Common (Translated Scientific) Name: Eastern Cottonwood - Green Ash - Silver Maple Flooded & Swamp Forest Division
Colloquial Name: Eastern North American-Great Plains Flooded & Swamp Forest
Hierarchy Level: Division
Type Concept: This division comprises floodplain and swamp woodlands and forests ranging from the western Great Plains east to the Atlantic Coast, north into southern Canada and south to the south-central United States, north of the Gulf Coastal Plain, except along the Mississippi River. Ruderal flooded and swamp forests are also considered part of this division. Floodplain examples are located along small to large rivers or small streams with alluvial soils. They occur on sandy to sandy loam soils along sandbars, riverfronts, and levees of rivers and small streams. Swamp forest examples occur in depressions, along lakeshores or small streams. Soils are typically acidic and nutrient-poor, although some examples can range from circumneutral to alkaline with richer nutrient levels. These depression wetlands tend to be poorly- to very poorly-drained and saturated most of the growing season. Some examples can have a hummock-and-hollow microtopography. Tree species common in examples of this division vary based on geography and type of wetland (floodplain versus depression or flatwood). Typical floodplain species include Celtis occidentalis, Fraxinus pennsylvanica, Populus deltoides, and Salix spp. in the central and western range of this division. Acer saccharinum, Celtis laevigata, Fraxinus pennsylvanica, Liquidambar styraciflua, Platanus occidentalis, and Ulmus americana become more dominant from the central to the eastern range of this division. Acer rubrum is the most common species associated with swamp forests within this division. Other common tree species include Nyssa sylvatica, Liriodendron tulipifera, and Liquidambar styraciflua. Larix laricina and Tsuga canadensis are the most widespread and more northern conifers associated with this division. Picea rubens, Picea mariana, Pinus strobus, and Abies balsamea can be common northern associates as well. Common shrubs across the division include Cornus spp. and Salix spp. Understory species vary widely across the division. Flooding influences the majority of forests and woodlands within this division. Microtopography and fluctuating moisture levels can influence communities and species occurring within this division. Fire also can be important in some examples. Many areas within the division also have a history of some kind of human disturbance such as logging or a change in the hydrologic regime. These may lead to ruderal conditions, where dominant trees are either early-successional native species adapted to wet conditions, especially Acer negundo (exotic in some parts of the range), Acer rubrum, Acer saccharinum, Fraxinus pennsylvanica, and Salix spp., or, less commonly, exotic trees such as Salix alba or Salix fragilis. Disturbed sites can be heavily invaded in the understory by exotic or invasive shrub and herb species.
Diagnostic Characteristics: This division is characterized by flooded and swamp forests ranging from the western Great Plains eastward to the Atlantic Coast. Diagnostic tree species include Celtis occidentalis, Fraxinus pennsylvanica, Populus deltoides, and Salix spp. in the central and western range of this division. Acer saccharinum, Celtis laevigata, Fraxinus pennsylvanica, Liquidambar styraciflua, Platanus occidentalis, and Ulmus americana become more dominant from the central to the eastern range of this division. Acer rubrum is the most common species associated with swamp forests within this division. Other common tree species include the hardwoods Nyssa sylvatica, Liriodendron tulipifera, and Liquidambar styraciflua in the central hardwoods region and the conifers Larix laricina and Tsuga canadensis in the northern region, along with localized occurrences of Picea rubens and Picea mariana.
Rationale for Nominal Species or Physiognomic Features:
Classification Comments: This division occurs in azonal conditions across a wide geographic area and can overlap with similar divisions to the north, south, and west of its range.
Similar NVC Types:
D016 North American Boreal Flooded & Swamp Forest, note: "occurs within similar biophysical locations, and there may be some overlap with this division along its northern border."
D062 Southeastern North American Flooded & Swamp Forest, note: borders to the south and may overlap this division along its southern border.
D326 North American Great Plains Forest & Woodland, note:
Physiognomy and Structure: Stands of this division are composed of broad-leaved deciduous trees in the Great Plains and central region, and deciduous, mixed, or coniferous trees in the northern region. Canopies range from dense to partially open; shrub layers may be well-developed or sparse. In northern stands, hummock-and-hollow microtopography is characteristic, and mosses, especially species of Sphagnum, are common and usually abundant. Floodplain stands in the Great Plains can be particularly open, due to a combination of drought and fire.
Floristics: In central floodplain forests, the most common trees are Acer negundo, Acer saccharinum, Celtis occidentalis, Fraxinus pennsylvanica, Platanus occidentalis, Populus deltoides, and/or Ulmus americana. Celtis laevigata and/or Liquidambar styraciflua are important constituents in the southern and midwestern portions of the range. Associated tree species include Acer rubrum, Betula nigra, Carya cordiformis, Carya illinoinensis, and/or Ulmus rubra. In portions of the floodplain that are flooded for shorter durations, associates include Acer saccharum, Carya ovata, Fraxinus americana, Juglans nigra, Liriodendron tulipifera, Prunus serotina, Quercus alba, Quercus macrocarpa, and Quercus rubra. Parthenocissus quinquefolia, Toxicodendron radicans, and Vitis spp. are common vines. Central swamp forests, ranging from wet to xero-hydric flatwoods, include an equally diverse, but distinctive set of tree species, including Acer rubrum var. trilobum, Acer saccharinum, Betula nigra, Fagus grandifolia, Fraxinus pennsylvanica, Liriodendron tulipifera, Liquidambar styraciflua, Nyssa biflora, Nyssa sylvatica, Platanus occidentalis, Quercus alba, Quercus bicolor, Quercus lyrata, Quercus michauxii, Quercus palustris, Quercus phellos, and Quercus stellata.
In the Great Plains, Populus deltoides is the most common tree of the floodplains, and depressional swamps are rather rare. Other dominants include Acer negundo, Fraxinus pennsylvanica, Salix nigra, Salix amygdaloides, and, in the southeastern portion of this division's range, Celtis laevigata and Platanus occidentalis.
To the north, Acer rubrum is a relatively constant species throughout the range of these swamps. At the northern end of the range, canopy trees Betula alleghaniensis, Larix laricina, Picea rubens, Pinus strobus, and Tsuga canadensis are characteristic. Occasionally, colder and saturated conditions favor Abies balsamea, Picea glauca, or Picea mariana.
Disturbed stands may contain a wide variety of ruderal native and non-native species. Species composition varies with time since and nature of disturbance, available seed sources, and habitat characteristics, but common generalist native dominants in the tree strata are Acer negundo (exotic in parts of the range), Acer rubrum, Acer saccharinum, Fraxinus pennsylvanica, Platanus occidentalis, and Salix nigra. In a few sites, exotic trees such as Crataegus spp., Salix alba, or Salix fragilis may be dominant. The understory tree Morus alba can occur on floodplains. Ruderal stands are more often characterized by exotic and native invasive species that together cover at least 80% of the understory. Shrubs include exotics such as Berberis thunbergii (mostly in floodplains and temporarily flooded swamps), Frangula alnus (= Rhamnus frangula), Ligustrum sinense, Ligustrum vulgare, Rhamnus cathartica, and Rosa multiflora (mostly in floodplains), with occasional generalist native species such as Cornus amomum and Cornus sericea.
Dynamics: Floodplain examples are located along small to large rivers or small streams with alluvial soils that typically flood in early spring. Flooding may persist for as little as seven days, or over a month. Floods may cause scouring and create sandbars, leave silty deposits, fine litter and coarse woody debris on the forest floor. Swamp forests in depressions, along lakeshores or small streams, may have relatively stable saturated or flooded soils, or briefly flood in spring, then draw down. Many flooding regimes have been altered by dams, dikes, and ditches.
Environmental Description: Central and northern floodplain forests are found along medium to large rivers or along low-gradient reaches of smaller rivers and streams where a flat floodplain develops. A variety of alluvial soil types may be found within the floodplain from very well-drained sandy substrates of alluvial fans and levees to very dense clays in depressions. By contrast central swamp forests encompass various primarily non-alluvial wetlands of the eastern and central United States, including ponds and depressions, as well as various kinds of flatwoods. Flatwoods often contain an impermeable clay layer or fragipan creating a shallow, perched water table; soils are poorly-drained to very poorly-drained, and surface water may be present for extended periods of time, rarely becoming dry. To the west, in the Great Plains, stands occur in floodplains and riparian settings along large to small rivers. Soils are primarily alluvial and range from sandy to clay. To the north, hardwood-conifer swamp occurs on a variety of landforms, including poorly-drained outwash channels and outwash plains and depressions on medium- to coarse-textured end moraines, ground moraines, and glacial lakeplains (Kost et al. 2007). The community occupies sites influenced by groundwater seepage, usually where the water table is at or near the soil surface. Hardwood-conifer swamp occurs on gently sloping to flat topography along headwater streams or in association with relatively inactive portions of floodplains of low order streams, where they form backswamps or occur in meander scars (Tepley et al. 2004).
Soils/substrate: This division is found in floodplains and riparian settings along large to small rivers. Soils are primarily alluvial and range from sandy to clay. This macrogroup can occur in deep or shallow river valleys but slopes within stands are typically gentle or nonexistent.
Geographic Range: This division ranges from the western Great Plains east to the Atlantic Coast, north into southern Canada and south to the south-central United States, north of the Gulf Coastal Plain, except along the Mississippi River.
Nations: CA, US
States/Provinces: AB, AL, AR, CO, CT, DC?, DE, FL, GA, IA, IL, IN, KS, KY, LA, MA, MB, MD, ME, MI, MN, MO, MS, MT, NB, NC, ND, NE, NH, NJ, NM, NS, NY, OH, OK, ON, PA, PE, QC, RI, SC, SD, SK, TN, TX, VA, VT, WI, WV, WY
|US Forest Service Ecoregions (2007)|
Southwest Plateau and Plains Dry Steppe and Shrub Province
Confident or certain
Confident or certain
Confidence Level: Moderate
Confidence Level Comments:
Synonomy: > Elm-Ash forest (Ulmus-Fraxinus), Type 101 (Küchler 1964) [Includes the most extensive swamps in the Midwest (Ohio, Michigan, Indiana) but doesn't include the many minor central swamps.]
> Northern floodplain forest (Populus-Salix-Ulmus), Type 98 (Küchler 1964) [Swamps and flatwoods are not included in this concept.]
Concept Author(s): A.W. Kuchler (1964)
Author of Description: S. Menard and D. Faber-Langendoen
Acknowledgements: Scott Franklin, Chris Lea
Version Date: 27Oct2015
- Braun, E. L. 1950. Deciduous forests of eastern North America. Hafner Press, New York. 596 pp.
- Faber-Langendoen, D., J. Drake, S. Gawler, M. Hall, C. Josse, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, L. Sneddon, K. Schulz, J. Teague, M. Russo, K. Snow, and P. Comer, editors. 2010-2019a. Divisions, Macrogroups and Groups for the Revised U.S. National Vegetation Classification. NatureServe, Arlington, VA. plus appendices. [in preparation]
- Golet, F. C., A. J. K. Calhoun, W. R. DeRagon, D. J. Lowry, and A. J. Gold. 1993. Ecology of red maple swamps in the glaciated Northeast: A community profile. USDI Fish & Wildlife Service, Washington, DC. 151 pp.
- Kost, M. A., D. A. Albert, J. G. Cohen, B. S. Slaughter, R. K. Schillo, C. R. Weber, and K. A. Chapman. 2007. Natural communities of Michigan: Classification and description. Report No. 2007-21, Michigan Natural Features Inventory, Lansing. 314 pp. [http://web4.msue.msu.edu/mnfi/reports/2007-21_Natural_Communites_of_Michigan_Classification_and_Description.pdf]
- Küchler, A. W. 1964. Potential natural vegetation of the conterminous United States. American Geographic Society Special Publication 36. New York, NY. 116 pp.
- Tepley, A. J., J. G. Cohen, and L. Huberty. 2004. Natural community abstract for southern floodplain forest. Michigan Natural Features Inventory, Lansing, MI. 14 pp.