You wouldn’t think that living in the “Tension Zone” would be a good thing, but those of us who live in Winnebago County do and are fortunate to do so.
In the 1950s, John Curtis, a botany professor at UW-Madison set out to classify the plant communities of Wisconsin. With help from his students, a description of Wisconsin’s natural systems was developed.
If you’ve done any traveling at all in Wisconsin, you’ve certainly noticed that the north woods doesn’t look anything like the open prairie grasslands of the southern part of the state.
Botanists have determined that there are two separate sets of plant species in Wisconsin, one in the south and the other in the north. The species found in the south are referred to as prairie forest flora and those in the north are called northern hardwoods flora. These plant species mark the edges of two of the major North American biomes: the eastern deciduous forest and the western grasslands. A biome is a major community of plants and animals with similar requirements of environmental conditions. In addition, the northern boreal forest biome reaches down from Canada into northern Wisconsin.
Of course, there isn’t a definite demarcation where the northern species stop and the southern species start, but the overlap is narrower than you might think.
The overlap between the biomes is called the Tension Zone, and it ranges from only ten to as much as thirty miles wide. The Tension Zone begins in Polk County in the northwest part of Wisconsin, and then swoops down through the state toward the southeast, covering the counties surrounding Lake Winnebago. Then it makes a sharp right turn parallel to Lake Michigan, and ends in Racine County.
Living in the Tension Zone, we are blessed with a greater variety of native plant species than in any other part of the state. Where woodlands are left undisturbed, more native species of wildflowers abound than you will see in wooded areas north or south of the Tension Zone, even as close as Waushara County to the west or Shawano County to the north. The same is true of prairie species, in the few fragments of native prairie that remain.
What does living in the Tension Zone mean for us besides feeling fortunate? It means that our climate and soils are well adapted to many more native plants than that of our neighbors to the north or south. Those people who look to design a native landscape have a much wider choice of plant materials that will thrive.
It also means that we should strive to protect the few pristine woodlands and prairie areas that still exist within the Tension Zone by controlling invasive plants and guarding against uncontrolled development. By chance or intention, we live in the Tension Zone. Let’s not waste the gift.
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