Anaerobic decomposition contributions to greenhouse gas emissions of agriculturally used peatlands.

Globally, peatlands store one third of global soil carbon. Peatlands accumulate carbon under waterlogged anoxic conditions, but drainage increases oxygen availability causing peatland degradation. Therefore, drainage is responsible for ~2% of anthropogenic greenhouse gas (GHG) emissions. GHG emission estimates from drained peatlands are often based on hydrological proxies. In this research, we propose to improve these estimates by adding the redox potential that controls peat degradation more directly compared to hydrological proxies. We quantified in-situ soil production rates of CO2 and CH4 by combining in-situ redox potential measurements with corresponding laboratory basal respiration rates scaled to in-situ soil temperature. Using this approach, we estimated soil CO2 and CH4 production rates for 12 field sites over multiple years and validated these estimates by comparing them to aboveground Net Ecosystem Carbon Balance (NECB) measurements. We show that (1) laboratory incubation measurements can serve as a strong basis to estimate field-scale CO2 and CH4 emissions, (2) compared to water table depth, the redox potential is a more reliable parameter for estimating soil CO2 production, and (3) anaerobic respiration processes contribute substantially to peat decomposition and soil CO2 production. Our results provide valuable new insights for assessing GHG emissions from drained peatlands and enhances our understanding of aerobic and anaerobic peat decomposition processes.