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Total Rangeland and Percent Change in Area, 1992 - 1997

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Description

This shaded polygon map shows the percent change in the amount of rangeland area from 1992 to 1997 within each 8 digit hydrologic unit, using 1992 as a base year. The percentages are presented in five categories based on the following divisions: an increase of more than 25%, an increase of 5% to 25%, little change (less than 5% change), a decrease of 5% to 25%, and a decrease of over 25%. The total amount of rangeland is indicated by brown dots with each dot representing 25,000 acres. There was a total of 406 million acres of rangeland in 1997, 5.2 million acres increased from 1992, 401 million acres did not change, 6.6 million acres decreased from 1992. Areas where rangeland occupy less than 5% of the total area in either year are hatched. Areas with 95% or more Federal area are shaded gray.

Cautions for this Product:
Areas with small amounts of rangeland may have very high rates of change. This map may not be used to determine site-specific information. Within an 8-digit hydrologic unit, dot counts represent acreage totals correctly plus or minus one dot to account for remainders. Data are not collected on Federal land. Data are not available for Alaska or the Pacific Basin. Data for Puerto Rico and the U.S. Virgin Islands are aggregated by 6-digit hydrologic unit.



Sources

Source: National Resources Inventory, 1997
Distributor: USDA-NRCS-RIAD
Reliability:
NRI sample data are generally reliable at the 95% confidence interval for state and certain broad substate area analyses. Generally, analyses that aggregate data points by smaller geographic areas and/or more specific criteria result in fewer data points for each aggregation and therefore less reliable estimates. NRI maps reflect national patterns rather than site- specific information.


Layers

Aggregate Layer: Cross of State with 8 Digit Hydrologic Units and Federal Land
Other Layers Displayed: States, Rivers


Definitions

Federal land:
A land ownership class designating land that is owned by the Federal Government. It does not include, for example, trust lands administered by the Bureau of Indian Affairs nor Tennessee Valley Authority (TVA) land. No data are collected for any year that land is in this ownership. [NRI-97]

Land cover/use:
A term that includes categories of land cover and categories of land use. Land cover is the vegetation or other kind of material that covers the land surface. Land use is the purpose of human activity on the land; it is usually but not always related to the land cover. The NRI uses the term (land cover/use) to identify the categories that account for all the surface area in the United States [BS-1982; NRI-97]

Rangeland:
A Land cover/use category on which the climax or potential plant cover is composed principally of native grasses, grasslike plants, forbs or shrubs suitable for grazing and browsing, and introduced forage species that are managed like rangeland. This would include areas where introduced hardy and persistent grasses, such as crested wheatgrass, are planted and such practices as deferred grazing, burning, chaining, and rotational grazing are used, with little or no chemicals or fertilizer being applied. Grasslands, savannas, many wetlands, some deserts, and tundra are considered to be rangeland. Certain communities of low forbs and shrubs, such as mesquite, chaparral, mountain shrub, and pinyon-juniper, are also included as rangeland.


Product Information

Product ID: 4977
Production Date: 12/13/00
Product Type: Map


For additional information contact the Resources Inventory and Assessment Division. Please include the Product ID you are inquiring about. nri@wdc.usda.gov or 1400 Independence Avenue SW - P.O. Box 2890 - Washington D.C. 20013. If you use our analysis products, please be aware of our disclaimer.