The Facts About Southern Deepwater Swamp Forests

Southern deepwater swamp forests are a type of freshwater wetland often found along the floodplains of large rivers. They are filled with water most or all of the year, and often form a 1- to 2-mile wide band extending from the river marshes to the bottomland forests along creeks that flow into the river. Swamp forests are home to a host of plants and animals.

PLANT LIFE IN SWAMP FORESTS

The depth of flooding, and its duration, influences the types and density of trees in the swamp. The primary tree species in southern swamp forests are bald cypress and water tupelo, two trees adapted to the flooded conditions of their environment. But for seeds to germinate, bald cypress and water tupelo need periods when the water level is at or below the soil surface.

In addition to bald cypress and water tupelo, swamp forests at the 310-square-mile Savannah River Site (SRS) near Aiken, S.C., also are home to a variety of other trees, especially on islands and ridges in the swamp. They include black gum, water ash, water elm and red maple. Shrubs in swamp forests include Virginia willow and buttonbush. Vines include pepper-vine, greenbrier, honeysuckle and catbrier. Herbs include false nettle and St. John's-wort. Duckweed is a small plant that floats on the surface of standing water in many swamps.

WILDLIFE IN SWAMP FORESTS

The primary wildlife inhabitants of swamp forests are reptiles, amphibians, fish, birds, raccoons, opposums, wild pigs and invertebrates.

Reptiles and amphibians are prevalent in swamps because of their ability to adapt to fluctuating water levels. Reptiles found in swamps include snakes such as the cottonmouth, also known as the water moccasin, various non-poisonous water snakes, king snakes, turtles and alligators. Amphibians include various species of frogs and salamanders.

Fish are both temporary and permanent residents of swamps in the Southeast. Some fish use sloughs and backswamps for spawning and feeding during the flood season. Common species of fish found in swamps include bowfin, minnows and mosquitofish. Most larger fish, such as largemouth bass, are temporary residents of swamps.

Birds include wood ducks, herons, ibises, egrets and occasionally wood storks.

A wide variety and high numbers of invertebrates are found in permanently flooded swamps. These include various species of crayfish, clams, snails, freshwater shrimp and immature (larval) stages of many insects.

RESEARCH

At the Savannah River Ecology Laboratory (SREL), studies in swamp forests along stream and river floodplains have indicated the significance of fluctuating water levels to the establishment and survival of seedlings, or young trees. Floods and changing water levels -- resulting from SRS activities and upstream control of water releases from reservoirs on the Savannah River -- may limit forest regeneration, reduce growth of trees and affect the long-term maintenance of a forest's biological structure. The same is true in swamp forests throughout the Southeast.

In other research, scientists at SREL have used aerial photography and satellite images with a computer-based technique called geographic information systems (GIS) to create a vegetation map of the Savannah River Swamp and to measure changes in the vegetation over time. Various types of vegetation reflect different patterns of light in a satellite image. The various colors on a GIS map indicate the types of vegetation.

DID YOU KNOW?

• Cypress trees, a common swamp species, have "knees" that extend from the root system to well above the average water level. The functions of the knees have been an issue of speculation for the past century. Some scientists believe they anchor the tree, while others think they are a means of respiration for the tree. Perhaps they do both.

• The trunks of cypress and water tupelo trees often have swollen bases when they grow in flooded conditions. The height of the swollen base is a response to flooding, with the greatest swelling occurring where there is a continual wetting and soaking at the tree trunk but where the trunk is also above the normal water level.

• Bald cypress trees may live more than 1,000 years, though few remain that are more than 200 years old because virgin stands of cypress in the United States were logged during the past two centuries. One bald cypress at the SRS is estimated to be at least 600 years old. The wood, because of its resistance to decay, was used extensively for building materials.

• Southeastern swamps often have a high level of biological productivity because they are rich in nutrients due to the fluctuating water levels.

RANGE

Bald cypress swamps extend from eastern Texas into Louisiana, Mississippi, Alabama, Arkansas, western Tennessee, southeastern Missouri and as far north as southern Illinois. They are found throughout the Southern Coastal Plain in Mississippi, Alabama, Florida, Georgia, South and North Carolina. They extend as far north as southern New Jersey along the Atlantic Coastal Plain.

SWAMP FOREST VALUES

Southern deepwater swamp forests (and other wetlands) perform many valuable functions. Among them are:

• habitat for endangered and threatened species, for example the American alligator and wood stork.
• flood control because of their capacity to store water during and after heavy rains and storms.
• improvement of water quality because they can remove organic and inorganic nutrients and toxic materials from water that flows across them.
• aesthetic value because of their visually and educationally rich environments.
• a part in the maintenance of water and air quality on a global scale, for example the role of wetlands in global cycles including nitrogen, sulfur, methane and carbon dioxide.
• recreation, fishing and hunting.

Last review:  October 12, 2007