Florida’s Forested Wetlands

Alluvial Forest
Alluvial forest occurs in river floodplains and occupies low levees along channels, expansive flats located behind levees, low ridges alternating with swamps, and successional point bars. It is usually intermixed with lower areas of floodplain swamp and higher areas of bottomland forest, baygall, or upland hardwood forest. Soils are variable mixtures of sand and alluvial sediments that have been deposited by the current drainage system and are often distinctly layered. Alluvial forest occupies an elevation within the broader floodplain that is inundated seasonally from river bank overflow for one to four months of the year during the growing season.

Primary trees found include overcup oak (Quercus lyrata), swamp laurel oak (Q. laurifolia), water hickory (Carya aquatica), American elm (Ulmus americana), green ash (Fraxinus pennsylvanica), water locust (Gleditsia aquatica), river birch (Betula nigra), and red maple (Acer rubrum). A great diversity of less flood-tolerant hardwoods or swamp species such as cypress (Taxodium spp.) and tupelo (Nyssa spp.) may also be present, but not dominant elements. Shrubs, small trees, and vines are usually sparse or moderate in abundance with green hawthorn (Crataegus viridis), swamp dogwood (Cornus foemina), eastern swampprivet (Forestiera acuminata), dwarf palmetto (Sabal minor), coastalplain willow (Salix caroliniana), black willow (S. nigra), American hornbeam (Carpinus caroliniana), Hypericum spp., possumhaw (Ilex decidua), and laurel greenbrier (Smilax laurifolia) common.

Basin Swamp
Basin swamp is a basin wetland vegetated with hydrophytic trees and shrubs that can withstand an extended hydroperiod. Basin swamps are highly variable in size, shape, and species composition. This natural community typically occurs in any type of large landscape depression such as old lake beds or river basins, or ancient coastal swales and lagoons that existed during higher sea levels. Basin swamps exist around lakes and are sometimes headwater sources for major rivers, such as the Suwannee. Soils are generally acidic, nutrient-poor peats often overlying a clay lens or other impervious layer.

While mixed species canopies are common, the dominant trees are pond cypress (Taxodium ascendens) and swamp tupelo (Nyssa sylvatica var. biflora). Other typical canopy and subcanopy trees include slash pine (Pinus elliottii), red maple (Acer rubrum), dahoon (Ilex cassine), swamp bay (Persea palustris), sweetbay (Magnolia virginiana), loblolly bay (Gordonia lasianthus), swamp laurel oak (Quercus laurifolia), sweetgum (Liquidambar styraciflua), water oak (Quercus nigra), green ash (Fraxinus pennsylvanica), American hornbeam (Carpinus caroliniana), and American elm (Ulmus americana). Depending on the hydrology and fire history, shrubs may be found throughout a basin swamp or they may be concentrated around the perimeter. Common species include Virginia willow (Itea virginica), swamp dogwood (Cornus foemina), swamp doghobble (Leucothoe racemosa), coastal sweetpepperbush (Clethra alnifolia), myrtle dahoon (Ilex cassine var. myrtifolia), fetterbush (Lyonia lucida), wax myrtle (Myrica cerifera), titi (Cyrilla racemiflora), black titi (Cliftonia monophylla), and common buttonbush (Cephalanthus occidentalis).

Baygall is an evergreen forested wetland of bay species on wet soils at the bases of slopes, edges of floodplains, in depressions, and in stagnant drainages. The soils are generally composed of peat with an acidic pH (3.5 – 4.5). Seepage from uplands, rainfall, and/or capillary action from adjacent wetlands maintains a saturated peat substrate.

Loblolly bay (Gordonia lasianthus), sweetbay (Magnolia virginiana), and/or swamp bay (Persea palustris) form an open to dense tree canopy and are also dominant in the understory along with fetterbush (Lyonia lucida), large gallberry (Ilex coriacea), dahoon (I. cassine), myrtle dahoon (I. cassine var. myrtifolia), titi (Cyrilla racemiflora), black titi (Cliftonia monophylla), wax myrtle (Myrica cerifera), coastal doghobble (Leucothoe axillaris), swamp doghobble (L. racemosa), red maple (Acer rubrum), Florida anisetree (Illicium floridanum), coco plum (Chrysobalanus icaco), and/or Virginia willow (Itea virginica). Loblolly pine (Pinus taeda), slash pine (P. elliottii), and/or pond pine (P. serotina) are often found in the canopy, as well as sweetgum (Liquidambar styraciflua), and in the Panhandle, Atlantic white cedar (Chamaecyparis thyoides). Wetter baygalls may also contain swamp tupelo (Nyssa sylvatica var. biflora) and/or pond cypress (Taxodium ascendens).

Composition of the understory varies regionally; coco plum is restricted to South Florida, Florida anisetree to the central and western Panhandle. Black titi is a dominant component of baygall in the Florida Panhandle, but uncommon in other areas. The canopy and understory do not generally form distinct strata but may appear as a dense, tall thicket. Vines, especially laurel greenbrier (Smilax laurifolia), coral greenbrier (S. walteri), and muscadine (Vitis rotundifolia), may be abundant and contribute to the often impenetrable nature of the understory.

Bottomland Forest
Bottomland Forest may be found on higher terraces and levees within riverine floodplains, and in somewhat isolated depressions that do not flood frequently. Soils are a mixture of sand, clay, and organic materials.

Bottomland forest is a deciduous, or mixed deciduous/evergreen, closed-canopy forest. Dominant species include sweetgum (Liquidambar styraciflua), spruce pine (Pinus glabra), loblolly pine (Pinus taeda), sweetbay (Magnolia virginiana), swamp laurel oak (Quercus laurifolia), water oak (Q. nigra), live oak (Q. virginiana), swamp chestnut oak (Q. michauxii), and sugarberry (Celtis laevigata). More flood tolerant species that are often present include American elm (Ulmus americana) and red maple (Acer rubrum), as well as occasional swamp tupelo (Nyssa sylvatica var. biflora) and bald cypress (Taxodium distichum). Evergreen bay species such as loblolly bay (Gordonia lasianthus), and sweetbay are often mixed in the canopy and understory in acidic or seepage systems. Smaller trees and shrubs often include American hornbeam (Carpinus caroliniana), swamp dogwood (Cornus foemina), possumhaw (Ilex decidua), dahoon (I. cassine), dwarf palmetto (Sabal minor), swamp bay (Persea palustris), wax myrtle (Myrica cerifera), and highbush blueberry (Vaccinium corymbosum). The understory is either dense shrubs with little ground cover, or open, with few shrubs and a groundcover of ferns, herbs, and grasses. In the drier forests of this type, American holly (Ilex opaca), Gulf Sebastian bush (Sebastiania fruticosa), and sparkleberry (Vaccinium arboreum) may be frequent.

Dome Swamp
Dome swamps are most often found on flat terraces, where they develop when the overlying sand has slumped into a depression in the underlying limestone, creating a rounded depression connected to a shallow water table. Soils in dome swamps are variable but are most often composed of a layer of peat, which may be thin or absent at the periphery, becoming thicker toward the center of the dome.

Dome swamp is an isolated, forested, depression wetland occurring within a fire-maintained community such as mesic flatwoods. These swamps are generally small, but may also be large and shallow. The characteristic dome shape is created by smaller trees that grow in the shallower waters of the outer edge, while taller trees grow in the deeper water in the interior of the swamp. Pond cypress (Taxodium ascendens) often dominates, but swamp tupelo (Nyssa sylvatica var. biflora), may also form pure stands or occur as a co-dominant. Other canopy or subcanopy species include red maple (Acer rubrum), dahoon (Ilex cassine), swamp bay (Persea palustris), slash pine (Pinus elliottii), sweetbay (Magnolia virginiana), loblolly bay (Gordonia lasianthus), and, in South Florida, coco plum (Chrysobalanus icaco) and pond apple (Annona glabra). Shrubs are typically sparse to moderate, but often are absent in dome swamps with a high fire frequency or dense in swamps where fire has long been absent. Shrubs common in dome swamps include Virginia willow (Itea virginica), fetterbush (Lyonia lucida), common buttonbush (Cephalanthus occidentalis), coastalplain willow (Salix caroliniana), wax myrtle (Myrica cerifera), titi (Cyrilla racemiflora), and St. John’s wort (Hypericum spp.).

Hydric Hammock
Hydric hammock occurs on low, flat, wet sites where limestone may be near the surface and soil moisture is kept high mainly by rainfall accumulation on poorly drained soils. Periodic flooding from rivers, seepage, and spring discharge may also contribute to hydric conditions. Hydric hammock is inundated only for short periods following heavy rains. The normal hydroperiod is seldom over 60 days per year. Fire may be rare or occasional depending on several factors including how often the surrounding community burns and hammock size.

Hydric hammock is an evergreen hardwood and/or palm forest with a closed canopy of oaks and palms, an open understory, and a sparse to a moderate groundcover of grasses and ferns. The canopy is dominated by swamp laurel oak (Quercus laurifolia) and/or live oak (Q. virginiana) with varying amounts of cabbage palm (Sabal palmetto), American elm (Ulmus americana), sweetbay (Magnolia virginiana), red cedar (Juniperus virginiana), red maple (Acer rubrum), sugarberry (Celtis laevigata), sweetgum (Liquidambar styraciflua), and water oak (Q. nigra). Cabbage palm is a common to dominant component of hydric hammock throughout most of Florida. Loblolly pine (Pinus taeda) may be frequent in some areas, but slash pine (Pinus elliottii) is less frequently encountered. In addition to saplings of canopy species, American hornbeam (Carpinus caroliniana) is frequent in the understory and various other woody species may be present including swamp dogwood (Cornus foemina), small-leaf viburnum (Viburnum obovatum), common persimmon (Diospyros virginiana), swamp bay (Persea palustris), wax myrtle (Myrica cerifera), dwarf palmetto (Sabal minor), American beautyberry (Callicarpa americana), and needle palm (Rhapidophyllum hystrix). Vines may be frequent and diverse; common species are eastern poison ivy (Toxicodendron radicans), peppervine (Ampelopsis arborea), rattan vine (Berchemia scandens), trumpet creeper (Campsis radicans), climbing hydrangea (Decumaria barbara), yellow jessamine (Gelsemium sempervirens), greenbriers (Smilax spp.), summer grape (Vitis aestivalis), and muscadine (Vitis rotundifolia).

Floodplain Swamp
Floodplain swamp is located within floodplains of any permanently moving stream or river ranging from narrow strips of cypress along primary and secondary streams to expansive stands along large rivers to tidally influenced freshwater swamps near river mouths. It is a closed-canopy forest on frequently or permanently flooded hydric soils adjacent to stream and river channels and in depressions and oxbows within floodplains. Floodplain swamp can often occur within a complex mixture of communities including alluvial forest, bottomland forest, and baygall. This produces a variable assemblage of canopy and subcanopy species, with less flood tolerant trees and shrubs found on small hummocks and ridges within the swamp. Trees are often buttressed, and the understory and groundcover are sparse.

The canopy is sometimes a pure stand of bald cypress (Taxodium distichum), but more commonly bald cypress shares dominance with one or more of the following tupelo species: water tupelo (Nyssa aquatica), swamp tupelo (N. sylvatica var. biflora), or ogeechee tupelo (N. ogeche). Other canopy trees capable of withstanding frequent inundation may be present but rarely dominant, including water hickory (Carya aquatica), overcup oak (Quercus lyrata), red maple (Acer rubrum), green ash (Fraxinus pennsylvanica), American elm (Ulmus americana), and swamp laurel oak (Q. laurifolia). Pond cypress (T. ascendens) is sometimes present in backswamps and depressions of the more hydrologically isolated areas of the floodplain. Shrubs and smaller trees such as Carolina ash (Fraxinus caroliniana), planer tree (Planera aquatica), black willow (Salix nigra), titi (Cyrilla racemiflora), Virginia willow (Itea virginica), common buttonbush (Cephalanthus occidentalis), cabbage palm (Sabal palmetto), and dahoon (Ilex cassine) may be present.

Mangrove Swamp
Mangrove swamp occurs in flat coastal areas along saline or brackish portions of rivers, the edges of low-energy estuaries, and the seaward fringes of salt marshes and rockland hammocks. Soils are generally anaerobic and are saturated with brackish water at all times, becoming inundated during high tides. Mangrove swamp occurs on a wide variety of soils, ranging from sands and mud to solid limestone rock. Soils in South Florida are primarily calcareous marl muds or calcareous sands and, along the Central Florida coastline, siliceous sands.

The dominant plants of mangrove swamp are red mangrove (Rhizophora mangle), black mangrove (Avicennia germinans), white mangrove (Laguncularia racemosa), and buttonwood (Conocarpus erectus). These four species can occur either in mixed stands or often in differentiated, monospecific zones that reflect varying degrees of tidal influence, levels of salinity, and types of substrate. Red mangrove often dominates the lowest (or deep-water) zone, followed by black mangrove in the intermediate zone, and white mangrove and buttonwood in the highest, least tidally-influenced zone. Buttonwood often occupies an ecotone, or transition zone, to the adjacent upland community.

Strand Swamp
Strand swamp is a shallow, forested, usually elongated depression or channel situated in a trough within a flat limestone plain. Strand swamp soils are peat and sand over limestone. Swamps with larger cypress and a more diverse understory are on deep peat that acts as a wick to draw moisture from groundwater up into the root zone during droughts. Swamp edges, however, often have little organic matter over deep sand. The normal hydroperiod ranges from 100-300 days.

These communities are dominated primarily by bald cypress (Taxodium distichum), but smaller strand swamps and shallow edges may instead contain pond cypress (T. ascendens). Small, young cypress trees at the outer edge of strand swamps grade into large old ones in the deeper interior, giving a strand a distinctly rounded cross-sectional profile. The variable woody understory contains a mixture of temperate and tropical elements, mainly red maple (Acer rubrum), pond apple (Annona glabra), swamp laurel oak (Quercus laurifolia), cabbage palm (Sabal palmetto), strangler fig (Ficus aurea), swamp bay (Persea palustris), sweetbay (Magnolia virginiana), coastalplain willow (Salix caroliniana), wax myrtle (Myrica cerifera), myrsine (Rapanea punctata), and common buttonbush (Cephalanthus occidentalis). In the Fakahatchee Strand, Florida royal palm (Roystonea regia) may also be present in the subcanopy.

Source: Guide to the Natural Communities of Florida, 2010 Edition