Glossary

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V

Vadose Zone
The layer(s) of soil or rock between the base of a waste disposal site and the underlying water table or aquifer..
Valid Existing Rights
Those rights which existed prior to the date of enactment of an Act, whereby the application of any of the prohibitions contained in the Act to the property interest would effect a taking of that property, which would entitle the party to compensation under the fifth and fourteenth amendments to the U. S. Constitution.
Valid Mining Claim
See Mining Claim, Valid.
Value Added
For a given enterprise, the market value of products or goods completed, less the cost of materials purchased from others.
Value Judgement
A subjective opinion about the worth (e.g., good, evil, beauty) of a thing, action, or entity (even when evaluators state their lack of prejudice).
Values (Value System)
The particular (frequently subjective) positive point of view of an individual or the common point of view of a group on an issue, way of life, or concerning the worth of things or experiences. Values may range from those that are subjectively meaningful to a given individual to those that are shared cultural norms. They influence the selection of the means and ends of actions, and they serve as criteria by which objects or actions are evaluated.
Variable
(1) A quantity which may take any one of a specified set of values. It is convenient to apply the same word to denote non-measurable characteristics, e.g. "sex" is a variable in this sense since any human individual may take one of two "values," male or female. It is useful, but far from being the general practice, to distinguish between a variable as so defined and a random variable or variate. (2) Any structural element in an ecosystem that varies over time, also "component." (3)A condition of a system in which elements or a performance measure take different values.
Variable, Driving
Independent or extrinsic variables that cause the system to change, but themselves are not affected by the system.
Variable, Rate Process
A variable in a simulation model which describes the physical movement of materials between state variables and which is zero when the system is at rest.
Variable, State
An interactive component of a system that varies over time and the value of which at each point in time reflects the condition or "state" of that variable. When applied within systems ecology, the term refers to an ecosystem component the state of which both influences and is influenced by the conditions of other state variables in that system. Ecosystem state variables interact with each other through abiotic or biotic feedback mechanisms.
Variance (Zoning Variance)
A license to act contrary to the usual rule. The granting of relief from the terms or conditions of a building or zoning law by a public agency vested with the power to authorize it. It may be given when the application of the law creates unnecessary hardship; where equally safe methods or materials may be used; where there are practical difficulties in meeting the existing requirements literally; or where the deviation or exception would not affect substantial compliance with the regulations and not threaten health or safety.
Variety Class
A particular level of visual variety or diversity of landscape character, described as Distinctive (Class A), Common (Class B), or Minimal (Class C).
Vegetation Cover Type
See Cover Type.
Vegetation Management
Management actions that change the composition or structure of plant communities including, but not limited to timber harvest, mining, livestock grazing, and fire.(USFS 1999)
Vegetation Type
A plant community, assemblage, or aggregation with distinguishable characteristics.
Vegetative Manipulation
Changing one vegetation type to another. It can be done by mechanical means, chemical, grazing, or fire. Usually, this is done to increase forage for livestock and can be a beneficial tool for wildlife.
Veneer
Thin sheets of wood (usually less than 1/4" thick) produced by slicing or peeling a log.
Veneer Log
A log of high quality and desirable species suitable for conversion to veneer. Logs must be large, straight, of minimum taper, and free from defects.
Vertebrates
Animals with backbones or spinal columns. Examples include people, fish, and amphibians.
Vertical Diversity
The diversity in an area that results from the complexity of the above ground structure of the vegetation. The more tiers of vegetation or the more diverse the species make-up, or both, the higher the degree of vertical diversity.
Viability
A population of sufficient numbers and reproductive potential to maintain its existence over time in spite of normal fluctuations in population levels.
Viable Populations
A wildlife or fish population of sufficient size and reproductive potential to maintain its existence over time in spite of normal fluctuations in population levels.
Virgin Forest
A natural, usually-mature forest never harvested and virtually uninfluenced by human activity. Also called "ancient" and "old-growth", these have the characteristic of little of no perceived human influence.
Viruses
A class of ultramicroscopic, filterable, infectious agents, chiefly protein, which are typically inert except when in contact with certain living cells.
VIS (Visitor Information Service)
A service provided to the public in which the public is supplied with information regarding opportunities or activities on the land; usually but not restricted to recreational opportunities.
Visible Area
The ground or vegetation thereon that can be directly seen from a given lookout point under favorable atmospheric conditions.
Visit
Presence of one person upon a site (e.g., a National Wildlife Refuge.)
Visitor Day
The use of an area for a total of 12 person-hours by one or more people, either continuously, or simultaneously or spread over several visits. (MVD - Thousand visitor days)
Visitor Opportunities
The spectrum of settings, landscapes, scenery, facilities, services, access points, information, learning-based recreation, wildlife, natural features, cultural and heritage sites, etc. available for National Forest System visitors to use and enjoy (36 CFR 219.16).
Vista
A point or area along a route of travel which affords a panoramic, unusual, or highly pleasant view.
Visual Absorption Capacity
The relative difficulty or cost of achieving VQO's. It measures the land's capacity to absorb the visual impact of management activities.
Visual Character Subtype
Areas of significant size and visual difference within visual character type units, e.g., steep mountain lands, foothill lands, rolling plateau lands. "Visual character subtypes" are delineated when a larger "visual character type" unit is too broad or has too great a visual character diversity to provide a logical frame of reference to classify usefully physical features.
Visual Character Type
A large area of land that has common distinguishing visual characteristics of landform, rock formations, water bodies, and vegetation patterns. The "visual character type" concept and the types of land units it produces should be about the same as morphological region and physiographic regions. "Visual character type" units are used as a frame of reference for classifying the physical features of a given area as to their degree of scenic quality.
Visual Distance Zones
Areas of landscapes denoted by specified distances from the observer. Used as a frame of reference, in which to discuss landscape characteristics or activities of man. The three zones are foreground (fg), middleground (mg), and background (bg).
Visual Impact
The effect management activities have upon scenic or aesthetic quality.
Visual Landscape
A landscape that, due to its juxtaposition with areas of human use, is vulnerable to critical observation by various segments of the public.
Visual Landscape Character (Characteristic Landscape)
The overall impression created by a landscape's unique combination of visual features (such as land, vegetation, water, structures) as seen in terms of form, line, color and texture. The naturally established landscape being viewed as visually represented by the basic vegetative patterns, landforms, rock formations and water forms that are in view.
Visual Management Program
Also referred to as "Landscape Management" or "Visual Resource Management"; planning and administering the use of forest lands in such ways that the visual effects maintain or upgrade people's psychological welfare. It is the planning and design of the visual aspects of multiple-use land management.
Visual Management System
A logical and orderly method developed by the Forest Service to assess the visual resource on National Forest System lands in terms of measurable objectives for specific land areas, to estimate the magnitude of the effort required to attain those objectives, and to measure accomplishment as the land management plan is implemented.
Visual Quality Objective
A set of measurable goals for the management of forest visual resources. The stated goals of this visual management system are: (1) preservation, (2) retention, (3) partial retention, (4) modification, and (5) maximum modification. Except for "preservation", each goal describes a different degree of acceptable alteration of the natural landscape based upon the importance of aesthetics. "Preservation" allows only natural ecological changes. "Retention" allows management activities which are not visually evident. "Partial retention" allows management activities which are visually subordinate to the characteristic visual landscape. "Modification" allows management activities that may visually dominate the original "characteristic visual landscape", but, when vegetation and land forms are altered, which must use the form, line, color, texture and/or scale of that landscape for its visual characteristics. "Maximum modification" allows vegetation and landform altering management activities that dominate the "characteristic visual landscape" in the foreground and middleground but which have the same visual characteristics as the surrounding area when seen as background. Two additional short-term management goals may be required. The first, "rehabilitation", is used to upgrade landscapes containing visual impacts that do not meet the quality objectives set for that particular area. The second, "enhancement", is for landscapes having a potential for greater natural-appearing variety. Once one of the short-term goals is attained, one of the five quality goals is then applied.
Visual Resource
The composite of basic terrain, geologic features, water features, vegetative patterns, and land use effects that typify a land unit and influence the visual appeal that the unit may have for visitors.
Visual Sensitivity Level (Sensitivity Level)
A three-level rating system used to delineate areas receiving different amounts of exposure (present or potential) to user groups with differing attitudes towards changes in scenic quality (such as might occur as a result of management activities). The system initially classifies all travel routes, special interest areas and water bodies into areas of primary and secondary aesthetic management importance on the basis of their national importance, number of users, duration of use and area size. The system next uses the assumptions that aesthetic quality will be of major concern to recreational users and minor concern to functional users of forest areas (such as daily commuters and loggers) as the other basis for classifying the entire planning area into the three sensitivity levels.
Visual Variety Class (Variety Class)
A classification system for establishing three visual landscape categories according to the relative importance of the visual features i.e., landforms, vegetation patterns, stream or lake water forms and rock formations. The class A ("distinctive") category contains those landscape features of unusual or outstanding visual quality, and, that are usually not common in the visual character type or visual character subtype. The class B ("common") category contains those landscape features which tend to be common throughout the visual character type or subtype and thus are not of outstanding visual quality. The class C ("minimal") category contains those areas with few distinguishing landscape features -- including all areas not classed as A or B. This classification system is based on the premise that all landscapes have some visual values, but that those with the most variety or diversity of visual features have the greatest potential for being or attaining high scenic value.
Visual Vulnerability
The degree to which human-caused changes might be seen in the landscape and their potential for degrading scenic quality in essence, the landscape's resistance (or susceptibility) to visual changes.
Volume
The amount of wood in a tree or stand according to some unit of measurement, (board feet, cubic feet, etc.) or some standand of use (pulpwood, sawtimber, etc.)
Volume Table
A table of figures used to estimate the volume of wood contained in a standing tree, based on dbh and merchantable height.
Voucher Specimen
Those specimens retained in a collection as representatives of a study, and that are presumed to be accurately identified by competent authorities. Such collections are often erroneously referred to as "type collections."


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Last revision January 17, 2000.