Tuesday, November 17, 2009

Cedar Islands

For a place of dry prairies, Blue Jay Barrens certainly has a lot of islands. One common type of island is formed by a single large cedar or a very small group of cedars isolated in the middle of the tall grass prairie.

The cedar forms a pocket of shade that reduces sunlight and lowers the temperature of the ground beneath the tree. This creates a micro-climate with characteristics sometimes drastically different from the surrounding prairie.

The shadow also tracks around the tree as the day progresses. The subtle difference made by this wandering shadow can also create a slightly different climate in the adjacent area.

The population of sun loving prairie plants is diminished by the shade and other species move in to fill the void. Many types of shrubs and flowers grow from the shaded base of the cedar. Native plants tend to prevail in these zones, but a few invasives can also get a start here. A small patch of tall fescue can usually be found on the northern side of these cedars. Being a plant that thrives during the cool time of the year, tall fescue remains green when the prairie grass turns brown.

Interesting collections of mosses and lichens can grow in the tiny cedar thickets. These growths often become quite diverse and form extensive colonies on the dead branches that fall to the ground.

As the tree ages, lower branches begin do die and lose their needles. This allows more sunlight to access the ground beneath the tree and the prairie grasses are able displace the shade tolerant plants. This process can be accelerated by pruning the lower branches from the tree, if you’re willing to destroy those transitional island communities. It’s not something I’ve studied enough to prove, but I think there are some special things occurring in these cedar island communities that are worth saving.

1 comment:

  1. Very interesting. Now I know why some of some of the cedar trees in our area hold a lot of Oregon grape plants. I never noticed it until this year when that was the only place I could find enough Oregon grapes for making jelly.