Increased moisture and methanogenesis contribute to reduced methane oxidation in elevated CO2 soils

Jean E.T. McLain, Dianne M. Ahmann

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

Awareness of global warming has stimulated research on environmental controls of soil methane (CH4) consumption and the effects of increasing atmospheric carbon dioxide (CO2) on the terrestrial CH4 sink. In this study, factors impacting soil CH4 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 μL L-1) or elevated (ambient+200 μL L-1) CO2 since August 1996. Over 1 year, nearly 90% of the 360 incubations showed net CH4 consumption, confirming that CH4-oxidizing (methanotrophic) bacteria were active. Soil moisture was significantly (p<0.01) higher in the 25-30 cm layer of elevated CO2 soils over the length of the study, but soil moisture was equal between CO2 treatments in shallower soils. The increased soil moisture corresponded to decreased net CH4 oxidation, as elevated CO2 soils also oxidized 70% less CH4 at the 25-30 cm depth compared to ambient CO2 soils, while CH4 consumption was equal between treatments in shallower soils. Soil moisture content predicted (p<0.05) CH4 consumption in upper layers of ambient CO2 soils, but this relationship was not significant in elevated CO2 soils at any depth, suggesting that environmental factors in addition to moisture were influencing net CH4 oxidation under elevated CO2. More than 6% of the activity assays showed net CH4 production, and of these, 80% contained soils from elevated CO2 plots. In addition, more than 50% of the CH4-producing flasks from elevated CO2 sites contained deeper (25-30 cm) soils. These results indicate that subsurface (25 cm+) CH4 production contributes to decreased net CH4 consumption under elevated CO 2 in otherwise aerobic soils.

Original languageEnglish (US)
Pages (from-to)623-631
Number of pages9
JournalBiology and Fertility of Soils
Volume44
Issue number4
DOIs
StatePublished - Mar 1 2008
Externally publishedYes

Keywords

  • CH
  • Elevated CO
  • Methanogenesis
  • Methanotrophy

ASJC Scopus subject areas

  • Microbiology
  • Agronomy and Crop Science
  • Soil Science

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