• Allotment An area of federal lands designated for the grazing use of a designated number and kind of livestock under a specific plan of management.
  • Allowable Use The degree of utilization considered desirable and attainable on various parts of a ranch or allotment considering the present nature and condition of the resource, management objectives and level of management.
  • Animal Impact The sum total of the direct physical influences animals have on the land: trampling, dunging, urinating, salivating, rubbing, digging, etc.
  • Animal unit day The amount of dry forage consumed by one animal unit per 24-hour period. Animal unit day is used to express the quantity of forage intake for a period of time and may be extrapolated to other time periods, such as week, month, or year.
  • Annual Plant A plant that completes its life cycle and dies in 1 year or less.
  • Annual Range Range on which the principal forage plants are self-perpetuating, annual, herbaceous species.
  • Apparent Trend An interpretation of trend based on observation and professional judgment at a single point in time (see Trend).
  • Arid Applied to a climate or region where rainfall is barely sufficient to support vegetation; deficient in rainfall
  • A.U. Abbr. Animal-UnitSyn. basal cover
    Considered to be one mature cow (1000 lb, 455kg) either dry or with a calf up to 6 months of age, with an average daily forage consumption of 15 kg of dry matter. Livestock which consume more or less forage than the standard animal unit, because of kind, class, or size are rated on an animal unit equivalent (e.g. 1300 lb cow = 1.3 AU; 1 sheep = 0.1 AU)
  • Available Forage That portion of the forage production that is accessible for use by a specified kind or class of grazing animal.
  • Available Soil Moisture Water in the soil that is available for plant growth and development


  • Bare Ground All soil surface not covered by vegetation, rock or litter
  • Basal Area Cross sectional area of the stem or stems of a plant or of all plants in a stand. Herbaceous and small woody plants are measured at or near the ground level; larger woody plants are measured at breast or other designated height. (synonym - basal cover)
  • Base Property See Commensurate Property
  • Biennial A plant that lives for two years, producing vegetative growth the first year and usually blooming, fruiting, and dying in the second year. Usually grouped with annuals.
  • Biomass The total amount of living plants and animals above and below ground in an area at a given time
  • Biome A major biotic unit consisting of plant and animal communities having similarities in form and environmental conditions, such as the desert, chaparral or grassland biomes.
  • Brittle Environments Characterized by unreliable precipitation (regardless of amount), poor distribution of precipitation through the year as a whole, high rate of oxidation and physical decay (weathering) in old plant and animal material, very slow successional development from bare and smooth soil surfaces and, with a lack of adequate physical disturbance for years, the plant communities become simpler, less diversified and less stable. A continuous scale exists from nonbrittle to brittle environments.
  • Browse Leaf and twig growth of shrubs, woody vines, and trees available for use by animals. Also, to search for or consume browse.
  • Bunchgrasses Grasses that reproduce by seed and/or tillering and grow in tufts


  • JRS Journal of Rangeland Science