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Freshwater Shore Lines
Nature Bulletin No. 531-A May 25, 1974
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation
FRESHWATER SHORE LINES
Ashore is more than a line on a map where land meets water. Whether it
is the edge of a creek, river, lake or pond, a shore is a long narrow
world of its own, separate and distinct from the broad land mass and the
sheet of water next to it. Along this line many living things, both plant
and animal, crowd in and lead a double life -- part time on land and part
time in water. They form a community which is always active.
A conspicuous feature of most shores is a band of luxuriant upstanding
vegetation. As the water level rises during rainy weather or falls during
times of drought, this strip is alternately flooded or left stranded. There
is always a crop of marginal plants except on streams whose banks are
regularly scoured by freshets: or on lakes where high waves pound over
a sandy beach; or on artificial reservoirs where the water levels
fluctuate greatly because they are used for flood control, water power or
water supply.
Commonly, the different kinds of shore plants are arranged in zones.
Some of the bulrushes, for instance, grow upward from water so deep
that their roots are always submerged. The cattail, arrowhead and others
are in a higher zone -- sometimes in shallow water, sometimes on wet
mud. Still others, including such trees and shrubs as willow, silver
maple and buttonbush, grow above them where the soil is kept moist by
water drawn from below. The widths of these zones and the kinds of
plants in them depend on the slope of the shore, its type of soil, and the
changes in water level during the course of a season.
The Arrowhead, with broad glossy spear-shaped leaves, thrives on
muddy shores of both streams and lakes. The same plant growing in a
foot of water may have leaves as slender as a pencil. Its flowers, each
with three filmy white petals, appear in groups of three throughout the
summer. At the ends of long underground runners it bears starchy
tubers the size of a hen's egg. These are eaten by waterfowl and
muskrats -- hence the name Duck Potato. On their journey to the Pacific
Coast in the early 1800's, the Lewis and Clark Expedition bartered for
quantities of these tubers from the Indians who called them Wapato.
The Great American Bulrush sends up tall slender whip-like stems from
a mat of interlocking rootstocks below the low-water mark. They help
anchor loose soil and build new land. Their fruiting stems bear loose
clusters of seeds which, with the starchy roots and the bases of stems,
furnish an abundance of food for muskrats, wild ducks and shore birds.
Among the more common large shore plants of this region are the
Sweet Flag which, from its thick aromatic underground stem, yields the
drug calamus; the Pickerel Weed with its leathery green leaves and tall
spike of blue flowers; the Water Smartweed with its heads of "shocking
pink" blooms; and a host of different kinds of sedges and grasses.
The animal life of a shore is as distinctive as its plants. In or near this
vegetation are to be found the nests of the marsh wren, the red-winged
blackbird, coots, rails and little green herons. Water-dwelling toads and
salamanders lay their eggs in the water. Mink and raccoons prowl the
water's edge for crayfish, frogs, snails and snakes.
Small boys come prowling after them.
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