Carbon dioxide and methane gas exchange following sphagnum moss harvesting in boreal peatland

Understanding the impacts of Sphagnum moss harvesting on peatland carbon (C) balance is crucial due to its potential rise as an anthropogenic land use. We studied eight nutrient-poor peatlands in Finland, harvested between 2015 and 2021, focusing on net ecosystem exchange of CO₂ (NEE) and methane (CH₄) emissions. The greenhouse gas fluxes were measured to evaluate the sustainability of harvesting practices. Results showed significant variability in Sphagnum regeneration, with wet strip-harvested sites achieving 2-28% re-establishment in 2-8 years, while drier clear-harvested sites saw minimal spontaneous regeneration in 1-6 years. In addition to vegetation succession, GHG emissions were moisture dependent. In wet sites CH₄ emissions increased along with time since harvesting and Eriophorum vaginatum (L.) cover, while dry sites exhibited overall lower CH₄ fluxes. Younger (1-2 years post-harvest), dry sites were significant CO₂ sources due to low photosynthetic activity. Older dry site with sparse ericoid shrub vegetation acted as CO₂ sink. Wet sites initially had lower CO₂ sink capacity, but this increased as E. vaginatum spread, and reached a plateau when Sphagnum mosses emerged, highlighting the importance of suitable water table levels for efficient CO₂ sequestration.