Why Wisconsin Forests Look the Way They Do

Sunlight filtered through the maple and aspen leaves as we gathered on the narrow, dirt trail. John Kotar, emeritus professor of forest ecology from U W-Madison, gestured widely as he described tree species, shade tolerance, soil moisture, and glacial history. With the title “Why Wisconsin Forests Look the Way They Do,” John’s field trip aspired to summarize his life’s research in just a few hours.

Several years ago, Kotar developed an ecological classification system for Great Lakes forests, and he published “A guide to forest communities and habitat types of northern Wisconsin.” His in-depth knowledge of our forests means that wherever we stop along the trail, he has something to say.

“I’ve been trying to think of a good analogy for the way I see the forest versus how a regular person sees it,” he said. “Imagine that you enter a room filled with people you don’t know. There is a wide mix of ages, appearances, etc. You just see people. Few details would stick out, and you might not be able to derive any information from the assemblage. Now imagine walking in to your family reunion. You scan the crowd and instantly know who everyone is, how they’ve changed over time, and how they relate to everyone else in the room. That’s how I – that’s how foresters – see the forest. Most people just see trees.”

So, we swatted mosquitoes and looked a little closer. Sugar maple, with its smoother leaf margins and U-shaped inter-lobes stood tall near the trail. Its many children, stunted from shade, but tough and long-lasting, carpeted the opening as seedlings.

The presence of sugar maple indicates that this soil has a fair amount of moisture and nutrients. Soil moisture and nutrients are the two main factors that John focused on to develop his classification system. On the ground, the small, leathery leaves of wintergreen quietly contradict the sugar maple. Wintergreen is an indicator of poorer soils.

The nature of this forest, and any natural community anywhere, is the result of multiple factors. John’s two factors are intimately related another set of factors often used by ecologists to understand the landscape: geologic history, recent disturbance and current climate.

Here, just south of Lake Namakagon in Northern Wisconsin, the pertinent geologic history revolves around glaciers. The Superior and Chippewa lobes of the most recent Wisconsin Glaciation stalled out here for a while, dumping tons of clay, silt, sand, pebbles, cobbles and boulders in lumpy hills called moraines. This mix of sediment sizes moderates both the soil moisture and the soil nutrients, resulting in sugar maple and wintergreen growing together.

Behind us, a red maple, with sharp, toothy leaves and a cluster of smaller trunks reminded us of the most widespread recent disturbance –logging. The forest in this recreational area has been logged a few times since the initial cut in the late 1800’s.

Dying paper birch on the edge of the opening also express the forest’s memory of a sunnier time. As a pioneer species, paper birch need full sun to get established. Then, as more shade tolerant trees grow up around them, they surrender their place, or hope for a fire. Shade-tolerant balsam fir forms thickets in the understory, and will rise to the top over time.

Our current climate, with adequate rainfall, cold winters, and hot summers plays a major role in determining which plants even have the option of living here. You won’t find a cactus in this forest, and neither will you find a baobab tree. Microclimates affect the forest on a local scale, with black ashes growing in low, wet spots, while oaks might claim a dry, sunny hill.

In the crisp fall sunshine, we wander down the trail a little. The forest changes gradually as we pass through an aspen grove, a balsam thicket, and more maples. Someone asks about how these forests have changed over time. While white pines were the most commonly logged species at the turn of the century, they weren’t necessarily a bigger part of the forest. Their ability to float on rivers to reach sawmills was their downfall.

Today, white pines tower above their neighbors on almost every combination of soil nutrients and moisture in Wisconsin. While we (we on this hike, and we as ecologists both) started off by describing which trees do best where, scientists are always trying to look deeper and ask “why?” or “how?”

Sometimes it is not just about one species, but how several work together. In 2001, soil ecologists discovered that white pine and other trees get some of their nitrogen from tiny soil arthropods called springtails. But first, a fungus, the bicolored deceiver (Laccaria bicolor), must kill and decompose the springtail using special enzymes. Then, then fungus forms a sheath around the roots of the white pine, and transfers the nitrogen and other nutrients to the tree in exchange for sugars produced during photosynthesis. About ninety-five percent of plants get some nutrients from fungi, allowing them to live in poorer soils.

Even small variations in the look of our forests – like the extra-vibrant fall colors in swamps, have explanations if we can figure them out. In 2003, a grad student found that in places where the soil was lower in nitrogen and other important elements (like swamps), red maple trees produced more of the red pigment anthocyanin in the leaves. This sunscreen pigment allows them to recover more nutrients from the leaves before they fall.

I love looking at a forest on the broad scale, and thinking about the giant chunk of ice that shaped my home. I also love finding out about these detailed and cryptic connections. But you don’t have to delve into the science to enjoy the fact that Wisconsin forests, especially in autumn, look the way they do.

A Boundary Waters Journal

Day 1

We pulled up to the Blankenburg Landing on Seagull Lake at about 2 p.m. As we hefted full portage packs out of the car onto the grassy landing, another group blew in off the lake, their trip ending. By the energized banter and their relief to be on shore, we knew that our first crossing would be windy. 

Nevertheless, my battered old green Penobscot 16 Royalex canoe (blemished even when new, fifteen years ago) carried us safely six miles across the lake, past the gray wooden sign announcing our entry into the Boundary Waters Canoe Area Wilderness (BWCAW), and to our first campsite.

The wind and mist howled around fire grate on top of our rocky point. Lighting a stove there was impossible. Instead, we hung a tarp and huddled in a grove of northern white cedar trees down on the lee-side of the point. As the pot began to boil, I carefully tore a sprig of cedar leaves off our windbreak and stuck it in my tea mug. Soon, the hot, citrusy, Vitamin C-rich tea was warming my hands and my belly.

Day 2

The wind did not subside overnight, but braving the wind and rain, we portaged out of Seagull and into Alpine, Jasper, and Ogishkemuncie Lakes.

The charred, fire-ravaged landscape still shocks me. Pink granite knobs stand out in stark contrast to charred trees and vivid green saplings. Along sheltered, damp shorelines, live green cedars still grow out over the water, as if lunging away from the fire. Adult trees have no fire resistance except their preference for low, wet ground, or inaccessible cliffs, but seedlings prosper on recently burned areas.

Day 3

A long day of paddling and portaging – from Kekekabic Lake we paddled 10.5 miles and portaged 317 rods through Pickle, Spoon, Dix, Skoata, and Missionary Lakes.  We saw more loon chicks than people, but we did meet one group on a portage.

We were just picking up our packs as their last person came walking down the hill to the landing with a beautiful cedar strip canoe up onto his shoulders. I was hit with more than a little bit of canoe envy. Kevlar may be light and bulletproof, Royalex cheap and indestructible, but nothing beats the elegance of a richly hued cedar strip canoe.

“Did you make that yourself?” I asked as he gently flipped it into the water, but he hadn’t. Perhaps we both still have something left on our bucket lists.

Day 4

We began the morning with a long portage into Knife Lake. Everything felt big here – the lake, the sky, the hills and cliffs on both sides, and the mature pines towering along the shore.

As we pulled up on a rocky campsite for lunch, I heard a high-pitched whistle. Looking up to the dead top of a cedar tree growing out of the rocks, I saw the distinctive yellow tail band of a cedar waxwing.

As we got out our peanuts and raisins, the cedar waxwing flitted out from the tree and back, supplementing its fruit-based diet with protein-rich insects. Come winter, these colorful birds will earn their name by eating cedar berries (which are actually the tiny fleshy cones from Eastern redcedar trees or juniper bushes).

Day 5

As we drank our morning tea (cedar, of course) on a high rocky ledge, we watched a slight breeze swirl fog across the glassy water. It brought to mind a passage from Sigurd Olson’s The Singing Wilderness: "In the morning when the white horses of the mists are galloping out of the bays…"

The wind stayed calm throughout the morning, and we portaged quietly into Otter Track Lake so as not to break the spell. I guided the canoe close to the steep, rocky cliffs, and we marveled at how faithfully the water reflected each detail of the overhanging cedar trees. We floated on the intersection of heaven and earth.

Stepping out onto the landing at Monument Portage, I noticed that rangers had done a lot of work to prevent erosion on the rocky hillside. One waterbar curved and tapered with the telltale shape of a cedar trunk, its rot-resistant wood holding back soil for the long haul.

Day 6

We had a guest today for our final breakfast. As we perched on a rocky point overlooking the islands of Saganaga Lake, a rustle in the cedar tree brought our focus in closer. The cutest little red squirrel was perched on a cedar twig, eating the fresh, bright green cones as if his life depended on it, or he had drunk too much coffee, or both.

We opted for one more cup of cedar tea instead of coffee, and reveled in our last minutes of wilderness peace. Many things make the Boundary Waters a special place for me, and Eastern white cedars are one of them. As wind blocks, hot drinks, scenery, building materials, and habitat, they are an important and beautiful part of canoe country. To make your own cup of tea, simply put a sprig in your mug, pour just-boiled water over it, and wait until it is cool enough to drink. Enjoy this taste of the wilderness!

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI, at 13470 County Highway M. The current exhibit, “Deer Camp: A Natural and Cultural History of White-tailed Deer,” opened in May 2013 and will remain open until April 2014.

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com/.

One Long Muscle

“I think this is the prettiest world--so long as you don't mind a little dying, how could there be a day in your whole life that doesn't have its splash of happiness?” (Mary Oliver, “Kingfisher.”)

Autumn is certainly pretty. Crimson leaves on the swamp maples shine through the fog, and the sweet smell of wet leaves rises from the forest floor. Bracken ferns and dogbanes glow yellow from the dry ditches, while up above them, birch and aspen leaves hang crinkled and brown. Here and there, a sugar maple reveals its hiding place with a flame of orange.

Of course, the thing about all this beauty is that it precedes death, and death-like dormancy. Past and recent droughts have stressed the plants and rushed the fall color changes, but even in a perfect weather year the dying would come eventually. It’s not just the plants, either.

The other evening, a giant insect buzzed against my lamp-lit screen. Imagine a dragonfly’s ugly stepbrother. This dobsonfly had two pairs of clear wings with brown markings, a long, lumpy body, and huge mandibles (jaws). Dobsonflies spend two to three years in an aquatic larval stage, during which they are called hellgrammites, "grampus," or "go-devils," and are familiar to anglers who use them as bait. The huge mandibles on this male dobsonfly are used exclusively to mate. I hope that is a big enough splash of happiness for him! Neither he nor she can eat, and each lives only seven days. By the time you read this, he will be dead.

You can think of dozens of other things that are dying this time of year. Soon, bald-faced hornets will freeze to death in their papery nests. On my window frames, the exoskeletons of dark fishing spiders cling to their nursery webs, dried legs curled beneath them. Deer lay bloated along the highway, and more will soon hang in hunters’ sheds.

But what is death in the natural world, really? That dobsonfly’s body will be eaten by a bird, or a fish, or bacteria. His cells will be broken down into their chemical components, and his carbon will become bird, or fish, or soil, or the air you are breathing. Sweet-smelling leaves are being decomposed by bacteria, who feed the complex food web in soil. The deer’s components will fly off as a crow, or fuel the hunter’s footsteps. The form changes, but life continues.

“And that’s when you know you will live whether you will or not, one way or another, because everything is everything else, one long muscle.” (Mary Oliver, Pink Moon: The Pond)

Even you are dying, a little bit at a time, and being recycled. Dead skin sloughs off as you sleep, and is eaten by (ew!) dust mites in your pillow. Elements that were once part of your body – filling your lungs, flowing through your veins, building the cells of your liver, spleen, bones, and hair – are passed back and forth between you and the world. Maybe that maple tree that you walked under today will have a little bit of you in it soon—just like your elements were once part of a photosynthesizing tree, or that tomato you ate for lunch.

“I take the deep breath of happiness, and I think how unlikely it is that death is a hole in the ground…” (Mary Oliver, Heron Rises from the Dark, Summer Pond.)

Reading Mary Oliver and studying ecology have certainly given me a different view of death. Of course, I love being me, but how exciting to think about decomposing into the crimson leaves on a swamp maple, or the wings of a dobsonfly, or a breath of wind.

“…everything sooner or later is a part of everything else…” (Mary Oliver, Pink Moon: The Pond)

So, as I sit here, thinking about death on a beautiful autumn day, I do take a deep breath of happiness. Death in nature is part of life. This IS the prettiest world, and we will forever continue to be part of its one long muscle.

Parasitoid Wasps – Even More Drama!

Not long after my encounter with a parasitic wasp on the Mississippi River bluffs, a Museum member brought in a photograph of a mystery wasp. Its skinny, two-inch long body was ringed by rusty brown, black, and yellow stripes. We couldn’t see the ovipositor, because it was curled up under the wasp and boring down into wood, but after a quick Google Images ID search, we determined that this was a “giant ichneumon wasp” (Megarhyssa macrurus) and its ovipositor can be four inches long! (Macrurus means “long tail” in Greek.)

While wasps with such huge projections on their abdomens can be quite scary, they are actually harmless to humans. Their ovipositor is specialized for piercing through wood, or into certain prey. Some are able to sting us, some aren’t, but why would they want to? These solitary wasps don’t build up an enormous empire to defend.

(In contrast, social wasps build large colonies that allow for a division of labor. The queen lays all the eggs, and the worker females can use their ovipositors for stinging. They are more likely to sting in defense, since all of their eggs are in one basket…..uh…nest.)

The giant ichneumon wasp uses its super long ovipositor to drill into a dead or dying tree – right into the tunnel being carved out by the larvae of another wasp – the pigeon tremex horntail wasp (which doesn’t sting at all). The ichneumon wasp will sting the horntail larva to stun it, then squirt an egg or two through its ovipositor onto what will be the ichneumon larvae’s first meal.

As we flipped through the Museum member’s other photos, sure enough, we came to a picture of the reddish-brown body and yellow and black abdomen of the pigeon tremex horntail.

The horntail feeds on dead wood, and it has forged a special relationship with a fungus. As the female horntail lays her egg, she also introduces a white rot fungus. This fungus grows within the wood ahead of the horntail larvae and helps them digest their fibrous food. This type of symbiotic relationship, in which both parties benefit, is known as a mutualism.

The sneaky and dedicated giant ichneumon wasp has discovered the fungi’s relationship to the horntail, though, and uses the fungi’s presence to find trees that house the ichneumon’s prey.

Parasitism is a type of symbiotic relationship. In parasitism, one party benefits and the other is harmed, but isn’t killed. Ticks, fleas, and mosquitoes are parasites. These wasps are actually parasitoids. Parasitoid wasps spend a significant portion of their lives with a single host victim in a relationship that is essentially parasitic. Unlike a true parasite, however, a parasitoid ultimately kills the host.

Even the parasitoid itself is not safe, however, since other ichneumon wasps, who lack such a formidable ovipositor, may re-use the giant ichneumon’s holes to lay their own eggs. Then their larvae destroy the original eggs, and eat the horntail larva themselves. If you like big words, these pirates are known as hyperparasitoids.

Once you remove the big words, all we’re saying is that the wasp larvae eat other creatures alive. Nature can be more gruesome than any horror film, but the plot lines are more complex, and the scenery is more beautiful.

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI, at 13470 County Highway M. The current exhibit, “Deer Camp: A Natural and Cultural History of White-tailed Deer,” opened in May 2013 and will remain open until April, 2014.

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com/.

Parasitic Wasps

The three-sided log shelter at the trail overlook was a welcome sight for sore legs. High on a bluff above the Mississippi River, naturalists on a field trip stopped to catch our breath. The view was breathtaking. Eagles soared over the vast channels of the Mississippi River, and through binoculars we could see turkey vultures riding the air currents over bluffs on the opposite side.

We admired the view of water, rocks, trees, and birds for a little while, but soon got distracted by other things. While Richard Louv, author of “Last Child in the Woods,” praises nature as an antidote to attention deficit disorder, I find that it actually causes my attention deficit. I hardly have time to admire or investigate one thing, when another critter or question pops up. Sometimes, when something catches my eye, I change topics mid-sentence. That didn’t happen before I became a naturalist.

When our guide paused during his stories about the history of the river, a fellow easily- distracted naturalist piped in, “What are these holes in the ground?” We all stopped to look, and found that the packed-dirt trail was dotted with half-inch diameter holes. What could make such a small hole in such hard dirt? The guide continued with his spiel, but all eyes were on the ground. “Pssst …there’s something in this one.” I crawled over with my camera to peer in the hole, and found a little head, with two antennae, and two big compound eyes looking up at me. 

“I just saw one go in this hole!” called someone else. “Here’s one in the grass! And it has something!”  Perched on the dangling seed head was a small, black wasp with a few yellow stripes. Its feet clasped tightly to a drab gray insect every bit as big as the wasp itself.

Ah ha! The mystery was solved. These holes were nurseries dug by parasitic wasps. More than 100,000 species of wasps are parasites, and they each do a version of what this wasp was about to do. They stun or otherwise subdue their prey, often using coma-inducing chemicals injected with their ovipositor; hide their prey in a safe spot, if it wasn’t already there; and lay eggs in or on their prey, using their long, piercing ovipositor.

When the wasp larvae hatch, they have a fresh meal. Most parasitic larvae even eat their prey in a set pattern–nonessential parts first—to keep it alive and fresh as long as possible. Body fat is the appetizer. The main course includes the prey’s digestive organs, and its heart and nervous system are saved for dessert. Some wasps even pupate right inside the hollowed out shell of their buffet.

Once the wasp larvae metamorphose into adults, their diet changes to nectar, a much less gruesome fare.

Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important for agricultural pest control. In fact, nearly all insects are attacked by one or more insect parasites, and some parasitic wasps are parasitized by other wasps.

Panoramic views of the Mississippi River almost seem tame alongside such drama in the diminutive world of wasps!

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI, at 13470 County Highway M. The current exhibit, “Deer Camp: A Natural and Cultural History of White-tailed Deer,” opened in May 2013 and will remain open until April, 2014.

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com/.