Comparing the effect of organic matter quality on aerobic and anaerobic greenhouse gas production in a temperate peatland

Rachel Shaw, Lauren Bryan, Alexis Koehl, Michael Philben 

Peatlands have an outsized contribution to both carbon storage and methane (CH4) emissions relative to their land surface area. The factors controlling these fluxes are uncertain, but critical to predicting the future trajectory of greenhouse gas emissions from peatlands. While the biochemical composition of organic matter (termed organic matter “quality”) has been shown to be correlated with its future vulnerability to decomposition under oxic conditions, few experiments have assessed its impact on anaerobic respiration and CH4 production. In this study, we assessed the relationship between environmental parameters, organic matter quality, and potential greenhouse gas production under both oxic and anoxic conditions. We used samples from multiple depths and microtopographies within a temperate bog to capture peats with a range of decomposition states and botanical origins. A multiple regression model successfully predicted approximately 65% of the variance in carbon dioxide (CO2) production in oxic incubations. However, we found that the model was less successful in predicting anaerobic CO2 and CH4 production in anoxic incubations, explaining 31% and 42% of the variance in greenhouse gas production, respectively. These results suggest that biochemical composition has an important influence on potential CO2 production under oxic conditions, but exerts less influence on rates of anaerobic respiration and CH4 production. As climate change and drainage increase the oxygen exposure time of peats, organic matter quality will likely play an increasing role in determining the trajectory of CO2 emissions from peatlands.