Abstract
The mechanisms controlling the extraordinarily slow carbon (C) mineralization rates characteristic of Sphagnum-rich peatlands ("bogs") are not fully understood, despite decades of research on this topic. Soluble phenolic compounds have been invoked as potentially significant contributors to bog peat recalcitrance due to their affinity to slow microbial metabolism and cell growth. Despite this potentially significant role, the effects of soluble phenolic compounds on bog peat C mineralization remain unclear. We analyzed this effect by manipulating the concentration of free soluble phenolics in anaerobic bog and fen peat incubations using water-soluble polyvinylpyrrolidone ("PVP"), a compound that binds with and inactivates phenolics, preventing phenolic-enzyme interactions. CO2 and CH4 production rates (end-products of anaerobic C mineralization) generally correlated positively with PVP concentration following Michaelis-Menten (M.M.) saturation functions. Using M.M. parameters, we estimated that the extent to which phenolics inhibit anaerobic CO2 production was significantly higher in the bog-62 ± 16%-than the fen-14 ± 4%. This difference was found to be more substantial with regards to methane production-wherein phenolic inhibition for the bog was estimated at 54 ± 19%, while the fen demonstrated no apparent inhibition. Consistent with this habitat difference, we observed significantly higher soluble phenolic content in bog vs. fen pore-water. Together, these findings suggest that soluble phenolics could contribute to bogs' extraordinary recalcitrance and high (relative to other peatland habitats) CO2:CH4 production ratios.
Highlights
MethodsUnder the IsoGenie Project, our team maintains field permits with the Abisko Scientific Research Station and its parent organization, the Swedish Polar Research Secretariat, to collect samples from Stordalen Mire
GHGc production rates generally increased with PVP concentration
Fen 10 ± 4 14 ± 4 N/Ac a%Phenolic Inhibition estimates were calculated via Eq12. bCtot represents the sum of CO2 and CH4 production rates. cAs PVP concentration had no significant impact on CH4 production in fen peat, %Inhibition could not be determined
Summary
Under the IsoGenie Project, our team maintains field permits with the Abisko Scientific Research Station and its parent organization, the Swedish Polar Research Secretariat, to collect samples from Stordalen Mire. Peat for the laboratory incubation experiments was obtained from two sites: one bog (19.04923 ̊N, 68.35559 ̊W) and one fen (19.04620 ̊N, 68.35443 ̊W). These sites were selected because they were (1) determined to be representative of the plant community and hydrologic conditions of their respective habitats and (2) within 50 m of one another. Each core was sectioned using a razor blade and a subsection from 9–19 cm depth was set aside for incubation analysis. This depth range was selected because at this depth peat is generally below the water table, facilitating anaerobic decomposition (which is the focus of this study). The peat was stored at -20 ̊C from the point of collection up until the experiment start date—20 and 29 months for bog and fen, respectively
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