Natural Connections: Snags And Nurse Logs

Note: Emily Stone is the Naturalist/Education Director at the Cable Natural History Museum.

Although the depths of winter have passed, this is the season when we northerners really feel the cabin fever. Gone are the freshly groomed tracks on the ski trails and dry, fluffy drifts. Now the weather alternates between slush and sleet. Warm days are lovely, of course, but they make the freezing temps that follow just a little more frustrating.

This year, mud season will be much harder. Without the option to travel south for a break, there’s a good chance some of us will go stir-crazy! One nice thing about living in the Northwoods, though, is that our vast natural areas provide us with excellent options for social distancing. The Forest Lodge Nature Trail is one of those options. This 1.5-mile loop trail is dotted with numbered posts that correspond to an interpretive booklet. I’m updating that booklet this spring, and sharing the new text with you.

We started the trail by priming our senses: listening to birds, smelling sweetfern, and remembering the sweet taste of ripe blackberries. We walked through an old field crammed with young white pines just getting their start, and entered a dark, mature pine forest with huge stumps, reminding us of the big trees who once dominated the landscape.

In the midst of that mature pine forest, we now come upon the skeleton of a tree. Its bark lies in piles at its base. The top, and most branches, are gone. Holes riddle its pale trunk.

Life after Death

This old, dead tree was once a stately white pine. The low limbs on this snag are a clue that the pine was growing in a field. As the years went by, this tree’s seeds grew up to become many of the younger white pines in the surrounding forest.

Although this tree has been dead for many years, it still supports an abundance of life. Insects like carpenter ants tunnel through the trunk. Hairy, downy, and pileated woodpeckers can easily pick away at the soft wood in search of the larvae of ants and other insects. Big cavities house the nests of woodpeckers, chickadees, nuthatches, flying squirrels, and owls. Do you see the pile of pine cone bracts on the ground? A red squirrel sat there to shuck and eat the seeds out of pine cones. This animal’s trash heap is called a midden.

Before it died, only the outer layers of wood and bark, the twigs, the roots, and the needles of this tree were alive. Now the living, breathing cells of bacteria, fungi, and insects burrow through every inch of the trunk. Some ecologists say that a tree is more alive when it’s dead.

What do you think?

Nurse Stump or Nurse Log

Mosses are tiny, bright green plants with simple leaves that soak up water like a sponge. Photo by Emily Stone.

As old stumps and fallen logs decompose, they become the perfect place for tiny seeds to get their start. Mosses and lichens like this habitat, too. A balsam fir seed fell onto this stump. It found a good home with more sunlight, more nutrients, fewer fallen leaves, fewer dangerous bacteria, and enough moisture to grow.

The roots of the new tree will grow around the stump or log and into the ground. The old tree will continue to rot away. Eventually the log will be gone, and you will just see a funny-looking tree up on stilts!  

As you continue down the trail, look for nurse stumps and logs and the new life they support.

Lichens and Mosses

Do you see the green stuff on the bark of a nearby birch tree?

Lichens can be pale green, gray, black, yellow, or even bright orange. They can look like a leaf, a crust, or even tufts of hair. Photo by Emily Stone.

These mosses and lichens are using the tree trunk as a ladder to the sun. They do not harm the tree. Both organisms use sunlight to make food from water and carbon dioxide during a process called photosynthesis. Mosses often look feathery, fuzzy, or like tiny trees. They are tiny, bright green plants with simple leaves that soak up water like a sponge. Moss also dries out quickly, but that’s OK. When water returns, moss can spring back to life in as little as 20 minutes.

Lichens form through a partnership between a fungus and an alga. The fungus provides the structure that holds them both onto the tree. Inside the structure, little cells of algae do photosynthesis and make sugars that feed them both. Lichens can be pale green, gray, black, yellow, or even bright orange. They can look like a leaf, a crust, or even tufts of hair. Without the algae, the fungus would starve. Without the fungus, the algae would blow away. Together they can grow on bare rocks and even survive in outer space. Despite their toughness, lichens will die if there is too much air pollution.

Continue looking for lichens and moss as you walk down the trail (or even into your own backyard). How many different kinds can you see?

Emily’s second book, Natural Connections: Dreaming of an Elfin Skimmer, is now available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Our Pollinator Power exhibit ends after February 29, but our Curiosity Center remains open, and Mysteries of the Night will open on May 1, 2020. Call us at 715-798-3890 or email emily@cablemuseum.org.