Life On The Edge

 

The view from the Satulah Mountain overlook. Rock cliffs fall away from many of the Blue Ridge peaks, providing habitat for animals and plants that have evolved to the unique, yet harsh, environment. (Photos courtesy of Owen Carson)

For much of history, cliffs have been considered dangerous and inhospitable places, precipitous environments that offer little to no habitat for living things. This notion dates far back; with some of the earliest cave paintings depicting herds of animals being forced over sheer faces by Neolithic hunters. Cliffs also appear in ancient writings, often associated with fire, fear and death. Even early explorers who searched our region steered clear of outcrops, assuming that the rich forests they botanized were far more diverse than open stone. But in recent years, with better technology and increased curiosity, we've engaged in more intensive studies of these poorly understood environments and the findings have been nothing short of a paradigm shift.

In order to appreciate the wonders of the cliff environment, it is helpful to explore the geologic processes that produced the unique landscape of the southeastern United States. In a nutshell, roughly 270 million years ago the continental landmasses ancestral to North America and Africa collided, forcing huge masses of rock inland from the eastern margin of North America, aggregating to form what we now know as the Appalachian Mountains.

During these collisions, molten rock also rose from within the earth, some reaching the surface, some crystallizing before getting there. The latter, known as igneous plutons, have since been exposed via erosional forces and are now prominent across the landscape – one of the more recognizable of these is Looking Glass Rock, a large granitic pluton, also known as a granitic dome. Granitic domes are iconic landforms, rising above the surrounding coves and ridges, visible for miles. And while Looking Glass Rock is one of North Carolina's largest, these communities are scattered all across the Western part of the state. For the past week I've had the pleasure of studying some of these outcrops that occur in the Highlands area. Contrary to what we used to believe, these environments can be quite unique and support a number of rare and endemic species.

The surrounding forest approaching granitic domes generally consists of oaks and hickories, but species of pine also co-occur, including pitch and Table Mountain pine. Due to the extreme exposure that most of these outcrops experience, trees at the apex of the open domes are gnarled and stunted, beaten by wind, rain and cold. Dwarfed red oaks, thick patches of blueberry and huckleberry, and even species of juniper, such as the dwarf juniper on Satulah Mountain, can be found in the diminutive forests along with numerous species of laurel and rhododendron.

Also, domes that experience the influence of a more basic, higher-pH parent rock will support a wider suite of flora. On these you may find yellow honeysuckle, fringetree, ash trees and other small plants with an affinity for richer soils. The influence of bedrock seepage on and around the cliffs can also play into the diversity of these environments.

Often times ground and rainwater will perch in flat or pitted areas that have been weathered away faster than the surrounding rock, providing a refuge for wetland plants even in a seemingly dry, inhospitable place. These "vertical bogs" can look floristically identical to flat examples, supporting peat mosses, sedges, viburnums, lilies, orchids, grass-of-Parnassus, and even carnivorous plants such as sundews. The biodiversity can be amazing.

Out on the bare rock soil formation is slow, and what little exists is in a constant state of flux, supporting an interesting succession of lichens, fungi and plants. Crustose lichens, those that are appressed to rock, are generally the pioneers of granite domes.

They become established in microhabitats created by the heterogeneous surface of the rock. These lichens radiate outwards, forming large patches. More complex species, such as leafy lichens and mosses, begin to aggregate in pits where weathered rock dust and water collect, establishing dense organic mats.

With continued soil development comes the succession of larger plants–grasses, sedges, and rushes, wildflowers, small shrubs and even some trees can be found.

However, the forces of nature, wind, rain and bears, included, can often work to strip these mats from the rock's surface, driving a constant cycle of birth and death.

Let's not forget about the fauna, either – where plants that provide food and shelter exist, so do animals. A number of insects can be found on granitic domes, the most overlooked of which may be the lichen grasshopper, which derives its name from its unique camouflage. Different species of beetles and spiders also inhabit outcroppings. The prehistoric-looking lampshade spider sits in the center of a web that looks exactly like a lampshade, awaiting the unsuspecting flies that float along the rock's surface. A number of mammals also inhabit rock outcrops. Transient species such as bears and skunks will regularly flip organic mats over in search of tunneling grubs or yellow jacket nests, while some mammals, like the smoky shrew, appear to occupy the rock year-round, living in crevices or in surrounding forest.

One of the more iconic species of granitic domes is the timber rattlesnake, which will often retreat to cracks or boulders to den up and mate – keep an eye out for shed skins and be careful sticking your hand where you can't see!

Finally, high elevation granitic domes are one of the best places to see ravens and peregrines, both rare in North Carolina. And if you're lucky, you also might catch a glimpse of a ruby-throated hummingbird visiting one of the many flowering plants on the cliff's face.

Parnassia asarifolia, or kidney leaf grass.

The relatively recent exploration of cliff environments has led us to understand that while these places may look barren, the opposite is actually the case.

These places, although difficult to reach and dangerous to study; support an overwhelming amount of life. The relationships between the plants and animals that occupy these cliffs are only beginning to be understood, and thus the need for more exploration is high. So, next time you decide to take a hike, consider the steep ascent up Looking Glass Rock. You may be pleasantly surprised by what you find at the top!

(Owen Carson is a botanist with Equinox Environmental. He is a Brevard College graduate and lives in Brevard with his wife and kids.)

 
 

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