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For information on Wisconsin's natural communities, contact:
Ryan O'Connor
Natural Heritage Inventory Ecologist

Floodplain Forest

State Rank: S3     Global Rank: G3?   what are these ranks?


Detailed Community Description from Ecological Landscapes of Wisconsin

General natural community overview

Counties shaded blue have documented occurrences for Floodplain Forest in the Wisconsin Natural Heritage Inventory database.

This lowland hardwood forest community type occurs along large rivers-usually 3rd order streams or higher. Most of these rivers originate in northern Wisconsin and flow southward, growing in size as the volume of water they carry increases. As the stream gradients diminish, the floodplains become broader. Periodic floods, particularly in the spring, are the key natural disturbance event to which species of this community have adapted. Silt deposition and development of microtopography during flood events create suitable sites for tree germination and establishment. Floods also carry seeds and propagules of plant species. The most extensive occurrences of floodplain forest are found along the large rivers of southern Wisconsin, but the community also occurs at scattered locations in the north. This community was uncommon historically, occupying only about 3% of the Western Coulees and Ridges Ecological Landscape and even smaller percentages of other ecological landscapes (Finley 1976). Canopy dominants vary, but may include silver maple (Acer saccharinum), river birch (Betula nigra), green ash (Fraxinus pennsylvanica), black ash (Fraxinus nigra), hackberry (Celtis occidentalis), swamp white oak (Quercus bicolor and its hybrids with bur oak), and eastern cottonwood (Populus deltoids). Black willow (Salix nigra), basswood (Tilia americana), red oak (Quercus rubra), and red maple (Acer rubrum) are associated species found in these forests. Historically, elms were highly significant components of the floodplain forests, but Dutch elm disease has eliminated most large elm trees that formerly provided supercanopy structure, snags and den sites, and large woody debris. Northern occurrences of this type tend to be less extensive, are often discontinuous, and relatively species-poor compared to those in the south. Silver maple and green ash are still dominant, but balsam-poplar (Populus balsamifera), bur oak (Quercus macrocarpa), and box elder (Acer negundo) replace some of the southern tree species.

Understory composition is also quite variable and follows the pattern exhibited by the canopy species-the most extensive stands and highest plant species diversity occur in southwestern Wisconsin. Buttonbush (Cephalanthus occidentalis) is a locally dominant shrub that may form dense thickets on the margins of oxbow lakes, sloughs, and ponds, which are often important aquatic habitats in these forests. Wood nettle and stinging nettle (Laportea canadensis, Urtica dioica), sedges (e.g., Carex grayi, C. lupulina, C. hystericina, C. tuckermanii), native grasses (e.g., Cinna arundinacea, Elymus villosus, Leersia virginica), ostrich fern (Matteuccia struthiopteris), and green-headed coneflower (Rudbeckia laciniata) are important understory herbs, and lianas such as Virginia creeper (Parthenocissus quinquefolia), grapes (Vitis spp.), Canada moonseed (Menispermum canadense), and poison-ivy (Toxicodendron radicans) along with the shrub form of poison ivy (T. rydbergii) are often common. Among the more striking herbs of this community are cardinal flower (Lobelia cardinalis), fringed loosestrife (Lysimachia ciliata), and green dragon (Arisaema dracontium).

The sprawling floodplains found along the largest rivers sometimes consist of several terraces capable of supporting forests that are subject to floods with differing frequencies and levels of inundation, and support patches of varying floristic composition depending upon local elevation differences, edaphic factors, and disturbance history. The lower terraces experience the most frequent, severe, and long-lasting floods while the uppermost terraces flood infrequently, and the rich alluvial soils can support mesophytic trees species and rich groundlayers similar to those of the mesic hardwood forests.

Defining Characteristics and Similar Communities

Floodplain forests are characterized by their location along major rivers and seasonal flooding and associated scouring, silt deposition, and removal of organic detritus. They share similar species with southern hardwood swamps, which are also seasonally wet and usually dry out by mid-late summer. However, southern hardwood swamps are found in lakeplains, poorly drained till plains, and along small streams rather than large river systems, and water is supplied by rain and snowmelt rather than over-bank flooding.

Floodplain forests are distinguished from northern hardwood swamps by their vertically fluctuating water levels and lateral movement of floodwaters rather than a relatively stable supply of groundwater, thus have a lower proportion of peat (muck) soils due floods removing fine organic matter and soil drying out by mid-late summer allowing remaining organic matter to decompose. Floodplain forests also tend to have a higher component of plant species that prefer these hydrologic conditions (see characteristic species above), whereas northern hardwood swamps have a higher prevalence of species preferring saturated soils such as marsh marigold (Caltha palustris), swamp raspberry (Rubus pubescens), orange jewelweed (Impatiens capensis), purple-stemmed aster (Symphyotrichum puniceum), lake sedge (Carex lacustris), blue-joint grass (Calamagrostis canadensis), and groundwater-loving species like bristle-stalked sedge (Carex leptalea), American golden saxifrage (Chrysosplenium americanum), and swamp saxifrage (Micranthes pensylvanica).

Floodplain forests share some characteristics with the mesic floodplain terrace community, but the latter is extremely uncommon, limited to alluvial terraces associated with large northern rivers on the Lake Superior clay plain (e.g., Bad River in Ashland County), and is characterized by a flora rich in spring ephemerals.

Rare animals

Species of Greatest Conservation Need

Wisconsin Wildlife Action Plan graphic

The following Species of Greatest Conservation Need are listed according to their level of association with the Floodplain Forest natural community type, based on the findings in Wisconsin's 2015 Wildlife Action Plan.

Scores: 3 = high association, 2 = moderate association, and 1 = low association. See the key to association scores for complete definitions.

Four-toed SalamanderHemidactylium scutatum3
Pickerel FrogLithobates palustris2

Ants, wasps, and beesScore
Confusing Bumble BeeBombus perplexus1

Aquatic and terrestrial snailsScore
Dull GlossZonitoides limatulus3
Broad-banded ForestsnailAllogona profunda2
Wing SnaggletoothGastrocopta procera1

A Predaceous Diving BeetleLaccophilus undatus2

Great EgretArdea alba3
Kentucky WarblerGeothlypis formosa3
Prothonotary WarblerProtonotaria citrea3
Red-shouldered HawkButeo lineatus3
Rusty BlackbirdEuphagus carolinus3
Yellow-crowned Night-HeronNyctanassa violacea3
American WoodcockScolopax minor2
Cerulean WarblerSetophaga cerulea2
Common GoldeneyeBucephala clangula2
Least FlycatcherEmpidonax minimus2
Red-headed WoodpeckerMelanerpes erythrocephalus2
Yellow-throated WarblerSetophaga dominica2
Acadian FlycatcherEmpidonax virescens1
American BitternBotaurus lentiginosus1
Black-crowned Night-HeronNycticorax nycticorax1
Brewer's BlackbirdEuphagus cyanocephalus1
Eastern Whip-poor-willAntrostomus vociferus1
Long-eared OwlAsio otus1

Butterflies and mothsScore
A Noctuid MothBagisara gulnare2
Gray CopperLycaena dione2

Dragonflies and damselfliesScore
Swamp DarnerEpiaeschna heros3
Spangled SkimmerLibellula cyanea2

Grasshoppers and alliesScore
A Spur-throat GrasshopperMelanoplus foedus2
Bog ConeheadNeoconocephalus lyristes1
Spotted-winged GrasshopperOrphulella pelidna1

Big Brown BatEptesicus fuscus3
Little Brown BatMyotis lucifugus3
Eastern PipistrellePerimyotis subflavus2
Northern Flying SquirrelGlaucomys sabrinus2
Northern Long-eared BatMyotis septentrionalis2
Silver-haired BatLasionycteris noctivagans2
Water ShrewSorex palustris2
American MartenMartes americana1
Woodland Jumping MouseNapaeozapus insignis1
Woodland VoleMicrotus pinetorum1

Eastern MassasaugaSistrurus catenatus3
Wood TurtleGlyptemys insculpta3
Blanding's TurtleEmydoidea blandingii2
Butler's GartersnakeThamnophis butleri2
Gray RatsnakePantherophis spiloides2
Timber RattlesnakeCrotalus horridus2

Please see Section 2. Approach and Methods of the Wildlife Action Plan to learn how this information was developed.

Rare plants

The Natural Heritage Inventory has developed scores indicating the degree to which each of Wisconsin's rare plant species is associated with a particular natural community or ecological landscape. This information is similar to that found in the Wildlife Action Plan for animals. As this is a work in progress, we welcome your suggestions and feedback.

Scores: 3 = "significantly associated," 2 = "moderately associated," and 1 = "minimally associated."
Scientific Name Common Name Score
Arnoglossum reniforme Great Indian-plantain 3
Boechera dentata Short's Rock-cress 3
Carex backii Rocky Mountain Sedge 1
Carex festucacea Fescue Sedge 1
Carex formosa Handsome Sedge 2
Carex laevivaginata Smooth-sheathed Sedge 3
Carex lupuliformis False Hop Sedge 3
Chaerophyllum procumbens Spreading Chervil 3
Cuscuta polygonorum Knotweed Dodder 1
Diarrhena obovata Ovate Beak Grass 3
Didiplis diandra Water-purslane 1
Eclipta prostrata Yerba-de-tajo 1
Equisetum palustre Marsh Horsetail 2
Gymnocladus dioicus Kentucky Coffee-tree 3
Hydrophyllum appendiculatum Great Water-leaf 2
Hypericum mutilum Slender St. John's-wort 1
Hypericum sphaerocarpum Round-fruited St. John's Wort 2
Iodanthus pinnatifidus Purple Rocket 3
Jeffersonia diphylla Twinleaf 2
Juglans cinerea Butternut 2
Leucophysalis grandiflora Large-flowered Ground-cherry 2
Melica nitens Three-flowered Melic Grass 3
Myosotis laxa Small Forget-me-not 3
Napaea dioica Glade Mallow 2
Nyssa sylvatica Black Tupelo 2
Platanthera flava var. herbiola Pale Green Orchid 2
Platanus occidentalis Sycamore 3
Ptelea trifoliata ssp. trifoliata var. trifoliata Wafer-ash 2
Quercus palustris Pin Oak 3
Sagittaria montevidensis ssp. calycina Long-lobed Arrowhead 2
Senna hebecarpa Northern Wild Senna 3
Silene nivea Snowy Campion 1
Spiranthes lucida Shining Lady's-tresses 3
Trillium nivale Snow Trillium 1
Viburnum prunifolium Smooth Black-haw 2
Viola striata Striped Violet 2


The following Ecological Landscapes have the best opportunities to manage for Floodplain Forest, based on the Ecological Landscapes of Wisconsin Handbook.

Map of the Ecological Landscapes of Wisconsin.

Major (3 on map)
A major opportunity for sustaining the natural community in the Ecological Landscape exists, either because many significant occurrences of the natural community have been recorded in the landscape or major restoration activities are likely to be successful maintaining the community's composition, structure, and ecological function over a longer period of time.

Important (2 on map)
Although the natural community does not occur extensively or commonly in the Ecological Landscape, one to several occurrences do occur and are important in sustaining the community in the state. In some cases, important opportunities may exist because the natural community may be restricted to just one or a few Ecological Landscapes within the state and there may be a lack of opportunities elsewhere.

Present (1 on map)
The natural community occurs in the Ecological Landscape, but better management opportunities appear to exist in other parts of the state.


Wisconsin Wildlife Action Plan graphic

What are conservation actions?

Conservation actions respond to issues or threats, which adversely affect species of greatest conservation need (SGCN) or their habitats. Besides actions such as restoring wetlands or planting resilient tree species in northern communities, research, surveys and monitoring are also among conservation actions described in the WWAP because lack of information can threaten our ability to successfully preserve and care for natural resources.

Threats/issues and conservations actions for natural communities


The following are additional considerations for Floodplain Forest in Ecological Landscapes with opportunities for protection, restoration, and/or management. For more information, see the Wildlife Action Plan.

Central Lake Michigan Coastal

A significant part of the Lower Wolf River corridor is within this Ecological Landscape and merits strong protection. Public ownership is scattered here, and isolated rather than connected.

Central Sand Hills

Protection and management opportunities occur along the Wisconsin, Lower Baraboo, and Montello Rivers.

Central Sand Plains

The development of forested lowland habitat for cranberry farming has affected the Floodplain Forests of the Yellow River and its tributaries. Gravel mining occurs in some parts of the floodplain of the Black River. There are good examples of this community type on the Black, Yellow, Lemonweir, and Wisconsin Rivers. There are areas of public ownership on the Black River State Forest, at the confluence of the Yellow and Wisconsin Rivers at Buckhorn State Park, and on the Lower Lemonweir River.

Forest Transition

Opportunities for management are limited here but include significant sites along the Lower St. Croix River, and some parts of the middle stretches of the Wisconsin River and its tributaries

North Central Forest

This type is at the northern edge of its range in this Ecological Landscape. Opportunities are limited but there are several important occurrences and large blocks of public ownership. Existing large blocks and connectivity should be maintained where possible (e.g., along the Wisconsin, Chippewa, Jump, Yellow, and Black Rivers), and managed as part of a mosaic of other forest communities.

Northern Lake Michigan Coastal

Opportunities are limited but there are several important occurrences. This community type should be maintained where it exists along the Lower Wolf and Peshtigo Rivers. Large occurrences of a similar community, hardwood swamp, exist in the Ecological Landscape near the west shore of Green Bay.

Southeast Glacial Plains

Significant opportunities for management and protection occur on the Milwaukee, Lower Wolf, and Sugar Rivers, and to a lesser extent, on the Rock River at Lake Koshkonong. Public ownership is scattered and patchy.

Superior Coastal Plain

Floodplain forest is at its northern range extremity here. In this Ecological Landscape the type is uncommon, and generally supports fewer species than more southerly occurrences. Floodplain corridors around the best occurrences (e.g., those on the Nemadji, Bad, and White Rivers) should be protected and maintained. Protection of high quality examples of this type would contribute significantly to the maintenance of regional diversity, as many plants have been documented on the floodplain terraces of the Superior Coastal Plain that occur in no other habitat this far north. Invasive plants are present but do not appear to be a large problem at this time. A long-term monitoring program is needed.

Western Coulee and Ridges

This Ecological Landscape offers the best opportunities to manage for this community type. Large, relatively continuous areas of floodplain forest occur along the Mississippi, and the lower stretches of the Wisconsin, Chippewa, and Black Rivers. Smaller rivers are also associated with significant stands of this type, including the Red Cedar, Yellow, Hay, and Lemonweir. All of these sites are important to floodplain specialists (e.g., the prothonotary warbler) as well as many forest interior species. Public ownership is extensive at some locations, e.g., the Mississippi River (USFWS, USACOE, WDNR), the Lower Wisconsin River (WDNR), the Lower Chippewa River (WDNR), and the Lower Black River (WDNR).

Western Prairie

The most significant sites containing this type are on the Lower St. Croix River in Polk and St. Croix Rivers. The protection level is relatively high, as this area is within the St. Croix-Namekagon National Scenic Riverway administered by the National Park Service, but recreational use of this area is very high and impacts should be monitored. Residential development on the bluffs above the floodplain has increased rapidly in recent years, and the conservation implications include the inadvertent introduction of invasive species, loss or disturbance of the forested blufflands adjoining the floodplain, and generally higher levels of human use.


Floodplain Forest Photos

Floodplain Forest Photo

Large silver maples along the Sugar River. The understory is dominated by the invasive reed canary grass.

Photo by Drew Feldkirchner.

Floodplain Forest Photo

Photo by Thomas Meyer.

Floodplain Forest Photo

Photo by Thomas Meyer.

Floodplain Forest Photo

Floodplain forest along the Wisconsin River at flood stage.

Photo by Ryan O'Connor.

Floodplain Forest Photo

Floodplain forest along the Wisconsin River at flood stage.

Photo by Ryan O'Connor.

Note: photos are provided to illustrate various examples of natural community types. A single photograph cannot represent the range of variability inherent in a given community type. Some of these photos explicitly illustrate unusual and distinctive community variants. The community photo galleries are a work in progress that we will expand and improve in the future.

Last revised: Wednesday, June 16, 2021