The Primary class includes natural communities that occur on bedrock, cobble, and exposed mineral soils and are characterized by little to no soil development. The Primary class includes 24 natural community types, which are organized into seven ecological groups based on substrate composition, substrate orientation, landscape setting, and community structure. The Primary ecological groups are Dunes, Sand/Cobble Shore, Bedrock Lakeshore, Bedrock Grassland, Bedrock Glade, Lakeshore Cliff/Bluff, and Inland Cliff. Further classification to natural community type within each ecological group is based on substrate type, community structure, landscape setting, and species composition.