HR: 1340h
AN: B33E-1085    [Abstracts]
TI: Simultaneous Micrometeorological Flux Observations of CO2 and CH4 at a Sub-Arctic Black-Spruce Forest in Alaska
AU: * Harazono, Y
EM: y.harazono@uaf.edu
AF: IARC, UAF, 930 Koyukuk Dr., Fairbanks, AK 99775 United States
AU: Ueyama, M
EM: ueyama@iarc.uaf.edu
AF: IARC, UAF, 930 Koyukuk Dr., Fairbanks, AK 99775 United States
AU: Miyata, A
EM: amiyat@niaes.affrc.go.jp
AF: National Institute for Agro-Environmental Sciences, Kannondai, Tsukuba, 305-8604 Japan
AB: Carbon dioxide (CO2) and methane (CH4) fluxes were measured at a black spruce forest over discontinuous permafrost in central Alaska since November 2002. CO2 flux was measured by open-path eddy correlation system and CH4 flux was measured by gradient method continuously. CO2 uptake was observed during daytime after DOY 60 when the forest floor was snow-covered with low temperature (<-10 °C). At the moment, CH4 flux was negative (uptake) during daytime and nearing to zero at night, which varied with surface temperature. During snow melt and following permafrost thawing periods (around DOY 110-140, 2003), nocturnal CO2 efflux was larger than daytime uptake resulted in a daily CO2 source, and CH4 flux became small positive in daytime and nearing zero at night resulted in a weak daily CH4 source. After DOY 140 in 2003, CO2 flux was strong uptake and the maximum level was 1.0 g m-2 h-1 in late July around 10:30h when 3 hr earlier than solar noon. During mid summer (DOY 180-230, 2003), daytime CH4 uptake was weak and was near zero at night resulted in a weak daily CH4 sink. 2004 was low snow fall and draught summer, the seasonal patterns of CO2 and CH4 fluxes shifted more than 3-weeks earlier than that in 2003, resulted in high CO2 and CH4 emissions in early summer. Daily amount of CH4 flux in mid summer 2003 and 2004 were 1.2 and 0.5 mg CH4 m-2 d-1, respectively. Sum of observed NEE and CO2 storage term within the canopy, NEP were -482 and -366.6 gCO2 m-2 y-1 in 2003 and 2004. However, application of u* filtering correction made NEP reduce to the ranges between -434.8 and -315.9 gCO2 m-2 y-1 (under u<0.05 ms-1 and u<0.2 ms-1) in 2003 and to -282.5 and -215.9 gCO2 m-2 y-1 in 2004. The low NEP in 2004 was caused by high temperature and low precipitation during growing season. CH4 emission was also higher in 2004. CO2 and CH4 exchanges at sub-arctic forest were quite sensitive to draught and summer temperature.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0428 Carbon cycling (4806)
DE: 1823 Frozen ground
SC: Biogeosciences [B]
MN: Fall Meeting 2005