THE PIEDMONT: The
rocky shoals community
Rocky shoals are restricted
to the upper and middle piedmont. The community is characterized by the
abundance of small boulders or bedrock near the surface (shoals) during
periods of low water flow. The shoals are mostly submerged during periods
of high water flow Rocky shoals are most extensive near the fall line
that separates the piedmont from the coastal plain on major rivers such
as the Saluda, Savannah, Broad, and Congaree.
The rocky islands
that are mostly submerged during high water are occupied by emergent aquatic
or semiaquatic plants. Three species characterize this habitat:
American waterwillow (Justicia americana),
and riverweed (Podostemum ceratophyllum).
Riverweed, with its
tiny dissected leaves and fleshy discs, which are used to attach the plant
to submerged rocks, resembles an alga more than a vascular plant. Its
flowers have no showy parts, and the plant must be viewed with a magnifying
lens to fully appreciate its unusual nature.
often present in great abundance, with its five-foot stalks and large
whitish flowers, is spectacular. In June of 1773, William Bartram, while
at the shoals on the Savannah River at Augusta, stated, "nothing
in vegetable nature was more pleasing that the odoriferous Pancratium
fluitans [Hymenocallis coronaria of todays taxonomy], which
almost alone possess the little rocky islets which just appear above the
water. The greatest display of spiderlily today is at the rocky
shoals of the Catawba River at Landsford Canal State Park.
A wide variety of
rooted and emergent aquatics, species typical of marshy habitats or weeds
typical of wet disturbed habitats, may be associated with the rocky shoals.
Brazilian elodea (Egeria densa),
broadleaf arrowhead (Sagittaria latifolia),
red tooth-cup (Ammania coccinea),
winged monkey-flower (Mimulus alatus),
and a variety of rushes, sedges, spikerushes, and bulrushes.