Cataract bog


A cataract bog is a rare ecological community formed where a permanent stream flows over a granite outcropping. The sheeting of water keeps the edges of the rock wet without eroding the soil; in this precarious location no tree or large shrub can maintain a roothold. The result is a narrow, permanently wet, sunny habitat.
While a cataract bog is host to plants typical of a bog, it is technically a fen. Bogs get water from the atmosphere, while fens get their water from groundwater seepage.
Cataract bogs inhabit a narrow, linear zone next to the stream and are partly shaded by trees and shrubs in the adjacent plant communities. Algae growing on the rocks can make the surface slippery and dangerous for those exploring a cataract bog.

Typical species

The rushing water carves out small depressions where soil accumulates, forming micro-islands that play host to plants that thrive with low levels of nutrients and shallow root structures. Typical species include Sphagnum moss; carnivorous plants such as round-leaf sundew, pitcher plants, and horned bladderwort ; several orchid species such as common grass pink, small green wood-orchid, rose pogonia, and nodding ladies'-tresses. Other plants found in cataract bogs are limeseep grass-of-Parnassus, Indian paint brush, stiff cowbane, Appalachian bluet and northern sundrops.
The plant communities are fragile because of their tenuous attachment to thin soil above the rock substrate. During prolonged drought, the stream may dry up and the edges of the micro-islands curl up. Heavy rainfall can then wash away the micro-islands, so a cataract bog is in a continual state of change and renewal.

Location

Cataract bogs are found only in the southern Appalachian Mountains of the United States, at elevations of between. They are restricted to the Blue Ridge Escarpment region of South Carolina and a small area of North Carolina, a region with exceptionally high rainfall.