Document: GLE-3-34-68

An elevated soil temperature and water table manipulation experiment in the Arctic tundra ecosystem at Barrow, Alaska.

KINOSHITA, G.Y.*, W.C.OECHEL, R.C.ZULUETA and S.J.HASTINGS

San Diego State University, San Diego, CA 92182, USA ¹

Abstract:
Northern arctic ecosystems comprise 14% of the earth's landmass but make up 25% of the terrestrial soil carbon pool. Under changing climate, these ecosystems have the potential to affect local and global carbon budgets. In order to understand how northern ecosystems will respond and adapt to predicted climate changes and to improve climate and ecosystem models, an elevated soil temperature and water table manipulation was installed in the arctic coastal tundra ecosystem at Barrow, Alaska at the beginning of the 1999 summer growing season. The experiment is a complete factorial design of six treatments: a control, elevated soil temperature, elevated water table, lowered water table, elevated temperature and elevated water table, and elevated temperature and lowered water table. There are three replicates of each treatment in three blocks for a total of 18 experimental plots. The water table manipulation and soil temperatures of treatments were determined based on predicted changes in temperature and water table for 2050 from GCM predictions. Temperatures are expected to increase while an increase as well as a decrease in water table has been forecasted. Measurements taken during the 1999 season include CO₂ fluxes, active layer depth, and soil moisture content. Changes in the soil carbon balance were detected after one full season of manipulation. Ecosystem respiration was most affected by elevated soil temperatures, with almost double the CO₂ efflux compared to the controls and water table manipulations. Gross ecosystem productivity was also affected, with a significant increase in productivity with the presence of an elevated water table. These results give an indication of the direction and magnitude of ecosystem response due to these changes. With a decreased water table and elevated temperatures, the increased CO₂ efflux may be an indication of increased microbial activity due to soil aeration, while the elevated water table plots may suppress decomposition and encourage additional plant growth. These results give an indication of ecosystem response to changes in precipitation and elevated temperatures. Depending on future conditions, there is the possibility of large changes in the soil carbon pool of this region.

Keywords: arctic, climate change, CO₂ flux, ecophysiology, hydrology, tundra

This abstract is being presented at: 3:30 PM in session:
CLIMATE CHANGE