|Red Cedar trees that have invaded a dry prairie in Eastern Iowa. Cedars require full sun and will likely be succeeded by Elms, Dogwoods, and Black Cherry which are more shade tolerant.|
|An early succesional stage, or pioneering stage, forest composed of Willow and Cottonwood.|
|An older pioneering forest composed of primarily of Ash. There are some smaller younger Oaks growing in the shade of these Ashes. The Oaks will one day replace the Ashes and this will likely become an Oak-Hickory forest.|
Again though, lurking in the understory may be trees that will soon become the next successional stage, also called the climax stage. If you are in an Oak-Hickory forest and find an abundance of small Maple trees growing in the shade you can know that in several decades this will become a Maple forest. Maples and Basswood are very shade tolerant trees. If an Oak-Hickory or other type of forest becomes overly shady the Oaks and Hickories will not be able to reproduce being they require sunlight to grow. Maples and Basswood are quite at home growing in the shade and will slowly grow until the larger trees die or are shaded out. In Iowa the Maple-Basswood forest is the most stable forest type because these trees are able to continue reproducing themselves, even in their own shade. So, without any disturbances the Maple-Basswood forest is very stable and will grow indefinitely, and for this reason they are called a "climax community". Another community of trees will not replace this community until fire, floods, logging, disease, drought, or storms disturb this community, killing off the trees. Once the community is disturbed we start over with the original pioneering, early successional stage.
Pioneering Stage: Shade intolerant trees
Mid-successional Stage: Partial shade tolerant trees
Climax Stage: Very shade tolerant trees
Disturbance during any one of these stages starts the process over at pioneering.
|This grove of Bigtooth Aspen and Sumac are in the middle of an Oak forest. It is likely that this area was an Oak forest that was disturbed by logging, which caused the pioneering Aspen and Sumac trees to become established in the full sunlight.|
1. What types of trees are present in the canopy? Are they pioneering, mid-successional, or climax species? Use the list of trees in the descriptions above to find out. You can also use this list of trees by shade tolerance to help you find out.
2. What types of trees grow in the understory? If they are Oaks, Maples, or Basswood they will eventually replace the current forest type.
3. Look for evidence of disturbance. Do you find old stumps as evidence of logging? Dead trees as evidence of flooding or disease? These things should result in a return to a pioneering forest. Or do you find charred woody materials as evidence of burning? This should result in an Oak forest or savanna and the absence of other species.
4. Where are you in the landscape? Uplands or bottomlands? Is the soil sandy and therefore dry or have higher clay content and therefore wetter? Drier soils will more likely climax with Oaks, especially if fire is present. Wetter soils will more likely climax with a Maple-Basswood forest.
So along with simply enjoying the magnificent trees you hike through, with this information you can hopefully do a little detective work. Often this process can be difficult but it sure can add a lot to you knowledge of the forest making you hike a little more interesting.