HR: 1340h
AN: B33E-1083    [Abstracts]
TI: Simulating net ecosystem productivity and the sensitivity of a sub-arctic boreal forest ecosystem
AU: * Ueyama, M
EM: ueyama@iarc.uaf.edu
AF: International Arctic Research Center, 930 Koyukuk Dr., Fairbanks, AK 99775 United States
AU: Harazono, Y
EM: Y.Harazono@uaf.edu
AF: International Arctic Research Center, 930 Koyukuk Dr., Fairbanks, AK 99775 United States
AU: Kim, Y
EM: Kimyw@iarc.uaf.edu
AF: International Arctic Research Center, 930 Koyukuk Dr., Fairbanks, AK 99775 United States
AU: Tanaka, N
EM: norit@iarc.uaf.edu
AF: IORGC, JAMSTEC, 2-15 Natsushima-cho, Yokosuka, 237-0061 Japan
AB: BIOME-BGC was used to examine how air temperature and precipitation affect NEP in a sub-arctic black spruce forest. The model was tuned using data from the eddy correlation measurement site in UAF black spruce forest during 2003 and 2004. The climate dataset of Fairbanks airport between 1949 and 2004 was used for the model spin-up. The model almost reproduced the observed NEE, in which climate in 2003 was normal and that in 2004 was drought in summer. The model, however, failed to simulate the late winter NEE, during which obvious daytime uptake were observed under extreme low temperature. Annual simulation of GPP and ecosystem respiration was 2.2 and 1.8 kg CO₂ m^-2 yr^-1 in 2003 and 2.4 and 1.9 kg CO₂ m^-2 yr^-1 in 2004. While warm growing season temperature enhanced the photosynthesis and respiration in 2004, significant drought in August 2004 were restricted both the photosynthesis and heterotrophic respiration. Simulated annual NEE was 0.2 kg CO₂ m^-2 yr^-1 in 2003 and 0.3 kg CO₂ m^-2 yr^-1 in 2004.
The simulation explored the impact of seasonal warmer (+5^oC), wetter (120% of precipitation) and drier (80% of precipitation) spells on net ecosystem productivity, comparing the long term Fairbanks weather between 1980 and 2000. Wetter condition in either season did not significantly affect annual NEP. While drought summer decreased annual NEP by 30% mainly due to reduction in GPP by 9%, low snowfall winter also reduced the annual NEP by 19%, in which low snow water brought drought stress in following summer and then suppressed both GPP to 93% and ecosystem respiration to 96%. Warmer summer and autumn decreased annual NEP to 37% and 65%. In this case, GPP did not increase and maintenance and heterotrophic respiration were enhanced to 120% and 126%, respectively, in warmer summer and 103% and 107%, respectively, in warmer autumn. The simulation unambiguously showed productivity of the sub-arctic boreal forest was significantly sensitive to warmer temperature in summer and autumn and low precipitation in summer and winter.
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0438 Diel, seasonal, and annual cycles (4227)
DE: 0466 Modeling
DE: 0476 Plant ecology (1851)
DE: 0490 Trace gases
SC: Biogeosciences [B]
MN: Fall Meeting 2005