BIOGEOCHEMICAL CONSTRAINTS ON METHANE EMISSIONS FROM A NORTHERN FEN
David Valentine, William M. Pulliam, Elisabeth A. Holland, and David S. Schimel

Wetlands constitute the single largest natural source of atmospheric methane, and are a prominent feature of boreal forests. How methane emissions from boreal wetlands will respond to changing climate depends not only on direct effects, such as patterns in temperature and precipitation, but also on indirect effects, such as plant productivity, vegetation composition, and nutrient cycling. As part of the BOReal Ecosystem Atmosphere Study (BOREAS), we manipulated carbon and nitrogen supplies in a minerotrophic fen in central Saskatchewan, Canada, through a factorial addition of wheat straw and urea to the peat surface. N fertilization significantly (p=.058) increased methane emissions, while emissions after C additions remained constant or decreased slightly. We also measured decomposition rates using wheat straw litter bags to assess the treatment impacts on likely substrate supply rates to methanogenic bacteria populations. Despite relatively low variability among replicates, no treatment effects on litter decomposition could be discerned statistically. This suggests that the observed effect on methane emissions may have resulted not from an increase in the amount produced in the saturated zone, but rather from a decrease in the amount consumed in the unsaturated zone. 

David W. Valentine, Ph.D. 
Natural Resource Ecology Laboratory, NESB B219
Colorado State University
Fort Collins, CO 80523-1499
USA
Voice 970/491-0240
FAX 970/491-1965
Email davev@NREL.ColoState.EDU

Affiliation (after 9/1/96):
     David Valentine
     Assistant Professor of Forest Soils
     Dept. of Forest Sciences, SALRM
     University of Alaska, Fairbanks
     Fairbanks, AK 99775
     Telephone: unknown
     Fax: (907) 474-7962

William M. Pulliam
Research Associate
Natural Resource Ecology Laboratory
Colorado State University
Fort Collins, CO  80523

Elisabeth A. Holland
Director
NATO ASI on Soils and Global Change
National Center for Atmospheric Research
Atmospheric Chemistry Division
P.O. Box 3000
1850 Table Mesa Drive
Boulder, CO 80307-3000

David S. Schimel
Section Head
Ecosystem Dynamics and the Atmosphere
National Center for Atmospheric Research
Climate and Global Dynamics Division
P.O. Box 3000
1850 Table Mesa Drive
Boulder, CO 80307-3000