HR: 0830h
AN: B31C-0305    [PDF]
TI: The Timing of Spring Thaw and its Impact on Carbon Exchange in a New Hampshire Fen
AU: * Varner, R K
EM: ruth.varner@unh.edu
AF: Complex Systems Reserach Center, Institute for the Study of Earth Oceans and Space University of New Hampshire, Durham, NH 03824 United States
AU: Crill, P M
EM: patrick.crill@unh.edu
AF: Complex Systems Reserach Center, Institute for the Study of Earth Oceans and Space University of New Hampshire, Durham, NH 03824 United States
AU: Bubier, J
EM: jbubier@mtholyoke.edu
AF: Environmental Studies Program, Department of Earth and Environment Mount Holyoke College, South Hadley, MA 01075 United States
AB: Exchange of carbon dioxide (CO$_{2}$) in a wetland during the winter/spring transition is traditionally thought of as a combination of an initial abiological pulse due to build up under the snow/ice cover over the winter months and the onset of biological processes controlling CO$_{2}$ exchange. Manual sampling during this period will either underestimate or miss these processes. Automated chamber systems allow us to quantify these processes because of their high sampling frequency throughout the thaw period. Net ecosystem exchange (NEE) measurements were made using an automated system of 10 automatic chambers completing a set of measurements every 3 hours at Sallie's Fen in Barrington, NH. Data for 2001, 2002 and 2003 reveal three diverse thaw periods. Depending on the severity of the winter (snow pack versus ice coverage), the ground temperature and the time of maximum photosynthetic ally active radiation (PAR), the thaw varies from day 82 in 2001, day 86 in 2002, and day 101 in 2003. Years 2001 and 2003 showed a very low level of NEE ($>$ - 1.5 æmol CO$_{2}$ m$^{-2}$ s$^{-1}$) throughout the winter months. In 2002, NEE was not measurable until the mid February thaw then persisted at the same low level as observed in 2001. The timing and magnitude of the abiological pulse of CO$_{2}$ also varies between years. Year 2001 showed a thaw in early February that released a large pulse of CO$_{2}$ with subsequent smaller pulses throughout the late winter. Two large pulses on days 53 and 60 coinciding with increased air temperatures were observed in 2002. In 2003 there were smaller pulses dispersed throughout the thaw period. The winter of 2002 was characterized by little snowfall therefore a thick ice pack developed on the surface of the wetland. When the ice melted, the accumulated CO$_{2}$ was released in a large pulse. 2003 was characterized by a thick snow pack thereby insulating the peat surface and allowing for more evenly dispersed emission as the snow melted. The variability in the timing of the abiological pulse(s) and the onset of biological exchange of CO$_{2}$ is controlled by weather. Increased temperature and a lengthened growing season in Northern latitudes will affect the rate of carbon exchange and the carbon balance of wetland environments.
DE: 0315 Biosphere/atmosphere interactions
DE: 0394 Instruments and techniques
DE: 0400 Biogeosciences
DE: 1615 Biogeochemical processes (4805)
DE: 1890 Wetlands
SC: Biogeosciences [B]
MN: 2003 Fall Meeting