Ecological
Succession and Foredunes:
On Thursday, we focused on the idea of
ecological succession, which is the idea that communities shift and change. As
certain organisms change the conditions of the environment, the ecosystem
changes. So, first consider the four main ecosystems of the Indiana Dunes
National Lakeshore:
1. Open
Beach – no trees, few plants, right against Lake Michigan. Home for
shorebirds.
2. Foredune
– also known as simply “the dune.” A big mountain of sand, held together by
special plants like marram grass and cottonwood. These plants have extensive
root systems that hold the dune together.
3. Oak
Savannah – further inland from the dune, characterized by oak trees (of
course) and areas of treeless prairie created by forest fire. The tree cover
isn’t very dense and light allows smaller plants to grow. Lots of deer and
mammals are found here, as well as wildflowers and insects in the prairie.
4. Eastern
Deciduous Forest – features deciduous trees other than oak (maple and
sassafras, for example), and a wide range of animals. This ecosystem is found
the furthest inland.
So, if you start with an open beach
ecosystem, created by a dynamic lake, over many years it will turn into a
foredune as wind blows the sand around and pioneer plants anchor this soil. As
these plants grow, die, and decay, the soil becomes richer and can hold more
water and nutrients – and oak saplings are able to colonize the ecosystem,
turning it into an oak savannah. Oak savannah gradually becomes eastern
deciduous forest as the soil becomes even more nutritious. This enriched soil
can support a wider diversity of plant species, as well as larger trees.
To better understand this idea of
ecological succession, we played a game where everyone starts as a foredune and
tries to grow into an oak savannah and an eastern deciduous forest. This game,
in which students play “rock paper scissors” to determine which who will
progress to the next ecosystem, ended with some students as each ecosystem.
This demonstrates that not every foredune becomes an oak savannah, and not
every oak savannah becomes an eastern deciduous forest – only where the
conditions are right!
For our creative project, we focused on
the foredune, an ecosystem that is extremely special at the Indiana Dune National
Lakeshore. We discussed the extensive root system of marram grass, which will
be disturbed if you step on it. We also talked about how the cottonwood
tree can shoot roots out of its trunk, so as it is covered with sand it can hold
that sand together. Cottonwood trees grow as the dune grows!
We also looked at jack pine trees and sand cherries, as well as killdeer, prairie warblers, mice and other dune animals. Using these species, we created 2 fantastic, colorful murals of foredunes at sunset. Our drawings are full of important creatures and plants. The foredune is a key part of dune biodiversity, and we had a great time discovering how plants can shape a changing environment!
