The climate benefits of topsoil removal and Sphagnum introduction in raised bog restoration

Abstract

Many raised bogs in Central Europe are in an unfavorable state: drainage causes high emissions of carbon dioxide (CO 2 ) and nitrous oxide (N 2 O), while rewetting may result in high methane (CH 4 ) emissions. Also, the establishment of typical bog species is often hampered during restoration. Measures like topsoil removal (TSR) or introduction of target vegetation are known to improve restoration success in other systems, but experiences on bogs after long-term agricultural use are scarce and their climate effects including carbon losses from TSR are unknown. In a field trial in north-western Germany, consisting of seven plots (intensive grassland, IG, and six restoration approaches), we explored the effects of rewetting, TSR and Sphagnum introduction on greenhouse gas (GHG) emissions. We measured GHG fluxes to obtain two-year GHG budgets and applied a radiative forcing model to assess the time-dependent climate effects. Existing uncertainty of decomposition processes in the translocated topsoil has been incorporated by different topsoil accounting scenarios. According to our data, rewetting alone reduced CO 2 emissions by approximately 75% compared to IG, but substantially increased CH 4 emissions. After TSR and rewetting, on-site CO 2 emissions were close to zero or, with Sphagnum introduction, net negative while CH 4 emissions remained very low. The climatic warming effect of TSR including C export becomes less climate warming than rewetting nutrient-rich peatlands after a few decades. For raised bog restoration, we therefore recommend a TSR sufficient to achieve nutrient-poor and acidic conditions needed for rapid Sphagnum establishment.

Effects of brackish water inflow on methane-cycling microbial communities in a freshwater rewetted coastal fen

“…Flux data analyses were done in R (R Core Team 2021). CH 4 fluxes were estimated with the fluxx function of the R package flux (Jurasinski et al, 2014) as described in Huth et al (2012), Günther et al (2015) and Huth et al (2021). We used the atmospheric sign convention, meaning that positive fluxes indicate a release from the ecosystem to the atmosphere and negative fluxes indicate an uptake by the ecosystem.…”

Rewetting prolongs root growing season in minerotrophic peatlands and mitigates negative drought effects

“…CO 2 , CH 4 ) biweekly using transparent and opaque closed chambers on five permanently installed collars per site (Köhn et al, 2021). Based on the data gathered from October 2017 to September 2019, we derived the two consecutive annual exchange balances of CO 2 and CH 4 per site using artificial neural network models (Huth et al, 2022). Using the average annual balances per site, we summed up the resulting CO 2 ‐C and CH 4 ‐C values to derive annual carbon balances (see Table S2).…”

Ecological resilience of restored peatlands to climate change

“…does not mean that those sites cannot be restored; rather, it may take a long period of time to achieve success. Likewise, new methods could be developed to help ensure restoration success, such as topsoil removal in the case of heavily damaged systems 92 . A point worth mentioning is the dearth of old restored sites that could be used to know how, when, or if resilience returns.…”