The Coastal Plain Oak Forest is closely aligned with the location of sandy soils in the Coastal Plain region of the park. Sediments in the Coastal Plain were deposited by rivers and reworked by the ocean. Below the sediments lie metamorphic rocks similar to those in the Piedmont and Mountains. Much of the Coastal Plain terrain administered by Rock Creek Park (including the Fort Circle Parks east of Rock Creek) was cleared during the Civil War in the 1860s to build forts and maintain open sight lines for soldiers defending the nation’s capital. This oak forest has grown up since then in these disturbed areas.
At Rock Creek Park, the Coastal Plain Oak Forest does not border wetlands, as would be typical for this natural community. Instead it’s surrounded by urban neighborhoods or occurs on hillsides along the circle of Civil War forts ringing D.C. It may be that the presence of the Coastal Plain Oak Forest in these places is a clue to the previous existence of wetlands nearby and/or an underlying clay layer that slows the drainage of water. Or perhaps a larger Coastal Plain Oak Forest once inhabited a more typical setting nearby, and these are remnants. At this point, these forested stands are not entirely understood.
Maybe, on the other hand, these oak forests in Rock Creek Park's Coastal Plain will prove to need a separate classification—a new name to set them apart from the Coastal Plain Oak Forest that truly does border wetlands. Not every acre of forested land in the Mid-Atlantic has been assessed. In the future there may be many more acres of similar forest found, with no adjacent wetlands. If there prove to be significant differences in function and form between these oak stands in the Fort Circle Parks and the true Coastal Plain Oak Forest, it may warrant a new name. Ecobit: Lumping and Splitting