Peat oxidation in an abandoned cutover peatland

Drained and cutover peatlands represent a persistent source of atmospheric CO 2 . Contemporary, intermediate, and long-term rates of peat oxidation were measured in an abandoned cutover peatland to estimate the mass of lost in order to determine if the oxidation rate has changed with time since abandonment. Contemporary rates were measured six times per week at 25 locations within the peatland using a portable infrared gas analyser and an enclosure system. Mean daily peat oxidation was 7.7 g CO 2 m -2 d -1 or 4.8 mm yr -1 . Intermediate (2-13 yr) oxidation rates were estimated using dendrochronological techniques. Over 325 birch (Betula spp.) shrubs, an invasive group of species in abandoned cutover peatlands, were removed from the peatland after measuring the distance to the existing peat surface from the collar of the trunk. Dating the birches permitted the determination of the rate of peat oxidation and erosion since the establishment of individuals. Long-term oxidation (19 yr) was estimated with over 10 000 measurements on exposed stable tree stumps. The mean intermediate and long-term oxidation rates were 6.2 ± 2.9 mm yr -1 and 5.7 ± 1.1 mm yr -1 , respectively. These results suggest that peat oxidation rates remain high even after two decades of post-extraction abandonment. Since oxidation is an irreversible process, these results carry important implications for restoration work as well as for the determination of the long-term source of atmospheric CO 2 . Key words: Peatland, organic soil, oxidation, carbon dioxide, dendrochronology, peat extraction