Long-term flux measurements suggest dynamic emission factors are needed for rewetted peatlands

Abstract

Rewetting drained peatlands is recognized as a leading and effective natural solution to curb greenhouse gas (GHG) emissions. However, rewetting creates novel ecosystems whose emission behavior is not well captured by the currently used emission factors (EFs). These EFs are static and do not capture the temporal dynamics of GHG emissions. Hence, they often do not reflect the true emission reduction potential after rewetting. Here, we provide long-term data showing a mismatch between actual emissions and default EFs and revealing the temporal patterns of annual CO2 and CH4 fluxes in a rewetted peatland site in northeastern Germany. We show that site-level annual emissions of CO2 and CH4 approach the IPCC default EFs and those suggested for the German national inventory report only between 13 to 16 years after rewetting. Over the entire study period, we observed a source-to-sink transition of annual CO2 fluxes with a decreasing trend of -0.36 t CO2-C ha-1 yr-1, and a decrease in annual CH4 emissions of -23.6 kg CH4 ha-1 yr-1. Our results indicate that EFs should represent the temporally dynamic nature of peatlands post rewetting and consider the effects of site characteristics to better estimate associated GHG budgets.