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You’re close to the top of a dune that’s been piled up and carved by the wind. This is the youngest, newest dune you’ll see--the dioramas that follow will show older dunes farther from the beach. Marram grass has colonized the dune. In addition, some plants that were here before the sand piled up have since been smothered by it.
Marram grass (Ammophila breviligulata)
Between the edge of the water and the beginning of the dunes, dry sand
is constantly in motion--dancing, shifting and floating. This makes the
beach a treacherous place for plants to take root. One kind of plant that
does live here is marram grass. It spreads its tuberous roots just under
the surface of the sand, and forms an underground web that helps hold the
sand in place.
Though marram grass stabilizes the soil for its own survival, an inadvertent side effect is that it makes it possible for other kinds of vegetation to begin to take hold. Other plants take advantage of the increased stability of the soil surface and start to colonize areas the marram grass helped make safe.
Cottonwood (Populus sp.)
Cottonwood trees may take hold in the inhospitable conditions of the
dunes, once marram grass has begun to calm the shifting sands. Slender
young trees are trying to grow here. Cottonwoods are tough trees that can
thrive even on the streets of Chicago, one of the hardest places for a
tree to grow. In early June, keep an eye out for its seeds-- adult trees
sends their seeds floating off on pale, fluffy structures that look like
pieces of cotton or feathers. Sometimes the seeds fall in blankets so thick
it resembles snowfall.
Tops of trees
Why are just the tops of the branches sticking out of the sand? That’s
because the tree was there before the sand dune was. The tree was thriving
when the wind began to heap the sand around it. Eventually it was trapped
under the dune.
| Bald eagle (Haliaeetus leucocephalus) The feathers on the head and tail of bald eagles turn brilliant white when an eagle is fully mature, around four years of age. |
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