History
and Disturbance Patterns
History
Evidence of humans and their impacts on Wisconsin's
forests goes back 11,000 years, when Indians burned large oak savannas
to maintain habitat for wildlife and promote the growth of edible plants.
Then Indian populations greatly declined due to disease brought by Europeans
in the 1630s. Indians were no longer able to manage oak savannas by fire
in the south, or harvest trees in the north, which allowed forest cover
to increase. When Europeans eventually started pouring into Wisconsin
in the mid-1800s, they found forests throughout most of the state, totaling
between 22 and 30 million acres, which covered approximately three-quarters
of Wisconsin's land base.
Ecological Landscapes of Wisconsin/Basic Forest Ecology
The state has two major forest categories—the
Northern Mixed Forest and the Southern Broadleaf Forest. Due to differences
in climate and soil type, the two regions support different species. In
the north, pine, spruce and tamarack are more abundant. The southern region
supports more oak, hickory, maple and basswood.
An S-shaped band that runs from Polk County in the north to Milwaukee
in the south is a transitional area between the two regions called the
Tension Zone, which supports species from both regions.
Natural and Human Disturbance Patterns
Forest ecology is a dynamic process that is continually changing due to both natural and human disturbance patterns. It is no different in Wisconsin, where fire, wind, disease or land use patterns can permanently alter the forest landscape. In our state, a significant disturbance pattern occurred between the 1850s and 1930s when almost half of the state’s 17 million acres of forest land was either cleared for land conversion or high-graded, which is removing only the most valuable timber, leaving less desirable species to take over. This degradation of Wisconsin’s forests was a "progressive" idea that fueled the growth of Midwestern cities like Chicago, Minneapolis/St. Paul and St. Louis. This period is known as the Cut-over Era.
Conservationists and programs such as the Civilian Conservation Corps were able to replant many of the trees that were lost during this time. They added to the natural regeneration that was already occuring. However, impacts from the Cut-over Era are still apparent today. Endangered savannas in the south and barrens in the north may never totally recover because of changes in land use.
For more information on this topic, check out the following books:
Farming the Cutover by Robert Gough (published in 1997 by the
University of Kansas Press)
Planning a Wilderness by James Kates (published in 2001 by the
University of Minnesota Press)
Natural events also shape the forest landscape. Patches of forest that are damaged by insects are places where young trees can get enough light to thrive. Moderate fires in woodlands help to keep too much dead plant material from accumulating.
When these natural events become more powerful than the normal impact trees or forest soils have on woodlands, they can be devastating. Fires, diseases, tornadoes or straight-line winds, insects and wildlife can damage trees and the forest ecosystem. For example, Dutch elm disease and chestnut blight greatly altered our forests, while European gypsy moth and other exotic species continue to challenge forest managers today. Futhermore, after many years without a burn because of climatic factors and human suppression, fires can become more intense. This can lead to the sterilization of forest soils as well as dead trees.
Some available management options seek to mimic these natural disturbance patterns. Certain long-term or permanent land uses can fundamentally alter the forest ecosystem causing pollution, forest fragmentation and a hastening of extinction rates.
While disturbance is a natural part of a healthy forest, woodland owners like you need to monitor the disturbance in your forest to make sure it's within limits your forest can handle, and when possible, consistent with your management objectives.