HR: 1340h
AN: B33B-1033    [Abstracts]
TI: Seasonal and Interannual Variability in Growing Season Carbon Budget at a Rice Paddy Field in Central Japan
AU: * Mano, M
EM: mmano@niaes.affrc.go.jp
AF: National Institute for Agro-Environmental Sciences, 3-1-3, Kannondai, Tsukuba, 305-8604 Japan
AU: Miyata, A
EM: amiyat@niaes.affrc.go.jp
AF: National Institute for Agro-Environmental Sciences, 3-1-3, Kannondai, Tsukuba, 305-8604 Japan
AU: Nagai, H
EM: iagan@niaes.affrc.go.jp
AF: National Institute for Agro-Environmental Sciences, 3-1-3, Kannondai, Tsukuba, 305-8604 Japan
AU: Yamada, T
EM: yamadatm@niaes.affrc.go.jp
AF: National Institute for Agro-Environmental Sciences, 3-1-3, Kannondai, Tsukuba, 305-8604 Japan
AU: Ono, K
EM: onok@niaes.affrc.go.jp
AF: National Institute for Agro-Environmental Sciences, 3-1-3, Kannondai, Tsukuba, 305-8604 Japan
AU: Han, H G
EM: hangh@niaes.affrc.go.jp
AF: National Institute for Agro-Environmental Sciences, 3-1-3, Kannondai, Tsukuba, 305-8604 Japan
AU: Kobayashi, Y
EM: yosikazu@niaes.affrc.go.jp
AF: National Institute for Agro-Environmental Sciences, 3-1-3, Kannondai, Tsukuba, 305-8604 Japan
AB: Rice paddy in eastern Asia emits methane because it is irrigated during most of the growing season. Therefore it is necessary to measure carbon dioxide and methane fluxes simultaneously in order to estimate the carbon budget of the rice paddy. We continue a long-term flux measurement using micrometeorological methods at a customarily cultivated rice paddy in Central Japan. In this study we examine seasonal and interannual variability of carbon budget of the rice paddy by comparing fluxes in two years, 2004 and 2005, which had quite different water managements. At the study site rice is transplanted in early May and harvested in early or middle September. Midsummer drainage is conducted to remove unfavorable gases in the soil and compact the soil to prevent fall down of rice and so on. Fluxes of carbon dioxide and methane were measured by the eddy covariance and the gradient method respectively. We analyzed data obtained from May 2nd, which was the transplanting day in both years, to the end of August. The 2004 summer was the third warmest since 1945, while the 2005 summer was similar to the normal. There were no major differences in the maximum daily uptake of carbon dioxide between the years. Accumulated carbon dioxide, however, showed differences: the net uptake of C during the season in 2004 was 538 g C m^-2, that was 28 % greater than that in 2005. This is because of high temperature and large amount of solar radiation in 2004. The daily methane emission in 2004 became obvious in late May, increased to 0.2 g C m^-2 d^-1 in June and 0.4 g C m^-2 d^-1 in August, and then decreased to near zero. In 2005, although the seasonal variation of the methane emission was almost same until late June, the emission decreased to 0.1 g C m^-2 d^-1 in late July. This may have resulted from a decline of methane production by methanogens owing to soil aeration because the longer midsummer drainage was conducted (22 days in 2005 and 9 days in 2004). The total methane emission in 2005 (11 g C m^-2) was small in comparison with that in 2004 (18 g C m^-2). Our results suggest that the carbon budget at the rice paddy field was influenced not only by weather conditions but also by water management, i.e., length of drained period.
DE: 0428 Carbon cycling (4806)
DE: 0490 Trace gases
SC: Biogeosciences [B]
MN: Fall Meeting 2005