Wetland Plant Communities

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Wetland Plant Communities

Coastal Saltmarshes
Coastal saltmarshes occur on low wave-energy shorelines interspersed with mangroves. Saltmarshes may also extend into tidal rivers and occur as a narrow zone between the mangroves and freshwater marshes.

Many areas within salt marshes are dominated by one plant such as smooth cordgrass (Spartina alterniflora), saltgrass (Distichlis spicata), and needle-rush (Juncus roemerianus). The species existing in any one area depends on the frequency of inundation by tides.

Smooth cordgrass typically occupies the lower areas and often borders tidal pools and creeks. Needle-rush occurs over vast areas and is inundated less frequently, while the highest areas of the marsh are vegetated by saltgrass or such succulents as saltwort (Batis maritima), glasswort (Salicornia perennis), and sea ox-eye (Borrichia frutescens).

The functioning of salt marshes centers primarily on salinity and tides. The harsh conditions associated with daily inundation, desiccation, and high salinities contribute to a low animal and plant species diversity. However, those organisms that have adapted to this environment can be very productive. Tides also provide an important ecological relationship with adjacent estuaries.

Coastal marshes have been affected primarily by waterfront residential developments. Current wetland regulations appear to be successful in preventing major losses of this community for the time being, although scattered losses continue.

Freshwater Marshes and Wet Prairies
Freshwater marshes are herbaceous plant communities occurring on sites where the soil is usually covered or saturated with surface water for one or more months during the growing season.

Wet prairies are characterized by shallower water and more abundant grasses, and usually fewer of the tall emergents, such as rushes (Juncus spp.), than marshes.

Approximately fifteen separate types of marshes or wet prairie have been described in Florida. Major ones include sawgrass (Cladium jamaicense) marshes; flag marshes dominated by pickerel weed (Pontederia cordata), arrowhead (Sagittaria spp.), alligator flag (Thalia geniculata), and other non-grass herbs; cattail (Typha spp.) marshes; bulrush (Scirpus spp.) marshes; spike rush (Eleocharis spp.) marshes; maidencane (Panicum hemitomon) prairies; and grass, rush, and sedge prairies. Any single marsh may have different areas composed of these major types, and there is also almost complete intergradation among the types.

Fire and water fluctuations are largely important in the maintenance of marshes and wet prairies. Fire, especially when combined with seasonal flooding, serves to stress plants not adapted to these conditions and reduces competition from upland species.

Drainage for agriculture activities has been the dominant factor in marsh losses. Existing wetland regulations and a relatively small amount of agriculturally suitable marsh systems remaining in private ownership have reduced past rates of loss of these large systems. Ephemeral, isolated, smaller marshes are more vulnerable to both agriculture activities and urban development.

Scrub Cypress
Scrub cypress areas are found on frequently flooded rock and marl soils in south Florida. The largest areas occur in the Big Cypress region of eastern Collier County and northern Monroe County.

Scrub cypress forests are primarily marshes with scattered, dwarfed cypress (Taxodium spp.). Much of the vegetation is similar to other relatively sterile marshes with scattered sawgrass, beakrushes (Rhynchospora spp.), St. John's-wort (Hypericum spp.), and wax myrtle occurring commonly. Bromeliads, as well as orchids and other epiphytes, are often abundant on the cypress trees. Most scrub cypress in the Big Cypress is in public ownership and does not appear threatened.

Cypress Swamps
Cypress swamps are usually located along river and lake basins or interspersed through other habitats such as flatwoods and dry prairies. In addition, they also occur as strands within shallow, usually linear drainage systems. These swamps have water above or at ground level for a portion of the year. Bald cypress (Taxodium distichum) is the dominant tree. Other associated trees and shrubs that are found within bald cypress swamps include slash pine, pop ash (Fraxinus caroliniana), red maple (Acer rubrum), red bay (Persea borbonia), buttonbush (Cephalanthus occidentalis), sweet bay (Magnolia virginiana), and wax myrtle. Other plants include various epiphytes, ferns (Pterudophytes), poison ivy (Toxicodendron radicans), greenbrier (Smilax spp.), and corkwood (Stillingia aquatica), with arrowhead, pickerel weed, sawgrass, and other marsh plants often found in the open water within cypress domes or strands.

Cypress swamps occur in saturated or submerged soils. Fire is an additional factor in drier cypress domes or heads. These factors are important in reducing competition and preventing the community from advancing to one dominated by evergreen hardwood swamps (the bayhead community). There has apparently been a shift from cypress to hardwood swamps in areas where harvesting of cypress has occurred in the past and the surviving hardwoods subsequently prevented cypress regeneration (i.e., Fakahatchee Strand).

Cypress swamps are reasonably well protected by wetland regulations and the high cost of converting them to other land uses. However, cypress heads and ponded areas are susceptible to modification, and altered drainage patterns and flows from urban development.

Hardwood Swamps
Deciduous hardwood swamps are found bordering rivers and lake basins where the forest floor is submerged or saturated during part of the year. The wetter portions of these forests usually overlap with bald cypress swamps and consist of pond apple (Annona glabra) and pop ash. In slightly higher areas this community is characterized by such trees and shrubs as red maple, laurel oak, buttonbush, Carolina willow (Salix caroliniana), and strangler fig (Ficus aurea). Groundcover is sparse in most of these swamps.

The periodic flooding of the swamps is a dominant factor in the fluctuating of the system, and different communities will become established if these fluctuations are eliminated. All species within this community must be able to withstand or avoid the periodic stresses imposed by high water.

Hardwood swamps share the common threat with shrub swamps and cypress swamps; whereas, the wetter and the more contiguous with open waters or strands, the stronger the regulatory protection.

Mangrove Swamps
Mangroves occur along low wave-energy shorelines on both coasts from Cedar Keys on the Gulf of Mexico to St. Augustine on the Atlantic Ocean. Some of the best examples of mangrove forests are located in the Ten Thousand Islands area of southwest Florida.

Three species of mangroves dominate the composition of mangrove swamps. The red mangrove (Rhizophora mangle), with its stilt root system, is typically located on the fringe with the most

exposure to salt water. Further inland, but usually covered by water at high tides, are the black mangroves (Avicennia germinans), with white mangroves (Laguncularia racemosa) yet farther inland. Buttonwood trees are often found above the reach of salt water. Other plants commonly found among the mangroves include saltwort, glasswort, and a variety of other salt-marsh species.

The mangrove community contributes to the productivity of surrounding estuaries. Leaf fall from the mangroves provides food or substrate for numerous organisms, ranging from bacteria to large fish such as the striped mullet (Mugil cephalus). Detritus-feeding organisms support much of the estuarine trophic structure in mangrove areas including such gamefish as tarpon (Megalops atlanticus), snook (Centropomus undecimalis), and spotted sea trout (Cynoscion nebulosus).

Mangrove swamps are mostly in public ownership and the remainder are reasonably well protected by wetland regulations although losses due to residential and marina developments occur on a relatively small scale.

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