The effects of peatland restoration on methane and carbon dioxide fluxes

Peatlands play an important role in the global carbon cycle. With rising levels of CO2 and CH4 in the atmosphere, a greater understanding of the controls on the flux of these gases from peatlands is important. In recent years, many peatlands have undergone restoration in attempts to reverse the damage caused by drainage. Therefore, the long-term effects of restoration on CO2 and CH4 fluxes are poorly understood. Peatland management strategies need to take the long-term responses of gaseous fluxes into account, and several hypotheses on these responses have been developed, despite the lack of data in this area. Thorne and Hatfield Moors, two lowland raised bogs in Eastern England were subjected to drainage and peat extraction over several centuries. Restoration has occurred in stages on these peatlands (1997, 2003-2005, 2008), and there is also an area where restoration has not yet occurred, providing an excellent space-for-time substitution. Data showed that CH4 fluxes were significantly larger at the two older sites in comparison to the younger site. Net ecosystem exchange and values of global warming potential were all positive (release to the atmosphere), and on average were larger at the two older sites in comparison with the unrestored site. Diurnal variations in gaseous fluxes were also explored. Methane fluxes were significantly larger at night-time from areas dominated by Eriophorum spp., which suggests that CH4 fluxes measured during the daytime could be underestimations. Carbon dioxide fluxes measured at night-time were larger than any of the daytime measurements of ecosystem respiration, where night-time conditions were simulated using a shroud to block the light. Therefore, ecosystem respiration measurements taken during the daytime could be underestimations. Sphagnum cuspidatum samples showed no evidence of a symbiosis with methanotrophs. Neither drought nor submergence of the Sphagnum sub-samples had any significant effect on rates of methanotrophy. However, drought had a significant effect on rates of methanogenesis, with higher rates from sub-samples that had been allowed to dry out.