The Mixed Oak / Heath Forest is a natural community of dry hilltops. The soils are dry and acidic because rainwater runs rapidly off these high surfaces or percolates quickly through the soil. This leaches away basic elements like calcium and magnesium.

The Mixed Oak / Heath Forest is found in two geologic settings:

1. Acidic bedrock (typically Laurel Formation) underlies some stands. Soils formed here are fairly fine-textured loams (made of sand, silt, and clay in approximately equal proportions). Because they are at relatively high elevations in the park, rainwater runs off quickly and the soils tend to be dry.
2. Remnants of ancient river terraces underlie many stands. Soils are infertile, coarse, sandy sedimentary deposits with smooth cobbles and gravel, and do not hold moisture. Ecobit: Ridgetop River Terraces Riddle

The full common name of this natural community is Mixed Oak / Heath Forest (Low-Elevation). "Low-Elevation" doesn’t refer to its relative position in Rock Creek Park; rather it contrasts this natural community to other oak/heath forests that occur at higher elevations in the mountains.