To study impacts of longer, hotter summers, ecologists haul 5,000 pounds of sand up a mountain

As spring unfolds into summer each year on Niwot Ridge, just north of Nederland, snowdrifts give way to small shrubs and colorful lichens on this exposed tundra, resembling a coral reef at 10,000 feet above sea level. A portion of the landscape will also soon be covered in what looks like more like heaping mounds of chocolate chip ice cream.

For the past five years, a small team of research assistants and volunteers have hiked up Niwot Ridge in late May to set the stage for a unique experiment in which they spread 5,000 pounds of black sand across portions of the remaining snowpack.

Their goal? To simulate the not-so-distant future effects of a warming planet on alpine ecosystems. Researchers want to know what may happen as mountain snowpack melts sooner and summer lasts longer each year due to rising temperatures from climate change.

“We’re seeing a large influence of these longer summers. When things warm up and melt out earlier, those seem to be years that really affect the system—the plants, the pikas and the water quality,” said Katharine Suding, lead investigator of the project, and professor of distinction in the Department of Ecology and Evolutionary Biology and the Institute of Arctic and Alpine Research (INSTAAR). “And the best way to figure out what might happen in the future is to test it out.”

Suding’s team uses simple, cheap and environmentally friendly sand to naturally attract more sunlight, heat up snow and melt it faster. It’s made of the same glassy silica particles used in fire pits and ash trays.Each season, the team spreads the sand on top of the snow at five test plots across the ridge, leaving some snow next to it untouched. Throughout the summer, dozens of graduate students, volunteers and faculty run soil sensors, collect vegetation and gather data about pollinators to see what kinds of changes, if any, the snow melting sooner causes on the tundra beneath.

The project is just one of dozens of research projects conducted by CU Boulder scientists and partner institutions at the century-old Mountain Research Station. The effort is also part of the Niwot Long-term Ecological Research Program.

“It’s quite an ambitious project,” said Jennifer Morse, climate technician at the Mountain Research Station, who oversees the execution of experiments like this one.

Peak snowpack typically occurs around late May or early June, although it may at first seem a misnomer. While the snow is still yards deep in some places, requiring snowshoes or skis to cross, in others it’s already long gone. The goal is to apply the sand when the snow is no longer accumulating and is instead starting to melt, so the sand they apply isn’t covered up by additional snowfall.

This timing makes for a formidable feat. Hauling 5,000 pounds of sand up the mountain in late spring requires the use of a utility task vehicle (UTV) with snow treads, as windswept and melting mounds of snow along the road from the station to the sites would prove impossible for a regular vehicle.

Once the researchers have ridden or skied up the ridge, they visit each of the five test plots over the course of a few days. They first gather snow depth measurements at set intervals on both sides of each test plot, which they’ll do every two weeks until the snow fully melts.


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