COASTAL PLAIN: The calcareous forest communities
The calcareous forest
communities do not occupy significant acreage in the coastal plain; however,
they do contribute considerable diversity to the flora of the coastal
plain as numerous rare and uncommon species are found there. Most of the
undisturbed sites of this community are found on private lands that are
not publicly available.
The calcareous forests
occur on bluffs, slopes, or moist flats that overlay calcareous substrates.
The substrate is either marl or limestone that was laid down as marine
deposit when the ocean covered the coastal plain. The calcium from the
underlying substrate is a major factor shaping the diversity and composition
of the vegetation. Certain species of plants, referred to as calcicoles,
thrive in a basic to circumneutral soil that results from the presence
of calcium ions. These species generally are mixed with the flora of the
surrounding community to form a diverse community. Classification of the
various calcareous communities is not well developed; however, we do recognize
two well-developed types.
Calcareous bluff forests
occur on mesic sites that overlay shallowly buried or exposed marl or
limestone formations. These forests occur along rivers and creeks where
erosion has exposed or brought the marl or limestone formation close to
Trees that characterize
the calcareous bluff forests include
oak (Quercus muehlenbergii),
hop hornbeam (Ostrya virginiana),
white basswood (Tilia heterophylla),
slippery elm (Ulmus rubra),
Carolina buckthorn (Rhamnus caroliniana),
black walnut (Juglans nigra),
and southern sugar maple (Acer barbatum).
Elements of the other
deciduous forest communities occur and include
and eastern red cedar.
are common and include many that are found in other deciduous communities
of the piedmont and coastal plain. Several species, however, are either
confined to or are more common in this community. They include
shadow-witch (Ponthieva racemosa),
mottled trillium (Trillium maculatum),
and thimbleweed (Anemone virginiana).
Often, where the calcareous
substrate has been exposed, it hardens. Rainwater then erodes the substrate,
forming recesses in which two rare ferns are able to become established
by spore dispersal:
and Wagner's spleenwort (Asplenium heteroresiliens).
Three sites that harbor
this community are Old Santee Canal Park and Wadboo Creek in Berkeley
County and Santee State Park in Orangeburg County.
flat, calcareous forests
This calcareous community
occupies low, wet flats adjacent to river systems. The underlying marl
formation is not exposed, but it is close enough to the surface to influence
plant composition. It is not a common community in the coastal plain.
In fact, it has been studied only along the western side of the Cooper
River in Berkeley County and in several sites in and around Huger Creek
in the Francis Marion National Forest (FMNF). It is not known to what
extent it occurs throughout the coastal plain.
Recent studies on
Mulberry and Lewisfield Plantations reveal the distinct flora of the community.
The calcicoles that are present include mottled trillium, crested coral-root,
shadow-witch, and American alumroot. These species also occur in the calcareous
bluff forests. Two rare woody species are
nutmeg hickory (Carya
and prickly-ash (Zanthoxylum americana).