HR: 0800h
AN: B51C-0962    [Abstracts]
TI: Interannual Variability in Growing Season Carbon Budget at a Customarily Cultivated Rice Paddy Field in Central Japan
AU: * Mano, M
EM: mmano@niaes.affrc.go.jp
AF: National Institute for Agro-Environmental Sciences, 3-3-1, Kannondai, Tsukuba, 305-8604 Japan
AU: Miyata, A
EM: amiyat@niaes.affrc.go.jp
AF: National Institute for Agro-Environmental Sciences, 3-3-1, Kannondai, Tsukuba, 305-8604 Japan
AU: Nagai, H
EM: iagan@niaes.affrc.go.jp
AF: National Institute for Agro-Environmental Sciences, 3-3-1, Kannondai, Tsukuba, 305-8604 Japan
AU: Yamada, T
EM: yamadatm@niaes.affrc.go.jp
AF: National Institute for Agro-Environmental Sciences, 3-3-1, Kannondai, Tsukuba, 305-8604 Japan
AU: Ono, K
EM: onok@niaes.affrc.go.jp
AF: National Institute for Agro-Environmental Sciences, 3-3-1, Kannondai, Tsukuba, 305-8604 Japan
AU: Han, G
EM: hangh@niaes.affrc.go.jp
AF: National Institute for Agro-Environmental Sciences, 3-3-1, Kannondai, Tsukuba, 305-8604 Japan
AU: Yoshikoshi, H
EM: yosysuos@mbox.nc.kyushu-u.ac.jp
AF: Kyusyu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka, 812-8581 Japan
AU: Saito, M
EM: msaito@suiri.tsukuba.ac.jp
AF: University of Tsukuba, 1-1-1, Tennodai, Tsukuba, 305-8572 Japan
AB: Rice paddy fields in eastern Asian countries are irrigated during most of the growing season. Since flooded paddy fields are favorable for methanogenesis, it is necessary to measure both carbon dioxide flux and methane flux in order to estimate carbon budget of the paddy fields. As one of AsiaFlux network sites we continue long-term measurements of carbon dioxide and methane fluxes at a customarily cultivated paddy field in central Japan. At the study site rice is transplanted in early May and harvested in early or middle September. We are measuring carbon dioxide flux by the eddy covariance method and methane flux by the gradient method. In 2003 we had the coolest summer in these 10 years, while the 2004 summer was the third warmest since 1946: Air temperatures averaged from June to August in 2003 and 2004 were 0.6 $\deg$C below and 1.3 $\deg$C above the 30-year average, respectively. Carbon dioxide flux showed distinct seasonal variation with rice growth. In 2004, net daily carbon dioxide uptake by the ecosystem became obvious in late May, increased to the maximum daily uptake of 11 gC m$^{-2}$ d$^{-1}$ in July, and then decreased to nearly zero at the end of August. In 2003, carbon dioxide uptake showed temporary decrease in mid-growing season because of small amount of solar radiation and low temperature. The sum of carbon dioxide uptake by the ecosystem from the transplanting to the end of August was 443 gC m$^{-2}$ in 2003, and 553 gC m$^{-2}$ in 2004. Methane emission in 2004 started a month after transplanting, increased gradually and reached midsummer peak of 331 mgC m$^{-2}$ d$^{-1}$ in late July with a flush of methane at the final drainage. The seasonal variation of methane flux in 2003 was generally similar to that in 2004, but flushes of methane at midsummer drainages as well as final drainage were observed more distinctly than in 2004. Despite small amount of methane flushes, seasonal methane emission in 2004 was greater than that in 2003 by 2 gC m$^{-2}$. Higher soil temperature and larger supply of photosynthate in 2004 presumably enhanced methane production in soil and resulted in larger methane emission. The ratio of methane emission to carbon dioxide uptake was about 4% and showed little difference between 2003 and 2004.
UR: http://ecomdb.niaes5.affrc.go.jp/
DE: 4806 Carbon cycling
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting