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The characteristic zones of
parabolic dunes are the beach, foredune, interdunal wetland or trough,
and the backdune, each with
its distinctive physical character and biota.
The beach is the most
dynamic zone, where wind, waves, and coastal currents create an ever
changing environment.
Wind velocity is highest at the shoreline, as is the frequency of flooding
and the wave energy.
Because of these extremes, few plants and animals are adapted to live on
the beach.
The foredune is the zone
where pioneering grasses cause sand to begin accumulating. It can consist
of a distinctive, low dune feature, or merely a low landward continuation
of the beach. Not only
must plants of the foredune tolerate periodic burial, they must also
survive extreme tempera-tures, low
moisture levels, and low levels of nutrients. Extreme temperatures cause
many of this zone’s
inhabitants, such as Fowler’s toad, the eastern hognose snake, and
spider wasps to burrow during
the day to reach cooler temperatures.
Behind the protective
foredune, winds are lighter and sand accumulation is slower, allowing
trees to establish and
form forests. The rich forest floor supports a diversity of spring wild
flowers, including
common and nodding trilliums, jack-in-the-pulpit, and squirrel corn.
Animal diversity is
also high, including forest songbirds, eastern box turtle and salamander.
Blowouts are U-shaped areas
of open, migrating sand that occur on dunes otherwise stabilized by
forest vegetation. Blowout
formation is closely linked with Great Lake high-water levels.
Small ponds are common
between the foredune and the backdune in many dune complexes. As a result
of water level fluctuations, both the plant and animal life can change
dramatically from year to
year.
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