Sources and Methods

Key Sources:

The authoritative source for statewide Virginia Natural Communities insight and data is the Department of Natural Heritage website:

A nationally focused deep look at individual Natural Communities is found on NatureServe Explorer website:

The unique characteristics of the Natural Communities in Northern Virginia have been explored by Rod Simmons and publications are available on the Alexandria City website entitled The Flora Project: . Particularly useful are the following documents:

•Simmons, R.H. 2015. Native vascular flora of the City of Alexandria, Virginia. City of Alexandria Department of Recreation, Parks, and Cultural Activities, Alexandria, Virginia. 104 pp.

•Simmons, R.H. 2017. Forest Communities and Geology of Washington and Vicinity ; Presentation available on The Flora Project Website.

•Simmons, R.H> 2017. Narrative script to accompany Forest Communities and Geology of Washington and Vicinity ; Available on The Flora Project Website

Additional detail on the Natural Communities of the Potomac Gorge can be found in:

•Fleming, G.P. 2007. Ecological communities of the Potomac Gorge in Virginia: composition, floristics, and environmental dynamics. Natural Heritage Tech. Rep. 07-12. Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond. Unpublished report submitted to the National Park Service. 341 pp. plus appendices.

Authoritative information on the plants found in Virginia can be found on the Flora of Virginia Project website:

A fantastic website that explains Natural Communities in accessible terms is found at: The website is a collaboration between the National Park Service and NatureServ but unfortunately, it is expected to cease in the relatively near future. This website draws heavily and directly from the material in the Explore Natural Communities website. Any page which is primarily drawn from this source material is designated with "ENC" at the bottom of the page.

Natural Communities in 270 U.S. National Parks are maintained by the National Park Service and are available at:

Key insight on how to Categorize the species within each Community was provided by Avolio et. al, "Demystifying Dominant Species" New Phytologist, 2019


Data on Virginia Natural Communities was downloaded from the Virginia Department of Natural Heritage (DNH) website.

Additional data was matched to each species in the DNH resources

Common name (sourced from material provided by DNH and the Atlas of Virginia). To simplify matching, “ssp.” and “var.” epithets were removed unless necessary to distinguish within a species found in Northern Virginia

Form (sourced from a variety of sources including DNH, EarthSangha, and the web; errors and omissions are the responsibility of the author)

Invasive or not: Sourced from material provided by DNH; the DNH defined these species as "exotic" which meant not native to Virginia or of uncertain nativity.

Local Documented: Arlington County and City of Alexandria documented species (called “Local Documented” in the data sets) sourced from the Atlas of Virginia for Arlington County and Simmon (2015) for City of Alexandria.

Detailed plot data was provided by the DNH, for all plots in the dataset. Plots to be considered “Local” to Northern Virginia were selected based on mapped location in consultation with local experts. Plots identified as Local were extracted from the DNH data and the variety of summary statistics were compiled based on this data.

Any terms defined by the DNH were employed for the Local Plots.

In two cases, a new metric was defined:

“Mean Cover When Present”. This metric was calculated for both local and statewide data sets to provide comparability. The metric is the Mean Cover of plots in which the species was found.

“Consistency in Presence Across Plots": This measure was created by aggregating NOVA plots into 4 categories of cover when the species was present—Up to 1%, 1-5%, 5-25%, and over 25%. The plot count was converted to percentages by category and the maximum was defined. High variability was defined as the Maximum Percentage less than 45%.

The final abundance metric was defined based on an adaptation of the approach in the 2019 publication: Avolio, et al., Demystifying Dominant Species, New Phytologist, 2019

Final data for Natural Communities used in this website are available for download upon request. See the Contact section on the home page.