Plant Succession on Granite Rock in Eastern North Carolina

1. The transition between Piedmont and Coastal Plain provinces, called the fall line, has numerous outcrops of granitic rock scattered along its length throughout North Carolina, South Carolina, and Georgia. 2. Rocks are unfavorable habitats for plant colonization and these are particularly so because of the long dry summers with high temperatures. Especially adapted plants, including several rock endemics, grow here in spite of the extreme conditions. Succession on the North Carolina rocks follows two major lines, originating (1) anywhere on the rock surface and (2) in depressions. The depressions may be dry, moist, or pools. 3. The bare rock surface is invaded by Grimmia or crustose lichens. The latter do not contribute to further succession. Grimmia forms mats which are successively invaded by stages dominated by (1) Cladonia-Selaginella, (2) Polytrichum, (3) Andropogon, (4) conifers. 4. Dry depressions retain little water and are floored with a clayey soil. The soil is too thin to support species which lead to a successional series and too deep to permit the beginnings of a normal rock succession. They support scattered succulents like Talinum and Portulaca, and sometimes dry, fibrous individuals like Fimbristylis and Stenophyllus. 5. Damp depressions represent the best development on the rocks. The stages are essentially like those on the rock surface but the additional moisture results in richer and more rapid growth, with hardwoods appearing in the later stages. 6. Pools are usually intermittent but regularly support marsh species. The margins have the normal rock series spreading from the pool and Cyperaceae predominate among the soil builders in the water or mud. Late stages are dominated first by mesophytic shrubs and later by hardwoods. 7. Margins are irregular. Where seepage occurs there may be small boggy areas dominated by Sphagnum. Dry margins are usually fixed and rarely show evidence of migration upon the rocks. Shaded margins, protected from washing, produce a distinctive pioneer community upon the debris which accumulates. Entodon is the dominant. 8. The exposures must owe their origin to factors which caused the fall line. Considering the time since this line was formed and the rate of plant succession, it is proposed that the rocks were once entirely covered although probably not so richly forested as the surrounding country. The activities of man resulted in repeated fires and erosion which again uncovered the rock, and today drought,