摘要 : Awareness of global warming has stimulated research on environmental controls of soil methane (CH) consumption and the effects of increasing atmospheric carbon dioxide (CO) on the terrestrial CH sink. In this study, factors impact... 展开 Awareness of global warming has stimulated research on environmental controls of soil methane (CH) consumption and the effects of increasing atmospheric carbon dioxide (CO) on the terrestrial CH sink. In this study, factors impacting soil CH consumption were investigated using laboratory incubations of soils collected at the Free Air Carbon Transfer and Storage I site in the Duke Forest, NC, where plots have been exposed to ambient (370 oL L-p#) or elevated (ambient + 200 oL L-p#) CO since August 1996. Over 1 year, nearly 90% of the 360 incubations showed net CH consumption, confirming that CH-oxidizing (methanotrophic) bacteria were active. Soil moisture was significantly (p < 0.01) higher in the 25-30 cm layer of elevated CO soils over the length of the study, but soil moisture was equal between CO treatments in shallower soils. The increased soil moisture corresponded to decreased net CH oxidation, as elevated CO soils also oxidized 70% less CH at the 25-30 cm depth compared to ambient CO soils, while CH consumption was equal between treatments in shallower soils. Soil moisture content predicted (p < 0.05) CH consumption in upper layers of ambient CO soils, but this relationship was not significant in elevated CO soils at any depth, suggesting that environmental factors in addition to moisture were influencing net CH oxidation under elevated CO. More than 6% of the activity assays showed net CH production, and of these, 80% contained soils from elevated CO plots. In addition, more than 50% of the CH-producing flasks from elevated CO sites contained deeper (25-30 cm) soils. These results indicate that subsurface (25 cm+) CH production contributes to decreased net CH consumption under elevated CO in otherwise aerobic soils. 收起