HR: 0800h
AN: GC31A-0112    [Abstracts]
TI: Using Bryophytes and Stable isotopes to Assess Paleohydrological Changes in a Subarctic Alaskan Peatland
AU: * Jones, M
EM: mjones@ldeo.columbia.edu
AF: Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964,
AU: Peteet, D
EM: peteet@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964,
AU: Peteet, D
EM: peteet@ldeo.columbia.edu
AF: NASA Goddard Institute for Spaces Studies, 545 W. 112 St, New York, NY 10025,
AU: Sambrotto, R
EM: sambrott@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964,
AB: Hydrologic changes resulting from climate change have important effects on vegetation change and global feedback cycles in the high latitudes. In an attempt to move beyond pollen analysis to interpret past climate, a number of geochemical and biological proxies were used, including bulk peat δ ¹³C, δ¹⁵N, and bryophytes, to make paleohydrological inferences from peat cores in south central Alaska. Bryophyte species distribution and composition are sensitive to water table position and pH, making them good candidates for paleohydrologic analyses. Bryophyte species were identified in \1-m² plots from the forest edge to the wettest swale across numerous peatland sites on the Kenai Peninsula, taking pH, conductivity, and temperature measurements for each plot. This modern calibration was used to conduct bryophyte analysis from two peatland cores from the Kenai Peninsula lowlands dated to 14.2 ka and 18.8 ka. Both records exhibit good preservation of both leaves and stems, allowing for analysis and identification. Late-glacial domination of brown moss species denotes rich fen conditions, and high moisture availability, as is indicated in the δ¹³C record. Increased δ¹³C values ca. 10 ka indicate a shift from moister to drier conditions, and the bryophyte species switch to higher hummock brown moss species and Sphagnum spp. Similar shifts in δ¹⁵N from negative values to near 0‰ suggest a switch of nutrient input to the fen from combined nitrogen pools to atmospheric nitrogen sources. The bryophyte species composition shows a dominance of acidic poor fen conditions in the mid- to late- Holocene. These shifts corroborate what was previously interpreted in the pollen and macrofossil record from these peatland sites.
DE: 0469 Nitrogen cycling
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 1807 Climate impacts
DE: 4950 Paleoecology
DE: 4952 Palynology
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting