Glossary

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D

DARDC
Device for Automatic Remote Data Collection. A telemetry system interface used to enter in situ sensor data (e.g., water levels) into a landline, line of sight radio, or satellite telemetry system.
Data Base
A group of data stored together and organized according to characteristics that the data have in common.
Data Base Administrator
The person or group of persons responsible for overall control of a data base system.
Data Family
Those data records vertically related as one branch of an hierarchical tree.
Datum
Any level surface, line, or point used as a reference in measuring elevations. Also any single observation. "Data" is the plural.
DBH
Diameter at breast height. The diameter of a tree at 4.5 feet above the ground.
Death Rate
(1) Deaths within a cohort divided by the number of individuals in that cohort at the beginning of an age or time period; (2) proportions of deaths in a population.
Debark
To remove the bark from trees or sections of trees, usually mechanical rather than manual.
Deciduous Trees
Thise which lose all of their leaves during the winter season.
Decision Criteria
Decision criteria are essentially rules or standards used to rank alternatives in order of desirability. They are measurements or indicators that are designed to assist a decisionmaker to identify a preferred choice from an array of possible alternatives. They tend to indicate how well a prescribed course of action meets a set of goals, objectives, and targets in comparison to other alternatives.
Decision Theory
A body of knowledge and related mathematical techniques which have been developed from the fields of statistics, mathematics, and logic and which are designed to aid in making decisions under conditions of uncertainty. Decision theory is similar to game theory in several respects but a major difference between the two is that in game theory the decision is being made vis-a-vis an opponent, whereas in decision theory the only opponent is "nature" with its related uncertainty.
Decision Variable
A component of an alternative in which activities and their costs, outputs, and benefits are identified and used for analysis and decision making. All activities and costs necessary to accomplish the outputs and benefits are included.
Decomposer
An organism, usually a bacterium or a fungus, that breaks down the bodies of dead plants and animals into simpler substances usable by green plants. These organisms mineralize organic matter.
Decreaser Plant Species (Decreaser)
Plant species of the original vegetation that will decrease in relative amount with continued overuse, e.g., grazing.
Deep Chiseling
Deep chiseling is a surface treatment that loosens compacted mine spoils. The process creates a series of parallel slots on the contour in the spoil surface that impedes water flow and markedly increases water infiltration.
Defect
Ant irregularity or imperfection in a tree, log, piece product, or lumber that reduces the volume of sound wood or lowers its durability, strength, or utility value. Defects in lumber may result from insect or fungus attacks, growth conditions and abnormalities, manufacturing or seasoning practices, etc.
Deferred Grazing
see Grazing, Deferred Rotation.
Degradation
Any significant reduction in the fertility of a soil. Also, general lowering of land surfaces by erosion.
DEIS
Abbreviation for Draft Environmental Impact Statement.
Delphi Method
A technique which allows people to arrive at a consensus about an issue of interest. It consists of a series of repeated interrogations, usually by means of questionnaires, of individuals whose opinions or judgments are of interest. After the initial interrogation of each individual, each subsequent interrogation is accompanied by information about the preceding round of replies. Each participant is thus encouraged to reconsider and, if appropriate, change his or her previous reply in light of the replies of other members of the group.
Demand
Estimates of the quantity of various outputs the public wants and would use relative to specific geographic areas. The amount of an output that users are willing to take at a specified price, time period, and condition of sale. The quantity of a service or commodity needed to meet the requirements of the user.
Demand Analysis
A study of the factors affecting the demand schedule for an output, including the price-quantity relationship, if applicable.
Demand Schedule
The relationship between price and quantity demanded. The demand schedule expresses how much of the good or service would be bought or consumed at various prices at a particular point in time.
Demand Species
Native and desired non-native species with high social, cultural, or economic values.
Demand Trends
The expected future need or desire for outputs, services, and uses.
Demography
The study and description of human population structure and dynamics.
Den
A rain proof, weather-tight cavity in a tree or a space dug by animals among rocks or in soil.
Dendrology
Study of the identification, habits, and distribution of trees.
Den Tree
A tree having one or more weather-tight cavities in its trunk or major limbs. The cavity serves as denning or escape cover for animals.
Density
The actual number of individuals of a defined group occurring in a specified unit of space and time.
Density-Dependent Factors
Any environmental factor that is dependent on populations density to be very effective. Example: Floods kill all animals in an area (assumed 100%). It is density independent. Some diseases kill many or few animals, dependent on the contagion and stresses related to the number of animals present.
Density, Stand
Number of individual plants of interest per unit of area, commonly expressed for forests as numbers of trees or stems per acre.
Den Tree
A tree with hollow spaces used by mammals as resting or nesting space.(Not a tree with only a leaf nest.)
Departure (Schedule)
A schedule which deviates from the principle of non-declining flow by exhibiting a planned decrease in the timber sale and harvest schedule at any time in the future. A departure can be characterized as a temporary increase, usually in the beginning decade(s) of the planning period, over the base sale schedule that would otherwise be established, without impairing the future attainment of a forest's long-term sustained yield capacity.
Depletion
Changes in the time distribution of physical rates of use (usually use exceeds replenishment). The redistribution of use is in the direction of the present, i.e., more use (or emphasis on availability of use) of a resource is to be made for times closer to the present than on use later.
Derived Demand
The demand (schedule) for a commodity that grows out of the desire to satisfy the demand for some other commodity. The demand for housing, for example, may create a demand for lumber, bricks, and many other things needed to build houses.
Design
The description (verbal, graphic, model, etc.) which shapes, limits, and controls the physical development and changes that will occur in time and space. Design sets the general guidelines for the character of development. Individual project level design sets the precise character, pattern and form of the project environment.
Designated Right-of-Way (ROW) Corridor
A parcel of land with specific boundaries identified by law, Secretarial Order, the land use planning process, or by some other management decision as being a preferred location for existing and future ROW facilities. The corridor may be suitable to accommodate more than one type of ROW use or facility or one or more ROW uses or facilities that are similar, identical, or compatible. A Designated corridor may already be occupied by existing utility facilities. It has been adequately analyzed to providefor a high degree of assurance that, in being identified as a "Designated corridor," it can accommodate at least one new additional utility facility.
Desirable Plant Species
Rangeland plant species of moderate to high palatability that are preferred by animals or beneficial in soil and water conservation.
Desired Condition
A statement describing a common vision for a specific area of land or type of land within the plan area. Desired conditions are aspirations and are not commitments or final decisions. Statements of desired conditions include the estimated time required for their achievement.They may be achievable only over a long time period. The social, economic, and ecological attributes toward which management of the land and resources of the plan area is to be directed. They also take into account the range of natural variability typical for the landscape, the uncertainty of natural disturbances, the effects of past management, the unique features or opportunities that forests and grasslands can contribute, and the human desires and possible uses of the land.
Desired Non-native Species
Those species of plants or animals that are not indigenous to an area but which represent a significant, and usually remnant segment of a gene pool.
Detention Storage
Surface runoff which is temporarily present in ground surface irregularities (or even on level surfaces) while it evaporates or flows overland toward stream channels.
Detergents
A term applied to a wide variety of cleansing agents used to wash clothes, dishes, and other articles. Generally, organic materials that are surfactants in aqueous solutions.
Detritivore (Detrivore)
An organism (plant or animal) that feeds on organic remains or organic (mostly plant) debris.
Developed Camping
The act of camping (or the site itself) in a site equipped with tent pad or clearing, garbage disposal, fireplace ring, picnic table, toilet facilities, and a water supply.
Developed Recreation
Recreation that requires facilities that result in concentrated use of an area. Examples of development are areas such as campgrounds and ski areas. Facilities might include: roads, parking lots, picnic tables, toilets, drinking water, ski lifts, and buildings.
Developer
Any person or persons who directly or indirectly, through any formal or informal combination or aggregation, own or control a tract or tracts of land for which such person or persons propose a project. "Person" includes any individual, partnership, corporation, association, unincorporated organization, trust, estate, or any other legal or commercial entity, except Federal, state or local government agencies. Specifying the developer as financially responsive makes certain that individuals cannot establish dummy corporations, trusts, or otherwise organize in a manner to avoid the size and time period limitations of the definition of projects (such as using an organization to hide two separate tracts comprising more than 25, but less than 50, units; selling or developing two such tracts which are functionally interrelated but separated by a short distance; selling or developing one such tract, waiting a few years, and developing a second tract).
Development
A built-up or intensive-use tract of land, especially used in the sense of a subdivision having the necessary utilities -- i.e., water, gas, electricity, paved areas, roads, etc. that utilizes the land only as a location, not for its natural resource properties. There may be types such as residential, commercial, or industrial.
Development, Human and Community
Activities to help people and communities to help themselves, usually with individuals and within programs directed toward improving the economy and the quality of the environment in rural areas and small towns.
Development Planning
Planning for economic growth and technological development in undeveloped regions or countries. Planning in these settings involves not only creating a strategy for resource development and allocation, but also creating the infrastructure and social institutions necessary for implementing the physical and economic features of such a plan.
Development Rights
A broad range of less-than-fee-simple ownership interests. It includes mainly various forms of the easement, a clearly defined property right. The landowner keeps the title but agrees to continue using the land as in the past, the right to develop the land resting in the holder of the easement.
Development Rights, Acquisition of
Ensures conformity of land use to a plan by purchasing for public ownership the landowner's right to use land for certain types of potential land uses -- such as subdivision housing or industry. The originating concept was that total public ownership was undesirable and typically fiscally unfeasible. The purchase of only selected property rights would be substantially less expensive than total purchase and would still allow the owner to continue making other economic uses of his or her land. In practice, public acquisition of development rights has often cost up to 95 percent of the full market value of land.
Development Rights, Transfer of
A method of separating and marketing the development rights of a property. Owners of developable property can buy rights to develop more intensively while the transferring property is preserved as open or less developed.
Development Type
Those land use types by which the formerly-open spaces of an area are prominently altered or made to appear built-up, i.e., buildings, paved areas, and other types of site alterations. (See Facilities.)
Diagrammatic Representation (Blob Diagram, Schematic Diagram)
An analytical technique in which the physical components (such as parking lots, garbage cans, picnic tables, beach etc.) in a plan are represented symbolically, usually just by their names written inside individual circles. The relationships between components then represented by lines connect those that have necessary or desirable support functions. The individual components are then shifted to minimize the extent to which different interconnecting lines cross each other. The resulting solution is assumed to represent the most efficient spatial relationship between project components, and thus represent idealized goal of the actual physical plan. Often, utilized at the project or site planning level, such diagrams may be used for studying the optimal relationships between vaguely defined components of a land use plan.
Diameter at Breast Height (DBH)
The diameter of a tree measured four feet, six inches from the ground level. "Ground level" can follow a convention; either the highest point off the ground touching the stem, or the mean of the highest and low points.
Diameter Tape
A tape calibrated to measure the diameter of a tree by measuring its circumference.
DIB
Diameter inside bark, usually measured at the small end of a log.
Dimension Lumber
Hardwood dimension lumber processed so that it can be used virtually in the sizes provided in the manufacture of furniture or other products. Softwood dimension lumber is boards more than 2 inches thick but less than 5 inches thick. Such wood is used in construction and is sold by units such as 2x4s, 4x8s, or 2x10s.
Direct Effect (Primary Effect)
A condition caused by an action or inaction without an intermediary causal agent; an effect characterized by a close causal relationship.
Disadvantaged Groups
Lacking in the basic resources or conditions (as standard housing, medical and educational facilities, civil rights) believed to be necessary for an equal position in society. Once "poor" and "underprivileged", the phrase covers more than the economic conditions associated with "poor" and does not have the implication of social or economic oppression contained in "underprivileged."
Discharge
The volume of water flowing past a point per unit time, commonly expressed as cubic feet per second (cfs), million gallons per day, gallons per minute, or cubic meters per second.
Discharge, Thermal
Commonly a discharge of heat energy from an industrial facility, usually in the form of heated air or water as a byproduct of operations.
Discing
Land preparation for crops or reforestation by pulling a harrow with large discs over a site; a type of earth scarification and competing plant removal.
Discount Rate
The interest rate used in formulating plans and evaluating the results of discounting future benefits and computing costs, or otherwise converting benefits and costs to a common time basis. It represents the cost or time value of money in determining present value of future costs and benefits.
Discounted Benefits
Total dollar benefits produced over a given period of time discounted to the present and expressed in current dollars.
Discounted Costs
Total dollar costs accrued over a given period of time discounted to the present and expressed in current dollars.
Discounting
An adjustment, using a discount rate for the values of money over time so that costs and benefits occurring in the future are reduced to a common point in time, usually the present, for comparison. The practice of placing a lesser value (economic or other) on future events than on present events for the purpose of comparison. An item received today is seen to be worth more than an identical item received next year. Discounting refers only to the timing of an event and should not be confused with reduced values based on the uncertainty of future events or on implied quality changes over time.
Disjointed Incrementalism
See Incrementalism.
Dispersed Recreation
Certain outdoor recreation activities that take place without facilities. Includes hiking, backpacking, hunting, fishing, snowmobiling, cross-country skiing, and driving for pleasure. Dispersed areas include general undeveloped areas, roads, trails, and water areas not treated as developed sites.
Dispersed Use
Recreation activities generally associated with low-density use that takes place throughout the entire forest such as hunting, fishing, hiking, etc.
Dispersion
(1)The pattern or distribution of organisms in space, (2) the movement of organisms in space from a point, (3) the movement of organisms in time, (4) a condition following such acts.
Dissolved Oxygen (DO)
DO in water is expressed in milligrams per liter and the amount present reflects chemical, physical, and biological activities in the water body. It can only be increased by aeration and the photosynthetic processes of aquatic plants.
Dissolved Oxygen Concentration (Dissolved Oxygen Level, DOL)
The amount of oxygen dissolved in a water sample expressed in parts per million. In unpolluted water, dissolved oxygen is usually present in amounts of 10 parts per million or less. Adequate dissolved oxygen is necessary for the life of fish and most other aquatic organisms. About 3 to 5 parts per million is the lower limit needed for the support of fish life over a long period of time.
Dissolved Solids
The total amount of solid matter (mainly inorganic salts) that remains after a filtered volume of water has been evaporated. The amount of residue of organic and inorganic matter is commonly expressed as a proportion of the original sample in parts per million parts of the original.
Distance Zones
Areas of landscapes denoted by specified distances from the observer. Used as a frame of reference in which to describe landscape characteristics or activities of people and described as foreground (fg), middle ground (mg), or background (bg).
Distinctive (Variety Class A)
Unusual and/or outstanding landscape varieties that stand out from the common features in the character type.
Disturbance Processes
Actions, functions, or events that influence or maintain the structure, composition, or function of the terrestrial or aquatic components of ecosystems. Natural disturbances include, among others, drought, floods, -wind, fires, insects, and pathogens. Human-caused disturbances include actions such as recreational use, livestock grazing, mining, road construction, timber harvest, land-use development, and the introduction of exotic species.
Disturbed Land
Terrestrial surface which has been altered --either physically, biologically, or chemically-- by the action of people, e.g., land on which excavation has occurred or upon which overburden has been deposited, or both.
Diurnal
Active during the day (as are many birds).
Diversion
Taking significant quantities of water from a stream or other body of water into a canal, pipe, or other conduit. Applies to groundwater stations when pumping is significant.
Diversion Ditch
A channel with a supporting ridge on the lower sside constructed across a slope to intercept surface water.
Diversity
(1) The distribution and abundance of different plant and animal communities and species within the area covered by a land and resource management plan. (2) The relative degree of abundance of wildlife species, plant species, communities, habitats, or habitat features per unit of area. (3) The total range in kinds and numbers of species potentially related in a defined area. (4) A numerical index which incorporates the total number of species in a biotic community and some rating of the relative importance (numbers, biomass, productivity, etc.) of individual species. Two commonly used indices are the Simpson and Shannon-Weiner indexes. See Biodiversity.
Diversity of Plant and Animal Communities
The distribution and relative abundance or extent of plant and animal communities and their component species, including tree species, occurring within an area.(USFS 2005) See Ecological Composition.
Dominance, Ecological
The condition in communities or in vegetation strata in which one or more species, by means of their numbers, coverage, or size, have considerable influence or control upon the conditions of existence of associated species.
Dominance, Social
The determination of the behavior of one or ore animals by the aggressive behavior or otherwise of other individuals, resulting in establishing a social hierarchy.
Dominant
The land against which an easement or privilege exists is called the servient tenement and the estate to which it is annexed is the dominant tenement and their owners are called respectively servient and dominant owner. A dominant plant typically receives the greatest amount of sunlight in a community. It is usually the most visually conspicuous plant but other characteristics or traits may make "greatest influence" the meaning.
Dominant Use
A concept in which land and water resources are classified and managed for one main type of use. Other uses may or may not be excluded but are always of secondary importance to the optimum development for the dominant use.
Dominant Use Management
Management based on the idea that although land may be capable of many uses, it will provide for one use better than any other. The land is managed for the single purpose of maximizing that use to the exclusion of other uses where conflicts exist. Devoting each land unit to its best use is assumed to be the most efficient allocation of resources. This assumption has been shown to be erroneous by "operations research", procedures, among others. Dominant use management is prohibited on the National Forests and elsewhere under "Multiple Use" legislation.
Dormant Seedling
Seedlings that have ceased visible growth due to high or low temperature, moisture, or other causes.
Doyle Rule
See Log Rules.
Dragline
An excavating machine that utilizes a bucket operated and suspended by means of lines or cables, one of which hoists or lowers the bucket from a boom; the other cable, from which the name is derived, allows the bucket to swing out from the machine or to be dragged toward the machine for loading.
Drain
A small artificial watercourse designed to drain swampy areas or irrigated lands. Theoretically, it is actually a small canal, but it is referred to as a "drain" in many localities.
Drainage Area
The drainage area of a stream at the specific location of the site is that area, measured in a horizontal plane, enclosed by a topographic divide from which direct surface runoff from precipitation would normally drain by gravity into the stream above the site.
Drainage Basin
The area from which water is carried off by a drainage system, a watershed, or a catchment area.
Drainage Density
Stream Length / Area, e.g., 2400 m / 100 ha. in a watershed or map area, i.e., kilometer of stream or river per square kilometer
Driller's Log
Description by a well driller of the geologic materials penetrated from the land surface to the greatest depth of a well.
Duff
Forest litter and other organic debris in various stages of decomposition on top of the mineral soil, typical of conifer forests in cool climates where rate of decomposition is slow and litter accumulation excedes decay.
Durability (Environmental Durability)
The relative ability of resources to tolerate sustained use, without degradation or destruction of the resource base (i.e., lowering productivity or desirable resource quality). This ability is sometimes rated on a qualitative scale extending from "fragile" to "durable". Durability in land use planning refers to those resource types or the evaluation process considers properties that are resistant to degradation in the presence of whatever types. For example, vegetated dunes may be classed as "environmentally fragile" for off-road vehicle uses while unvegetated dunes are "environmentally durable".
Dynamic Programming
A multistage decision process that systematically searches out a sequence of decisions which maximizes or minimizes some predefined objective function. The method is based on Bellman's Principle of Optimality which states that "an optimal policy has the property that whatever the initial state and initial decision are, the remaining decisions must constitute an optimal policy with regard to the state resulting from the first decision."
Dynamics, Population
Description of the change in abundance and structure of plnt or animal populations resulting from births, deaths, migrations, and related rate phenomena.
Dystrophic
Pertaining to lakes with brown water, high humic material and organic matter content, low nutrient availability, poor bottom fauna, and high oxygen demand; oxygen is continually depleted and pH is low. In lake aging, the "age" between a eutrophic lake and a swamp. See Oligotrophic.


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Last revision January 17, 2000.