Sandstone rock outcrops provide extreme environmental conditions for plants in a stress filled habitat. Little water or soil is available to support a plant community. Periods of available water usually only occur during spring and fall. Plants and animals, however, find an advantage to colonizing new unclaimed habitat. Those that succeed must adapt or evolve physiological or morphological changes to survive in this desert-like environment. This exhibit provides an overview of the sandstone rock community on Little River Canyon National Preserve.
Little River Canyon National Preserve contains sedimentary rocks of the Pottsville Formation, with lower portions of conglomeratic, sandstone, shale, coal and mudstone and upper portions of resistant conglomerates and sandstone. The Preserve landscape varies from gently undulating upland areas to sheer vertical cliffs to the narrow canyon floor.
Some plants take advantage of seasonal pools on Little River Canyon sandstone outcrops to complete their life cycle. Elf Orpine (Diamorpha smallii) is a winter annual that sprouts in the fall when rains fill vernal pools. Flowers and fruits form in the spring with the plant dying once fruits have fully formed and vernal pools dry from the oncoming summer heat.
Other plants find small pockets of shallow soil in rock depressions or crevices. Most try to squeeze in their life cycle requirements during the rainy spring and fall months. Typical plants that can be found in the spring include yellow sunnybell (Schoenolirion croceum) and Appalachian sandwort (Minuartia glabra).
Plants growing on sandstone outcrops must adapt to extreme environmental conditions in order to survive. Little River Onion (Allium speculae) is a plant that has actually evolved into a new species to acquire these needed adaptations. It is endemic to granite outcrops in north Georgia, where it is considered rare by the State of Georgia, and on sandstone outcrops in northeast Alabama.
Many plants have adapted to the extreme environmental conditions on sandstone outcrops. Some are more common along the edges of these outcrops where conditions are less severe, while others have found their own approach to colonizing and surviving desert-like interior sections of the outcrops . Outcrops represent an opportunity for plants to find new habitat and perpetuate their species. They, however, must adapt and find an advantage that allows them to survive. Some of the species encountered on sandstone outcrops of Little Canyon National Preserve include…..
Constructed and written by Bill Garland, photography by Bill Garland and Hal Yeagar.