HR: 1340h
AN: B23D-1606 [Abstracts]
TI: Experimental thawing of permafrost changes carbon cycling attributes in tussock tundra in N. Alaska
AU: * Nowinski, N
EM: nnowinsk@uci.edu
AF: Univ. of CA-Irvine, Dept. of Earth System Science
3200 Croul Hall, Irvine, CA 92697, United States
AU: Welker, J
EM: afjmw1@uaa.alaska.edu
AF: Univ. of AK-Anchorage, Environment and Natural Resources Institute
707 A St., Anchorage, AK 99501, United States
AU: Trumbore, S
EM: setrumbo@uci.edu
AF: Univ. of CA-Irvine, Dept. of Earth System Science
3200 Croul Hall, Irvine, CA 92697, United States
AU: Tavena, L
EM: lina.tavena@gmail.com
AF: Univ. of AK-Anchorage, Environment and Natural Resources Institute
707 A St., Anchorage, AK 99501, United States
AB:
Global warming is expected to be amplified in the arctic, causing increased permafrost thawing. However, few
studies have experimentally addressed the consequences deeper active layers as permafrost melts. The
consequences of thawed permafrost may be multifaceted, including deeper active layers, changes in vegetation
rooting depth and alterations in the pools and magnitudes of carbon efflux to the atmosphere. After 13 years, a
long-term snow addition experiment has doubled the active layer depth from ~30 to 60 cm, thawing permafrost in
a portion of tussock tundra at Toolik Lake, AK. We used radiocarbon to partition respiration into autotrophic and
heterotrophic components as well as gas probes to measure the C respired at depth under control and thawed
permafrost conditions. Radiocarbon signatures of field respiration were higher in the snow fence plots
(105‰, ±17) than in the control plots 69‰, ±12), reflecting higher 14C of heterotrophic
respiration and/or decreased root respiration in the experimental plots (p =0.027, t-test). The soil gas probes
near the maximum thaw depth in each treatment showed that the C respired had much lower 14C values in
the snow drift plots compared to the control plots (-106‰, ±39 vs. 41‰, ±18, p=0.007, t-test).
This corresponds to mean ages of approximately 1000 years old for the snow drift plots and less than 100 years
for the controls.
DE: 0428 Carbon cycling (4806)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting