenomenon through the analysis of data acquired by a device that is not in contact with the object and that uses wavelengths from the ultraviolet to radio regions of the spectrum.


Renewable resource: A natural resource that is capable of regeneration.


Resilience: The capacity of a community or ecosystem to maintain or regain the desired condition of diversity, integrity, and ecological processes following disturbance.


Respiration: The process by which an organism releases energy from food (glucose) to fuel  life-sustaining cellular activity; in most organisms, the process requires oxygen (aerobic respiration) and the by-products are carbon dioxide and water. 


Riparian zone: A strip of land of variable width adjacent to and influenced by a body of fresh water.


Run-off: That portion of the precipitation on a drainage area that is discharged from the area in stream channels.


Savannah: A major global biome characterized by open grasslands with scattered trees or shrubs.


Scarification: A method of seedbed preparation that consists of removing the forest floor or mechanically mixing it with the mineral soil to eliminate or reduce the dead organic material.


Selection cutting: Also called partial cutting. An uneven-aged silvicultural system in which trees are removed individually or in small groups continuously at relatively short intervals, resulting in a constant renewal of a forest crop.


Seral species: Plant species of early, middle, and late successional plant communities. The term is often used in a narrower sense in forest management to describe the dominant conifer vegetation that follows major disturbance episodes.


Seral stages: Also called successional stages. The series of plant community conditions that develop during ecological succession from bare ground (or major disturbances) to the climax stage.


Shelterwood cutting: A regeneration method used to establish even-aged stands; involves cutting most trees in a stand while retaining a few mature ones to provide seed and protection for the new crop.


Siltation: The filling-in of lakes and stream channels with soil particles, usually as a result of erosion on adjacent land.


Silviculture: The theory and practice of controlling the establishment, composition, growth, and quality of forest stands; can include basic silviculture (planting and seeding) and intensive silviculture (site rehabilitation, spacing, and fertilization).


Smog: Air pollution typically composed of a noxious mixture of fine particles (liquid or solid) and ground-level ozone.


Softwoods: Mostly applied by the forest industry in reference to the relatively soft quality of the wood of coniferous trees compared with that of most broadleaf species.


Stocked forest land: Land supporting tree growth, including seedlings and saplings. Stocking is a qualitative expression of the adequacy of tree cover on an area, in terms of crown closure, number of trees, basal area, or volume, in relation to a preestablished norm. In this context, tree cover includes seedlings and saplings; therefore the concept carries no connotation of a particular age.


Structure: The distribution of trees in a stand or group by age, size, or crown class.


Succession: Changes in the species composition of an ecosystem over time, often in a predictable order.


Tenure: The act of owning, using, or controlling land or the resources of that land under certain terms and conditions.


Troposphere: The lower layer of the earth’s atmosphere stretching from the ground to the upper atmosphere (stratosphere).


Turbidity: A measure of water clarity, or the degree to which water is rendered opaque by the suspended silt or other sediments.


Uneven-aged: Of a forest, stand, or forest type in which the intermingled trees differ in age by more than 1020 years.


Value-added production: Manufacturing that adds value to a primary product as it passes through various processing stages.


Variable-retention silvicultural system: Harvesting method by which some forest cover is retained.