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Wetlands are an often
misunderstoond but critical part of the functioning of the sand country
ecosystem. Sand is highly permeable to rainfall; very little surface runoff
occurs after a rain or snow melt in sand country. Instead, the water travels
directly downward into a shallow aquifer, which in most places in no more than
seventeen to twenty feet (about five meters) below the surface.
These two factors: (1) the ease with which water can travel down into the sand;
and (2) the shallow aquifer or water table, have a tremendous influence of sand
country ecology. The countryside of northwest Indiana is mostly flat and level.
However, the relatively minor variations in local surface elevation--usually no
more than fifteen to twenty feet within a few hundred yards--are sufficient to
result in extremes in hydrological conditions in the soil.
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Pictured above is a small sand marsh. It is simply a slight depression in an upland sand deposit. The depression is perhaps a meter deep, but because a group of sand hills three or four meters higher are nearby, the water table is nearly always near or above the surface. The result is an intriguing and rich assemblage of plants and animals, which is similar to that found in pannes along Lake Michigan about forty miles to the north. The sounds you are hearing (if you are MSIE 3.0 or better!) were recorded in June at the location shown in the photo. The pond or marsh sometimes dries up completely during late summer, and therefore cannot support fish. This makes it an ideal habitat for frogs and toads to breed because the adults, eggs, and tadpoles do not risk being eaten by predatory fish. Chorus frogs and spring peepers are abundant and vociferous in the early spring. Two state listed reptiles have been observed at this location: Eastern Mud Turtle, Kinosternon subrubrum subrubrum and Western smooth green snake, Opheodrys vernalis.
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