How Important is the Evasion Flux Term in the Carbon and GHG Balance of Peatlands?

Authors:
Michael F. Billett and Frank Harvey

Book:
Proceedings of the 14th International Peat Congress

Venue:
Stockholm

Keywords:
carbon-dioxide, dissolved-organic-carbon, evasion, flux, methane

Documentfile:
Billett, Harvey 2012: How Important is the Evasion Flux Term in the Carbon and GHG Balance of Peatlands?

Summary:

Theme X. Peatland carbon budgets and greenhouse gas (GHG) fluxes

SUMMARY

Instantaneous measurements of gas exchange from flowing surface waters in six UK peatland sites show that the CO₂ evasion rate per unit area of surface water (median 133, mean 367 μg C m^-2 s^-1) is more than a magnitude higher than the CH₄ evasion rate (median 0.22, mean 1.45 μg C m^-2 s^-1). Scaling to the whole catchment, using measurements of water surface area (0.07-0.41%) we show that the CO₂ evasion flux is a significant component of the aquatic C flux and regularly exceeds the downstream DOC flux, typically 10-25 g C m^-2 yr^-1 in most peatland catchments. We conclude that whilst the CO₂ evasion flux is highly variable and difficult to quantify at the catchment scale, it is a significant flux term in the carbon balance of many peatland landscapes, strongly controlled by hydrological extremes. Excluding aquatic CO₂ evasion from calculations of carbon balance may therefore lead to an overestimation of the sink strength of peatland systems.