By Alan Cameron
The technical name for the rock domes in DuPont Forest is Southern Appalachian Granitic Domes and they occur sporadically through the Blue Ridge and Piedmont Provinces of Virginia, North Carolina, Georgia, and Alabama.

The rock is not granite. Many millions of years ago it did start life as granite but since then it has gone through a metamorphosis and is now classified as gneiss. I have documented 83 of these domes in DuPont Forest. They can be as small as a dozen square meters or they can span dozens of acres.
Some of the domes have pock marks. Probably the best examples of these are on Cedar Rock Trail near its peak. These are called panholes. They began as tiny depressions or cracks where water collected. Panholes can expand from weathering and erosion but the main activity of how panholes expand is from biological weathering caused by rotting vegetation which makes the water acidic.

The large green mats growing on the domes are mostly composed of two elements. The darker plant is Twisted-hair Spikemoss (Selaginella tortipila) and the lighter patches are Reindeer Moss (Cladonia rangiferina). Neither of these plants are true mosses. They are phylogenetically more closely related to ferns than to any other group of living plants so are often referred to as fern allies. They are very tough plants. There is virtually no soil under them, their roots cannot penetrate the rock, they depend solely on rain for water and they are subject to fierce winter winds and intense summer sun. These mats can be hundreds of years old and they recover from abuse very slowly so stepping on them should be avoided.


Vegetation islands are a common feature of the domes. These appear and expand over time in a process that links vegetation and soil development, but they are eventually destroyed by windthrow, drought, other natural disturbances, or simply falling off the rock if it is slanted. The result is a pattern with mats of different levels of development at any given time. Mat dynamics are different in different parts of the rock, with older mats and more permanent patterns near the edges, and sparser, younger mats in the interior.

The thin soils make these communities sensitive to drought, especially the long-lived woody species. Below is an example of a small grove of pitch pines on a DuPont dome off of Corn Mill Shoals Trail. One of the trees has died and fallen and the wood twists around the tree. This is called spiraling and it is an adaptation to stress-bearing or load-bearing, as a spiral pattern theoretically gives more support to a tree trunk and allows it to bend more before splitting. There is also a hypothesis suggesting that a spiral pattern in the wood’s xylem allows for greater distribution of nutrients, particularly if all the water is being absorbed on one side of the tree. Spiraling happens frequently in conifers and is usually found in trees in exposed places like domes that are more susceptible to wind shear and desiccation than trees growing in deeper soils.


Many of the flora found on the domes are often endemic to the domes. But there are various fauna that also make use of the domes. One rarely found grasshopper called the Southern Green-striped Grasshopper (Chortophaga australior) can be found on DuPont domes. Also, gestating timber rattlesnakes, which are live-bearers and so do not lay eggs, require considerable direct sunlight to incubate their developing young so they will come to the domes in the spring to bask in the strong daylight until they give birth in the fall. Below is a photo of a gestating female rattler off of Cedar Rock Trail.

