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Soils that are low in supply of bases and have subsurface horizons of alluvial clay accumulations. They are usually moist, but during the warm season of the year, some are dry part of the time. The particle-size class (texture) ranges mostly for sandy-loam to clayey.
Unacceptable Risk
See Risk, Unacceptable.
Unavailable Forage
Forage which cannot be grazed by livestock.
Decision making in which there is no objective basis for assigning numerical probabilities to the different possible outcomes or in which there is no way to describe the possible outcomes. Under the Bayesian school of thought the distinction between risk and "uncertainty" is not useful and in fact may not exist. In any practical analysis all uncertain situations are assigned probability distributions, either explicitly or implicitly by the selection of the analysis method, whether or not the true probability distribution known. A probability distribution is selected for analysis purposes based on experience, intuitive feelings, knowledge, and the lack of knowledge.
Unconfined Aquifer
An aquifer that has a water table; contains unconfined ground water.
Unconstrained Maximum
Level of management defined as the highest possible level of a given output along with the costs associated with achieving it.
1) In logging, the notch cut in a tree to govern the direction in which the tree is to fall and to prevent splittng. 2) In forest management, the harvesting of a quantity of timber less than the budgeted cut.
Under Plant
To set out young trees or sow seed under an existing stand.
Underprivileged Groups
See Disadvantaged Groups.
(1)Placing a number of animals on a given area that will result in under-utilizing the available forage by the end of the planned grazing period.(2)A stand of trees so widely spaced that, even with full growth potential realized, crown closure will not occur. Understocking indicates a waste of resources, for certain purposes since the site is not fully occupied.
The lesser vegetation (shrubs, seedlings, saplings, small trees) within a forest stand which forms a layer between the overstory, the upper portions of adjacent trees and other woody growth, and the herbaceous plants of the forest floor.
Undesirable Species
Plant species that are not desirable because they are unpalatable or low in palatability, injurious to animals, poisonous, poor stabilizers of soil and water, etc.
Uneven-Aged Management
Applying a combination of actions simultaneously to maintain continuous high-forest cover, recurring regeneration of desirable species, and the orderly growth and development of trees through a range of diameter or age classes to provide a sustained yield of forest products. Specifying the number or proportion of trees of particular sizes to retain within each area, thereby maintaining a planned distribution of size classes usually regulates cutting. Cutting methods that develop and maintain uneven-aged stands are single-tree selection and group selection.
Uneven-aged Stand (All-aged Stand)
A forest stand composed of trees that differ markedly in age and sizes growing together on a uniform site. By convention, a minimum range of 10 to 20 years is generally accepted, though with rotations of less than 100 years, 25 percent of the rotation period may be the minimum.
Unique Resource (Irreplaceable Asset)
A resource not duplicated anywhere. A resource for which no equal (although different) resource in kind or excellence exists. Three classes of "irreplaceable" assets: One would be "gifts of individual genius" such as the work of Leonardo da Vinci or Rembrandt. A second might be called "gifts of collective genius", represented by the cultural antiquities of Egypt, Greece, and Rome, among others. Finally, we have the "gifts of nature", namely the accidents of geomorphology, biological evolution, and ecological succession. These natural endowments differ among (1) the factors of production, that are transformed through some production technology into other goods in process or into final consumption goods, (2) and natural endowments that give rise to stimuli eliciting satisfaction in an ultimate consumption of final good sense. If a natural resource is used as a good in process, technology may provide a wide spectrum of substitutes for the particular input without significantly altering the final product either in appearance or performance.
Unit Planning
The activity of developing a comprehensive general long-range plan for a planning unit.
See Planning Unit.
Universal Soil Loss Equation
See Soil Loss Equation.
Unpalatable Species
Species that are not readily eaten by animals.
Unplanned Ignition
A fire started at random by either natural or human causes, or on purpose by an arsonist.
Unregulated Land - (Pre-1980 Terminology)
Forest land that is suitable and available, but not organized for timber production under sustained yield principles; where timber harvest is permissible but not a goal of management.
This includes portions of the commercial forestland that will not be organized for regular periodic timber production under sustained yield principles. See also Unsuitable Forest Land.
Unregulated Acres
Commercial forestland not organized for sustained yield production of wood. A timber harvest may be produced in conjunction with the areas primary need. Recreation areas and their buffer zones and administrative sites are included in this category.
Unroaded Areas
Any areas without the presence of a classified road (a road at least 50 inches wide and constructed or maintained for vehicle use). The size of the area must be sufficient and in a manageable configuration to protect the inherent values associated with the unroaded condition. Unroaded areas do not overlap with Designated roadless areas.
Unsaturated Zone
The zone between the land surface and the water table, containing water held by capillary forces, and containing air or gases generally under atmospheric pressure.
Unsuitable Forest Land
Forest land that is not managed for timber production because: (1) the land has been withdrawn by Congress, Secretary, or Chief; (2) the land is not producing or capable of producing crops of wood; (3) technology is not available to prevent irreversible damage to soils, productivity, or watershed conditions; (4) there is no reasonable assurance that lands can be adequately restocked within 5 years after final harvest based on existing technology and knowledge; (5) there is, at present, a lack of adequate information to responses to timber management activities; or (6) timber management is inconsistent with or not cost efficient in meeting the management requirements and multiple use objectives specified in the plan.
Unsuitable Range
See Range, Unsuitable.
Urban and Built-up Land and (Urban and Built-up Areas)
Cities, villages, and built-up areas of more than 10 acres; industrial sites (except strip mines, borrow and gravel pits); railroad yards; cemeteries; air ports; golf courses; shooting ranges; institutional and public administration sites; and similar kinds of areas. Road and railroad acreage is included, and intermingled Federal acreage may be included. Farmland acreage inside city and village limits is not included. The "urban and built-up land" category takes precedence over others when the criteria for more than one category are met. Thus, residential areas that have sufficient tree cover to meet forestland criteria may be placed in the residential category.
Urban Forest
All trees and associated plants and animal species that live in cities. It includes single tree streets, yards, vacant lots, and landscaped areas as well as forested areas. It may include non-tree areas like roads, trails, and ponds. (From, P. Jahnige, 2002:97)
Urban Forestry
(1) The practice of forestry in an urbanized environment; (2) A specialized branch of forestry that has as its objective cultivating and managing trees in urban areas and the evaluating their contribution to the physiological, sociological, psychological (and sometimes economic) well-being of urban society.
Urban Land
(1) Areas within the legal boundaries of cities and towns; suburban areas developed for residential, industrial, or recreational purposes. (2) An area so altered or obstructed by urban works or structures that identification of soils is not feasible. (3) A miscellaneous land type mapping unit.
Urban Planning (City Planning)
A distinction is sometimes made between "city planning" (planning activities that take place within or at the level of a specific city boundary) and "urban planning" (planning for areas which are in predominantly urban uses but which are larger in extent than a single city's boundaries.)
Urban ROS Class
A classification of the Recreation Opportunity Spectrum in which the natural setting is dominated by human-made structures and the sights and sounds of people predominate.
Urban Sprawl
The irregular and often poorly planned spreading of urban development into adjoining land areas. Many suburban residential developments are examples of urban sprawl.
Urbanized Area
Such areas consists of a central city, or cities, and surrounding closely settled territory. The specific criteria for the delineation of an urbanized area are as follows: (1) a central city of 50,000 inhabitants or more; or twin cities (i.e., cities with contiguous boundaries and constituting, for general social and economic purposes, a single community) with a combined population of at least 50,000. (2) Surrounding closely settled territory, including incorporated places of 2,500 inhabitants or more; or, incorporated places with fewer than 2,500 inhabitants, provided that each has a closely settled area of 100 housing units or more; or, parcels of land normally less than one square mile in area having a population density of 1,000 inhabitants or more per square mile. An urbanized area is sometimes divided into the "central city (or cities)" and those in the remainder of the area or the "urban fringe." The central city category consists of the cities, having 250,000 inhabitants or more, named in the title of the urbanized area. The urbanized area can be characterized as the physical city as distinguished from both the legal city and the metropolitan community. Generally, urbanized areas are smaller than and in most cases are contained in standard metropolitan statistical areas (SMSA). However, in a few instances, the fact that political lines, and those of urbanized areas determine the boundaries of SMSA's by the pat tern of urban land use, means that there are small segments of urbanized areas that lie outside SMSA's. In general, then, urbanized areas represent the thickly settled core of the SMSA's, with the exceptions noted above.
Use (Utilization)
Range management usage. The proportion of the current year's forage production that is consumed or destroyed by grazing animals. Range grazing, bedding, shelter, trailing, watering, etc.
Use (Allowable)
The degree of use estimated to be proper until proper use is known. Forty or fifty percent of the annual forage growth (by weight) is often used as a rule-of-thumb on ranges in good or excellent condition that allows the amount of forage accelerated range rehabilitation.
Use (Capability)
The first of G.A. Hills' three-level system for land evaluation. The process begins with evaluating for "use capability" based upon inherent usability potentials, then to "use suitability" on the basis of management level potentials, and finally to "use feasibility" evaluation on the basis of usability under present and forecasted socio-economic conditions.
Use (Degree Of)
Utilization or consumption of weight of plant growth expressed in qualitative terms e.g., unused, slight, moderate, full, close, severe, over, extreme, destructive, etc., or as percent of weight for either an individual plant or the vegetation as a whole.
Use (District)
A section of a city Designated by a zoning ordinance that prescribes the use of its land and the type and characteristics of the structures that may be placed on it. The most common form of zoning in the United States is that in which "use districts" are Designated (e.g., light manufacturing, commercial, single-family residential) and only the permitted use or a "higher" one is allowed. Thus in an area zoned for heavy industry, all other uses would theoretically be permitted (though there are some exceptions to this under the principle of exclusive zoning), whereas in an area of single-family residences, no other uses are likely to be permitted.
Use (Factor)
An index to the grazing use that is made of forage species, based on a system of range management that will maintain the economically important forage species.
Use Feasibility (Feasibility)
Evaluating land based on usability under present and forecasted socio-economic conditions.
Use (Full)
Maximum use that can be made of a range during a grazing season without inducing a downward trend in range condition.
Use, Non- (Non-utilization)
Lack of exercising (temporarily) of a grazing privilege on grazing lands (without loss of preference for future consideration.)
Use (Nonconforming)
A building or use that is inconsistent with a use district's zoning regulations. If erected after the enactment of the ordinance it may be ordered removed. If it is in being before the enactment, it may continue in use, but a new nonconforming or different nonconforming use may not be substituted. Its extension or enlargement is not permissible. Many ordinances permit rebuilding the nonconforming premises when destroyed by fire. Once the use is abandoned, however, the right to its restoration falls, and the future use of the premises must conform to the zoning. Some states allow for the abatement of such uses at the end of a prescribed and usually lengthy period of time.
Use (Over)
Utilizing an excessive amount of the current year's growth which, if continued, will result in range deterioration or over grazing.
Use (Pre-existing)
A land use that does not conform to a zoning ordinance but that existed before the enactment and that therefore may not be banned until its abandonment. Sometimes the "pre-existing use", if a nuisance, can be abated by court action. In some jurisdictions "pre-existing uses" have been banned after the lapse of a reasonable period equivalent to a prescribed "depreciation period" or amortization of its use by time zoning.
Use (Proper Utilization)
The degree and time of use of current year's range growth which, if continued, will either maintain or improve the range condition consistent with conservation of other natural resources.
Use (Suitability)
Classification based upon the degree to which a unit, in its present condition, can respond to specific management practices. In land evaluation, the process begins with evaluating "use capability" based upon inherent usability potentials, then to evaluating "use suitability" on the basis of management level potentials, and finally to evaluating "use feasibility" on the basis of usability under present and forecasted socioeconomic conditions.
User Costs
Values that users of a good or output pays to gain access or be able to use a good or service. Such costs include transportation costs, concession fees, and similar payments to other than the resource owner.
U.S. Geological Survey, U.S. Department of Interior.
A political philosophy based on the principle of "the greatest good of the greatest number". Public objective assessment of utility is possible.
The usefulness or satisfaction-causing qualities of a good or service.
Utility Corridor
A tract of land of varying width forming a passageway through which various commodities such as oil, gas, and electricity are transported.
Utility Theory
A theory of valuation using some measure of individual preferences or intrinsic usefulness and satisfaction. The valuation can occur either in cardinal units of utility (called utils) or as a comparison to other available goods given by indifference curves. An indifference curve delineates of all combinations of two goods with which an individual would be equally pleased (i.e., the area of indifferent between them). In attempting to place a value on goods that are not traded in the marketplace, proxy values can be derived by developing indifference curves between the non-market good and a good with a well-established price. In choosing among alternatives where the outcome of each alternative is uncertain, each possible outcome is weighted by its probability of occurrence. A cardinal value of the outcome of each alternative is the expected utility. The alternative with the highest expected utility is typically chosen.

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Last revision January 17, 2000.