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Harvard Forest REU Symposium Abstract 2017

  • Title: The Role of Manganese on Litter Decomposition Along an Oxic-anoxic Interface
  • Author: Sarah A Pardi (Loyola Marymount University)
  • Abstract:

    Soils play an important role in carbon cycling, releasing three times more CO2 emissions into the atmosphere than anthropogenic factors through forest floor litter decomposition. Studies have shown that manganese concentration is positively correlated to the rate of litter decomposition. Using extracellular enzymes such as oxidase and peroxidases, fungi can oxidize Mn2+ to Mn3+, a soluble and potent oxidant that decomposes lignin. At present, the environmental factors influencing the rates of Mn3+ formation and its use in litter decomposition in soils are not known. Here we examined the oxidation potential and the forms of Mn along a soil moisture gradient. We hypothesized that Mn3+ concentrations would be greatest along oxic-anoxic interfaces. To test this hypothesis, we found that soils with intermediate moisture, characterized by clear oxic-anoxic transitions in the A horizon, had the greatest oxidative potential. Our results also showed that this soil layer had the highest concentrations of pyrophosphate extractable Mn3+. Furthermore, the largest quantities of extractable soil organic carbon were generated in this horizon, indicating greater decomposition. Our results suggest that the potential for Mn3+ formation is most pronounced in the suboxic zone, where enhanced decomposition may be responsible for the production of soluble compounds. As precipitation and temperature patterns change in New England, soil moisture is gong to change as well. How climate change alters the natural Mn cycle will have to be taken into consideration if we want to estimate the soil carbon balance and predict the release of CO2 in the future.

  • Research Category: Soil Carbon and Nitrogen Dynamics