KUCHLER TYPE DESCRIPTION
Kuchler Type: Southern floodplain forest


PHYSIOGRAPHY : 
The southern floodplain forest includes bottomland hardwood stands and
deep, alluvial swamps.  Boundaries are hard to distinguish, but the type
is found where streams and rivers occasionally flood beyond their
channels and in deepwater swamps that are inundated for most of the
growing season.  The southern floodplain forest can range in area from
broad river floodplains to narrow strips along small stream channels.
Many areas are characterized by sloughs, oxbow lakes, and natural levees
of coarse material deposited by flooding.  Topographic relief is low,
but these levees form high points on the floodplain [18].


CLIMATE : 
The climate of the southern floodplain forest is variable throughout its
range, but rainfall averages 50 inches (1,270 mm) annually.  Near the
coast summers are wetter than winters; rainfall is distributed more
evenly inland.  In all areas, drying occurs in late summer and early
fall.  Average temperature for the southern region is 70 degrees
Fahrenheit (21 deg C).  Average number of frost-free days is 240,
ranging from 200 days in the North (Virginia and southern Indiana, Ohio)
to 320 days in the South (Florida and parts of the Gulf Coast) [18].


SOILS : 
Southern floodplains have alluvial sediments from 15 to 240 feet (5-80
m) thick.  Physiochemical characteristics of soils are listed by zone
[18].  Soils range in texture from silty clay and clay to sand.  High
clay content results in greater phosphorus content.  Soils are somewhat
acidic, with pH ranges between 5 and 6.  Organic matter content is
usually 2 to 5 percent higher than in upland soils.  High organic matter
content accounts for higher nitrogen concentrations and may explain, in
part, why bottomland forests tend to be more productive than upland
forests.  Organic matter content has been reported as high as 36 percent
in black tupelo (Nyssa sylvatica) swamps.  Nutrients are readily
available and are continually replenished by flooding [18].


VEGETATION : 
Canopy dominants include one conifer, baldcypress (Taxodium distichum),
and several hardwood species, particularly oaks (Quercus spp.) and water
tupelo (Nyssa aquatica) [12].  This report will refer to both
baldcypress and pondcypress (Taxodium distichum var. nutans) as cypress.

Species composition in southern floodplain forests is a function of
constantly shifting factors like stream migration, soil erosion, and
deposition, which change the substrate.  Plant species differ in their
tolerance of flooding and shade and in their colonizing abilities [18].

Recently formed point bars and levees along stream channels are
colonized by black willow (Salix nigra), eastern cottonwood (Populus
deltoides), river birch (Betula nigra), and sugar maple (Acer
saccharinum).  River levees are colonized by American sycamore (Platanus
occidentalis) and sugar maple.

Species on older substrates, for example in sloughs, oxbows, and swamps,
support water tupelo, baldcypress, and water-elm (Planera aquatica).  On
poorly-drained sites overcup oak (Quercus lyrata), laurel oak (Q.
laurifolia), red maple (Acer rubrum), American elm (Ulmus americana),
green ash (Fraxinus pennsylvanica), water hickory (Carya aquatica),
sugarberry (Celtis laevigata), and hackberry (C. occidentalis) are
interspersed with black tupelo and cypress.  Ridges in low areas with
short hydroperiods and few herbaceous species support sweetgum
(Liquidambar styraciflua), willow oak (Quercus phellos), water oak (Q.
nigra), cherrybark oak (Q. pagoda), swamp chestnut oak (Q. michauxii),
hickories (Carya spp.), and black tupelo [18].  Higher ridges may have
understory species of ferns, orchids, bromeliads, and epiphytic ferns.
Other understory species include buttonbush (Cephalanthus occidentalis),
strangler fig (Ficus aurea), pond apple (Annona glabra), grape (Vitis
spp.), peppervine (Ampelopsis arborea), deciduous holly (Ilex decidua),
water locust (Gleditsia aquatica), Alabama supplejack (Berchemia
scandens), common trumpetcreeper (Campsis radicans), and redbay (Persea
borbonia) [18].

Plant communities in the southern floodplain forest have been classified
across an anaerobic gradient.  However, this classification may be
oversimplified and not useful for all wetland ecology [18].

For detailed information on cypress stands not related to fire refer to
Ewel and Odum [5].


WILDLIFE : 
A wide variety of invertebrates, fish, amphibians, reptiles, birds, and
mammals occur in the southern floodplain forest.  Some include mollusks
and other crustaceans, spiders, minnows, pickerels, salamanders, frogs,
snakes, turtles, herons, egrets, ducks, warblers, woodpeckers, beavers,
otters, nutria, mink, white-tailed deer, bobcats, rabbits, and squirrels
[18].


ECOLOGICAL RELATIONSHIPS : 
Groundwater levels and flooding determine the type and productivity of
vegetation in the southern floodplain forest.  Hydroperiod ultimately
limits species composition.  Flooding during the growing season has a
greater effect on species survival than during the nongrowing season.
Floodplain forests may be important for providing nutrients to
downstream ecosystems [18].

Climatic climax communities rarely occur in southern floodplain forests
because of the dynamic nature of the ecosystem.  Successional trends are
complex, and it is difficult to define distinct seral community stages.
However, newly-formed sandbars along stream and river margins are
generally colonized by black willow, black cottonwood, sugar maple, and
river birch.  As these stands mature, sites with short hydroperiods
usually develop into sycamore-sweetgum-American elm or
sugarberry-American elm-green ash stands.  Cypress and tupelo stands
grow best on sites inundated for long periods and persist indefinitely
on these sites.  On poorly drained sites overcup oak and water hickory
stands can be interspersed with cypress and tupelo.  If these sites are
drained they succeed to sugarberry-American elm-green ash.  Chestnut oak
and cherrybark oak usually indicate the more stable communities [18].

For more detailed information on ecological relationships of the
individual species mentioned here, refer to Eyre [6].

If the substrate and hydroperiods remain stable, mixed hardwood species
typically form climax communities [23].  Also, black tupelo and slash
pine (Pinus elliottii) may dominate cypress swamps in fire's absence
[3].  Because mature cypress are more resistant to fire than swamp
hardwoods, infrequent fires of low intensity favor cypress dominance
[1,8].  Cypress may dominate in drained areas with periodic surface
fires, although pines invade cypress domes following extended droughts
[4].

Severe fires (usually following drought conditions or drainage and
drying of the peat layer) in cypress-mixed hardwood swamps often
eliminate the prefire vegetation, allowing willow species to invade by
seed.  Willow sprouts with frequent fire.  If relict cypress and
hardwood species remain in these sites, they will reestablish their
dominance in the absence of fire [3,8].

Related categories for Kuchler Type: Southern floodplain forest