Carbon budget of a drained peatland in Western Iceland and initial effects of rewetting

Abstract

Northern peatlands store vast amounts of organic carbon in their soils. They play an important role in the context of climate change, as they act as a valuable key source and sink for all the main greenhouse gases. In their natural stage, peatlands act as sinks of atmospheric CO2 and sources of CH4, but with drainage this is reversed. Icelandic peatlands have been intensely drained or disturbed since the 1940´s for agricultural use but large proportion has never been cultivated. In recent years peatland restoration has increased and since 2011 wetland rewetting is a possible method for reducing emissions within the Kyoto Protocol´s second commitment period. This study examined the carbon fluxes from an uncultivated drained peatland in Iceland and estimated the annual CO2 budget. During the research period the site was rewetted and initial response in gas fluxes were estimated. Gas flux measurements were done regularly for a 17 months period, including two growing-seasons, using the chamber method.The results showed that the drained site was a net annual source of CO2 and a negligible sink of CH4. Net annual emission was 4.1 ±0.9 t C ha-1 yr-1 with CO2 contributing 91.9% of the emission of the pathways examined. Methane emission from ditches contributed approximately 3% and POC and DOC roughly 5%. First response after rewetting indicated an instant lowering of soil respiration and increased methane emission. These results verify the importance of water table on gas fluxes from soil, the effectiveness of the rewetting method and how immediate the response is.