On the Relationship Between Methane Production in Anaerobic Incubations of Peat Material and In Situ Methane Emissions

Abstract

Anaerobic incubations of peat have been widely used to explore soil processes, but this in vitro technique raises many questions as to how well it reproduces in situ conditions. To investigate this, we conducted 60–100 days (+25 days pre-incubation) anaerobic, temperature-controlled incubation experiments across a temperature range of 1–26°C on samples from bog and fen habitats, at two different depths (9–19and 25–35 cm). We observed exponential increases in CO₂ and methane production with temperature in all conditions. We then compared field-based measurements of methane emission with modeled expectations by extrapolating incubation-determined methane production rates based on (a) soil temperature profiles, (b) the observed incubation temperature-methane production relationship, and (c) seasonal thaw depth from each site. The resulting incubation-extrapolated methane production agreed with measured emission rates within a factor of two at both sites and corresponded to 182 ± 54% and 59 ± 14% of the measured average yearly fluxes from the field for the bog and fen, respectively. The underestimation of fen methane fluxes may be due to the lack of living plant root-derived dissolved organic carbon inputs in incubations, a key process in fens. Conversely, the overestimation in bogs could be attributed to methane oxidation in the field, which is absent in anaerobic incubation conditions. Nonetheless incubations predicted greenhouse gas emissions from a northern peatland within a factor of two.