Does energy, water and gas transport determine carbon sequestration and methane release in anoxic peatland soils? - Testing a novel hypothesis.

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Northern peatlands represent an important global carbon stock and source of methane to the atmosphere. The long-term fate of carbon in these environments under changed hydrologic conditions is thus of considerable scientific importance. Our knowledge of peatland carbon cycling is especially deficient with respect to the effects of energy-, water-, and gas transport that may ultimately control carbon sequestration and methane release. We will address this research gap using peat soil model systems in which geochemical conditions, water and gas transport can be controlled and the effects on key processes in anaerobic peat decomposition and methane release be quantified. Preliminary work documented that absence of water transport can result in an inactivation of peat decomposition and methane release. The quantitative effects of increased rates of water and gas transport on key processes in peat decomposition urgently need to be addressed and the effect of physical and chemical conditions to be identified. Specifically, the project will analyze:- how accumulation of carbon dioxide and methane in peats diminishes methane release and anaerobic respiration and whether such effects can be attributed to a lack of free energy,- how such product inhibition is controlled by geochemical and physical factors, such as temperature, soil acidity and chemical quality of the peat,- how enzymatic activity responds to accumulation of carbon dioxide and methane, and geochemical and physical factors,- how and to what extent rates of solute transport and ebullition control methanogenic decomposition in peats, - if residence time of water in peats can be used to predict rates of anaerobic peat decomposition in peatlands.Apart from closing an important knowledge gap, the project provides process-level data for the improvement of ecosystem models that aim at understanding and predicting the response of peatland carbon cycling to changing hydrologic conditions. Progress in this direction will allow for a more accurate analysis of climate change impacts on this important type of ecosystem in future studies.