LINKING DISSOLVED ORGANIC CARBON DYNAMICS WITH TERMINAL REMINERALIZATION PROCESSES IN PEATLANDS

Past studies of the carbon cycle in peatlands have generally emphasized terminal decomposition of peatland carbon largely through aerobic respiration and methanogenesis (i.e., production of the greenhouse gasses CO₂ and CH₄). In contrast, far less is known about the initial steps in the decomposition of peat carbon, e.g., the breakdown of complex polyphenolic compounds, and the overall production and consumption of dissolved organic carbon (DOC) compounds during decomposition that ultimately produces these gaseous end-products. The slight imbalance between DOC production and consumption often results in DOC export from peatlands, and this can represent an important loss term in peatland carbon budgets, often-times rivaling methane and CO₂ gas fluxes. In this talk we will describe a simple model for organic carbon remineralization in peatlands that links DOC production and consumption with terminal decomposition processes such as methanogenesis (CO₂ reduction and acetate fermentation), acetogenesis, and acetate oxidation coupled to humic acid reduction. The model will be applied to published peat incubation studies as well as field results to examine the controls on carbon cycling in contrasting peat systems (e.g., bogs versus fens). Preliminary work with the model suggests acetate oxidation coupled to humic acid reduction could play some role in helping to explain imbalances between methane and CO₂ production seen in some peats.