Ecosystems of South Florida

http://sofia.usgs.gov/virtual_tour/ecosystems/index.html

South Florida is home to a variety of ecosystems. Small variations in elevation (in some cases, only inches), water salinity (a measure of salt content), soil type, and fire frequency dictate which landscape community will prevail. Below are descriptions and photographs of some of South Florida's unique ecosystems.

Coral Reefs

Star and staghorn coral found in the Florida Keys. Photo courtesy of Eugene Shinn. [larger image]

Corals that grow in sunlit areas depend on tiny algae called zooxanthellae that live in their soft tissue. The zooxanthellae help provide oxygen and food for the polyps. Corals that live in deep water, where there is no sunlight, do not have zooxanthellae.

Freshwater Marsh

Freshwater marsh in Water Conservation Area 3. [larger image]

Freshwater marshes are generally wetlands with an open expanse of grasses, sedges, rushes, and other herbaceous plants. Freshwater marshes generally contain few, if any, trees and shrubs. Marshes have standing water for much of the year and act as natural filters. As water passes over the marsh, water flow is reduced, and suspended particles settle out.

Wet prairies, sawgrass marshes, ponds, and aquatic sloughs are freshwater marsh communities common in South Florida. The word "slough" (pronounced "slew") is used to describe Everglades areas where the water is slightly deeper than in the surrounding marshes and where a slow current is present.

Animals found in the marsh can include fish, invertebrates, frogs, snakes, alligators, white-tailed deer, the Florida panther, and other mammals. Many waterbirds and wading birds nest and forage in marshes as well.

Hardwood Hammock

Hardwood hammock in Fern Forest Park. [larger image]

Hardwood hammocks are localized, thick stands of hardwood trees that can grow on natural rises of only a few inches of land. Hammocks in the Everglades perpetuate themselves by building up thick layers of soil and peat, thus providing high ground for the trees to grow. In South Florida, hammocks occur in marshes, pinelands, and mangrove swamps. Hammocks rarely flood because of their slight elevation. Woodland that is not logged or burned for 20 or more years will develop into a hammock.

Hammocks may contain trees of a temperate or tropical climate origin, such as the sabal palm, live oak, red maple, mahogany, gumbo limbo, and cocoplum. The diverse flora found in hammocks also includes many additional tree species, epiphytes ("air plants"), and ferns. More epiphytes are found in South Florida hammocks than in any forest in the United States.

Wildlife in hammocks can include tree snails, raccoons, opossums, birds, snakes, lizards, tree frogs, and large animals such as the Florida panther, bobcat, and deer.

Salt Marsh

Salt marsh at Everglades National Park. [larger image]

Salt marshes exist along the coast, where fresh water and marine water meet. These areas are at least occasionally inundated with salt water and contain non-woody, salt-tolerant plants. Marshes generally contain few, if any, trees and shrubs.

Most of the animals in coastal salt marshes can tolerate variable water depth and salinity. Animals that may be found in these areas include small mammals, juvenile and adult fish, shellfish, and birds.

Scrub community at Jonathan Dickinson State Park. [larger image]

Scrub

Generally, scrubs are communities dominated by pinewoods with a thick understory of oaks and saw palmetto. Scrubs occupy well-drained, nutrient-poor, sandy soils. Plants that grow here have adapted to dry conditions. Fires play an important role in scrub ecosystems; in the absence of fires, a hardwood forest of oak will develop.

Animals that live in the scrub are adapted to hot, desert-like conditions. Gopher tortoises, scrub jays, lizards, insects, and spiders are commonly found here.

Dunes

Close-up of dunes at Blowing Rocks beach. [larger image]

Dunes are created by wind, but are held in place by grasses that trap sand grains as they are being moved across the beach. Dunes stabilized by grasses protect the coast against winds and pounding waves. The vegetation found within Florida's dunes varies and is dependent upon many factors, including storm waves, windblown sand, salt spray, substrate (soil), and climate.

Florida beaches are important nesting sites for sea turtles and shorebirds. A loss of beach habitat to real estate development, erosion, and rising sea level has caused a decline in the nesting shorebird and sea turtle populations.

Freshwater Swamp

Freshwater swamp in Loxahatchee National Wildlife Refuge. [larger image]

Although the freshwater swamp seen in this picture is dominated by cypress trees, other freshwater swamps found in Florida can be dominated by bay trees (i.e. sweetbay, sweet gum) or hardwoods (i.e. oak, elm, red maple). Other plants found in swamps include epiphytes ("air plants") growing on trees, vines, and ferns. Influences on the characteristics of a swamp include temperature, fire frequency, the length of time soils are covered with water, and the amount of accumulated organic matter.

Many animals spend part of their lives in the swamp, moving as water levels rise and fall. Wood storks, herons, many other birds, otters, black bear, and the Florida panther are only a few of the animals that find food, homes, and nesting sites in Florida's swamps.

Pinelands in Everglades National Park grow on porous limestone or limestone with a thin soil cover. [larger image]

Pinelands, or pine flatwoods, are the most common plant communities in Florida. Pinelands occur on nearly level land composed of coarse, poorly drained soil, or on porous limestone. Longleaf pine and slash pines are the dominant trees in pinelands. Understory plants commonly include saw palmettos, wildflowers, and ferns.

Plants that grow in the pinelands must be resistant to fire because pinelands are maintained by fire. Fires are beneficial to the pines because young pine seedlings require lots of sunlight to survive, and the fires destroy hardwood competitors. When fires occur, hardwood seedlings and other understory plants are affected, but the thick bark of the pine resists fire damage. Without fires, hardwoods would eventually overshadow the pines, and a hardwood hammock would emerge.

Wildlife commonly found in pinelands includes deer, squirrels, bobcats, skunks, opossums, raccoons, birds, snakes, and tortoises.

Mangroves

Early settlers to South Florida regarded mangrove forests as being useless, mosquito-infested, uninhabitable lands. Today, ecologists realize their important role in coastal ecosystems. Mangrove leaves, trunks, and branches fall into the water and are transformed into detritus and peat, which is the basis of an elaborate food chain. Mangroves provide protected habitat, breeding grounds, and nursery areas to many terrestrial and marine animals. Mangroves also provide shoreline protection from wind, waves, and erosion.

Many terrestrial and marine animals including invertebrates, fish, amphibians, reptiles, birds, mammals, and mosquitoes find food and shelter within Florida's mangrove forests.