The Acidic Cliffs and Talus Ecological System in Harpers Ferry National Historical Park occurs on steep slopes covered in boulders and rock outcrops. Soil is infertile and is limited to spaces between boulders or thin mats on top of rocks, so there are few plants. Within this ecological system, the Sweet Birch - Chestnut Oak Talus Woodland occurs in scattered locations and has an open tree canopy. The Acidic Boulderfield, mapped in one location in the park, seems devoid of plants and is dominated instead by lichens.