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Oxidation of methane in boreal forest soils: a comparison of seven measures

  • Author(s): Whalen, SC
  • Reeburgh, WS
  • Barber, VA
  • et al.
Abstract

Methane oxidation rates were measured in boreal forest soils using seven techniques that provide a range of information on soil CH4oxidation. These include: (a) short-term static chamber experiments with a free-air (1.7 ppm CH4) headspace, (b) estimating CH4oxidation rates from soil CH4distributions and (c)222Rn-calibrated flux measurements, (d) day-long static chamber experiments with free-air and amended (+20 to 2000 PPM CH4) headspaces, (e) jar experiments on soil core sections using free-air and (f) amended (+500 ppm CH4) headspaces, and (g) jar experiments on core sections involving tracer additions of14CH4. Short-term unamended chamber measurements,222Rn-calibrated flux measurements, and soil CH4distributions show independently that the soils are capable of oxidizing atmospheric CH4at rates ranging to < 2 mg m-2d-1. Jar experiments with free-air headspaces and soil CH4profiles show that CH4oxidation occurs to a soil depth of 60 cm and is maximum in the 10 to 20 cm zone. Jar experiments and chamber measurements with free-air headspaces show that CH4oxidation occurs at low (< 0.9 ppm) thresholds. The14CH4-amended jar experiments show the distribution of end products of CH4oxidation; 60% is transformed to CO2and the remainder is incorporated in biomass. Chamber and jar experiments under amended atmospheres show that these soils have a high capacity for CH4oxidation and indicate potential CH4oxidation rates as high as 867 mg m-2d-1. Methane oxidation in moist soils modulates CH4emission and can serve as a negative feedback on atmospheric CH4increases. © 1992 Kluwer Academic Publishers.

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