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Differences in CH 4 oxidation and pathways of production between rice cultivars deduced from measurements of CH 4 flux and δ 13 C of CH 4 and CO 2
Author(s) -
Bilek Rebecca S.,
Tyler Stanley C.,
Sass Ronald L.,
Fisher Frank M.
Publication year - 1999
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/1999gb900040
Subject(s) - cultivar , growing season , chemistry , fractionation , flux (metallurgy) , fermentation , stable isotope ratio , methanogenesis , mars exploration program , botany , biology , food science , methane , chromatography , quantum mechanics , physics , organic chemistry , astrobiology
We report measurements of CH 4 flux and δ 13 C and δD values of emitted CH 4 and sediment CH 4 and CO 2 during the 1995 rice growing season in Beaumont, Texas. Four rice plant cultivars, Lemont, Mars, Cypress, and Della, and an unplanted plot were studied to provide possible explanations for the differences in CH 4 emissions between cultivars. Using the measured isotope values, along with data of CH 4 and CO 2 concentrations and other ecosystem data, we determined differences between cultivars in the processes of oxidation and production throughout the growing season. For instance, rhizospheric CH 4 oxidation increased as the season progressed in both Mars and Lemont cultivars. Late in the season, however, 71±10% of CH 4 produced in the Mars plot was oxidized compared to only 39±10% in the Lemont plot. The contribution of acetate fermentation to methanogenesis at specific times during the season was calculated using measured isotopic values and assuming identical isotopic fractionation factors in methanogenic pathways for the cultivars. In these calculations a range of values for the contribution to CH 4 production from acetate fermentation and CO 2 reduction with H 2 was estimated by considering different fractionation factors for the methanogenic CO 2 reduction pathway and the possibility of a 10% contribution to CH 4 production from acetate produced by homoacetogenesis. In general, a steady increase in the CH 4 portion produced by acetate fermentation was noted in the Lemont cultivar, while an increase followed by a decrease near the end of the season was observed for the Mars cultivar.