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NATURAL HERITAGE

THE NATURAL COMMUNITIES OF VIRGINIA
CLASSIFICATION OF ECOLOGICAL COMMUNITY GROUPS


Second Approximation (Version 2.6)
Information current as of July, 2013



FORMAT OF THE ECOLOGICAL COMMUNITY GROUP DESCRIPTIONS

Units are organized by the System and Class levels, and summary information is provided for all 94 units at the Ecological Community Group level. As a rule, this information includes a concise statement of the group's concept; distribution within Virginia; environmental and site conditions; vegetation structure and general floristic attributes; threats; associated rare species; and an assessment of the rarity of included community types, if known and applicable. The term "globally rare" indicates that a community or species is rare throughout its range. Characterization of habitats, soil chemistry, vegetation, and floristics is based almost exclusively on plot and other data collected by DCR-DNH ecologists. Literature pertinent to a group is cited at the end of the description; full citations are provided in the Literature Cited and Additional References section. Definitions of many scientific and technical terms are provided in a Glossary of Technical Terms and Abbreviations.

An assessment of the status of classification efforts, as well as skeletal information on finer-scale community types that are nested within the ecological community groups, are now provided under the heading "Representative Community Types." Most of the listed community types reflect the results of analysis of regional data sets, both within-state and for projects that included plot data from adjacent states (Fleming and Coulling 2001, Coulling 2002, Fleming 2002a, Patterson 2008, Taverna and Patterson 2008, NatureServe in prep, Fleming and Patterson 2009).

The scientific and common names of most community types are based on occurrences in Virginia and may not always match the Global Name in the U.S. National Vegetation Classification (USNVC). The scientific name (State Name) is based on Latin names of dominant or characteristic plant species. Those species occurring in the same stratum are separated by a hyphen ( - ); those occurring in different strata are separated by a slash ( / ). Species found less consistently in all occurrences of a community type, are placed in parentheses. Subspecies and varieties of nominal species are not included in community names unless they are explicitly diagnostic.

Synonymy with the USNVC is indicated, followed by the USNVC Global Element code; in some cases, this synonymy may be uncertain, approximate, or lacking. Where possible, hyperlinks are provided to the descriptions of the USNVC global types in NatureServe Explorer. Note that neither provisional types nor modified and ruderal types (ranked GNA) are included in NatureServe Explorer's treatment of ecological communities.

Community type names with the parenthetical modifier "PROVISIONAL" should be considered tentative. In most cases, these putative types are based on limited data and analysis, and are subject to reinterpretation or changes in concept as additional data become available.

Global conservation ranks reflect those in the USNVC and state ranks were assigned by DCR-DNH ecologists. Note that the status of many community types is poorly or imperfectly known and that many ranks are indefinite (see GNR, GU and SU below) or subject to change as more information becomes available.

Global Conservation Ranks
The Nature Conservancy, NatureServe, and all state Natural Heritage programs use the following system for ranking the range-wide conservation status of vegetation types at the association level. Intermediate ranks (e.g., G3G4) may also be used. A question mark added to a rank expresses an uncertainty about the rank in the range of one either way on the 1-5 scale. For example a G2? rank indicates that the rank is thought to be a G2, but could be a G1 or a G3. A "Q" added to a rank denotes questionable taxonomy. It modifies the degree of imperilment and is only used in cases where the type would have a less imperiled rank if it were not recognized as a valid type (i.e., if it were combined with a more common type).

  • G1 - critically imperiled throughout range.
  • G2 - imperiled throughout range.
  • G3 - rare or uncommon.
  • G4 - widespread, abundant, and apparently secure, but with cause for long-term concern.
  • G5 - demonstrably widespread, abundant, and secure.
  • GU - rank uncertain due to lack of information.
  • GNR - unranked; conservation status has not yet been assessed.
  • GNA - not applicable because the community is not a suitable conservation target; usually assigned to ruderal, modified / disturbed, or managed vegetation.

State Conservation Ranks
DCR-DNH ecologists employ a similar system for ranking the state-wide status of community types. Intermediate ranks (e.g., S3S4) may also be used.

  • S1 - extremely rare, generally with = five occurrences state-wide, and/or covering < 50 ha (125 ac) in aggregate; or covering a larger aggregate area but highly threatened with destruction or modification.
  • S2 - very rare, generally with six to 20 occurrences state-wide, and/or covering < 250 ha (600 ac) in aggregate; or covering a larger aggregate area but threatened with destruction or modification.
  • S3 - rare to uncommon, generally with 21 to 100 occurrences state-wide; or with a larger number of occurrences subject to relatively high levels of threat; may be of relatively frequent occurrence in specific localities or geographic parts of the state.
  • S4 - common, at least in certain regions of the state, and apparently secure, but with cause for long-term concern.
  • S5 - very common and demonstrably secure.
  • SU - rank uncertain because of lack of information.
  • SNR and SH; unranked; conservation status has not yet been assessed.
  • SNA - not applicable because the community is not a suitable conservation target; usually assigned to ruderal, modified / disturbed, or managed vegetation.

Botanical nomenclature follows The Flora of Virginia (Weakley, Ludwig, and Townsend 2012); Click here to download a standard list of this flora in Excel format. Because recent advances in the systematic treatment of North American flora have led to many changes in plant names, synonymy with more traditional names is provided where appropriate (e.g., Oclemena acuminata, = Aster acuminatus). In the ecological group descriptions, pertinent subspecific taxa are identified to the extent possible. However, many varieties and subspecies intergrade extensively in Virginia or have within-state distributions that are poorly understood. As a result, some subspecific taxa are not recognized in this document even though they are included in the Flora of Virginia. Photographs of more than 950 plant and animal species referenced in the text may be viewed by clicking on the highlighted species name.

For treatments of Virginia physiography and biogeography, as well as a map depicting the state's major provincial divisions, see the Overview of the Physiography and Vegetation of Virginia and Woodward and Hoffman (1991). Click on the physiographic relief map below to open a larger image in a separate window.


Physiographic/biogeographic regions of Virginia used for element tracking and mapping by DCR-DNH: AM = Allegheny Mountains. CM = Cumberland Mountains. NC = Northern Coastal Plain. NB = Northern Blue Ridge. NP = Northern Piedmont. OC = Outer Coastal Plain. RV = Ridge and Valley. SC = Southern Coastal Plain. SP = Southern Piedment. SB = Southern Blue Ridge.



The counties and major incorporated cities of Virginia. Click on the counties map to open a larger image in a separate window.