The drift dweller

Colorado scientists track the ubiquitous mountain snow mold

  • Ken Wilson, left, and Alan Meyer, collect samples of snow mold from the tundra above treeline near the University of Colorado’s Mountain Research Station on Niwot Ridge.

  • Snow mold

    Ken Wilson

Name Snow molds

Home Generally the subalpine forests and alpine tundra of the West and possibly the world, though they can grow in most habitats -- even the plains.

Finding them Check out the perimeter of the nearest melting snowbank that’s been around at least one month.

Family Snow molds are a mixed fungal bag, though most are zygomycetes, a group that produces some common bread molds. A few, like a prominent white coral fungus, are in the group of fungi that make most mushrooms, and others that make tiny bright orange cups are in a group that includes the much-sought-after morel mushroom and baker’s yeast.

The Right Stuff Schmidt’s future work could involve testing snow molds’ physiological limits -- just how cold can they grow? -- as well as searching for viable antibiotics, and (unsurprisingly) antifreeze compounds.

On an early evening in mid-June near Nederland, Colo., Ken Wilson cautiously piloted his SUV up a backwoods "road" best described as obstacle course when dry and creek bed when wet. The aspen were just flushing green and the first of a series of tea-colored puddles lurked ahead.

"Well, there's water," Wilson said. "And where there's water, there's snow."

A few minutes later, he was on his knees hacking at a swiftly melting pile. Ringing it were the gossamer filaments of what may be the one of the most common -- and important -- winter creatures you have never heard of: a snow mold.

In the last few years, scientists at the University of Colorado led by microbial ecologist Steve Schmidt -- including Wilson, the deputy mayor of Boulder, Colo., who, post-retirement, worked with Schmidt as a grad student -- have discovered that these fungi are ubiquitous under snow in Western subalpine conifer forests and tundra. Samples from the Himalayas indicate they may occupy similar habitats worldwide.

Though they may be abundant, not all snow molds are alike. Some sprout white coral-like arms an inch or so long. After the snow melts, they collapse into wet-toilet-paper-esque patches that soon dry and dot the forest floor year-round. One less-common species blossoms into tiny orange cups. But most, like the film that outlines retreating snowbanks, are just plain moldy, forming lacy mats of milky strands finer than spider's silk.

The molds mine the semi-frozen forest floor for food, and most vanish shortly after the snow does. In the process, they help cycle nutrients through the soil. What's more, they may be responsible for a mighty 10 percent of the carbon dioxide released by subalpine forests each year, according to Schmidt's research. Understanding how these fungi respond to new conditions might help predict how carbon dioxide emissions will change in similar forests worldwide as the planet warms and snowpacks diminish. Yet until a few years ago, no one had even documented the existence of snow molds, possibly because scientists assumed that subalpine fungi followed subalpine plants in going dormant during winter.

Schmidt first picked up the snow molds' trail in the mid-'90s in an unlikely place: an art exhibit. There he discovered the work of Colorado artist Mary Ellen Long, who buried paper under mountain snow and retrieved it in spring -- each now-moldy sheet its own one-of-a-kind print in splotches of sepia, gray and black. Later, Schmidt's lab found that winter snow seeped substantial quantities of the gases methane and carbon dioxide -- likely the work of organisms feeding underneath. He decided to see what dwelt under the drifts. Once his lab started looking, it became clear that snow molds were everywhere.

They are, it seems, taking advantage of a time and place most other creatures couldn't even think of functioning in. Most snow molds can grow at temperatures as low as the -2°C typical of the soil under late-winter snow, Schmidt's research suggests, which means they're first in line for the rich all-you-can-absorb nutrient buffet produced by the spring thaw. But what they're eating is not yet clear. They don't possess the machinery to digest freshly fallen wood and needles, says Cathy Cripps, associate professor of mycology at Montana State University. So they may feed on the byproducts of other organisms' initial digestion of plant litter, the food spilled out of frozen and thawed needles and leaves, or on sugars exuded by the roots of trees like lodgepole pine.

Regardless, the combination of cold, damp and detritus is snow-mold heaven. In an arid forest where the ground dries practically hours after the snow is gone, late winter and early spring are the only time the soil is reliably swimming in life-giving moisture, and little else can tolerate the temperatures. "It's a very exclusive environment," says Cripps, "and they have it all to themselves."

But they don't just live under these conditions. They thrive. The fastest snow molds can grow from a single microscopic spore to about 20 square inches in a mere two months in subzero temperatures -- a record-breaking pace that outstrips by a factor of 10 similar fungi that have been studied in Antarctica.

For humans, this would be like trying to write War and Peace in a few months working exclusively between the hours of 3 and 6 a.m. without the help of caffeine -- or electricity. "They're very aggressive," Schmidt says.

Back in the forest on the mid-June evening, the mold lingered only under pine cones and a small, sad patch of snow. Wilson stood and surveyed the newly exposed forest floor: snow-white marsh marigolds blossoming next to a burbling stream, shrubs sprouting tender leaves, and crumbling logs glowing with lichen and moss.

"I forget this is up here," he observed. "It's covered in snow too much of the year."

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