NSSH Part 649

Land Resource Regions and Major Land Resource Areas

Definition (649.00)

Land resource regions and major land resource areas are separated on the basis of significant differences in use and management of the soils as reflected in land use patterns. These regions and areas represent nearly homogeneous areas of soil, climate, land use, water resources, elevation, topography, and potential natural vegetation.

1. Land Resource Regions
   
   Land resource regions (LRRs) are geographically associated groups of major land resource areas and consist mainly of areas that have very broadly related patterns of soil, climate, water resources, and land use. Land resource regions are delineated only on small scale national maps (1:7,500,000; 1:10,000,000; or smaller) and are most useful for national and regional program planning. Land resource regions are unique, continuous delineations, which approximate physiographic regions on small scale national maps.
    
2. Major Land Resource Areas
   
   Major land resource areas (MLRAs) are based upon aggregations of geographically associated land resource units and identify nearly homogeneous areas of land use, elevation, topography, climate, water resources, potential natural vegetation, and soils. Major land resource area boundaries reflect an appropriate generalization of land resource unit boundaries (as derived from state soil geographic database map unit boundaries). The approximate minimum size of a major land resource area that may be delineated is 580,644 hectares, or 1,434,803 acres. This minimum delineation is represented at the official major land resource area map scale of 1:7,500,000 by an area approximately 1 cm by 1 cm (0.4 inch by 0.4 inch). Minimum linear delineations are at least 0.3 cm (0.1 inch) in width and 2.5 cm (1 inch) in length. The Pacific and Caribbean Islands, which have land areas less than 580,644 hectares (1,434,803 acres) in size are excluded from the minimum delineation rule. Large existing major land resource areas may be subdivided to create more homogeneous areas as needed, provided that cartographic criteria regarding minimum delineations are met. The descriptions of the map units on major land resource area maps emphasize land use and water resource management. Generally, a major land resource area occupies one continuous delineation; but it may occupy several separate ones. Major land resource areas are most useful for statewide planning and have value for interstate, regional, and national planning.
    
3. Land Resource Units
   
   Land resource units (LRUs) are derived from the aggregation of map units of the state soil geographic (STATSGO) database. This is possible because each state soil geographic database map unit has a major land resource area designation in the state soil geographic database attribute file. The STATSGO-ARCMAP or ARCGIS Interface software is a useful geographic information system tool for generating the first draft of the land resource unit map from a state soil geographic database. Based on a shared 1:250,000 scale, map unit boundaries on land resource region maps mostly coincide with those in the state soil geographic database. Land use exceptions are described in part 649.05 of this handbook. Cartographic standards regarding the minimum size of delineations for land resource unit maps are equivalent to those for the state soil geographic database. Land resource units may occur as single delineations but commonly occur as several separate delineations. Land resource unit maps often depict areas that are cartographically too small to be delineated on the national major land resource area map at 1:7,500,000 scale. Therefore, land resource units are not shown on the national major land resource area map. Land resource units are shown only on state maps.
    
4. USDA Agriculture Handbook No. 296
   
   USDA Agriculture Handbook No. 296, Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean and the Pacific Basin, (Soil Survey Staff, 2006), represents an assemblage of information currently available about the land for farming, ranching, forestry, engineering, recreational development, and other uses. This assemblage consists of the land resource region and major land resource area map and the supporting land resource region and major land resource area map unit descriptions. Such land resource information (both analog and digital) is used at National, Regional, and State levels:
    
   1. as a basis for making decisions about agricultural issues;
       
   2. as a framework for organizing and operating resource conservation programs;
       
   3. for the geographic organization of research and conservation needs and the data derived from these activities;
       
   4. for coordinating technical guides within and between states;
       
   5. for organizing, displaying, and using data in physical resource inventories; and
       
   6. for aggregating natural resource data.

Policy and Responsibilities (649.01)

1. The State Office
    
   1. suggests changes in land resource regions and major land resource areas to the MLRA Office; and
       
   2. assigns soil survey map units to the appropriate MLRA in the National Soil Information System.
       
2. The MLRA Regional Office
    
   1. submits suggested changes in land resource regions and major land resource areas to the National Soil Survey Center;
       
   2. obtains concurrence in suggested changes from other disciplines and states that share the land resource region or major land resource area;
       
   3. maintains the boundary, description, and documentation for each major land resource area that is assigned to the MLRA regional office (as given in Exhibit 649-1); and
       
   4. provides the National Soil Survey Center with a small scale copy of the major land resource area map for the responsible area.
       
3. The National Soil Survey Center
    
   1. approves proposed changes;
       
   2. keeps current the land resource region and major land resource area maps and descriptions;
       
   3. maintains the area symbol, area name and area acres for major land resource areas in the National Soil Information System;
       
   4. periodically issues revised editions of Agricultural Handbook 296, which provides supporting attributes to these map products;
       
   5. provides the NRCS Resources Inventory and Assessment Division an official copy of the LRR/MLRA data layers;
       
   6. keeps current the land resource region and major land resource area digital boundary maps; and
       
   7. provides assistance in maintaining the land resource region and major land resource area spatial maps.
       
4. The National Water and Climate Center
    
   1. Provides Parameter-based Regression on Independent Slopes Model (PRISM) data for new and/or subdivided Land Resource Regions and Major Land Resource Areas to the National Soil Survey Center in a timely manner to facilitate revising the Agriculture Handbook 296 on the defined schedule.
       
5. The NRCS Resources Inventory and Assessment Division
    
   1. Provides updated land use data on new and/or subdivided Land Resource Regions and Major Land Resource Areas to the National Soil Survey Center in a timely manner to facilitate revising the Agriculture Handbook 296 on the defined scheduled.
       
6. The National Technology Support Centers
    
   1. Provides a review of the updated sections of the Land Resource Regions and Major Land Resource Area descriptions prior to publication.

Land Resource Region and Major Land Resource Area Map Unit Descriptions (649.02)

The land resource region descriptions are summaries of the important characteristics of the major land resource areas. They are maintained by the National Soil Survey Center.

The dominant physical characteristics of major land resource areas are described under specified headings. Significant exceptions to these characteristics are described separately.

1. Land Use
   
   The extent of the land used for cropland, pasture, range, forests, industrial and urban developments, and other special purposes is indicated based on information provided from the most recent National Resource Inventory (NRI) and developed by the Natural Resources Conservation Service Resources Inventory and Assessment Division. The figures given are for the entire resource area unless stated otherwise. Also included is a list of the principal crops grown and the type of farming practiced. If significant, the relative extent of the federally owned land is indicated also based on National Resource Inventory data.
    

2. Physiography
   
   The topography and natural features of each area are described. A range in height above sea level and relief, including significant exceptions, if applicable, are provided for the area as a whole. The extent of the four-digit Hydrologic Unit Areas (Seaber and others, 1987) within each Major Land Resource Area is given in percent. The major rivers and/or streams draining each Major Land Resource Area and any National Scenic or National Wild and Scenic River reaches are also listed.
    

3. Geology
   
   The bedrock geology and surficial geology of each Major Land Resource Area is described. This information is derived from a wide variety of State and Federal maps and reports that are not included in the list of references.
    

4. Climate
   
   A range of mean annual precipitation for the driest and the wettest parts of the major land resource area and a range of the seasonal distribution of precipitation are given. Also given are a range of the mean annual air temperature and the average freeze-free period characteristic of different parts of the major land resource area. The mean annual precipitation, the mean annual air temperature, and the average freeze-free period should be referenced according to weather station and to a specific collection of 30-year normals (such as from 1961 to 1990), as summarized by the National Water and Climate Center staff. These data are derived from Parameter-based Regression on Independent Slopes Model (PRISM) data and supplied to the National Soil Survey Center by the National Water and Climate Center staff located in Portland, Oregon.
    

5. Water
   
   Information is given concerning surface stream flow, ground water, and the source of water for municipal use and irrigation. Also, dependency upon neighboring major land resource areas for water supply or ability to provide water to neighboring major land resource areas is described. The extent and number of irrigation districts in the major land resource area are given where pertinent. Also, the 8-digit U.S. Geological Survey Hydrologic Units are listed by relative extent.
    

6. Soils
   
   Soils are identified according to the principal taxonomic great groups as referenced in the state soil geographic database. Soil series that are representative of each great group are listed, and the relationship of soils to landscape position is described.
    

7. Biological Resources
   
   Major plant communities within the Major Land Resource Areas are described by dominant species utilizing common plant names. (see Exhibit 649-2 reference 2) Common fish and wildlife species occurring within the Major Land Resource Areas are also listed.

Land Resource Region and Major Land Resource Area Map Unit Names and Symbols (649.03)

Traditionally, the names of land resource regions and major land resource areas reflect certain unique relationships to agriculture or forestry, but there is no set standard for names or terms.

1. Names of Land Resource Regions
   
   The names of land resource regions are combinations of names of broad physiographic provinces and predominant land use; for example, Northwestern Forest, Forage and Specialty Crop Region.
    
2. Names of Major Land Resource Areas
   
   The names of major land resource areas commonly use the names of associated physiographic areas, landforms, and “natural geographic” areas; for example, Olympic and Cascade Mountains.
    
3. Symbols for Land Resource Regions
   
   The symbols for land resource regions are designated by capital letters; for example, A – Northwestern Forest, Forage and Specialty Crop Region.
    
4. Symbols for Major Land Resource Areas
   
   The symbols for major land resource areas are designated by an Arabic numeral or by an Arabic numeral and a letter if previously established areas have been subdivided to provide for more homogeneous areas; for example, 9 – Palouse and Nez Perce Prairies or 63A – Northern Rolling Pierre Shale Plains.
    

Procedures for Establishing and Revising Land Resource Regions and Major Land Resource Areas (649.04)

Proposals to change the existing land resource region or major land resource area map are submitted to the Major Land Resource Area Regional office responsible for the land resource region or major land resource area. Proposals for change can be requested by states or cooperators.

1. MLRA Regional Office Responsibilities
   
   The responsibility for maintaining individual major land resource areas is assigned to each MLRA Regional office, as listed in Exhibit 649-1. The MLRA Regional offices that share the major land resource area or land resource region ensure that the maps displaying these areas are joined and coordinated across boundaries. The responsible MLRA Regional office coordinates suggested changes with the National Soil Survey Center and the National Cooperative Soil Survey cooperators.
   
   The Major Land Resource Area Regional office submits the following complete documentation to the National Soil Survey Center:
    
   1. documentation and justification for the requested change(s);
       
   2. state land resource unit map that supports the suggested changes to the major land resource area; this is a computer generated film proof plot that shows land resource unit boundaries and symbols in black with an overlay showing the proposed major land resource area boundaries and symbols in red. For the purpose of hard copy presentation, this map is made at a scale of 1:500,000.
       
   3. draft major land resource area map with suggested change(s); this is a 1:7,500,000 scale map generated from the most current approved digital version of the major land resource area map. This map consists of a computer generated film proof plot showing proposed major land resource area boundaries and symbols in red and existing major land resource area boundaries and symbols in black.
       
   4. complete draft of major land resource area descriptions, including needed revisions to previously existing descriptions that are impacted by the proposal;
       
   5. letters from the MLRA offices of areas that share the major land resource area; these letters show concurrence on the change(s) and document a correct join if the change(s) affect the areas that share the major land resource area;
       
   6. descriptions of changes that impact boundaries between Major Land Resource Area offices or Major Land Resource Area Soil Survey Offices; and
       
   7. descriptions of changes that impact Common Resource Area and Land Resource Unit boundaries.
       
2. National Soil Survey Center Responsibilities
    
   1. Justification and complete documentation must be received and reviewed at the National Soil Survey Center prior to approval by the Director of the National Soil Survey Center.
       
   2. Approved changes are then digitally incorporated into the existing major land resource area and land resource region maps on a five year cycle (e.g. 2010, 2015, 2020) and new map products will be produced and released for official use.
       
   3. A 1:7,500,000 scale proof plot and major land resource area map unit descriptions that reflect the new revision are sent to the originating MLRA office for review.
       
   4. When the products are returned to the National Soil Survey Center, the documented changes will be made at the National level.
       
   5. Provides copies of the updated maps and documentation to appropriate Natural Resources Conservation Service users, National Cooperative Soil Survey cooperators, and others as requested.
       
   6. All documentation supporting approved change is archived by the National Soil Survey Center.
       
3. National Water and Climate Center Responsibilities
   
   The National Water and Climate Center provides revised climate data from the Parameter-based Regression on Independent Slopes Model (PRISM) for mean annual precipitation, mean annual air temperature, and average freeze-free period for Land Resource Region(s) and Major Land Resource Area(s) to the National Soil Survey Center as requested.
    
4. Resources and Inventory and Assessment Division
   
   The Resources and Inventory and Assessment Division provides revised land use data for the modified Land Resource Region(s) and Major Land Resource Area(s) to the National Soil Survey Center as requested.

Land Resource Unit Maps of States (649.05)

1. Definition
   
   Land resource units define major land resource areas based on significant statewide differences in climate, water resources, land use, potential natural vegetation, or other natural resource conditions that contribute to significant differences in use and management of the units.
   
   Major land resource area boundaries on state maps are identical and coincide with the boundaries on the national map. However, so that the state needs to express the major land resource area concept at a larger scale can be accommodated, the major land resource area map units are disaggregated or broken down into land resource units. Land resource unit boundaries generally coincide with state soil geographic database map unit boundaries with the following exception. State soil geographic database map units may be subdivided into land resource units if there are significant and mappable differences in water resources, land use, or type of farming. Due to differences in scale, most major land resource area and land resource unit boundaries are not exactly the same. However, major land resource area boundaries should reflect an appropriate generalization of land resource unit boundaries, just as land resource region boundaries should reflect major land resource area boundaries.
    
2. Prescribed Scale of State Land Resource Unit Maps
   
   The prescribed scale for state land resource unit map management generally is 1:250,000. In Alaska, land resource units are managed at a scale of 1:1,000,000. Land resource unit maps are derived from the state soil geographic database and serve as a companion geographic information system (GIS) data set. Land resource unit maps provide sufficient detail to permit their use for general planning of land resources at the State level. For the purpose of hard copy presentation, state land resource unit maps are made at a scale of 1:500,000.
    
3. Land Resource Unit Map Unit Names and Symbols
   
   The conventions used in giving names and symbols to land resource units are based on the major land resource area name and symbol. The land resource unit symbol uses the major land resource area symbol followed by a hyphen, an Arabic number, and the state alpha FIPS code. For example, 144A-1NY would represent the first land resource unit in major land resource area 144A in New York. This land resource unit map unit name would be New England and Eastern New York Upland, Southern Part, LRU-1NY. Land resource unit map unit names and symbols are specific to each state. Therefore, land resource units may not be presently referenced in place of major land resource areas on national data sets, such as the National Resource Inventory or the range site data set, which require correlation across state boundaries. Because of the need to coordinate field office technical guides across state boundaries, land resource units, unless they are coordinated with adjoining states, have limited application for this purpose.
    
4. Procedure for Establishing Land Resource Units
   
   The state conservationist establishes the procedures for developing and maintaining land resource unit boundaries and descriptions. Procedures and criteria are similar to those for establishing major land resource areas at the National level but are at a larger scale.

A List of Major Land Resource Areas Assigned to Each MLRA Regional Office (Exhibit 649-1)

All existing official MLRAs (circa 2006) and their descriptions will be regionalized in STATSGO and reviewed in a state-wide forum of participants within the context of Interagency Ecological Mapping.

References (available from the National Soil Survey Center) (Exhibit 649-2)

Jensen, S. 1992. One-Half Kilometer DEM coverage for the U.S. USGS. EROS Data Center, Sioux Falls, SD.

Kuchler, A.W. 1985 (revised). Potential Natural Vegetation. In National Atlas of the United States of America. Dept. of the Int., U.S. Geol. Survey.

NOAA Staff. 1962. Monthly Normals of Temperature, Precipitation, and Heating and Cooling Degree Days, 1931-60. In Climatography of the United States No. 81. U.S. Dept. of Com., Nat. Oceanic and Atmos. Admin., Nat. Climate Data Center, Asheville, NC.

NOAA Staff. 1972. Monthly Normals of Temperature, Precipitation, and Heating and Cooling Degree Days, 1941-70. In Climatography of the United States No. 81. U.S. Dept. of Com., Nat. Oceanic and Atmos. Admin., Nat. Climate Data Center, Asheville, NC.

NOAA Staff. 1982. Monthly Normals of Temperature, Precipitation, and Heating and Cooling Degree Days, 1951-80. In Climatography of the United States No. 81. U.S. Dept. of Com., Nat. Oceanic and Atmos. Admin., Nat. Climate Data Center, Asheville, NC.

NOAA Staff. 1992. Monthly Normals of Temperatures, Precipitation, and Heating and Cooling Degree Days, 1961-1990. In Climatography of the United States No. 81. U.S. Dept. of Com., Nat. Oceanic and Atmos. Admin., Nat. Climate Data Center, Asheville, NC.

Seaber, P.R., F.P. Kapinos, and G. L. Knapp. 1987. Hydrologic Unit Maps. Dept. of the Interior, U.S. Geol. Survey.

Soil Survey Staff. June 2006. Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean and the Pacific Basin. USDA, NRCS, Agriculture Handbook 296.

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