Open AccessCarbon isotopic composition, methanogenic pathway, and fraction of CH 4 oxidized in a rice field flooded year‐round
Author(s) -
Zhang Guangbin,
Zhang Xiaoyan,
Ji Yang,
Ma Jing,
Xu Hua,
Cai Zucong
Publication year - 2011
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2011jg001696
Subject(s) - methanogenesis , paddy field , growing season , δ13c , flux (metallurgy) , dry season , fraction (chemistry) , environmental science , methane , agronomy , zoology , environmental chemistry , chemistry , biology , stable isotope ratio , ecology , physics , organic chemistry , quantum mechanics
Values of δ 13 C were investigated of CH 4 trapped in the soil pore water and floodwater of and emitted from a rice field under continuous flooding throughout the fallow and following rice seasons, and CH 4 produced via different pathways and fraction of CH 4 oxidized was calculated by using the isotopic data. Pore water CH 4 was relatively 13 C depleted, with δ 13 C values about −65‰ over the season except between July and August (around −55‰). Also, hydrogenotrophic methanogenesis was very important (around 50%) for most of the season, while acetoclastic methanogenesis dominated (about 70%) only between July and August. Floodwater CH 4 was heavier in δ 13 C value (from −50‰ to −34‰) than pore water CH 4 (from −68‰ to −54‰) over the season, demonstrating that it is highly influenced by methanotrophy. The δ 13 C value of emitted CH 4 was negatively correlated with flux in temporal variation (P <0.05), and it was more positive in the fallow season (between −56‰ and −44‰) than in the rice season (between −68‰ and −48‰). This indicates that plant‐mediated CH 4 transport is probably a more important pathway and causes less CH 4 oxidation during the rice season than during the fallow season, which is further confirmed by the fraction of CH 4 oxidized being generally greater in the fallow season (60%–90%) than in the rice season (10%–80%). These findings suggest a low contribution of acetoclastic methanogenesis and a high fraction of CH 4 being oxidized in the field, especially in the fallow season.