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Sensitivity of boreal forest carbon balance to soil thaw
1M. L. Goulden, S. C. Wofsy, B. C. Daube, S.-M. Fan, D. J. Sutton, A. Bazzaz, J. W. Munger, Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA. J. W. Harden and T. Fries, U.S. Geological Survey, Menlo Park, CA.
Abstract:
We used eddy covariance; gas-exchange chambers; radiocarbon analysis; wood, moss, and soil inventories; and laboratory incubations to measure the carbon balance of a 120-year-old black spruce forest in Manitoba, Canada. The site lost 0.3 +/- 0.5 metric ton of carbon per hectare per year (ton C ha-1 year-1) from 1994 to 1997, with a gain of 0.6 +/- 0.2 ton C ha-1 year-1 in moss and wood offset by a loss of 0.8 +/- 0.5 ton C ha-1 year-1 from the soil. The soil remained frozen most of the year, and the decomposition of organic matter in the soil increased 10-fold upon thawing. The stability of the soil carbon pool ( approximately 150 tons C ha-1) appears sensitive to the depth and duration of thaw, and climatic changes that promote thaw are likely to cause a net efflux of carbon dioxide from the site.