HR: 12:05h
AN: C41D-08    [PDF]
TI: Carbon limitation of heterotrophic respiration under seasonal snowpacks: Implications for carbon balance in seasonally snow-covered ecosystems
AU: * Brooks, P D
EM: brooks@hwr.arizona.edu
AF: Hydrology and Water Resources University of Arizona, 1133 E. North Campus Drive, Tucson, AZ 85721 United States
AU: McKnight, D
EM: diane.mcknight@colorado.edu
AF: INSTAAR University of COlorado, PO Box 450, Boulder, CO 80309 United States
AU: Elder, K
EM: kelder@fs.fed.us
AF: Rocky Mountain Research Station, USDA Forest Service 240 West Prospect Road, Ft Collins, CO 80526 United States
AB: Longer growing seasons and higher atmospheric CO2 concentrations may increase the terrestrial carbon sink in the northern hemisphere. The fate of this newly-fixed carbon is not well known, but increased carbon uptake typically increases litter and labile carbon inputs to soil. Here, using CO2 flux surveys and additions of 13C-labelled carbon to snow-covered soil, we demonstrate that winter CO2 fluxes are likely to increase in response to increased carbon availability, potentially offsetting the growing season carbon sink. Mean daily over-winter CO2 fluxes were significantly related to soil carbon content at the landscape scale. Similarly, labile carbon additions to soil increased subnivian CO2 fluxes 25 to 80 percent after 24 hours and 76 to 85 percent after 30 days. Although fluxes remained elevated 30 days following carbon addition, isotopic analyses indicated that the source of the respired carbon was soil organic matter and not added carbon. The magnitude of the increase in CO2 fluxes, coupled with increased utilization of endogenous organic matter, suggest that increases in labile carbon availability from litter may prime heterotrophic mineralization of stored soil organic matter.
DE: 1615 Biogeochemical processes (4805)
DE: 1863 Snow and ice (1827)
DE: 4805 Biogeochemical cycles (1615)
SC: Cryosphere [C]
MN: 2003 Fall Meeting