Units are organized by the System and Class levels, and summary information is provided for all 98 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). 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).
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.
Botanical nomenclature follows a standard list of Virginia flora developed by DCR-DNH botanists and ecologists. Treatments generally follow Kartesz (1999), the Flora of North America where completed (Flora of North America Editorial Committee 1993, 1997, 2000, 2002a, 2002b, 2003a, 2003b, 2005, 2006a, 2006b, and 2007), or Weakley (in prep). In the future, nomenclature will follow the Flora of Virginia project, when completed. 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 listed in the DCR-DNH standard flora. Additionally, we have followed the USNVC standard of excluding redundant varietal and subspecific names in the names of community type associations (e.g., Acer saccharum var. saccharum is listed as Acer saccharum). Photographs of more than 900 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.