Natural Connections: Forest layers
By Emily Stone
Naturalist/Education Director at the Cable Natural History Museum
Who doesn’t feel inspired when they tilt their head back and gaze up at big white pine or hemlock? And how could you not admire the grace of a pure white birch tree? Here in the Northwoods, we love our trees. John Muir wrote, “Between every two pines is a doorway to a new world.” Happily, we’ve got lots of pines up here. I’m going to go walk between a bunch of them until I find a new world I like better. Who’s with me?
This is the final installment of topics from the Forest Lodge Nature Trail’s new interpretive booklet. I’ll do some final editing, and then send the text off to the Forest Service so they can do layout and printing. With any luck, the new booklets will be waiting for you at the trailhead when it’s safe to travel again. Remember this trail and many others are currently closed to the public, in alignment with current federal, state, and local guidance for social distancing.
Old Growth White Pines
Eastern white pines are majestic trees. They can live for up to 450 years, grow to 150 feet in height, and reach a diameter of more than 5 feet. White pines also are a valuable source of the wood we need to build homes, craft furniture and make paper. During the logging era of 1850-1920, almost all of the local forests were cut down.
Look down. The rotting stumps of large white pines still dot this forest. Both their growth, and their death, are important reminders of the history of this area.
Look up. The next era of majestic white pines are growing now. The oldest of them are probably about 100 years old. You can see their wispy branches poking up above the rest of the forest in a layer called the “super canopy.” In fact, white pines of all ages surround the trail. While they face many natural threats, this forest is now protected from logging. What do you think it will look like in another hundred years?
The tall trees in this grove are eastern hemlocks. They are easy to identify by the way the top leader gently flops to one side. Hemlocks often have shallow roots, and they sometimes topple over in strong winds. When a tree falls, more sunlight can reach the forest floor. Hemlock seedlings, which tend to sprout in the shade on the damp wood of a rotting stump or log, race toward this new sunlight in a spurt of growth. It’s hard to imagine that these majestic trees were once tiny seeds hidden inside small cones.
As hemlocks age, their bark becomes quite thick. That bark was once harvested for tannins, which are the chemicals used in tanning hides into leather. On average, it took the bark of one tree to tan one hide. Today, we use synthetic chemicals instead.
Look closely at the bark. A yellow-bellied sapsucker has made rows of tiny holes in order to feed on the hemlock’s sweet sap.
Sun Loving Birch
White or paper birch is a true beauty of the Northwoods. Its smooth, papery bark makes it easy to identify. The dark, horizontal lines on the bark are lenticels. These cells allow the tree to take in and give off carbon dioxide, oxygen, and water vapor.
Unlike the hemlock trees, whose seedlings can survive in deep shade, birch trees grow best in the bright sunshine available after a fire, windstorm, or other major disturbance. They are known as a pioneer species. While they grow quickly, birches are not long-lived. Firs and spruces often grow up in their shade, and are ready to take over when the birch trees succumb to disease, insects, or drought.
Birches do have some defenses, though. A chemical called betulin makes birch bark very resistant to rot. Native Americans use the birch’s strong, waterproof bark to make canoes, baskets, and homes. Betulin is also what makes birch bark flammable. The unique chemical is being researched as a treatment for cancer, diabetes, tuberculosis and more. Chaga mushrooms growing on birch trees concentrate betulin naturally, and some people make it in to a medicinal tea. Please be respectful of future visitors and do not harvest chaga near trails.
That’s it for this week’s hike. Next week I’ll see you back out on the trails with some new natural connections.
Editor’s note: Emily’s second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at www.cablemuseum.org/books.