Rewetting of drained boreal spruce swamp forests results in rapid recovery of Sphagnum production

1. Peatland rewetting aims to restore biomass accumulation from peat-forming plants for climate change mitigation, biotope conservation and water purification purposes. Boreal spruce swamp forests in Europe have suffered heavily from drainage for forestry and are now a focus of restoration efforts. 2. We measured Sphagnum height and biomass increment by allowing Sphagnum to grow through mesh nets located in nine undrained, nine drained and 18 rewetted boreal spruce swamp forests. 3. At the moss patch level, rewetting led to a recovery of Sphagnum growth: height increment and biomass increment at the rewetted sites (5·9 ± 0·7 cm year−1 and 147 ± 15 g m−2 year−1, mean ± SE) were similar to increment at the undrained sites (4·9 ± 0·5 cm year−1 and 128 ± 12 g m−2 year−1), while remnant patches of Sphagnum at the drained sites showed smaller increment (2·8 ± 0·8 cm year−1 and 76 ± 19 g m−2 year−1). Sphagnum in the ditches at the drained sites showed similar increment as the moss at the undra...