Wild Notes

Fall colors, I’ve discovered, are best enjoyed where hills become easels for the forest to paint. I grew up with the rich shades of oaks and maples in the surprisingly steep hills of the Driftless Area in Iowa. Later, I reveled in the palette of colors in the mountains of Vermont and Maine. Now, every fall, I hike to the top of St. Peter’s Dome in the Chequamegon-Nicolet National Forest in Northern Wisconsin. It is always a feast for my senses.

Wildflowers line the beginning of the trail, and even in October, the New England aster blossoms and sneezeweed flowers are a jumble of lavender and sunshine yellow. Robin Wall Kimmerer, author of Braiding Sweetgrass, has written eloquently about the way that these two complementary colors attract more bees to a field than either would alone. These sturdy blossoms also appeal to bees because they are the only ones left. Bumble bees’ fuzzy jackets allow them to stay active in cooler temperatures, but they do have limits. On rainy days, I spy them hiding under the blossoms, looking bedraggled.

Across the bridge and toward the edge of the swamp, sensitive ferns glow in the understory. They aren’t emotional, their leaves are sensitive to the first frost. As they turn brown and gold, their cells are outlined by a distinctive network of veins so that the whole thing resembles stained glass. Unlike the many lacy-leaved ferns in the woods, which can be tricky to tell apart, sensitive ferns have smooth, finger-like pinnae, at least near the tip. Rounded teeth scallop the edges of the lower pinnae. They won’t curl up if you touch them; that’s the tropical species called sensitive plant.

Entering the shady forest, I inhale deeply. The sweet smell of fall rushes through my nose and fills my lungs with air that feels cool and damp. I swear I even taste it. Scents are often linked to our memories, and this one takes me right back to the leaf pile in my childhood backyard. Then, as now, sugars and other carbohydrates in the leaves are being decomposed by bacteria and fungi, releasing sweet, musky scents. Each tree species will have a unique smell as it dies.

The log I pause to examine next died a while ago, yet still hums with life. The damp wood is spongy and moss-covered, and sprouting a single fawn-colored mushroom on a beige stem. I stroke the damp cap gently with the tip of one finger to enjoy the sleekness of the slime. This mushroom is the reproductive structure of the fungus. The main body is made of thread-like hyphae woven throughout the cells in the log, using enzymes and chemicals to break down the cellulose and lignin into sugars. Those sugars dissolve into water, and the fungi absorb it directly through their cell walls. Likely, the slime on the cap is a sign that bacteria are beginning to decompose the decomposer.

I’ve learned to hike fast between stops, because once I stop to bend close to the ground, there’s always more to see. Farther down the log, a cluster of small pink balls caught my eye. Wolf’s milk slime molds are amoebas, not fungi, but their penchant for rotting wood or damp leaves means that they are often mistaken for fungi. I know that if I find a small stick and poke one of these little balloons, a bubblegum pink paste of immature spores will ooze out onto the log.

Pink, purple, yellow—fall can feel like hiking through a rainbow. Plenty of green still lingers in the leaves, too. Green is the color of summer growth because it indicates the presence of a pigment called chlorophyll. Chlorophyll absorbs most wavelengths of light but reflects green back to our eyes. The rest of the light becomes energy to run the process of taking carbon dioxide and water, splitting those molecules into their component elements, and recombining them into sugar—the process of photosynthesis.

As the day length shortens in fall, leaves stop producing chlorophyll and begin to slurp nutrients like nitrogen and phosphorus back into the twigs where they stand ready to fuel leaf growth again in the spring. This reveals chlorophyll’s sidekicks. All summer, orange pigments within the leaves absorb different wavelengths of light and transfer the energy to chlorophyll. Yellow pigments intercept excess energy and release it as heat before it can damage the cells. These colors are revealed almost any time a leaf dies, whether from disease, or drought, or because the tree is getting ready for winter.

Meanwhile, some trees also produce red, blue, or purple pigments called anthocyanins. These absorb ultraviolet light and act as a sunscreen so the trees can glean as much from their leaves as possible before they succumb to decay. Once enough nutrients have been recovered from the leaves, the tree cuts them off, and they dance their way to the ground.

At the St. Peter’s Dome Overlook, I eat a snack while gazing at the beautiful but short-lived kaleidoscope of colors that stretches out before me. When I look at my feet to navigate the rocks, a new pattern catches my eye. The small feather is black with white spots, and stiff enough to power flight. Most likely, it belonged to a downy or hairy woodpecker. Even when the trees are bare, these tough little birds will stick around for the winter, their little calls brightening up the woods.