Rock Outcrop EcosystemState Rank: S4
Areas (not including alpine areas) where bedrock, with thin soil pockets in places, makes up the ground surface and vegetation is consequently sparse, with few if any trees. Vegetation is dominated by low shrubs and herbs which can tolerate the exposed, usually dry, and low nutrient conditions. Scattered trees (i.e., canopy cover totaling less than 30%) may be present, but will often be stunted or wind-flagged. Species composition will vary depending on the nature of the bedrock; the distinction made here is between circumneutral to calcareous rock versus acidic rock. Rock outcrop ecosystems generally grade into woodlands (rocky areas with tree canopies covering > 30-60%) or forests (tree canopies covering > 60%). This is a geographically broad type, and some of the communities listed are unlikely to be found together (e.g., Birch - Oak Talus Woodland and Rocky Summit Heath). Which communities make up any occurrence of this ecosystem will depend on geographic location, substrate pH, and probably other factors.