Title: National Coordinated Major Land
Resource Area (MLRA) Version 5.2
Originator:
U.S. Department of Agriculture, National Soil Survey Center
Abstract:
Major land resource areas (MLRAs) are geographically
associated land resource units (LRUs). Identification of these large areas is
important in statewide agricultural planning and has value in interstate, regional,and national planning.
The United States, Caribbean and Pacific Basin Major Land Resource Areas (MLRA)
Geographic Database serves as the geospatial expression of the map products
presented and described in Agricultural Handbook 296 (2006) located at: https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_050898.pdf.
To make this handbook more useful to other Federal agencies and private parties
using ecological regions for planning or evaluation of natural resources
programs and policies, Appendix I (Agriculture Handbook 296, 2006)
cross-references MLRAs with Environmental Protection Agency Level III
Ecoregions (USEPA, 2003; Omernik, 1987) and U.S.
Forest Service ecological sections (Cleland and others, 2005; McNab and others,
2005).
In Handbook 296, major land resource areas are generally designated by Arabic
numbers and identified by a descriptive geographic name. Examples are MLRA 1
(Northern Pacific Coast Range, Foothills, and Valleys); MLRA 154 (South-Central
Florida Ridge); and MLRA 230 (Yukon-Kuskokwim Highlands). Some MLRAs are
designated by an Arabic number and a letter because previously established
MLRAs have been divided into smaller, more homogeneous areas, for example,
MLRAs 102A, 102B, and 102C. The use of numbers and letters to identify the
newly created MLRAs requires fewer changes in existing information in records
and in databases. A few MLRAs consist of two or more parts separated for short
distances by other land resource areas. In places one of these parts is widely
separated from the main body of the MLRA and is in an adjoining LRR. The
description of the respective MLRA also applies to these outlying parts.
Also, see the Web-based MLRA Explorer Tool at: http://apps.cei.psu.edu/mlra/
Land resource categories historically used at state and national levels are
land resource units, land resource areas, and land resource regions. LRUs are
the basic units from which MLRAs are determined. They are also the basic units
for state land resource maps. LRUs are typically coextensive with state general
soil map units, but some general soil map units are subdivided into LRUs
because of significant geographic differences in soils, climate, water resources,
or land use. LRUs generally are several thousand acres in size. A unit can be
one continuous area or several separate areas that are near each other. In
2005, these areas were designated as common resource areas (CRAs) within the
Natural Resources Conservation Service (NRCS).
Common Resource Areas (CRA) are created by subdividing MLRAs by topography,
other landscape features, hydrologic units, resource concerns, resource uses,
and human considerations affecting use and soil and water conservation treatment
needs. Common resource areas, or land resource units, are not described in this
handbook and are not shown on the national map. Major land resource areas are
geographically associated land resource units. Land resource regions are a
group of geographically associated major land resource areas.
The MLRA Geographic Database was prepared for Agricultural Handbook 296
re-publication and is used to support decisions about regional and national
agricultural issues. MLRAs Geographic Database and Agriculture Handbook 296
helped to identify the need for research and resource inventories, and it
became the vehicle for extrapolating the results of research across political
boundaries. It also became the basis for organizing and operating natural
resource conservation programs. Today, USDA soil survey offices are organized
to serve groups of the major land resource areas defined in this handbook. The
handbook was updated in 1978, and the second edition was printed in 1981. This
2006 version of the handbook is the third edition.
Format: vector lines – Shapefile
Spatial Reference
Information: Decimal Degrees, North American Datum 1983
