Tundra an Early Riser Under North Slope Snow

The plants that make up tundra, the slow-growing mat that covers much of Alaska, would seem the most patient of organisms, but scientists are finding otherwise. Researchers working on Alaska's north slope recently found that tundra plants begin photosynthesis while still covered with snow.

Greg Starr and Steve Oberbauer made the discovery while testing the tundra near Toolik Field Station, an 88,000-acre research sanctuary managed by UAF's Institute of Arctic Biology. Toolik Field Station is just north of the Brooks Range, in the treeless foothills and plains of Alaska's arctic. Starr and Oberbauer are ecologists from Florida who travel north each summer to study at Toolik. I met them in 1997 when I walked into the field station with my dog Jane on our pipeline hike. On a day off from walking, I wrote a science column ("Counting Carbons in a Warmer Diet") about how Starr and Oberbauer were warming tundra with greenhouse plastic and electric coils. They wanted to see how the plants would react to a warmer climate. During their study, Starr and Oberbauer noticed some quirks that led to this year's discovery that some tundra plants are able to convert sunlight to energy while still beneath the snowpack.

First, they noticed some tundra plants emerged from the snowpack in the spring with a reddish brown tint. The rusty color was evidence the plants were producing anthocyanins, pigments that serve as sunblock and protect the plants from overdosing on too much sunlight. "We figured the plants must be getting a blast of light while under the snow or just after the snow melted," said Oberbauer, a professor at Florida International University in Miami.

To find out how much light was penetrating the snowpack, Oberbauer and Starr installed sensors under the snow; they found a good dose of sunlight under as much as 30 centimeters of snow. Starr, who was then working on a Ph.D. at Florida International and is now a postdoctoral fellow at the University of Florida, decided to see if plants were reacting to sun under the snowpack.

With equipment that allowed him to measure changes in carbon dioxide in and around the plants, Starr found that four species of plants-Labrador tea, mountain heather, lowbush cranberry, and cottongrass-were taking up carbon dioxide while buried with snow.

To test the bizarre notion that photosynthesis was happening beneath the snow, Oberbauer and Starr placed one of their gas-exchange chambers-a box covered with clear plastic that allows them to monitor what gases are leaking from the tundra-over tundra that was covered with snow. When they blocked sunlight by covering the box with a black cloth, carbon dioxide readings went up. Oberbauer and Starr also measured carbon dioxide levels at the base of the arctic snowpack and found them much higher at nighttime than during sunny spring days. Another group of scientists working in Barrow found a drop in carbon dioxide levels in springtime just before the snow disappears.

In late spring, the world beneath the snow is a fine place for photosynthesis, Starr said. Melting and refreezing of the surface creates ice lenses that allow sunlight through and allow plant leaves to dry somewhat; the snowpack also traps carbon dioxide and holds it in a perfect place for plants. Starr measured photosynthesis of Labrador tea, mountain heather, lowbush cranberry, and cottongrass under the snow and found the plants sometimes worked at 20 percent of their summer peak.

This revelation adds a new twist to whether the Arctic acts as a carbon "sink," in which plants take up more carbon dioxide than they release, or a carbon source, in which they add to carbon dioxide in the atmosphere that produces global warming. Starr estimated that the North Slope tundra could be sucking up 15 percent more carbon dioxide than scientists thought.