HR: 1340h
AN: B13C-0234    [Abstracts]
TI: Landscape variations in vegetation and soil: a moisture gradient at Bonanza Creek, Alaska
AU: * Pruett, L E
EM: lpruett@usgs.gov
AF: United States Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025 United States
AU: Harden, J W
EM: jharden@usgs.gov
AF: United States Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025 United States
AU: Turetsky, M R
EM: mrt@msu.edu
AF: Department of Plant Biology, Michigan State University, East Lansing, MI 48824 United States
AB: The boreal forests of Alaska contain large reserves of carbon that have the potential to act as sources or sinks of CO$_{2}$. To better understand how these reserves might respond to climate change, one must consider environmental differences such as moisture regime and plant community. Alaskan landscapes reflect a wide range of vegetation and soil types. Carbon cycling studies utilize information such as carbon content and isotopic composition to help partition the sources of CO$_{2}$ over various landscapes. In an effort to understand this partitioning, we examined $\delta$$^{13}$C and $\delta$$^{14}$C in plants, dissolved organic carbon (DOC) leached from soils, and CO$_{2}$ respired from soils. Four stations were established along a moisture gradient, which was located near Fairbanks, AK. Each station varied widely in height of water table, plant community composition, and soil depth. The wettest station had soils at or beneath the water table and was dominated by {\it Carex} and {\it Equisitum} spp. with a poorly developed bryophyte layer. The intermediate stations had well developed moss layers dominated by {\it Drepanocladus} and {\it Sphagnum} spp. The driest station had permafrost 65 cm beneath the moss surface and was dominated by willow, bog birch, and drier {\it Sphagnum} species. In July of 2004, we collected 14 samples from the top 5 cm of the moss and/or soil across this gradient. All samples were incubated in room air for approximately four weeks to determine potential CO$_{2}$ production rates. Preliminary data show that samples from the wettest and driest stations respire 3 times less CO$_{2}$ than those from the intermediate moisture stations. This suggests that microbial activity is limited at both high and low moisture contents in boreal organic soils. Future work will test whether fluctuating water levels at our intermediate moisture stations contribute to greater plant and microbial productivity at this site. In conjunction with respiration rates, $\delta$$^{13}$C and $\delta$$^{14}$C signatures of the bulk soil and DOC fractions will better assess the relationship between vegetation, soil respiration and substrate quality along this moisture gradient.
DE: 1040 Isotopic composition/chemistry
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting