Most of us recall those maps in high school where we learned the extent of the continental glaciers of the last ice age, roughly 10,000 years ago. During those millennia, the Great Lakes were formed, along with many other lakes, rivers, and landforms.
For me, Mr. Harrington was the teacher that sparked my interest in “reading the landscape”. That “itch” was exacerbated by an extra-curricular course of the same topic.
Since then, my eyes have been peeled for these clues along the highways and byways. My kids, years ago, would roll their eyes as I explained the formation of eskers, kames, drumlins, and kettle holes. My son thought I was nuts when I read Dorr and Eschman’s “Geology of Michigan” for pleasure. A textbook; “really Dad”?
Recently, a 12,000 mile journey through the far north provided a cornucopia of glacial evidence. And, the scene along northbound I-75 near Indian River continues to each time catch my breath as I imagine how it appeared as the glaciers were melting.
Michigan and Wisconsin are loaded with evidence of past glaciation. The drumlin fields of Menominee County are clearly seen with satellite imagery. Hiking trails sometimes follow meandering eskers. The boulder fields of terminal and lateral moraines have become popular places to build second homes.
The rise and fall of the Great Lakes left major marks of what is now “inland”. The sand dunes along the current day lakeshores are evident to most folks, such as those at Sleeping Bear. The inland dunes, from when the Great Lakes were higher, now mostly forest-covered, are less obvious.
In geological time, our landscapes are fresh and brand new. Ecological volatility still has the wide mood swings of an adolescent. This brings us to forests and forest soils.
The detritus that fell out of the melting glaciers, and subsequently shifted around by wind and water, created an overburden of material that hosted the migration of tree species and forests back into our region. This overburden is incredibly diverse and served as parent material for what would become the soils (and forests) of today.
The massive and deep sandy outwash plains consist mostly of low fertility soils. Here, jack pine and red pine tend to grow. Siltier soils, where water pooled, grew the softwood and hardwood swamps, which exist today, where they have not been drained for agriculture. The Clay Lake Plains of the eastern U.P. are good examples. The jumble of soils that make up moraines easily support our oak and northern hardwood forests.
My own property straddles a tight transition between rolling sandy loam hills and the sandy outwash of the Whitefish River valley. My uplands grew northern hardwoods before the homesteaders painstakingly cleared the trees. The lowland sandy soils underlie centuries of wetland peat accumulation, now supporting cedar, spruce, and tamarack.
Thousands of years of forest cover altered the soil surfaces, adding nutrients and textures. The massive wildfires of a century ago burned-off much of this ecological progress in some places. Soil scientists have mapped over 400 soil types and given each series a name, such as Michigan’s state soil “Kalkaska Sand”.
Knowing the soils and their characteristics has much to do with what now grows there, as well as the potential for what might grow there in the future. Quality sugar maple simply will not happen on deep sands or wetland mucks. The red oaks become mangled if they try to grow on poorly drained soils.
I know of many aborted management attempts because the forestowners failed to consider the soils, along with many more where the soils were successfully used as guidelines.
The U.S. Department of Agriculture has mapped the soils of the United States (an astounding feat!). This information can be accessed online at Web Soil Survey. The tool is a bit awkward but, with practice, can provide some very useful information.
Soil types and soil origins ought to be considered when managing a forest. A consulting forester can help explain the soil relationships to forest health and the possible future.
