Seeds on the Snow

Sunlight streamed through clouds and trees, and spun webs of shadow through the white woods. A fresh layer of crystals sparkled on top of the graceful drifts and glittered invitingly from the wide expanse of the ski trail. In dry winters, a sprinkling—or more—of pine needles and oak leaves often mar the ski trails and drift into the tracks. This year, storm after storm has buried them. 

Which is why, as momentum swooped me around a corner and back uphill, a mess on the snow caught my attention. Most of the brown sprinkles were on the outside edge of the trail, but one brown comma-shape, less than an inch long, had ventured close enough to the tracks for me to get a good look. Not that it took much to recognize the classic shape of a maple tree’s winged seed. If my thick gloves locked in pole straps had not been so unwieldy, I would have flung the helicopter high and watched it spin down.

My cell phone photos of the mountain maple seeds didn't turn out, but they look very similar to this red maple seed. Photo by Emily Stone. 

Eyes roving away from the single seed, I examined the messy snow where more of the seed’s kin lay scattered. Perhaps some birds had perched above and made a meal of last summer’s bounty. I looked up to see. Where I’d been expecting the stoic gray of a young red maple tree, I found a lithe bouquet of slender trunks with tan bark and red twigs. “Mountain maple!” I exclaimed in my head, and was pleased to see this old friend who is more common farther north.

Back when I was learning plants, someone had given me the mnemonic “mountain man maple,” as a helpful reminder. The lower stems, just a few inches in diameter, were clothed in buckskin-colored bark, and the upper stems resembled the red plaid of a mountain man’s shirt. Moose maple (they love to browse on the twigs), mountain maple, and spike maple are descriptive names for the small, shrubby tree whom botanists call Acer spicatum.

Spike and spicatum refer to the finger-like racemes of flowers that poke upright from twigs in the spring, and later dangle under the weight of fat, pink, winged seeds. A few clusters of dried, brown seeds still dangled from the twigs—a lucky find for hungry wildlife when so much is buried deep beneath the snow. 

Here's a photo from early July. These are the flower spikes of mountain maple, and you can see the baby samaras (winged seeds), too!

It may also be beneficial for the maple itself to hold onto seeds until the woods are sparse and airy. The helicopters are built to sail on the wind, but wouldn’t get far in the leafy thickets where mountain maple often grows. 

In fact, several trees use the blank slate of snow—especially when it develops an icy crust—to help their winged seeds travel farther. Since icy roads and narrow trails have me looking at my feet so much lately, I’ve been enjoying the way that seeds on the snow help me keep track of the species I’m wandering among.

Just a little farther up the ski trail, I found the unique seeds of a basswood tree. Each cluster of nectar-rich, bee-loved basswood flowers comes with a graceful, finger-sized leaf called a bract. Those bracts often remain attached to the seeds that develop later on. Sure enough, dangling beneath the bract on long stems were two small, gray balls. These nutlike drupes, like small, hard cherries, each contain one or two seeds that ripened back in October. Basswood trees tend to blend in with the maples they grow among, but when their seeds dangle from twigs or litter the forest floor, the trees become easier to recognize. 

Basswood drupes and bract.

Ironwood trees also tend to be pretty inconspicuous. This slow-growing species with dense, hard wood does not often escape the understory. Lately, though, I’ve been spotting their seeds—encased in ½-inch-long, papery, pointed-oval husks—on the snow, and glancing up to discover a tree of respectable size in a place I wasn’t expecting it. You might also know them as “hophornbeam,” which is a reference both to their hard wood and way that their seed husks overlap like shingles to form clusters that resemble hops. 

The seed cluster of an American hophornbeam (which I call ironwood except when the "hops" are super obvious! It's Ostrya virginiana for any botanists out there.)

Here are a couple of ironwood seeds in their husks, next to my ski. Thanks to all my friends at the North End Ski Trails for not running me over while I did my photo/ski! 

Many of us have noticed the seeds of birches scattered like black pepper on the snow. Tiny, pointed-oval seeds have two elephant-ear-shaped wings. Looking up, you can often spot the ruffled, disintegrating clusters where more seeds wait to fall. In among the seeds are also little leaf-like bracts with three points in front and one in back. That shape makes me think of bird tracks, which is appropriate, since many little winter birds nibble on the seeds.

This catkin from a birch tree is disintegrating into a mess of bracts and seeds in the middle of the ski trail. Photo by Emily Stone. 

Paper birch bract on the left, and winged seed on the right. 

Here are some tracks from a ruffed grouse. Don't they resemble the shape of the birch bract?

Winter is a lovely time of year. And although the deep snow and treacherous ice can force us to look down more than we’d like, the blank canvas around our feet makes different things visible. Getting outside is a key antidote to cabin fever, and whenever I do, I find that looking down also inspires me to look up.

An ironwood tree above the ski trail. I looked UP because I saw the seeds on the snow!

These four species of winged seeds have decided that winter is a good time to fall through the forest and blow around on the snow. Photo by Emily Stone.

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. Come visit us in Cable, WI! Our new Curiosity Center kids’ exhibit and Pollinator Power annual exhibit are now open! Call us at 715-798-3890 or email emily@cablemuseum.org. 

The Joy of Sliding

Podcast

It was still dark when I pulled ski pants over yoga pants, zipped up my puffy coat, and headed out to clear fresh snow off my car. I knew that my plow guy would arrive soon, and I wanted to be ready to play musical parking spots. 

Shovel in hand, I shuffled through six inches of dense snow. Before reaching my car, though, I noticed that someone else had made tracks before me. I hadn’t expected that. This was the first measurable snowfall of the year, so the tracks hadn’t been sunk in a previous layer—they’d been made during the night, after half the stuff had already fallen. 

Feet held still now, I pivoted in place to follow the tracks without wrecking them. A surprised “ha!” escaped when I saw that tracks led right up to my doorstep. I’d just walked right past them. Leaning in, I saw the naily, 5-toed tracks of a Mustelid, daintily imprinted on the dusting of snow that had blown under the porch roof. My visitor should have knocked!

Otter tracks on my front doorstep!

Almost as big as the palm of my hand, I knew that these tracks couldn’t have been made by a mink or ermine. They were fisher or otter tracks for sure. I snapped a few photos before following the tracks back out across the driveway. On the smooth snow, three, interwoven sets of prints were interrupted by long troughs, in a dot-dot-dash, Morse Code-type pattern. 

Otter tracks on my unplowed driveway.

Otters, then: critters who are known to play, and who love to use sliding as a method of travel. Like grade-schoolers on a snow day, this romp of otters must have dashed joyfully into the swirl of flakes and the transformed world. Already dressed in warm and water-repellant fur, they didn’t even have to bother pulling on a snowsuit. Otters’ short legs and thick necks make them powerful swimmers, but less agile on land—unless there is snow. Then their bodies become streamlined sleds propelled by powerful, webbed feet. 

Here are some otter tracks on the ice of Lake Namakagon--taken in the daylight so you can see their Morse code pattern better!

Once, on a winter camping trip in the Boundary Waters, I skied beside a set of otter tracks that climbed up on the steep bank, only to slide back down. Up and down; up and down. There wasn’t anything to eat up on the lakeshore. It could only have been for fun. 

Cross-country skiers—and the 6-year-olds inside all of us—know exactly why you go to the trouble of climbing a snow-covered hill: so that you can slide thrillingly down the other side.

This otter slid down the sledding hill at my parents' house in Iowa!

Just a few days after that first snowstorm, while milling around the kitchen after Thanksgiving dinner, my dad noticed a red squirrel having difficulties on the shed roof. Just as we all paused to watch, it skittered off the edge in a cloud of snow and plopped to the ground. 

The little guy seemed not to remember how he’d gotten on to the roof in the first place, as he tried to climb the vertical walls (not grippy enough), summited a plow pile and tried to jump (not high enough YET), and finally scurried to the far side where a hemlock trunk provided the prefect ladder and launch. Just a few seconds after disappearing around the corner, his little nose appeared over the peak of the roof. “Now what?” we wondered.

As the squirrel plowed through the fluffy frosting toward the edge, we jeered and commentated on this journey. Suddenly, he took a flying leap off the edge, missed a spindly hemlock, and plopped into the snow. Was the squirrel playing? Would we be able to watch him dive into the snowdrift over and over with squeaks of glee?

This scene brought to mind the chapter “Moon Magic,” from Sigurd Olson’s book, The Singing Wilderness. On a full moon night near the Canadian border, Olson watched a mouse using the roof of his tent as a slide. “Faster and faster it ran, intoxicated by its new and thrilling experience; up along the edge straight toward the center of the ridge rope, a swift leap, belly down, legs spread wide to get the full effect of the exhilarating toboggan it had found, a slide of balloon silk straight to the needle-strewn ground below.”

So we watched eagerly as the squirrel re-summited the roof. Instead of a running jump, he crept down the roof slope—almost tunneling out of sight in the snow. At the eaves, he reached around and clung upside down to the edge of the shingles, like a mini Tyrolean traverse. While he slipped and scrambled, we shouted encouragement and ridicule. Until suddenly, he was gone. 

Red squirrel on the shed roof.

Here's what a Tyrolean Traverse looks like.
Climber uses tyrolean traverse to cross the Río Fitz Roy in Patagonia, Argentina.
By sergejf - https://www.flickr.com/photos/sergejf/8331796794/,
CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=47281250

Later, once we’d strapped on snowshoes to explore the woods, I took a detour to check out the squirrel’s vanishing point. Tucked up under the eaves was a grooved hole, obviously chewed by rodent teeth. So, the little guy had access to my garden tools and a tub full of compost-ready maple leaves. With the shed door blocked by the snowplow’s mountain, the situation will remain until spring. 

Of course, that “situation” also means a transformed world, blanketed in a magical layer of fluff, ready for anyone who wants to experience the joy of sliding. 

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. Come visit us in Cable, WI! Our new Curiosity Center kids’ exhibit and Pollinator Power annual exhibit are now open! Call us at 715-798-3890 or email emily@cablemuseum.org. 

Night Magic

Natural Connections books and phenology journals make great gifts! 

Just a suggestion ;-)

love,

Emily

Purchase at: https://www.cablemuseum.org/books/

Headlamp stretched over wool hat, I strapped on snowshoes and ventured into the snowy dark. 

A few flakes glittered through the air, but mostly the snow clung to trees and heaped on the ground. My light reflected brightly off white in all directions as I walked along in its bubble. The only sounds came from my snowshoes--creaking, squeaking, and shuffling.

Trees leaned out over the driveway, reaching their ice-encased, snow-frosted twigs toward my path. The lower edges of the iced twigs were scalloped with frozen droplets. Falling temperatures had slowed the drips to stillness. Unable to resist, I licked some fluffy snow-frosting off a birch twig.

Amazed at the beauty caught in every movement of my headlamp, I swept the light around in a wider arc, taking in the intricate patterns of twigs, needles, and snow. A ways off in an open area, the light caught something brighter. Two green eyes shone back at me. 

Eyeshine is caused by a layer of tissue called the tapetum lucidum (which means “bright tapestry” in Latin). This layer sits behind the retina, and increases the light available to the animal’s photoreceptors by reflecting visible light back through the retina. Deep sea creatures and nocturnal animals use the tapetum lucidum to increase their night vision. 

I was hoping that the two green orbs belonged to the neighborhood bobcat, but as the eyes moved, I could just barely make out the profile of a deer against the snow. Even so, I couldn’t stop my brain from imagining a monster or goblin behind those glowing spheres.

Undaunted by my overactive imagination, I followed a wandering herd of snowed-in deer tracks out the driveway and onto the trail. A snow-laden balsam arched across the trail at waist height, its tip buried under the crust. I gently swung it forward like a gate, and entered a tunnel fit for dwarves.

This section of trail sneaks through a thicket of balsam on an old road grade. It is always dark and narrow. Tonight, snowy balsam branches hung especially low and close as I bent down to shuffle through. The passageway heightened my sense of expectation and suspense, as if I really might pop out into the Narnian Empire at any time. 

Instead, the trail entered a spacious hemlock grove. As the trees opened up, the dark closed in. Through the open understory, I caught the shining green eyes of four more deer. As they bounded away, a soft whisper of wind tinkled through the treetops. Snowflakes drifted down. The whisper crescendoed to a rush of air, and bigger clumps of snow fell, plopping all around me. As I put up my hood and leaned toward the trunk of a large hemlock, I imagined Ents in a snowball fight. When the dull thumps of falling snow had subsided, I continued on through the aftermath of drifting clouds of crystals. 

A cute string of mouse tracks made me grateful for another sign of life. Most small mammals are hiding out under the thick, fresh snow, where a new world has just developed beneath our feet. This ephemeral habitat is called the subnivean layer. 

The subnivean layer, like so much of life on Earth, owes its existence to the unique chemistry of water. When frozen, water becomes light and airy, a wonderful insulator. Just as down feathers in your jacket trap a layer of air next to your body, retaining the heat you radiate, as little as a six-inch layer of snow traps air that retains heat from the Earth. 

Because of this insulation and radiating heat, a thin zone opens up under the snow, right at the surface of the ground, which stays at a pretty stable 32 degrees Fahrenheit. This becomes even more important as the temperature plunges into the single digits, and then below zero. Without snow to insulate the ground, frost burrows more deeply. 

Tree roots, invertebrates, and the myriad little critters in the upper reaches of the soil suffer in cold, dry winters. Snow provides not only provides warmth, it also facilitates easy access to food, and gives cover from predators. “To the mouse, snow means freedom from want and fear,” wrote Aldo Leopold in A Sand County Almanac.

I emerged from the woods onto the gravel road and turned off my light. The world went gray. A grove of balsams—their drooping branches and conical shape perfectly adapted to the heavy snow—stood like statues in the White Witch’s courtyard. A rosy-pink glow in the northern sky gave an otherworldly aura to the night.

Beams of warm yellow light beckoned me back inside, but I hesitated, reluctant to leave this magical world behind.

“And if you have not been enchanted by this adventure-Your life-What would do for you?” –Mary Oliver

Note; This article was first published in 2013. 

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. Come visit us in Cable, WI! Our new Curiosity Center kids’ exhibit and Pollinator Power annual exhibit are now open! Call us at 715-798-3890 or email emily@cablemuseum.org. 

Langmuir's Wind Lines

Today the winds are whipping fine crystals into drifts, and the world has transitioned to its winter white. While I love watching clouds of snow dance and swirl off the roof, a recent question from some Museum visitors has my thoughts drifting back to summer.

I LOVE seeing these white lines!

“What are those lines of foam you see on a windy lake?” the couple asked. Immediately I was transported to a vista high above a Boundary Waters lake. A stiff breeze tousled the water’s deep blue surface, which was striated with parallel lines of bubbles. The pattern was striking. Then another mental picture replaced that one: the face of my friend Sam, explaining the lines to me more than a decade ago. Unfortunately, that image no longer has a caption. What did Sam say those were called?  The visitors and I laughed about the difficulty of pulling up old memories and then moved on.

Photo by Andreas Thurnherr.
Check out the site: https://www.ldeo.columbia.edu/~ant/Langmuir.html for several more photos.

Now, what did you say again, Sam?

A couple of weeks later, though, I saw those lines of foam in the mouth of the St. Louis River as I was crossing the Blatnik Bridge in Duluth. Determined to jog my memory, I decided that I should write about the phenomenon, in hopes that explaining it in writing will cement the details in my own mind.

Begin with a large body of water—a lake or an ocean will do. Add some wind, typically blowing between 4.5 and 7 miles per hour. The wind creates shear force on the surface of the water. The top layer experiences the most stress, but as the surface water moves, it exerts a smaller force on the layer below it, which exerts an even smaller force on the layer below it.

As the wind pushes water away from one place, more water rushes up to fill its space, causing an upwelling. Where water comes together, some of it sinks to form a downwelling. These motions converge into tubes of spiraling water that point in the direction of the wind, and circulate perpendicular to the wind. Imagine that a lake’s surface is covered in a layer of huge PVC pipes. The pipes lay lengthwise with the wind and spin perpendicular to it.

Not only do the tubes of water spin perpendicular to the wind, they also spin opposite of their neighbors. If one tube spins clockwise, its neighbors spin counter-clockwise. This creates alternate bands of upwelling and downwelling. As the surface water sinks into an area of downwelling, air bubbles and other buoyant debris get caught in the convergent currents, but don’t follow them down. The downwelling currents become visible as lines of foam and flotsam streaming out parallel to the wind.

Diagram of Langmuir Circulation by Andrés E. Tejada-Martínez. From: Tejada-Martínez, Andrés & Akkerman, Ido & Bazilevs, Yuri. (2012). Large-Eddy Simulation of Shallow Water Langmuir Turbulence Using Isogeometric Analysis and the Residual-Based Variational Multiscale Method. Journal of Applied Mechanics. 576. 63-108. 10.1115/1.4005059]. Link.

The internet says that Irving Langmuir was the first to observe this pattern in 1927. That’s a bunch of hooey. Pirates and paddlers, Vikings and voyageurs would certainly have observed this pattern for millennia. It is common, and occurs on oceans, seas, lakes, estuaries, and rivers. Langmuir, however, was the first to publish a paper describing the phenomenon in the journal Science.

Photo by Nobel Foundation - Link
(Does anyone else think he kind of looks like Sam?)

An American-born chemist and physicist, Langmuir eventually was recognized with a Nobel Prize in 1932 for his work on surface chemistry. Back in 1927, he simply noticed that a type of free-floating seaweed called sargassum was converging into long windrows roughly parallel to the wind direction, and asked himself “Why?”

By Bogdan Giușcă (Bogdan Giuşcă (talk)) - Own work, Public Domain,
https://commons.wikimedia.org/w/index.php?curid=31475302

Close-up of Sargassum, showing the air bladders that help it stay afloat.

After returning home from his sailing trip to the Sargasso Sea in the North Atlantic, Langmuir found his pattern also visible in Lake George, New York. There he described what would become known as “Langmuir circulation” in greater detail, and measured that the downwelling currents move much faster than the upwelling currents.

On the open ocean, the windrows concentrate little critters who can’t overcome the currents; attract predators to eat those prey; and offer a calmer place for birds to rest. The currents also may play an important role in mixing water and nutrients.

While Langmuir currents can form at a wide variety of wind speeds, the sweet spot for visibility is between 4.5 and 7 miles per hour. This provides enough turbulence to create the foam by mixing air into surface scum, but not so much wind that the bubbles get broken or dissipated. Gentle breezes may not initiate the currents. Stronger winds will form the currents, but also whip up whitecaps that mask the pattern.

The lakes up here are currently painted solid white instead of striped. That’s just fine. I’ll tuck this information away until next spring. Hopefully when the next visitor asks about those lines of foam, the term Langmuir circulation will upwell easily from my memory and float merrily along the surface in an organized fashion.

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. Come visit us in Cable, WI! Our new Curiosity Center kids’ exhibit and Pollinator Power annual exhibit are now open! Call us at 715-798-3890 or email emily@cablemuseum.org.