The Palmetto Quarterly Magazine of the Florida Native Plant Society  Vol. 4, No. 3  September 1984

Natural Communities of Florida's Floodplains

by Linda Conway Duever

Floodplains are intricate posits of mud and debris on the generally have clear black water environments created by ongoing valley floor where the water slows streams bordered by acid swamps interactions of geological and enough for particles to settle out. with highly organic soils. The hydrological processes. They form Thus, the seemingly flat valley swamps along alluvial streams where a river crosses gently floor actually has a varied micro- have clayey soils deposited by the sloping terrain, flowing so slowly topography with sloughs where muddy rivers. that it meanders from side to side there were formerly channels and Floodplains are extremely across the valley bottom. During rises on old levees. And this useful ecosystems. They filter floods, the river overflows the floodplain may have complex soil river waters, allowing trees to channel banks and forces its most patterns, since sediment depo- effectively convert the nutrients powerful flows t h rough t h e sition patterns are influenced by into valuable timber. They straightest routes, scouring chan- topographic features. moderate high water flow rates nels where the velocity is most Floodplain characteristics vary and thus limit the magnitude of intense and leaving alluvial de- with river type. Sandy regions downstream flooding. And they retain water well into drought periods, preserving water supplies and providing vital habitat for fish and other wild life. All these benefits can easily be lost if the floodplain is mis- managed. The channelization of the Kissimmee River is a classic example. A giant straight ditch was gouged down the center of the meandering river's floodplain, draining productive marshes and dumping massive floodwaters and excess nutrients into Lake Okeechobee. An expensive restor- ation program is now being plan- ned to put the river back as it was and limit continuing impacts. Many floodplains have been des- troyed by dams, which both flood berry, Lyonia ligustrina, occur deposited there and the soils are upstream areas and upset flow on the other wetlands as com- coarser and sandier. patterns and biological cycles monly as on floodplains, but hazel A great variety of species downstream. Some floodplains alder, Alnus serrulata; may haw, assemblages are mixed within this have been destroyed by clearing Crataegus aestivalis; and swamp community. FNAI has distin- for agriculture, and others by log- privet, Forestiera acuminata, guished the following Plant Com- ging. seem to prefer this habitat. munities: Overcup Oak/Water Prominent herbaceous species Hickory Flat, Diamond leaf Oak FLOODPLAIN SWAMP include swamp lily, Crinum Flat, Water Oak Flat, Pioneer Floodplain Swamps and Flood- americanum; neverwet, Orontium Levee, Live Oak Levee, and plain Forests are found along aquaticum; blue flag, Iris vir- Oak/Magnolia Terrace. rivers throughout northern and ginica; lizard tail, Saururus Overcup oak, Quercus lyrata; central Florida, but are most cernuus; giant cutgrass, Zizan- water hickory, Carya aquatica; abundant in the Panhandle. opsis milacea; beakrush, Rhyn- and cabbage palm, Sabal pal- Swamps border the sloughs and chospora spp.; leather fern, Acros- metto, are the typical trees in low backwaters. These sites are gen- tichum spp.; royal fern, Osmunda spots and zones where Floodplain erally inundated at least half of the regalis; and marsh fern, Thely- Forest grades into Floodplain year, and some sites are under pteris palustris. Laurelleaf green Swamp. water almost constantly. Since brier, Smilax laurifolia, and Along a transect moving onto anaerobic conditions prevail much muscadine, Vitis rotundifolia, are higher sites, red maple, Acer of the time, peat accumulates the most common vines. rubrum; diamond leaf oak, wherever strong flows do not These species occur in a wide Quercus laurifolia; willow oak, Q. wash it away, and the soils usually variety of intergrading floodplain phellos; green ash, Fraxinus penn- have a substantial organic com- associations. FNAI has defined sylvanica; American elm, Ulmus ponent. the following Plant Community americana; winged elm, Ulmus Cypress, Taxodium distichum, is types as preliminary categories for alata; sweetgum, Liquidambar the classic dominant in this sorting information: Cypress stryaciflua; sugarberry, Celtis lae- habitat, but tupelo, Nyssa aqua- Swamp, Cypress/Cabbage Palm vigata; water oak, Quercus nigra; tica, is perhaps even more charac- Swamp, Cypress/Blackgum white cedar, Chamaecyparis thy- teristic of the community. It is Swamp, Cypress/Tupelo Swamp, oides, and ironwood, Carpinus especially prominent on alluvial Blackgum Swamp, Water Elm caroliniana, might be en- rivers. Other typical trees include Slough, Pop Ash Slough, countered. Black walnut, Juglans Ogeechee gum, Nyssa ogeche; Ogeechee Gum Slough, Slash nigra, and bitternut hickory, blackgum, N. biflora; water elm, Pine Swamp, Willow Bar, and Carya cordiformis, are occasion- Planera aquatica; pop ash, Frax- Sweet bay Swamp. ally encountered. Likely under- inus caroliniana; pumpkin ash, story species in this zone are blue Fraxinus profunda; slash pine, FLOODPLAIN FOREST palmetto, Sabal minor; possum Pinus elliottii; and water locust, Floodplain Forest occurs on haw, llex decidua; parsley haw, Gleditsia aquatica. Shrubs such as riverbank levees and floodplain Crataegus marshalli; shiny ly- wax myrtle, Myrica cerifera; terraces which flood practically onia, Lyonia lucida; yaupon, Ilex cocoplum, Chrysobalanus icaco; every year, but rarely for more vomitoria; floodplain blueberry, dahoon holly, Ilex cassine; myrtle- than a month or two of the Vaccinium fuscatum; swamp leaf holly, I. myrtifolia; large growing season. The soils are azalea, Rhododendron viscosum; gallberry, I. coriacea; swamp highly variable. Terraces generally hoary azalea, Rhododendron can- haw, Viburnum nudum; leucothoe, have a surface layer of fine clay escens; sebastian bush, Sebastiana Leucothoe racemosa; latherbush, settled out from standing water ligustrina; silverbell, Halesia spp.; Clethra alnifolia; Virginia willow, following flood periods. Since Virginia chain fern, Woodwardia Itea virginica; buttonbush, Ce- water flows more rapidly over virginica; netted chain fern, W. phalanthus occidentalis; willow, levees, fine materials are not areolata; cinnamon fern, Osmun- Salix caroliniana; and male- da cinnamomea; Jackson vine, Smilax smallii; coral green brier, in Florida. It is typically found on tooth violet, Erythronium umbel- Smilax walteri; poison ivy, Toxi- narrow floodplains alongside icatum; streambank spiderlily, codendron radicans; cross vine, small streams. Hymenocallis coronaria; service- Bignonia capreolata; supplejack, The following are rare species berry holly, Ilex amelanchier; and Berchemia scandens; peppervine, found on Florida floodplains: Curtiss' lythrum, Lythrum cur- Ampelopsis arborea; and wild *Panhandle buckthorn, Bumelia tissii. Most of these prefer wisteria, Wisteria frutescens. lycioides; Apalachicola wild in- Floodplain Forest habitats, but Fairly recent levees are the digo, Baptisia megacarpa; Pan- some may also occur in marshes preferred habitat for early suc- handle lily, Lilium iridollae; and swamps. All of them are on cessional species like willows, honewort, Cryptotaenia cana- the Florida Natural Areas Inven- Salix caroliniana and S. nigra; densis; bladdernut, Staphylea tri- tory Special Plant List. cottonwoods, Populus deltoides folia; wild comfrey, Cynoglossum and P. heterophylla, elderberry, virginianum; corkwood, Leitneria FLOODPLAIN MARSH Sambucus canadensis; river birch, floridana; pink root, Spigelia Marshes of herbaceous Betula nigra; silver maple, Acer loganiodes; cedar elm, Ulmus vegetation and low shrubs replace saccharinum; boxelder, A. neg- crassifolia; Florida merrybells, forests on floodplains in open flat undo; sycamore, Platanus occi- Uvularia floridana; Apalachicola country where fires frequently dentalis; catalpa, Catalpa bignon- river aster, Aster vimineus var. sweep across the prairies and into ioides; and indigo bush, Amorpha vimineus; variable-leaved Indian the river marshes. The vast bulk of fruticosa. plantain, Cacalia diversifolia; these sites are along the Grasses and sedges are most virgin's bower, Clematis Catesby- Kissimmee, Myakka, and Upper abundant in the intermediate ana; naked- stemmed panic grass, St. Johns rivers. Ecologists spec- zones of the floodplain. Typical Panicum nudicaule; spoon flower, ulate that a simple increase in fire species include Leersia lenti- Peltandra sagittifolia; slender- frequency is not the only reason cularis, L. virginica, Oplismenus leaved dragonhead, Physostegia these floodplains are not forested. setarius, Erianthus strictus, leptophylla; Florida willow, Salix Due to severe seasonal drought, Panicum agristoides, P. rigid- floridana; Florida water parsnip, fires in this region are also liable ulum, Chasmanthium laxa, Carex Sium floridanum; dimpled dog- to be more intense, and hence to intumescens, C. typhina, C. lurida, C. louisinica, and C. greyii. Dense stands of rivercane, Arundinaria gigantea, sometimes form exten- sive "canebrakes." Swamp chestnut oak, Quer- cus prinus; live oak, Q. virginiana loblolly pine, Pinus taeda; spruce pine, P. glabra; beech, Fagus grandiflora; Amer- ican holly, llex opaca; and mag- nolia, Magnolia grandiflora, may occur on the highest terraces at the outer edge of the floodplain. Cher- rybark oak, Quercus pagoda, which is characteristic of this zone farther north, in Florida grows only along the Apalachicola River. Tuliptree, Liriodendron tulipfera, invades northern flood- plains from the adjacent uplands, but seems restricted to wetter sites kill trees rather than merely marsh fimbristylis, Fimbristylis damage them. And the sandier castanea; Carolina fimbristylis, river deposits are less stable than Fimbristylis caroliniana; drop- the finer alluvial materials carried seed, Sporobolus virginicus; St. by north Florida rivers. Augustine grass, Stenotaphrum Since the herbaceous secundatum; glass-worts, Salicor- vegetation supplies organic debris nia spp.; sea purslane, Sesuvium and the dense stems trap it and portulacastrum; purple ludwigia, prevent it from being washed Ludwigia repens; and water away during high water, pennywort, Hydrocotyle umbel- Floodplain Marshes generally lata. have considerable peat in the soil. Parts of the St. Johns floodplain are influenced by seepage from ancient saltwater deposits, so This is the fifth in a series of articles Suggested citation for this article describing the Natural Communities Deuver, L. C. 1984. Natural Communities of some of the plants there are defined by .the Florida. Natural Areas Florida’s Floodplains. The Palmetto, 4(3):8- species adapted to brackish Inventory (FNAI). This classification 10. conditions. system must be viewed as a system of mental constructs imposed upon an Though the species assoc- infinite variety of growing, changing, inter- Articles from The Palmetto that appear on this iations are often difficult to gradmg, natural environments. Hence, website may be used in portion or entirely for define, FNAI has thus far recog- more often than not, a given site will not precisely fit the classic description of the non-commercial, informational or educational purposes, provided complete and accurate nized several Floodplain Marsh appropriate natural community. Plant Communities: Maidencane/ citation accompanies all usage. Citation must include authorship, photo credits, and the Sagittaria Marsh, Sawgrass website of the Florida Native Plant Society as Marsh, Buttonbush Marsh, and the source of publication. ABOUT THE AUTHOR: Linda Duever is along- Pickerel Weed Marsh. time FNPS member. Today she is president This article has been reproduced from the Maidencane, Panicum hemitom- and principal ecologist of Conway Consulting original using digital techniques (OCR) and on; button bush, Cephalanthus in Gainesville. Her posters of Florida native reformatted for use on the internet. plant communities can be obtained by Unintended inconsistences from the original occidentalis; and sawgrass, Cla- contacting her at may occur. dium jamaicense, are probably the [email protected]. normal dominant species in undisturbed Floodplain Marsh.

Other typical species include sand cord grass, Spartina bakeri; water smartweed, Polygonum punc- tatum; sagittaria, Sagittaria lancifolia; pickerel weed, Ponte- deria cordata; Cuban river grass,

Reimarochloa oligostachya; spikerush, Eleocharis cellulosa and E. parvula; soft rush, Juncus effusus; bulrush, Scirpus spp.; giant cutgrass, Zizaniopsis mil- iacea; bladder pod, Sesbania vesicaria; giant reed, Phragmites australis; salt jointgrass, Pas- palum vaginatum; wild millet,

Echinochloa walteri; Florida tick- seed, Coreopsis leavenworthii; agalinis, Agalinis maritima; salt-