Shift in tundra shrub growth could release more atmospheric carbon

December 9, 2019

Jeff Richardson
907-474-6284

University of Alaska Fairbanks scientists presented their work at the American Geophysical Union’s fall meeting in San Francisco this week. This article is part of a series highlighting UAF research from the world’s largest Earth and space science meeting.

A decades-old research project on Alaska’s North Slope indicates that deciduous shrubs shift more carbon from the soil to the atmosphere than the evergreen species they appear to be replacing.

University of Alaska Fairbanks researcher Syndonia Bret-Harte, who is leading the study, said the results suggest that changing species composition on Arctic tundra could be an important factor in carbon emissions as the climate continues to warm. She discussed the findings at the fall meeting of the American Geophysical Union on Monday in San Francisco.

Bret-Harte, a professor at UAF’s Institute of Arctic Biology, has monitored plant growth on a test plot near Toolik Lake for more than 20 years. Her work includes the removal of specific species in the plot to see how cycling of carbon and nitrogen in the ecosystem is affected.

Bret-Harte’s research determined that an increase in deciduous shrub growth corresponds with less carbon in the soil. That change is notable because scientists expect the composition of Arctic plant species to shift as the climate changes. On the Alaska tundra, that could mean that evergreen shrubs like lowbush cranberries and Labrador tea are replaced with deciduous shrubs such as dwarf birch and blueberry bushes.

The research plot, which is the longest-running experiment of its kind, is representative of about 500,000 acres of tussock tundra on the North Slope, Bret-Harte said.

Widespread species change on that landscape could significantly affect estimates of the amount of carbon that tundra will release in the future. Changing the composition of the research plot to include more deciduous shrubs caused the soil to lose about as much carbon during the past 20 years as autumn warming did in the past 10 years.

“It suggests that species matter and you should take them into account,” Bret-Harte said.