Experimental warming increased greenhouse gas emissions of a near-natural peatland and Sphagnum farming sites

Abstract Aims Drained peatlands are a major source of greenhouse gases (GHG). Paludiculture is the production of biomass under wet and peat preserving conditions. Despite the growing recognition as GHG mitigation measure, the potential influence of climate warming on paludiculture is still unknown. Methods For two years, we quantified the exchange of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) using manual chambers and surveyed the vegetation composition of warmed and control sites at a near-natural bog and two Sphagnum farming areas in North-Western Germany. Passive warming was achieved using Open Top Chambers (OTC). Results OTCs significantly increased air and soil temperatures, while soil moisture, humidity and light availability differed only marginally. The latter was considered when calculating gross primary production. Warming tended to increase vascular plant cover, but differences to the control plots were still small after two years. Emissions of CO2 and CH4 increased with warming, dominated by CH4 at the near-natural bog and by CO2 at the paludiculture areas, where vegetation was in a successional stage and topsoils temporarily dried out during summer. N2O emissions were negligible at the near-natural bog and ceased with increasing biomass at the paludiculture sites. Interannual variability was high due to a heatwave in the second measurement year. Conclusions Climate warming could increase GHG emissions from near-natural bogs and Sphagnum farming. In the latter case, this puts even more emphasis on water management systems ensuring high water table depths during dry periods. Further, control of vascular plants might both reduce CH4 emissions and improve biomass quality.