Mass Balances of a Drained and a Rewetted Peatland: on Former Losses and Recent Gains
2020
Almut Mrotzek | Dierk Michaelis | Anke Günther | Nicole Wrage-Mönnig | John Couwenberg
Drained peatlands are important sources of greenhouse gases and are rewetted to curb these emissions. We study one drained and one rewetted fen in terms of losses&mdash:and, after rewetting&mdash:gains of organic matter (OM), carbon (C), and peat thickness. We determined bulk density (BD) and ash/OM (and C/OM) ratios for 0.5 cm thick contiguous slices from peat monoliths to calculate losses. Whereas one site has lost 28.5 kg OM m&minus:2 corresponding to annual emissions of ~10 t CO2 ha&minus:1 a&minus:1 over 50 years of effective drainage, the other site has lost 102 kg OM m&minus:2, corresponding to an annual loss of ~30 t CO2 ha&minus:1 a&minus:1 for 30 years of intensive drainage and 6 t CO2 ha&minus:1 a&minus:1 during ~225 years of weak drainage before that. Height losses ranged from 43 to 162 cm. In the 20 years after rewetting, 2.12 kg C m&minus:2 was accumulated, equaling an average annual uptake of ~0.4 kg CO2 m&minus:2 a&minus:1. The results indicate that rewetting can lead to carbon accumulation in fens. This sink function is only small compared with the high emissions that are avoided through rewetting.
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