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Class Detail Report: C02
Mesomorphic Shrub & Herb Vegetation Class

The U.S. National
Vegetation Classification
Grasslands, shrublands, open tree savannas, marshes, bogs and fens dominated by broadly mesomorphic (including scleromorphic) shrub and herb growth forms (including broad-leaved, needle-leaved, and sclerophyllous shrubs, and forb and graminoid herbs) with an irregular horizontal canopy structure, mesomorphic trees typically <10% cover (but tropical tree savannas typically <40%), tropical to boreal and subalpine climates, and wet to dry substrate conditions.
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Translated Name:Mesomorphic Shrub & Herb Vegetation Class
Colloquial Name:Shrub & Herb Vegetation
Shrubs and herbs with broadly mesomorphic (including scleromorphic) growth forms (including broad-leaved, needle-leaved, and sclerophyllous shrubs, some types of rosette shrubs, and forb and graminoid herbs) dominate this type. Vegetation structure is typically moderately open to closed canopy, with irregular horizontal canopy spacing and variable height, but typically <5 m, and where mesomorphic trees have <10% cover and mesomorphic shrub and herb growth forms have the majority of cover compared to xeromorphic or cryomorphic growth forms. But in tropical upland savanna regions, trees may have up to 40% cover, are <8 m tall, and the vegetation has a substantial graminoid layer. Climates range from tropical humid to (seasonal) dry to boreal and subalpine, with fairly moderate moisture and temperature conditions. Substrate moisture conditions vary from dry to wet. Vegetation includes upland grasslands, shrublands, open tree savannas, wetland emergent marshes, bogs and fens.
Shrubs and herbs in non-tropical savanna regions are at least 10% cover, mesomorphic trees <10% cover, and the majority of cover is composed of mesomorphic shrub (broad-leaved, needle-leaved, sclerophyllous, and rosette shrubs) and herb (forbs and graminoids) growth forms compared to xeromorphic or cryomorphic shrub and herb growth forms. The vegetation structure has irregular horizontal canopy spacing. In tropical upland savanna regions, trees typically have up to 40% cover, are <8 m tall, and the vegetation has a substantial graminoid layer.
Vegetation Hierarchy
Name:Database Code:Classification Code:
Class 2 Shrub & Herb Vegetation C02 2
Subclass 2.A Tropical Grassland, Savanna & Shrubland S01 2.A
Subclass 2.B Temperate & Boreal Grassland & Shrubland S18 2.B
Subclass 2.C Shrub & Herb Wetland S44 2.C
This class includes both non-treed grasslands and shrublands, and open tree savannas, where tree canopy cover is typically <10%. Non-tropical tree savannas, defined by a strong graminoid layer (>50% in UNESCO 1973) and some level of open tree cover (10-25% cover in UNESCO (1973), 10-30% cover in Nelson (2005), 10-50% cover in Curtis (1959)), often closely resemble open upland grasslands and shrublands, especially in grassland regions. Thus, in this particular realm of vegetation, the open tree canopy, in combination with the ground layer, helps define savanna vegetation, distinct from forests or woodlands (e.g., Nelson 2005). But in many other regions and vegetation types (e.g., forested swamps and bogs, longleaf pine woodlands (Peet 2006), California oak woodlands (Barbour et al. 2007), subarctic woodlands), the role of canopy closure varies. Thus, in non-tropical regions, we generally place tree savannas, where trees >5 m have >10% cover, with woodland and forest. However, as Dixon et al. (2014) and others suggest, there may be good ecological reasons to treat upland tropical tree savannas, with up to 40% tree cover, trees <8 m tall, and a substantial graminoid layer, as part of 2. Shrub & Herb Vegetation Class (C02), and we allow for that option here.

Croplands with a spontaneous ground layer of "weeds," where the annual rotation of crops prevents a persistent ground layer of herbs, are treated in 7. Agricultural & Developed Vegetation Cultural Class (CCL01). If agricultural practices are abandoned, these sites may succeed to more persistent "ruderal" grasslands and shrublands (and forests) and would be placed in this class.

Where grasses and shrubs overtop low trees ("brush prairie"), the stands are placed here in Shrub & Herb Vegetation. These situations may often occur in grassland or cool semi-desert regions (e.g., North American Great Plains or Great Basin). Also challenging are some scrub trees, such as juniper (Juniperus spp.) or mesquite (Prosopis spp.), which can form shrub-like stands, and are typically <5 m tall at maturity in parts of their range. Where forms are not easily defined, woody plants equal to or >5 m at maturity are considered trees (FGDC 2008). In the United States, there are shrubby junipers (Juniperus communis, Juniperus pinchotii) that should be treated as shrubs. But pygmy conifers can potentially make 5 m and are treated as trees (Pinus edulis, Juniperus scopulorum, Juniperus monosperma, Juniperus occidentalis, Juniperus osteosperma).

There is a group of ephemerals that are generally mesomorphic, which can, under optimal rainfall conditions, grow on sand, including desert sands and pavement. They are adapted to deserts through their seed characteristics. Typically they do not occupy extensive deep shifting sands, only margins of sandsheets and more stable sands. They rely on seedbanks that may persist for decades in the sand and germinate under optimal winter or summer episodes of heavy rains. These are treated here as part of the mesomorphic shrub and herb class. Examples of psammophytic species include some sand verbenas (Abronia spp.) and several Asteraceae (e.g., Dicoria canescens, Palafoxia spp., etc.).
Synonomy: = Grassland Biomes (Woodward 2008) [Approximately equivalent. Although only grasslands are mentioned in the name, shrublands are considered as part of the concept.]
> Range Land (Anderson et al. 1976) [The authors exclude wet grasslands and shrublands, treating them as part of their "Wetlands" category.]

Related Type Name:

Short Citation:
  • Anderson et al. 1976
  • Bailey 1989
  • Barbour et al. 2007a
  • Curtis 1959
  • Dixon et al. 2014
  • Faber-Langendoen et al. 2015c
  • FGDC 2008
  • Kudryashov 2010
  • Minnesota DNR 2005b
  • Nelson 2005
  • Peet 2006
  • UNESCO 1973
  • Woodward 2008
States/Provinces:
Nations:
Range:In non-tropical regions, this type is most common in the Bailey (1989) steppe divisions of the Dry Domain, the subarctic divisions of the Polar Domain, and is less common in other divisions of Polar or Dry domains. In the tropics, this type is uncommon in Humid Tropical and Humid Temperate domains, but common in Semi-humid Tropical domains (savannas).
US Forest Service Ecoregions
Domain Name:
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Section Name:
Section Code:     Occurrence Status:
Growth Forms: Stands are dominated by any broadly mesomorphic (including scleromorphic) herb or shrub growth form, with or without a layer of nonvascular growth form (i.e., lichen, moss). Mesomorphic shrubs include broad-leaved, needle-leaved, sclerophyllous, and palm shrubs. Semi-shrubs are typically absent. Mesomorphic herbs include forbs (including flowering forbs, ferns, and succulent forbs) and graminoids. These herbaceous growth forms are not exclusive to the mesomorphic class, and more work is needed to assess whether additional herbaceous growth form types should be recognized that may be distinctive for this class.

Structure: Stands have irregular shrub or herb horizontal stem spacing, typically with a moderately open to closed shrub or herb layer. There is <10% mesomorphic tree cover (<40% in tropical tree savannas), and the majority of shrub and/or herb growth forms are mesomorphic, typically exceeding 10% cover (but may be as low as 1-10% cover). Nonvascular and dwarf-shrub growth forms may vary from 0 to 100%, and tree seedlings or saplings may be present at any level of cover if they are below the predominant heights of the shrubs and herbs. At maturity, dominant shrubs and herbs are typically >0.3 m (sometimes over 5-10 m).
Climate: Shrublands and grasslands occur in the following Trewartha Climatic zones: Aw = Tropical wet-dry; Am = Tropical wet-dry ("monsoon"); BS = Semiarid [BSh, hot semiarid]; BW = Arid Specifically BWh (hot Subtropical High desert); BWn (or Bn)) Climates (cool coastal deserts) "n" for nebel = fog; Cs = Subtropical dry summer "Mediterranean"; Do = Oceanic "Marine West Coast"; BS = Semiarid (BSk, cool semiarid); Dc = Continental.

Soil/substrate/hydrology: Dry to wet soils. Sand dune, including psammophytic, vegetation is placed here in mesomorphic shrub and herb vegetation. Kudryashov (2010) describes the characteristics of "psammophyte" (i.e., plants that thrive in shifting sands, primarily in deserts, and that have a number of adaptations that enable them to exist on wind-blown sands).
Moderate
No Data Available
Authors:
Hierarchy Revisions Working Group      Version Date: 17Oct2014


References:
  • Anderson, J. R., E. E. Hardy, J. T. Roach, and R. E. Witmer. 1976. A land use and land cover classification system for use with remote sensor data. USDI, Geological Survey Professional Paper No. 964. Washington, DC. 26 pp.
  • Bailey, R. G. 1989. Explanatory supplement to ecoregions map of the continents. Environmental Conservation 16:307-309 with separate map at 1:30,000,000. USDA Forest Service, Washington, DC.
  • Barbour, M. G., T. Keeler-Wolf, and A. A. Schoenherr, editors. 2007a. Terrestrial vegetation of California, third edition. University of California Press, Berkeley.
  • Curtis, J. T. 1959. The vegetation of Wisconsin: An ordination of plant communities. Reprinted in 1987. University of Wisconsin Press, Madison. 657 pp.
  • Dixon, A. P., D. Faber-Langendoen, C. Josse, C. J. Loucks, and J. Morrison. 2014. Distribution mapping of world grassland types. Journal of Biogeography 41(11):2002-2019.
  • Faber-Langendoen, D., T. Keeler-Wolf, D. Meidinger, C. Josse, A. Weakley, D. Tart, G. Navarro, B. Hoagland, S. Ponomarenko, J.-P. Saucier, G. Fults, and E. Helmer. 2015c. Classification and description of world formation types. General Technical Report RMRS-GTR-000. USDA Forest Service, Rocky Mountain Research Station, Fort Collins, CO.
  • FGDC [Federal Geographic Data Committee]. 2008. National Vegetation Classification Standard (Version 2.0). FGDC-STD-005-2008. Vegetation Subcommittee, Federal Geographic Data Committee, Reston, VA. 126 pp.
  • Kudryashov, V. 2010. The great Soviet encyclopedia. Third edition (1970-1979). The Gale Group, Inc.
  • Minnesota DNR [Minnesota Department of Natural Resources]. 2005b. Field guide to the native plant communities of Minnesota: The Prairie Parkland and Tallgrass Aspen Parklands provinces. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul.
  • Nelson, P. 2005. The terrestrial natural communities of Missouri. Third edition. Missouri Natural Areas Committee, Department of Natural Resources and the Department of Conservation, Jefferson City, MO. 550 pp.
  • Peet, R. K. 2006. Ecological classification of longleaf pine woodlands. Pages 51-93 in: S. Jose, E. J. Jokela, and D. L. Miller, editors. The Longleaf Pine Ecosystem: Ecology, Silviculture, and Restoration. Springer Science Business Media, LLC, New York.
  • UNESCO [United Nations Educational, Scientific and Cultural Organization]. 1973. International classification and mapping of vegetation. Series 6, Ecology and Conservation. United Nations Educational, Scientific, and Cultural Organization. Paris. 93 pp.
  • Woodward, S. 2008. Grassland biomes. Greenwood Press, Westport, CT.


USNVC Credits: Detailed Description of the National Vegetation Classification Types

Date Accessed:

To cite a description:
Author(s). publicationYear. Description Title [last revised revisionDate]. United States National Vegetation Classification. Federal Geographic Data Committee, Washington, D.C.

About spatial standards:
The United States Federal Geographic Data Committee (hereafter called the FGDC) is tasked to develop geospatial data standards that will enable sharing of spatial data among producers and users and support the growing National Spatial Data Infrastructure (NSDI), acting under the Office of Management Budget (OMB) Circular A-16 (OMB 1990, 2000) and Executive Order #12906 (Clinton 1994) as amended by Executive Order #13286 (Bush 2003). FGDC subcommittees and working groups, in consultation and cooperation with state, local, tribal, private, academic, and international communities, develop standards for the content, quality, and transferability of geospatial data. FGDC standards are developed through a structured process, integrated with one another to the extent possible, supportable by the current vendor community (but are independent of specific technologies), and publicly available.

About this document
This document contains type descriptions at the Class level of the U.S. National Vegetation Classification. These descriptions were primarily written by NatureServe ecologists in collaboration with Federal Geographic Data Committee Vegetation Subcommittee and a wide variety of state, federal and private partners as a part of the implementation of the National Vegetation Classification. Formation descriptions were written by the Hierarchy Revisions Working Group. The descriptions are based on consultation with natural resource professionals, published literature, and other vegetation classification systems. The Ecological Society of America's Panel on Vegetation Classification is responsible for managing the review and formal adoption of these types into the National Vegetation Classification. Partners involved in the implementation of the USNVC include:

U.S. Government
  • Department of Agriculture (USDA)
  • Department of Commerce (DOC)
  • Department of Defense (DOD)
  • Department of the Interior (USDI)
  • Forest Service (FS) - Chair
  • National Agriculture Statistical Service (NASS)
  • Natural Resources Conservation Service (NRCS)
  • National Oceanic and Atmospheric Administration (NOAA)
  • National Marine Fisheries Service (NMFS)
  • U.S. Army Corps of Engineers (USACE)
  • U.S. Navy (NAVY)
  • Bureau of Land Management (BLM)
  • Fish and Wildlife Service (FWS)
  • National Park Service (NPS)
  • U.S. Geological Survey (USGS)
  • Environmental Protection Agency (EPA)
  • National Aeronautics and Space Administration (NASA)
Non U.S. Government
  • NatureServe (NS)
  • Ecological Society of America (ESA)

Disclaimer:
Given the dynamic nature of the standard, it is possible a type description is incomplete or in revision at the time of download; therefore, users of the data should track the date of access and read the revisions section of the USNVC.org website to understand the current status of the classification. While USNVC data have undergone substantial review prior to posting, it is possible that some errors or inaccuracies have remained undetected.

For information on the process used to develop these descriptions see:

Faber-Langendoen, D., T. Keeler-Wolf, D. Meidinger, D. Tart, B. Hoagland, C. Josse, G. Navarro, S. Ponomarenko, J.-P. Saucier, A. Weakley, P. Comer. 2014. EcoVeg: A new approach to vegetation description and classification. Ecological Monographs 84:533-561 (erratum 85:473).

Franklin, S., D. Faber-Langendoen, M. Jennings, T. Keeler-Wolf, O. Loucks, A. McKerrow, R.K. Peet, and D. Roberts. 2012. Building the United States National Vegetation Classification. Annali di Botanica 2: 1-9.

Jennings, M. D., D. Faber-Langendoen, O. L. Louckes, R. K. Peet, and D. Roberts. 2009. Standards for associations and alliances of the U.S. National Vegetation Classification. Ecological Monographs 79(2):173-199.

FGDC [Federal Geographic Data Committee]. 2008. Vegetation Classification Standard, FGDC-STD-005, Version 2. Washington, DC., USA. [http://www.fgdc.gov/standards/projects/FGDC-standards-projects/vegetation/NVCS_V2_FINAL_2008-02.pdf]

For additional information contact:

  • Implementation of the U.S. National Vegetation Classification Standard - Alexa McKerrow (amckerrow@usgs.gov)
  • NatureServe's Development of NVC Type Descriptions - Don Faber-Langendoen (don_faber- langendoen@natureserve.org)
  • Ecological Society of America's Review of the Type Descriptions Scott.Franklin@unco.edu
  • Federal Geographic Data Committee - Vegetation Subcommittee's Activities - Marianne Burke (mburke@fs.fed.us)