Research Article: Microbial organic matter reduction in a peatland soil: the importance of water-table level

Abstract

Peatlands are among the most important ecosystems in the global carbon cycle. These wetlands store roughly one-third of the terrestrial soil organic matter (SOM) and are important sources of the potent greenhouse gas methane (CH4) to the atmosphere. Understanding carbon cycling, and in particular CH4 dynamics, within peatland soils has important implications for understanding biosphere-climate feedbacks. There is mounting evidence that under anaerobic conditions microbes can reduce organic terminal electron acceptors in place of oxygen in peatland soils. This microbial respiration of SOM can dominate anaerobic decomposition and competitively suppress CH4 production, but the controls of this process are not well understood. We explored SOM reduction in a peatland soil using laboratory microcosms that allowed for water-table level manipulations. Measurements of electron shuttling demonstrate that SOM was progressively reduced following flooding and was quickly re-oxidized following water-table draw down, with impacts on CH4 production in this peat soil. These results highlight that successive reduction and oxidization of SOM from changes in water-table level may be an important control on anaerobic carbon cycling in peatlands.