A Primer on Gas Phase CO2 Production and Transport in Peatland Soils

CO2 sequestered by peatlands is accounted for and offset against national emissions. Observational and modelling studies are used to estimate emission factors that dictate the rate of CO2 emissions or removals from peatlands accounted for within the Landuse and landuse change including forestry (LULUCF) sector and often use simple Tier 1 emission factors found in the IPCC (1996) guidebook. However, the current estimates are predominately based off peatland surface fluxes measured using either chamber methods or eddy covariance techniques. These methods do not focus on sub-surface conditions while this information may prove useful in understanding efflux rates and conditions that influence them. To help assess the potential significance of subsurface dynamics in overall CO2 efflux rates from peatlands this study proposes to review the literature dealing with subsurface conditions. The review found that the production of CO2 in the sub-surface layers was often uncoupled from emissions and that on short time-scales the storage of CO2 in soil pores and dissolved in soil water may account for this. The rate of production was found to be influenced by decomposition rate, vegetation type, nutrient availability and peat depth. The review also found that the mechanism of transport of CO2 within the sub-surface was important in accounting for efflux rates. While diffusion is often assumed the most significant form of transport, the quantification and dynamics of other non-diffusive transport methods were found to also be important and further research is required to ascertain the drivers of both diffusive and non-diffusive transport.