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NSSH Part 649

Land Resource Areas

Subpart A – General Information

649.0  Definition and Purpose

  1. Land resource areas are a hierarchal segmentation of the earth’s surface based primarily upon natural resource attributes and properties which influence use and management. The seven resource attributes used in defining land resource units are climate, geology, soils, vegetation, water resources, physiography, and land use. The role each attribute plays in the determination and naming of a resource area varies, and its importance depends upon the level within the hierarchy. Some resource areas exhibit a high degree of uniformity across the entire landscape. Other resource areas are characterized by a high degree of variation that occurs in a predictable and repeatable pattern. Still other resource areas represent significant or unique environments.
     
  2. The land resource region (LRR) is the highest level of the hierarchy and represents broad landscape divisions at a small scale. The major land resource area (MLRA) is the second highest level and generally represents broad landforms or a geologic region at a small scale. In many cases, it represents broad areas with similar potentials or limitations for use, such as forestland, or areas with similar resource limitations, such as arid climate. The third level of the hierarchy is the land resource unit (LRU). The land resource unit represents related landforms that make up the landscape. Land resource units are defined primarily by significant differences between one or two of the resource attributes. These differences affect land use and land management decisions at the landscape scale.
     
  3. Land resource regions are defined by their resource attributes. They are delineated on maps at a continental scale. They are used in describing regional attributes of the natural resources at a national scale. Major land resource areas are typically presented on maps at a national scale and used for State and regional planning. Examples are large river basin watersheds, forest regions, deserts, and expansive uniform areas of cropland. The land resource unit is typically delineated on State or regional maps and used at the State or local level.
     
  4. Information and maps of land resource areas are published in Agriculture Handbook 296. This information is not appropriate for site-specific conservation planning or specific site application. The maps of all three resource areas are generalized. The lines are smoothed in presentation and are not intended to represent a point of change on the ground. In addition, small areas may exist within the LRR or MLRA near transitions where inliers and outliers of adjacent MLRAs or LRUs occur that are not delineable on the map at the appropriate publication scale. Although these areas are not indicated on the generalized LRR or MLRA maps, they are described and associated in the STATSGO and SSURGO databases with the appropriate MLRA or LRU.
     

649.1  Policy and Responsibilities

  1. State Office—

    1. Works with cooperators or partners, or independently, to propose changes to LRRs, MLRAs, and LRUs to be presented to the soil survey regional office.
    2. Reviews soil survey map units to verify assignment to the appropriate MLRA and LRU in the National Soil Information System.
       
  2. Soil Survey Office—

    Works with cooperators or partners, or independently, to propose changes to LRRs, MLRAs, and LRUs to the soil survey regional office.

  3. Soil Survey Regional Office—

    1. Works with cooperators or partners, or independently, to propose changes to LRRs, MLRAs, and LRUs.
    2. Submits and coordinates proposed changes from other disciplines and States that share the LRR, MLRA, or LRU.
    3. Maintains the boundary, description, and documentation for each MLRA or LRU to which it is assigned.
    4. Ensures that the maps displaying LRRs or MLRAs are joined and coordinated across boundaries.
    5. Submits proposed changes to LRRs, MLRAs, and LRUs to the National Soil Survey Center, National Leader for Soil Survey Standards.
    6. Provides the National Soil Survey Center with the appropriate publication scale copy of the MLRA and LRU maps for the area of responsibility.
       
  4. National Soil Survey Center—

    1. Receives and reviews proposed changes for the Center Director’s approval.
    2. Keeps the maps, descriptions, and digital layers of land resource areas current.
    3. Maintains the area symbols, area names, and area acres for land resource areas in the National Soil Information System.
    4. Publishes Agriculture Handbook 296 containing resource area descriptions and maps.
    5. Provides the NRCS Resource Inventory Division an official copy of the geographic data layers of land resource areas.
    6. Works with soil survey regional offices to resolve disputed lines or concepts.Works with cooperators or partners, or independently, to propose changes to LRRs, MLRAs, and LRUs.
       
  5. Soil Science Division—

    1. The Division Director reviews and approves proposed changes.
    2. The Division Director provides the final decision on any disputed lines or concepts of land resource areas.Receives and reviews proposed changes for the Center Director’s approval.
       
  6. National Water and Climate Center—

    Provides the most recent Parameter-elevation Regression on Independent Slopes Model (PRISM) data for new and/or subdivided land resource areas to the National Soil Survey Center to facilitate revision of Agriculture Handbook 296. (Climate parameters to consider are the mean annual precipitation, mean annual air temperature, and frost-free days.)

  7. NRCS Resource Inventory Division—

    Provides updated land use descriptions of land resource areas to the National Soil Survey Center to facilitate revision of Agriculture Handbook 296.

  8. NRCS Resource Assessment Division—

    Provides supporting data for the modified or newly established LRRs and MLRAs to the National Soil Survey Center, as requested, for use in the their descriptions.

  9. National Technology Support Centers—

    Review and comment on the descriptions of land resource areas.
     

649.2  Descriptions

  1. Land Resource Regions

    Land resource regions (LRRs) are concepts of unique, mostly continuous broad landscapes. They are delineated on small-scale national maps used in national planning. LRRs are the geographical regionalization of the United States and its Territories. They consist mainly of broadly related patterns of geology, soil, climate, physiography, vegetation, water resources, and land use based on publication scale.

  2. Major Land Resource Areas

    Major land resource areas (MLRAs) are geographical concepts based on subdivisions within a land resource region. They identify areas with similar physiography, geology, climate, water resources, soils, biological resources, and land use based on publication scale. MLRAs are typically used in regional multi-State or individual State planning processes.

  3. Land Resource Units

    Land resource units (LRUs) are concepts of subdivisions of an MLRA that have one or more unique features within the MLRA criteria that make them more homogenous. The purpose of LRUs is to support the development of products such as soil survey updates, soil carbon assessments, and ecological site descriptions. LRUs are based on identifiable differences in physiography, geology, climate, water resources, soils, biological resources, or land use or other natural resource conditions that make them unique within the MLRA. These differences are important to the use and management of the LRU. LRUs can be used locally by States to support conservation programs and practices.

  4. State Soil Geographic (STATSGO2) Database

    The general soil map of the United States, or STATSGO2 (NSSH Part 644.07), represents a broad-based inventory of soils and non-soil areas that occur in a repeatable pattern on the landscape. The STATSGO2 map units are aggregated from SSURGO-level mapping. Whereas the SSURGO map units are delineated based on differing soil properties, the STATSGO2 map units are based on shared soil properties and related features, such as geomorphic position.

  5. Soil Survey Geographic (SSURGO) Database

    The SSURGO database provides detailed maps and data for soils in the United States and its Territories, Commonwealths, and Island Nations. Included with this soil data are ecological sites. Ecological sites are a land management unit used by NRCS that are correlated to soil map unit components (soil series phases). Ecological sites are spatially explicit soil- and climate-based classes of land with similar vegetation dynamics, soil, geomorphology, topographic position, and microclimate (see the National Ecological Site Handbook).

     

649.3  Resource Area Components

Land resource areas are defined by dominant land use, physiography, geology, climate, water, soil, and biological resources. These components are used to define the concepts and geography of each resource area (LRR, MLRA, and LRU). Resource area size and delineation are determined using the appropriate publication map scales.

  1. Land Use

    Common land use potentials include the arrangement, activities, and inputs used to produce, change, or maintain land cover type. Information on the extent of land used for cropland, pasture, rangeland, forestland, industrial and urban development, and other special purposes is provided by the most recent National Resource Inventory (NRI) or the USGS National Land Cover map (Homer et al., 2012). Summary statistics are provided for the whole resource area unless otherwise stated. Also included is a list of the principal crops grown and the type of farming practiced. The relative extent of federally owned land based on NRI data is also reported if relevant.
     
  2. Physiography

    Common physical geographic features include topography, landforms, and elevation ranges. Summary reports of the ranges in height above sea level and relief, including significant exceptions if applicable, are provided for the area as a whole. Physiographic section, province, and division are described for each resource area (Fenneman and Johnson, 1946). The extent of the hydrologic unit areas within each resource area (Seaber et al., 1987; 8-digit HUC for LRU, 4-digit HUC for MLRA, 2-digit HUC for LRR) is reported as a percent. Major rivers and/or streams draining each resource area and any National Scenic or National Wild and Scenic Rivers are also listed.
     
  3. Geology

    Common geologic features include the geologic material (rock type) and geologic age. Summary descriptions of surficial and bedrock geology are reported for each resource area. This information is derived from a wide variety of State and Federal maps and other reports.
     
  4. Climate

    Common climatic properties include the average annual precipitation, seasonal distribution of precipitation, average annual temperature, and average number of frost-free days. Summary reports of mean annual precipitation ranges for the driest and the wettest parts of the resource area and of the range of the seasonal distribution of precipitation are given. Also given are the range of the mean annual air temperature and the average frost-free period characteristic of the resource area. The mean annual precipitation, mean annual air temperature, and average frost-free period should be referenced according to weather station and to a specific collection of most recent 30-year normals (e.g., 1981 to 2010), as summarized by the National Water and Climate Center. These data are derived from Parameter-elevation Regression on Independent Slopes Model (PRISM) data (http://www.prism.oregonstate.edu/) by the National Water and Climate Center, located in Portland, Oregon.
     
  5. Water

    Water resource characteristics are commonly defined by water source, quantity, and quality. Defining features should include surface stream flow, ground-water characteristics, irrigation availability, and dependency upon neighboring resource areas for water. Summary reports of the resource area include surface stream flow, ground water, and the source of water for municipal use and irrigation. In addition, the dependency upon neighboring resource areas for water supply or the ability to provide water to neighboring resource areas is described. Extent and number of irrigation districts in the resource area are given if pertinent.
     
  6. Soils

    Common soil resources are the nature and properties of the soils. Soils are identified according to the principal taxonomic great groups as referenced in the SSURGO database or the STATSGO2 database (if SSURGO data are not available). Representative soil series of individual resource areas can further define resource area extents. Summary reports of common soil great groups, representative soil series, and the relationship of soils to landscape position are given.
     
  7. Biological Resources

    Biological resources are commonly defined by vegetation species, type, and phenology. Summary reports of major plant communities within the resource areas are described by dominant species, identified by common plant names (Kuchler, 1985). Fish and wildlife species common within the resource areas are also listed.
     

649.4  Cartographic Standards

The cartographic standards for land resource areas include the concepts of minimum mappable area and minimum management. The minimum mappable area concept is a concrete assignment applied by cartographers to the smallest area that can be presented on the map with a map unit symbol inside the polygon drawn at the published map scale. The minimum management concept is an abstract assignment applied by resource managers that reflects both the concrete parameters of the map scale and the inherent characteristics of the resource area. Although the published map scale allows for a minimum polygon size, the hierarchy of nesting resource areas requires acre limitations for the minimum mappable area concept.

  1. Land Resource Regions

    LRRs are delineated on national maps at small scales—1:7,500,000 for the conterminous U.S. and 1:10,000,000 for Alaska. These maps are most useful for national program planning. For maps at a scale of 1:7,500,000, the delineation of the minimum mappable area is approximately 1 cm by 1 cm (0.4 inch by 0.4 inch), or 227,000 hectares (560,000 acres). The minimum management area is approximately 8,000,000 hectares, or 20,000,000 acres.
     
  2. Major Land Resource Areas

    MLRAs are delineated on national maps at small scales—1:5,000,000 for the conterminous U.S. and the Pacific and Caribbean Islands and 1:7,500,000 for Alaska. These maps are most useful for national, regional, and State program planning. The delineation of the minimum mappable area is approximately 1 cm by 1 cm (0.4 inch by 0.4 inch), or 100,000 hectares (250,000 acres). Minimum linear delineations are at least 0.3 cm (0.1 inch) in width and 2.5 cm (1 inch) in length. The minimum management area is approximately 400,000 hectares, or 1,000,000 acres. (Note: The Pacific and Caribbean Islands, which have land areas less than 600,000 hectares, or 1,600,000 acres, in size are excluded from the minimum delineation rule due to individual island sizes and distribution.)
     
  3. Land Resource Units

    LRUs may occur as single delineations but commonly occur as several separate delineations. LRUs are delineated on national maps at small scales—1:1,000,000 for the conterminous U.S. and the Pacific and Caribbean Islands and 1:5,000,000 for Alaska. LRU maps often depict areas that are cartographically too small to be delineated at an MLRA map scale (i.e., 1:7,500,000). These maps are most useful for State and watershed-level program planning. The delineation of the minimum mappable area is approximately 1 cm by 1 cm (0.4 inch by 0.4 inch), or 4,000 hectares (10,000 acres). Minimum linear delineations are at least 0.3 cm (0.1 inch) in width and 2.5 cm (1 inch) in length. The minimum management area is approximately 40,000 hectares, or 100,000 acres. (Note: The Pacific and Caribbean Islands are excluded from the minimum delineation rule due to individual island sizes and distribution.)
     
  4. State Soil Geographic (STATSGO2) Database

    The STATSGO2 soil map units occur as single delineations and depict areas on national maps at larger scales—1:250,000 for the conterminous U.S. and the Pacific and Caribbean Islands and 1:500,000 for Alaska. The delineation of the minimum mappable area is approximately 1 cm by 1 cm (0.4 inch by 0.4 inch), or 252 hectares (623 acres). Minimum linear delineations are at least 0.3 cm (0.1 inch) in width and 2.5 cm (1 inch) in length. The minimum management area is approximately 400 hectares, or 1,000 acres.
     
  5. Soil Survey Geographic (SSURGO) Database

    The SSURGO database provides detailed soil maps and data for most areas in the United States and its Territories, Commonwealths, and Island Nations. The minimum polygon area is approximately 1 hectare (2 to 5 acres). This minimum delineation is represented on a 1:12,000- or 1:24,000-scale map by an area approximately 1 cm by 1 cm (0.4 inch by 0.4 inch). Size also depends on order of mapping. In the Caribbean Area, the minimum delineation is represented on a 1:20,000-scale map for Puerto Rico and a 1:12,000-scale map for the U.S. Virgin Islands.
     

649.5  Names and Symbols

Traditionally, the names of LRRs, MLRAs, and LRUs reflect unique relationships in agriculture, native plant communities, and landscape features.

  1. Land Resource Regions

    The symbols for LRRs are capital letters, and the names are combinations identifying broad physiographic provinces and predominant land use. An example is “M – Central Feed Grains and Livestock Region.”
     
  2. Major Land Resource Areas

    The symbols for MLRAs are Arabic numerals, and the names are commonly associated physiographic areas, landforms, and natural geographic areas. An example is “108 – Illinois and Iowa Deep Loess and Drift.”
     
  3. Land Resource Units

    The symbols for LRUs consist of a capital letter following the numeral for the MLRA of which it is a subdivision. The name consists of the MLRA name followed by an adjective describing the relative location or associated physiographic areas, landforms, or natural geographic areas. Examples are “108A – Illinois and Iowa Deep Loess and Drift, Eastern Part” and “116B – Ozark Highland, Springfield Plain.”
     

649.6  Establishing or Revising Land Resource Areas

  1. Any Agency office or National Cooperative Soil Survey (NCSS) partner can make a proposal to modify the maps or descriptions of existing land resource areas (LRR, MLRA, or LRU) or to establish a new land resource area. Proposals are submitted to the soil survey regional office responsible for the specific area.
     
  2. Soil Survey Regional Office—

    1. Reviews, vets, and compiles the proposals and forwards them to the National Soil Survey Center for consideration in the revision of Agriculture Handbook 296.
    2. Coordinates suggested changes with the National Leader for Standards at the National Soil Survey Center and with regional members of the NCSS. 
    3. Submits the following information to the National Leader for Standards:
      1. Documentation and justification for the requested change(s).
      2. The draft land resource area map, in support of the suggested changes, printed to the appropriate publication scale to verify cartographic standards.
      3. The GIS shape file used to create the land resource area printed map and the portable document format (PDF) that presents the original land resource area boundaries and symbols in black with an overlay showing the proposed land resource area boundaries and symbols in red.
      4. A complete draft of the appropriate land resource area descriptions, including needed revisions to previously existing descriptions impacted by the proposal.
      5. Letters from the SSROs and State Conservationists of areas that share the land resource area. The letters will show concurrence on the change(s) and document a correct join if the change(s) affect the areas that share the land resource area.
      6. Descriptions of changes that impact land resource area boundaries.
         
  3. National Soil Survey Center

    1. Reviews and concurs the justification and complete documentation prior to final approval by the Director of the Soil Science Division.
    2. Digitally incorporates approved changes into the existing LRR, MLRA, and LRU documentation and maps and produces and releases new map products for official use.
    3. Sends a 1:7,500,000-scale LRR proof plot, a 1:5,000,000-scale MLRA proof plot, and a 1:1,000,000-scale LRU proof plot, along with the appropriate map unit descriptions reflecting the revisions, to the originating SSRO for review and concurrence.
    4. Integrates the concurred changes into the most recent version of Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin, Agriculture Handbook 296.
    5. Provides copies of the updated maps and documentation to the appropriate NRCS users, NCSS cooperators, and others as requested.
    6. Archives all documentation supporting approved changes.
       

649.7  Publication

USDA Agriculture Handbook 296, Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin, is an assemblage of current information about land use, including farming, ranching, forestry, engineering, recreational development, and other uses. It is published as a digital product on the NRCS Web site. This assemblage consists of LRR, MLRA, and LRU maps and the supporting map unit descriptions for each. This land resource area 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.
     

Subpart B – Exhibits

649-10  References

Kuchler, A.W. 1985 (revised). Potential natural vegetation. In National Atlas of the United States of America. Dep. of the Int., U.S. Geol. Survey.

Seaber, P.R., F.P. Kapinos, and G.L. Knapp. 1987. Hydrologic unit maps. Dep. of the Int., U.S. Geol. Survey.

Homer, C.H., J.A. Fry, and C.A. Barnes. 2012. The National Land Cover Database. U.S. Geological Survey Fact Sheet 2012-3020, 4 p.

Fenneman, N.M., and D.W. Johnson. 1946. Physiographic divisions of the conterminous U.S. Geospatial_Data_Presentation_Form: map, http://water.usgs.gov/lookup/getspatial?physio