What a great diversity of habitats we encountered on our extended field trip to the northern reaches of Minnesota this past weekend. One of the first stops just north of Virginia, MN, was the Laurentian Divide, which I had never heard of. This modest rise of granite divides two watersheds: north of the divide rivers empty into Hudson Bay and the Arctic Ocean, while south of the divide, rivers drain into the Atlantic, either via the Mississippi River or the Great Lakes and St. Lawrence River.
I am standing on the Laurentian Divide that runs through the middle of North Dakota, northeastern MN, and most of southeastern Canada. This exposed granite was scoured clean of vegetation by past glaciation, and today is covered by thin soil and sparse vegetation.
The granite of the Laurentian Divide is part of a huge formation called the Canadian Shield that comprises the ancient core of the North American plate and today underlies most of Canada and part of the northeastern U.S. The exposed rock was formed approximately 2.7 billion years ago! during a series of volcanic events that resulted in upheaval of a vast area of rock that may have reached 39,000 feet elevation (12,000 m), but is largely eroded to modest hills today.
This boreal forest area of Minnesota is a composite of granite knobs, forested slopes, and boggy lowlands, each with their unique fauna and flora. In places where the land flattens out over river flood plains, there are expansive grassland hayfields, suitable only for grazing it seems.
Pale Corydalis colonized the barest, rockiest, driest areas of the granite knobs.
The flower reminds me a little of bleeding heart, but it is not in the same family.
A mixed deciduous-coniferous forest typical of northeastern Minnesota. Birch, apen, maple, and basswood are interspersed with red and white pines, and a dense fern understory.
Ground Pine (not a miniature pine but a Lycopodium species) was common in some places. The spores of the brown spikes at the top of the plant are harvested for a variety of uses, one of which is the flash powder used by magicians.
In the low areas at the base of the hills, black spruce and tamarack are the dominant species found in the bogs. Oxeye Daisys were one of the most common colonists of bare areas on granitic slopes.
Gray Jays replace Blue Jays in the mixed forest. They are smaller and much quieter than their jay cousins, but just as curious. They are resident year-round here, managing to eke out an existence and even raise their chicks during mid-winter when temperatures are coldest. They store food in the summer in sticky balls plastered to the vegetation for later consumption, and may eat anything from fruits and insects to small animals.
Lots of Showy Lady’s Slipper orchids were blooming in the understory, along roadsides, and even in open, wetter areas.
A hummingbird clearwing moth sipped nectar at the honeysuckle flowers. Swallowtail and Pearl Crescent butterflies also visited this plant along with the moth. I saw many more butterflies in the northern mixed forest than I have seen in my own garden.
Water percolates through this boggy landscape in channels. You would get really wet feet trying to walk through this area, which is why fur trappers moved their cargo primarily during the winter across the snow instead.
There is much to see in this northern boreal forest, but hikes are not really a pleasant experience right now with all the mosquitoes and flies that attack bare skin. Maybe that’s why the warblers like it here — lots of flies to eat.
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