Diel variation in methane emission from a midlatitude prairie wetland: Significance of convective throughflow in Phragmites australis

J. Kim, S. B. Verma, D. P. Billesbach, R. J. Clement

Research output: Contribution to journalArticlepeer-review

Abstract

Methane flux was measured at a Phragmites-dominated marsh in the Sandhills of north-central Nebraska from late July to September 1993. The eddy covariance . technique employing a tunable diode laser spectrometer was used to measure spatially integrated fluxes of methane. Rates of methane emission increased rapidly after sunrise and peaked (at up to 50 mg CH4 m-2 h-1) between midmorning and noon. The emission rates during midday hours were 2 to 5 times higher than the relatively constant rates observed at night. This marked diel variation was attributed to plant-mediated transport of methane by convective throughflow which typically accounted for about 60% of the total methane emission during the daylight hours. Our analysis suggests that the enhanced rate of plant-mediated methane emission during daytime is significantly correlated with changes in photosynthetically active radiation and the temperature difference between the canopy and the ambient air. Data on windy nights showed enhanced methane emission with increasing wind speeds, perhaps indicating an occurrence of Venturi-induced convection and/or enhanced ebullition. When averaged over the study period of 65 days, the methane flux was 25 mg CH4 m-2 h-1 during daytime and 8 mg CH4 m-2 h-1 during nighttime. Changes in the daily averaged methane flux were strongly correlated with sediment temperatures at 0-0.25 m depth.

Original languageEnglish (US)
Article number98JD02441
Pages (from-to)28029-28039
Number of pages11
JournalJournal of Geophysical Research Atmospheres
Volume103
Issue numberD21
DOIs
StatePublished - Nov 20 1998

ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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