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Ecology of Congaree National Park

Ecology of Congaree National Park

Within Congaree National Park there are 1,220 taxa, including 33 amphibians, 45 reptiles, 71 fish, 191 birds, 37 mammals, 328 terrestrial plants, 512 wetland plants, and three aquatic plants. Formerly the area that is Congaree National Park was home to red wolves, black bears and mountain lions. These species, however, no longer are found within the park. Congaree National Park hosts five national champion trees and 27 state champion trees, which can provide insights into old-growth ecosystems. The loblolly pine (Pinus taeda), swamp tupelo (Nyssa aquatica), laurel oak (Quercus laurifolia), possumhaw (Ilex decidua) and sweet gum (Liquidambar styraciflua) are among the species that are in American Forests’ National Register of Big Trees. By studying champion trees, scientists can discern optimum ecological conditions for these species.

There are invasive species within Congaree National Park, and the Southeast Coast Exotic Plant Management Team manages exotic plants throughout the park. Species that are being treated are Chinese wisteria (Wisteria sinensis), Chinese privet (Ligustrum sinense), Japanese climbing fern (Lygodium japonicum), beefsteak (Perilla frutescens), shrub lespedeza (Lespedeza bicolor), Japanese stiltgrass (Microstegium vimineum), Chinaberry (Melia azedarach), Japanese honeysuckle (Lonicera japonica), and kudzu (Pueraria montana).

This team also is removing the native invasive sweetgum to restore the longleaf pine habitat in part of the park. Longleaf pine forests are highly diverse, fire-dependent, open-canopy ecosystems. Wildfires caused by lightning resulted in habitats and vegetation that needed fire to be healthy, but fire suppression techniques have caused a change in the ecosystem. Sweetgum, oak, hickories, common persimmon, and southern magnolia have taken over some of the area that used to be occupied by longleaf pines, and these hardwoods create a closed canopy (instead of open, like longleaf pines). Longleaf pines are shade-intolerant, so they are less likely to survive in close canopy ecosystems.

Congaree National Park is working to restore the historic landscape and vegetation, including the longleaf pine by conducting fire treatments. These fire treatments will remove vegetation that competes with the native longleaf pine communities and creates healthy soil conditions.

Congaree National Park is known for the rich diversity of bird species. It contains three state-listed species of concern, including the bald eagle, American swallow-tailed kites, and wood stork, with 30 other priority species.

A image of a red bird sitting on a brown branch. Trees are in the background.
An image of a Summer Tanager, which can be found in Congaree National Park. These are medium-sized songbirds. NPS. 

Cypress trees are found within Congaree National Park. These trees contain cypress ‘knees’ which are distinctive cone-shaped structure that form above the roots of a cypress tree that can be seen on the surface. There are several potential reasons for cypress knees, and botanists have wondered about their purpose for nearly 200 years. One theory is that carbohydrates are stored within cypress knees in the presence of “granules,” however additional work needs to be complete to test whether this is correct. Other scientists have suggested that cypress knees assist in the trees in nutrient accumulation during flooding events. However, during one study no direct evidence of nutrient acquisition was seen. Another hypothesis is that cypress knees provide mechanical support that acts as an anchor during fluctuating water levels. Water marks from flooding events can commonly be seen on Cypress trees. An alternate hypothesis is that cypress knees evolved in due to environmental pressure that no longer occur, so that they currently serve no purpose.

An image of cypress trees flooded. Cypress knees can be seen.
The water level in this image is relatively high, covering an area near the boardwalk. Cypress knees can be seen in the image. Credit: Carrie McIntosh


Synchronic Fireflies at Congaree

For two weeks in mid-May and early June, synchronous quick flashes of male P. frontalis fireflies can be seen at Congaree National Park. Synchronous flashing displays are rare among North American fireflies, and the species of fireflies found within Congaree National Park live in a range that spans Alabama, Florida, Mississippi, North Carolina, South Carolina, and Tennessee with a preferred habit in mature forests and wet bottomlands. Fireflies flash to communicate and each flash length is unique to a certain species. Flashing begins shortly after sunset, lasting for an hour, and again just before dawn.

Male and female fireflies have distinct flashes from one another. Male fireflies have quick single flashes approximately twice per second, and the females then respond with their own flash pattern. Ultimately firefly flashing is a mating ritual called a photic dialog. Female P. frontalis fireflies are more difficult to find than the males because they are more susceptible to predation and hide to survive.

An image of fireflies at night. The light is yellow and many are lit up at the same time.
Synchronous fireflies, although rare in North America, can be found in Congaree National Park from mid-May to early-June. NPS.