Soil organic carbon in peatlands is an important terrestrial carbon pool that stores 15-30% of the world's soil carbon. Peatlands are typically considered carbon sinks because they maintain anaerobic conditions that impede microbial mineralization of CO2. In the face of a warming climate, environmental changes may induce peatlands into aerobic conditions. Predictions estimate that such events would lead to a rapid and large release of CO2 into the atmosphere, equivalent to 34-46% of current atmospheric carbon. Recent work has shown that minerals, particularly iron-bearing minerals, may impede this process by protecting organic carbon from microbial degradation. Here, we focused on quantifying the extent to which iron minerals inhibit organic carbon degradation under aerobic conditions. To do so, we isolated dissolved organic carbon from a bog in an old-growth boreal forest. We exposed this carbon to the native microbial population from the bog and measured CO2 and dissolved organic carbon concentrations over time in aerobic conditions with different amendments of colloidal iron oxides. These experiments provide insights into how iron minerals may inhibit microbial carbon oxidation in aerobic conditions. To better simulate natural environments, we intend to further study this process under reducing conditions and over multiple redox cycles.

Role of iron minerals in preserving organic carbon during aerobic degradation

251st National Meeting (2016)

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