The oxygen budget of a peatland – new approach to estimating ecosystem oxidative ratio

Abstract. The oxidative ratio (OR) of an ecosystem in the terrestrial biosphere is defined as the ratio of the O₂ released from that ecosystem to the CO₂ adsorbed by that ecosystem. This study proposes that the OR of a terrestrial ecosystem could be calculated for the C budget of a peatland environment where stoichiometry and thermodynamics are constrained. Using detailed elemental analysis within an ecosystem with a known C and N budget it is possible to understand the amount of O₂ consumed.

The study shows that, for the study site, although the majority of the O₂ is consumed in the processing of organic-C (68 %), 32 % of O₂ consumption is due to oxidation of NH₄. The total amount of O₂ consumed by organic C processing is not dependent upon the pathway after surface peat formation: O₂ consumption is independent of production of DOC or CH₄ or of deep peat. This approach shows that allowing for stoichiometric, energy and energy transfer efficiency constrains the ecosystem OR = 0.88. The calculated OR is consistent with disproportionation of C occurring in the environment. The implication of OR < 1 is that the annual flux of C to the terrestrial biosphere has been underestimated by 12 %.