May 3, 2014. I arrive at the visitor’s center parking lot early this cool morning to an overcast sky and rain threatening. From the low boardwalk I check the red-shouldered hawk nest in the muck swamp but see no activity.
The muck swamp is what most visitors think a swamp should look like – tall cypress and tupelo trees dripping with Spanish moss and standing in pools of stagnant water, set off by those exotic and mysterious cypress knees. Rather than the red and yellow clays that define most of the park’s soils, the muck swamp, more properly known as Dorovan muck, is an official soil type defined by the US Department of Agriculture as a “very dark brown mucky peat consisting of partially decomposed moss, leaves, roots and twigs…..extremely acid…… and associated with densely forested flood plains, hardwood swamps, and depressions in parts of the Southeast and Gulf states.”
The organic layer in a muck swamp may be more than ten feet deep. The one at Congaree is found along the northern edge of the floodplain, at the base of the upland. The sandy uplands act like a sponge that absorbs rainwater and slowly releases it as underground seepage that trickles into the muck swamp, where it tends to collect on the surface, even after periods of no rain when the rest of the floodplain is dry. During prolonged dry periods, however, the muck swamp will dry up, at least on the surface, but the water table is never far from the surface.
While a geology graduate student at the University of South Carolina, Dr. David Shelley (now Education Coordinator at Congaree’s Old Growth Bottomland Forest Research and Education Center) and his advisor, Dr. Art Cohen, conducted a fascinating study, using sediment cores, of the muck swamp.
For their deepest core, the scientists estimated an age of 21,000 years and based on the plant material, the muck swamp was then an oxbow lake with spruce trees growing nearby. By 3,500 years ago the lake had filled in with sediments and turned into a swamp. Pollen analysis revealed a forest that was becoming more similar to the current one, consisting of pines, sweetgums, alders, and maples, and for the first time, tupelo, cypress, and magnolia were showing up. The upper sediments closest to the surface had a pollen composition heavy with swamp tupelo, much like today’s muck swamp forest. Throughout most of the cores, the researchers were finding charcoal, indicating that fires were part and parcel of the prehistoric landscape.
The muck swamp is one of the more unusual plant and geologic community types found in the Congaree floodplain, but it only represents a small portion of the park which consists chiefly of a diverse and drier bottomland hardwood forest growing in fertile red or yellow clay sediments deposited by regularly occurring floodwaters.
muck swamp photo copyright NPS/jt-fineart.com