HR: 0800h
AN: B41A-0089    [Abstracts]
TI: Plant functional type modulates ecosystem response to warming: A case study from boreal forest ecosystems in interior Alaska
AU: * Randerson, J T
EM: jranders@uci.edu
AF: Department of Earth System Science, University of California, 3212 Croul Hall, Irvine, CA 92697 United States
AU: Liu, H
EM: Heping.Liu@jsms.edu
AF: Dept of Physics, Atmos. Sci. & General Sci., Jackson State University, P.O. Box 17660, Jackson, MI 39217 United States
AU: Welp, L R
EM: welp@its.caltech.edu
AF: Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 United States
AB: Over the last several decades, surface air temperatures have increased substantially in Arctic tundra and boreal forest biomes in the Northern Hemisphere, particularly during spring. The net effect of this warming on the net carbon balance of northern ecosystems remains uncertain because it simultaneously accelerates soil thaw, the onset of photosynthesis, and rates of soil decomposition, in addition to affecting other ecosystem processes. In April of 2002, we established eddy covariance systems to measure ecosystem-atmosphere CO2 exchange in a fire chronosequence with burns occurring in 1999, 1987 and ~1920. The sites are in a well-drained (upland) area in interior Alaska where perennial grasses are abundant at the 1999 burn site, aspen and willow are dominant at the 1987 burn site, and black spruce is dominant at the ~1920 burn site. Here we compared April to September CO$_{2}$ fluxes from 2002 with those from 2003. The spring of 2003 was warmer and drier than in 2002 with mean April air temperatures of -4øC in 2002 and 0.5øC in 2003. The warmer spring in 2003 substantially enhanced net ecosystem uptake in the 1920 burn in May and June. In contrast, enhanced net ecosystem uptake occurred in the 1987 burn only during June, suggesting less plasticity in the response of deciduous plant functional types to variability in spring climate than in evergreen conifers. The net ecosystem exchange (NEE) fluxes integrated from April to September for 2002 and 2003 were 0.0 and -0.3 g C m-2 day-1 for the 1999 burn site, -0.8 and -1.2 g C m-2 day-1 for the 1987 burn site, and -1.1 and -1.2 g C m-2 day-1 for the 1920 burn site.
DE: 1815 Erosion and sedimentation
DE: 1610 Atmosphere (0315, 0325)
DE: 0315 Biosphere/atmosphere interactions
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting