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Net Change in Acreage of Prime Farmland used as Forest Land, 1982 - 1997

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Description

This dot density map shows the general distribution of areas where there were net gains or losses in acreage of prime farmland used as Forest Land from 1982 to 1997 within each 8- digit hydrologic unit. Each red dot represents a net loss of 2,000 acres of prime farmland used as Forest Land. This loss may be due either to loss of prime farmland or to conversion of prime farmland to a non-Forest Land use. Each green dot represents a net gain of 2,000 acres of prime farmland used as Forest Land. This gain may be either new prime farmland or prime farmland that was previously not used as Forest Land. Dots were aggregated by and placed randomly within 8-digit hydrologic units. Areas with 95% or more Federal area are shaded gray. There was an increase of 3.3 million acres, a decrease of 1.4 million acres, for a net increase of 1.9 million acres.

Cautions for this Product:
Note that either a change in the amount of prime farmland or a change in how prime farmland is used will change the amount of prime farmland that is used as Forest Land. This map does not show the source 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]

Forest land:
A Land Cover/Use that is at least 10 percent stocked by single stemmed forest trees of any size which will be at least 4 meters (13 feet) tall at maturity. When viewed vertically, canopy cover is 25 percent or greater. Also included are areas bearing evidence of natural regeneration of tree cover (cutover forest or abandoned farmland) and not currently developed for nonforest use. For classification as forest land, an area must be at least one acre and 100 feet wide. [NRI-97]

Hydrologic units:
A hierarchical system developed by the U.S. Geological Survey that divides the United States and the Caribbean into 21 major regions, 222 subregions, 352 accounting units, and further subdivided into 2,150 cataloging units that delineate river basins having drainage areas usually greater than 700 square miles. [USGS]

Prime farmland:
Land that has the best combination of physical and chemical characteristics for producing food, feed, forage, fiber, and oilseed crops and is also available for these uses. It has the soil quality, growing season, and moisture supply needed to produce economically sustained high yields of crops when treated and managed according to acceptable farming methods, including water management. In general, prime farmlands have an adequate and dependable water supply from precipitation or irrigation, a favorable temperature and growing season, acceptable acidity or alkalinity, acceptable salt and sodium content, and few or no rocks. They are permeable to water and air. Prime farmlands are not excessively erodible or saturated with water for a long period of time, and they either do not flood frequently or are protected from flooding.[SSM, USDA Handbook No. 18, October 1993]

Product Information

Product ID: 6005
Production Date: 5/25/01
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.