Appendix C - Glossary of Selected Terms

ALLUVIUM — A general term for clay, silt, sand, gravel, or similar unconsolidated detrital material deposited during comparatively recent geologic time by a stream or other body of running water as a sorted or semisorted sediment in the bed of the stream. (Bates and Jackson 1980.)

CIRQUE — A deep steep-walled half-bowl-like recess or hollow situated high on the side of a mountain and commonly at the head of a glacial valley, and produced by the erosive activity of a mountain glacier. (Bates and Jackson 1980.)

COLLUVIUM — A general term applied to any loose, heterogeneous, and incoherent mass of soil material and/or rock fragments deposited by rainwash, sheetwash, or slow continuous downslope creep, usually collecting at the base of gentle slopes or hillsides. (Bates and Jackson 1980.)

DIVISION — An ecological unit in the ecoregion planning and analysis scale of the National Hierarchical Framework corresponding to subdivisions of a Domain that have the same regional climate. (ECOMAP 1993.)

DOMAIN — An ecological unit in the ecoregion planning and analysis scale of the National Hierarchical Framework corresponding to subcontinental divisions of broad climatic similarity that are affected by latitude and global atmospheric conditions. (ECOMAP 1993.)

DRY — A classification of climate based on the Köppen System for regions where evaporation exceeds precipitation. (Bailey 1980.)

ECOREGION — A scale of planning and analysis in the National Hierarchical Framework that has broad applicability for modeling and sampling, strategic planning and assessment, and international planning.  Ecoregions include Domain, Division, and Province ecological units.

ECOSYSTEM — A complete interacting system of organisms and their environment. (Forest Service Manual 2060.)

FLOODPLAIN — The surface or strip of relatively smooth land adjacent to a river channel, constructed by the present riven in its existing regimen and covered with water when the river overflows its banks. (Bates and Jackson 1980.)

LIFE ZONES — A classification of macroclimatic conditions based on temperature and precipitation that has been widely applied in tropical environments to delineate zones dominated by vegetative communities of characteristic physiognomy and composition. (Holdridge 1967.)

MAJOR LAND RESOURCE AREA (MLRA) — A broad geographical area that has a distinct combination of climate, soil, vegetation, management needs, and kinds of crops that can be grown (USDA, Natural Resources Conservation Service, 1981).

MORAINE — A mound, ridge, or other distinct accumulation of unsorted, unstratified glacial drift, predominantly till, deposited chiefly by direct action of glacier ice, in a variety of topographic landforms that are independent of control by the surface on which the drift lies. (Bates and Jackson 1980.)

PLANT ASSOCIATION — A potential natural plant community of definite floristic composition and uniform appearance. (Forest Service Manual 2060.)

PLANT COMMUNITY — A group of one or more populations of plants in a common spatial arrangement. (Forest Service Manual 2060)

PLAYA — A term used in the southwestern U.S. for a dry, vegetation-free, flat area at the lowest part of an undrained desert basin, underlain by stratified clay, silt, or sand, and commonly by soluble salts. (Bates and Jackson 1980.)

POTENTIAL NATURAL COMMUNITY — The biotic community that would be established if all successional sequences of its ecosystem were completed without additional human-caused disturbance under present environmental conditions.  Grazing by native fauna, natural disturbances, such as drought, floods, fire, insects, and disease, are inherent in the development of potential natural communities which may include naturalized exotic species. (Forest Service Manual 2060.)

PROVINCE — An ecological unit in the ecoregion planning and analysis scale of the National Hierarchical Framework corresponding to subdivisions of a Division that conform to climatic subzones controlled mainly by continental weather patterns. (ECOMAP 1993.)

REGIONALIZATION — A mapping procedure in which a set of criteria are used to subdivide the earth’s surface into smaller, more homogeneous units that display spatial patterns related to ecosystem structure, composition, and function. (ECOMAP 1993.)

SCALE — The degree of resolution at which ecological processes, structures, and changes across space and time are observed and measured. (ECOMAP 1993.)

SECTION — An ecological unit in the subregion planning and analysis scale of the National Hierarchical Framework corresponding to subdivisions of a Province having broad areas of similar geomorphic process, stratigraphy, geologic origin, drainage networks, topography, and regional climate.  Such areas are often inferred by relating geologic maps to potential natural vegetation groupings as mapped by Kiichler (1964). (ECOMAP 1993.)

SUBREGION — A scale of planning and analysis in the National Hierarchical Framework that has applicability for strategic, multi-forest, statewide, and multi-agency analysis and assessment.  Subregions include Section and Subsection ecological units.

SUBSECTION — An ecological unit in the subregion planning and analysis scale of the National Hierarchical Framework corresponding to subdivisions of a Section into areas with similar surficial geology, lithology, geomorphic process, soil groups, subregional climate, and potential natural communities. (ECOMAP 1993.)

SUBTROPICAL — A classification of climate based on the Köppen System for regions where there are eight months or more warmer than 50° F and the coolest month is warmer than 32° F but colder than 65° F. (Bailey 1980.)

TEMPERATE — A classification of climate based on the Köppen System for regions where there are four to eight months warmer than 50° F and the coldest month is cooler than 32° F. (Bailey 1980.)

TROPICAL — A classification of climate based on the Köppen System for regions where the coolest month is warmer than 65° F (Bailey 1980).

VEGETATION SERIES — An aggregation of taxonomically related plant associations which take the name of the late seral stage species that dominate, or have the potential to dominate the principal vegetative layer in a time frame appropriate to the vegetation or taxonomic group under consideration.