D

	Damaged timber: timber that has been affected by injurious agents such as wind (as in the case of blowdown), fire, insects, or disease.
	Danger tree: a live or dead tree whose trunk, root system or branches have deteriorated or been damaged to such an extent as to be a potential danger to human safety.
	DBH (diameter at breast height): the stem diameter of a tree measured at breast height, 1.3 metres above the ground.
	Deactivation: measures taken to stabilize roads and logging trails during periods of inactivity, including the control of drainage, the removal of sidecast where necessary, and the re-establishment of vegetation for permanent deactivation.
	Debris flows: mixture of soil, rock, wood debris and water which flows rapidly down steep gullies; commonly initiate on slopes greater than 30ฐ, but may run out onto footsteps of low gradient.
	Debris initiation and transport hazard: the relative risk of gully wall failure and/or debris movement in gully channels, as tempered by the stream runout distance.
	Deciduous: perennial plants which are normally leafless for some time during the year.
	Declination (magnetic): the angle between true (geographic) north and magnetic north (direction of the compass needle). Declination varies from place to place and can be 'set' on a compass for a particular location.

Deferred area: Defined in the Forest Practices Code of British Columbia Act Operational Planning Regulation as an area:

a) specified in a higher level plan where timber harvesting or other forest development activities have been postponed for a period of time, or;

b) that the district manager has determined should not be harvested or otherwise developed until a higher level plan for the area is completed.

	Deficit forest: a forest in which existing stands cannot provide enough harvest volume to maintain the harvest at the level of long run sustained yield until the stands created when existing stands are cut become available for harvest. See also Surplus forest.
	Defoliator: an agent that damages trees by destroying leaves or needles. Deforestation: clearing an area of forest on a non-temporary basis for another use. Clearcutting (even with stump removal), if shortly followed by reforestation for forestry purposes, is not deforesting.
	Degradation: the diminution of biological productivity or diversity.
	Deleterious substance: any substance that, if added to water, would degrade or alter the quality of the water so that it becomes deleterious to fish or fish habitat, or becomes unsuitable for human consumption or any other purpose for which it is legally licensed (such as irrigation and livestock watering).
	Depletion: an income tax allowance reflecting the purchase price paid for merchantable timber, usually on fee simple land. Also, a term used to refer to the process of harvesting your growing stock.
	Designated area: an identifiable geographic unit of the forest land base that requires a specific combination of forest practices to adequately protect important resource values.
	Designated heritage trail: a heritage trail designated under the Heritage Conservation Act.
	Designated official: not a defined term in the Forest Practices Code of British Columbia Act. However, commonly used to refer to a person designated by name or title to be a designated energy, mines and petroleum resources official, designated environment official, or designated forest official.
	Designated skid road/skid trail: a pre-planned network of skid roads or skid trails, designed to reduce soil disturbance and planned for use in subsequent forestry operations in the same area. Multiple passes by tracked or rubber-tired skidders or other equipment are anticipated.
	Designated wilderness: see Wilderness area.
	Desired future stand condition: a description of the characteristics of the future stand.
	Desired plant community: A plant community that produces the kind, proportion and amount of vegetation necessary for meeting or exceeding the land-use plan requirements or ecological site objectives. The desired plant community must be consistent with the site's capability to produce the desired vegetation through management, land treatment or a combination of the two.
	Determination: any act, omission, decision, procedure, levy, order or Standards made under that act by an official or a senior official.
	Detrimental soil disturbance: changes caused by forest practices in the physical, chemical, or biological properties of the soil, including the organic forest floor and the mineral soil extending from the surface to the depth at which the unweathered parent material is encountered. Such changes may result in a loss of productive growing site, reduced site productivity, or adverse impacts on resource values.
	Development: the advancement of the management and use of natural resources to satisfy human needs and improve the quality of human life. For development to be sustainable it must take account of social and ecological factors, as well as economic ones, of the living and non-living resource base, and of the long-term and short-term advantages and disadvantages of alternative actions.
	Development objectives: the short-term (often 5-year) planning objectives for a specific management area.
	Development plan: a specific plan outlining harvesting, road construction, protection, and silviculture activities over the short-term (often 5 years) in accordance with the approved forest management plan.
	Dewatering: condition in stream channel when all the water flow occurs within the permeable streambed sediments, so no surface water is left; common in small streams with considerable accumulations of gravel.
	Diameter limit: the removal of trees from a stand, based on the criterion of diameter. Generally, trees of less than a predetermined diameter are left unharvested.
	Diameter tape: a graduated tape based on the relationship of circumference to diameter which provides direct measure of tree diameter when stretched around the outside of the tree, usually at breast height. See DBH.
	DIB (diameter inside bark): the diameter of a tree or log excluding bark thickness.
	Dibble: a tool used to make holes in the ground for planting tree seedlings.
	Difficult site: forest sites with environmental conditions that are unfavorable for tree establishment and growth.
	Direct seeding: the application of tree seed to a denuded area to regenerate it with commercially valuable species.
	Disc trencher: a machine designed for mechanical site preparation. It provides continuous rows of planting spots rather than intermittent patches as provided by patch scarifiers. Consists of scarifying steel discs equipped with teeth.
	Discretionary authority: the power to make a decision where the choice of whether to make a decision is that of the decision maker.
	Dispersed retention: retaining individual trees scattered throughout a cutblock.
	District manager: the manager of a Forest Service district office.
	Disturbance: a discrete event, either natural or human-induced, that causes a change in the existing condition of an ecological system.
	Ditch block: a blockage that is located directly downgrade of a cross-drain culvert or cross-ditch and designed to deflect water flow from a ditch into a cross-drain culvert.
	DOB (diameter outside bark): the diameter of a tree or log including bark thickness.
	Dominant: trees with crowns extending above the general level of the canopy and receiving full light from above and partly from the side; taller than the average trees in the stand with crowns well developed.
	Dot grid: a transparent sheet of film (overlay) with systematically arranged dots, each dot representing a number of area units. Used to determine areas on maps, aerial photos, plans, etc.
	Down-rated bridges: bridges whose carrying capacity has been reduced.
	Drag scarification: a method of site preparation that disturbs the forest floor and prepares logged areas for regeneration. Often carried out by dragging chains or drums behind a skidder or tractor.
	Drainage basin: area of the earth's surface from which surface drainage all flows to a single outlet stream (a watershed in North America).
	Drainage structures: include metal and wooden culverts, open-faced culverts, bridges, and ditches.
	Drainage system: a system designed to control the flow of water within a road prism.
	Drawdown: the process of reducing allowable annual cuts to a sustainable level.
	Duff: the layer of partially and fully decomposed organic materials lying below the litter and immediately above the mineral soil. It corresponds to the fermentation (F) and humus (H) layers of the forest floor. When moss is present, the top of the duff is just below the green portion of the moss.
	Dust palliatives: chemicals or compounds applied to road surfaces to reduce dust created by traffic.