To restore drained wetlands by raising the groundwater table has been suggested as an efficient measure to reduce degradation of peat soils and in turn decrease atmospheric CO₂ emissions. Such restoration efforts are already being widely conducted across Sweden and the plan is to continue at large scales. However, limited information exists regarding the effects of restoration on lateral export of carbon (C) via the aquatic pathway. Any changes in the lateral C flux are critical to consider as it affects the overall wetland carbon balance and may offset any climatic benefits from the restoration. In addition to the carbon balance perspective, changes in the aquatic C export could affect downstream surface water quality. In this study, we monitored aquatic C (DOC, DIC and CH₄) in two streams draining a boreal wetland that was rewetted during autumn 2020. By comparing pre- (2018-2020) and post- (2020-2022) restoration periods we were able to detect any changes in the aquatic C pool. The results showed that the restoration effect was site-, season- and carbon component-specific. One of the stream sites showed no effect of the restoration on aquatic C, whereas the other site showed overall elevated (DOC) or highly elevated (CH₄) concentrations post restoration. For DOC, the increase mainly occurred during autumn and winter, whereas increased CH₄ concentrations were visible at all seasons. These results are fundamental when evaluating the environmental benefits of rewetting formerly drained wetlands.

Primary Presenter: Marcus Wallin, Swedish University of Agricultural Sciences (marcus.wallin@slu.se)

Authors:

Alberto Zannella, Swedish University of Agricultural Sciences  (alberto.zannella@slu.se)

Hjalmar Laudon, Swedish University of Agricultural Sciences  (hjalmar.laudon@slu.se)

Karin Eklöf, Swedish University of Agricultural Sciences  (karin.eklof@slu.se)