Southern New England Habitats III: Floodplain

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Southern New England Habitats III Floodplain

• Definition Floodplains develop in low-lying
  areas along rivers. They are periodically
  inundated by spring and storm flood waters that
  carry abundant nutrients.
• Physical environment The soils of floodplains
  range from sandy (large soil particles) and well
  drained along the riverbank to muddy (small soil
  particles) and poorly drained in the interior.
• DiversityRichness of terrestrial plant species
  may be low, because few possess the adaptations
  necessary to survive in an environment where
  mechanical damage, flooding and waterlogged soils
  are present. The density of these species may be
  high, however.

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Topography the Riverbank and Levee

• The bank is where the river meets the land.
  Because river water is moving, it is a high
  energy environment. River water deposits larger
  soil particles along the bank, and floodwaters
  deposit sands in a mound several feet high, the
  levee, directly behind the bank and paralleling
  the river.

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The Flat

• Interior soils are generally high in nutrients
  but waterlogged and low in oxygen.
• An impervious soil layer, a hardpan, may develop
  that keeps water near the soils surface.
• Tree species capable of tolerating wet soils and
  spending weeks underwater predominate in this
  environment.
• Shrubs are often sparse due to drowning and
  mechanical damage from flooding. Herbaceous
  plants can occur densely, however.

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The Slough

• In areas of lower microelevation, water may
  persist after other portions of the floodplain
  have drained of floodwaters.
• Such areas typically show delayed development of
  herbaceous vegetation.

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Floodplain Marshes

• In more extensive regions of lower
  microelevation, permanent standing water may
  prevent most tree and shrub growth.
• In these areas, a marsh community dominated by
  herbaceous plants develops.
• Typical marsh plant species include river
  bulrush, water horsetail, tuckahoe (foreground),
  cattail (background) and bullhead lily.

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Plant Diversity

• The moist, rich, well-drained and sandy soils of
  the bank and levee are vegetated by tree species
  like eastern cottonwood, American sycamore (lower
  left), American linden, shagbark hickory,
  bitternut hickory, river birch and white ash
  (upper left).
• The waterlogged clay and silt soils of the flat
  are dominated by species that tolerate these
  conditions like red maple, slippery elm, silver
  maple (upper right), green ash, pin oak (lower
  right) and swamp white oak.

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Profile of a Southern New England Floodplain
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Adaptations

• Many tree species produce seeds in early spring
  so that they may be dispersed by floodwaters.
• Trees often are multi-trunked and with shallow
  root systems, which help them to cope with
  floodplain conditions.
• Herbaceous species may initiate growth late in
  the season to compensate for spring flooding of
  the habitat.