Nine of the most common Natural Communities that are likely to be encountered in the parks and natural lands in Northern Virginia are summarized below. Most of these summaries are pulled directly from the “Forest Communities and Geology of Washington and Vicinity” presentation and accompanying text script, by Rod Simmons from 2017. See the Sources page for the full reference. Photos courtesy of Gary Fleming and Rod Simmons.
The communities are listed from highest to lowest in elevation in the landscape. Think tops of larger hills going down to areas near streams, or steeper areas going down to flatter areas.
This forest occupies a high spot in the terrain, usually on north-facing slopes and terraces, with Chestnut Oaks a dominant species. The community is an "evergreen" type of Oak-Heath Forest, with Mountain Laurel a dominant understory shrub. Witch Hazel is a common associate of this type of community, particularly above streams. The soil of all of the Oak-Heath forests are porous, dry, and relatively infertile.
This forest also occupies a high spot in the terrain. It is the "deciduous" type of Oak-Heath Forest , with extensive, intermixed colonies of deciduous heaths like Lowbush Blueberry, Black Huckleberry, and Deerberry co-dominant as low shrubs. The soil of all of the Oak-Heath Forests are porous, dry and relatively infertile.
This forest is typically found on steep ravine slopes and bluffs. It is similar to other Oak-Heath forests with the addition of American Beech in the overstory. This is the main Oak-Heath Forest type in southern Fairfax County. The soil of all of the Oak-Heath Forests are porous, dry and relatively infertile.
These diverse communities are common in the Piedmont, but along the Fall Line are essentially restricted to ancient colluvial slopes and benches of weathered Potomac Formation clay, and are largely absent from the Coastal Plain. This type generally occurs as a gradient between Oak-Heath Forest and Mesic Mixed Hardwood Forest, usually on dry to mesic, acidic, southwest facing slopes with high solar exposure. This is typically a floristically diverse community type along the Fall Line.
This is the most floristically diverse vegetation type of all Piedmont, Fall Zone, and Coastal Plain types. This community is distinguished from other oak-hickory forests by its patch-dominance of forest grasses and its strong association with sub-level topography and soils with an impermeable hardpan or shallow bedrock. It is found primarily in the Triassic Basin areas to the west of Washington D.C.
The Community is very common on slopes—either gentle or moderately steep—and in wide ravines above and around dissected streams. It also occupies rolling uplands with deep soils. Tulip Tree, American Beech, Northern Red Oak, and Christmas Fern occurring together, especially along lower slopes and stream banks, are diagnostic of this common forest community. This community is the most common in the area.
This Community is very common on lower and middle slopes, with fertile soils that hold water well but do not remain saturated. Lush colonies of spring ephemerals and other wildflowers are characteristic in the spring, and found in rolling uplands and ravines. The understory tends to be dense with Spicebush and Pawpaw.
This generally small-in-size community is found in areas where seeping groundwater forms permanent swampy areas, typically where water seeps into a relatively flat area from the base of an adjoining slope. The heavy presence of Red Maple, Black Gum, Cinnamon Fern, Possumhaw, Sweetbay Magnolia, and Netted Chain Fern is characteristic
These communities found within wooded areas are perennially damp. They tend to surround small streams fed by a mosaic of seeps and springs that emanate from the porous sandy-gravelly soils of slopes along the stream valleys. The trees are typical of moist conditions, but heavy concentrations of New York and other ferns are characteristic.