Counting Carbons in a Warmer Diet
It's been a long summer for some of the tundra near Toolik Lake.
Desktop-sized patches of the grasses, lichen, Labrador tea, and other plants that combine to make tundra are experiencing a longer-than-normal growing season. Researchers here prolong the tundra's short summer by shoveling snow off the tundra in spring, covering it with plastic when the frosts begin in arctic fall, and heating the soil beneath the plants with electric coils.
Steve Oberbauer and Greg Starr were recently tending to their plot of pampered plants here at Toolik field Station, a cluster of green trailers surrounded by 88,000 acres of land set aside for research of plants, animals, fish, and other things arctic. The research center is part of the Institute of Arctic Biology at the University of Alaska Fairbanks.
Oberbauer and Starr are both from Florida International University in Miami. Oberbauer is an associate professor; Starr is earning his doctorate degree there. I asked them why they were keeping tundra warm here near Toolik lake, 4,000 miles from home.
Carbon, they answered. A large proportion of Earth's carbon is locked beneath tundra in the form of peat and other former plant life that hasn't yet decomposed. As the stuff decays, it releases carbon in the form of carbon dioxide, a greenhouse gas that makes the planet warmer by blocking the escape of heat.
Oberbauer and Starr are among dozens of scientists ringing the northern portions of the globe who are studying tundra to see how the plants react to a longer growing season. It's a scenario that might not be too far away; researchers have shown that temperatures in the Arctic have been increasing steadily in recent decades. The arctic tundra, thought for years to be a carbon "sink" as plants took in more carbon dioxide than they released, may become an enormous source of carbon released into the atmosphere.
"That's bad news," Oberbauer said as he stood in fresh snow near his research plot, about a half mile by wooden walkway from the green trailer core of the research station. Behind him, a flock of geese winged their way south to the snow-covered Brooks Range.
Oberbauer, Starr and others have gotten to know the Toolik tundra intimately during the three years of the study. One of their tasks is to perform 10 different measurements on dozens of different tundra plants. Depending on what part of the summer it is, they check to see how plants' flowers are developing, how tall the stems have grown in a week, whether a seed pod has burst recently, and other such observations. They also cap squares of tundra with an instrument that measures how much carbon dioxide the plants are taking in and giving off.
The tundra at Toolik has reacted to three years of artificially enhanced growing season with subtle changes to the 20 or so species of tundra plants. Some plants begin growing earlier and then shut down earlier; some plants stay green longer than their control-group cohorts; and the canopy of all the plants has become thicker---less sunlight is reaching the soil than in the control groups.
These changes all seem to point to a possible shift in the makeup of tundra. Shrubs such as dwarf birch and willows thrive in a longer growing season, so they might dominate the tundra in a warmer climate. As tundra studies progress here at Toolik Lake, Oberbauer and other scientists are trying to foresee what will happen to the tundra if Earth continues to warm, a phenomenon tundra may also be partly responsible for.
