Using 'snapshot' measurements of CH4 fluxes from an ombrotrophic peatland to estimate annual budgets: interpolation versus modelling

Flux-chamber measurements of greenhouse gas exchanges between the soil and the atmosphere represent a snapshot of the conditions on a particular site and need to be combined or used in some way to provide integrated fluxes for the longer time periods that are often of interest. In contrast to carbon dioxide (CO₂), most studies that have estimated the time-integrated flux of CH₄ on ombrotrophic peatlands have not used models. Typically, linear interpolation is used to estimate CH₄ fluxes during the time periods between flux-chamber measurements. CH₄ fluxes generally show a rise followed by a fall through the growing season that may be captured reasonably well by interpolation, provided there are sufficiently frequent measurements. However, day-to-day and week-to-week variability is also often evident in CH₄ flux data, and will not necessarily be properly represented by interpolation. Using flux chamber data from a UK blanket peatland, we compared annualised CH₄ fluxes estimated by interpolation with those estimated using linear models and found that the former tended to be higher than the latter. We consider the implications of these results for the calculation of the radiative forcing effect of ombrotrophic peatlands.