These areas include closed to semi-closed canopies found in association with rivers and with hydric mucky soils. Fire is rare.
Alluvial forests occur in river floodplains on low elevation levees, that are slightly above floodplain swamps. They are distinguished by the occurrence of water hickory (Carya aquatica), overcup oak (Quercus lyrata), swamp laurel oak (Quercus laurifolia), green ash (Fraxinus pennsylvanica), American elm (Ulmus Americana), water locust (Gledistsia aquatic), and river birch (Betula nigra). Soils flood during river floods but do not contain standing water during dry portions of the year. These areas differ from basin swamps in that they have less flooding and/or standing water.
Bottomland forests are distinguished by a canopy of spruce pine (Pinus glabra), loblolly (Pinus taeda), water oak (Quercus nigra), and sweetgum (Liquidambar styraciflua). These areas differ from basin swamps and floodplain forests by rarely flooding. They may be associated with rivers or smaller bodies of water and isolated inland.
Basin swamps are distinguished by a canopy containing buttressed trees, including bald cypress (Taxodium distichum), pond cypress (Taxodium ascendens) and swamp tupelo (Nyssa biflora). The water source is precipitation and, to a lesser extent, river flooding. Basin swamps flood more than bottomland forests but not as much as floodplain swamps.
Floodplain swamps are distinguished by their location on the lowest portion of river floodplains and tree canopies that contain buttressed trees, including bald cypress (Taxodium distichum), swamp tupelo (Nyssa biflora), or Ogeechee tupelo (Nyssa ogechee). The water sources are precipitation and river flooding, with seasonal and prolonged flooding.