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Harvard Forest REU Symposium Abstract 2016

  • Title: Assessing Manganese Dynamics throughout a Moisture Gradient in a Temperate Forest
  • Author: Megan E Wilcots (Columbia University in the City of New York)
  • Abstract:

    Soils are an important carbon sink, holding up to three times more carbon than vegetation and atmosphere combined. Changes to this vast carbon reservoir could thus have larger ramifications on the global carbon cycle. Previous studies have shown that manganese (Mn) content of litter is positively correlated with litter decomposition rates. What remains elusive is the extent decomposition rates depend on Mn redox cycling, which (re)generates bioavailable and reactive forms of Mn3+ and Mn4+, both of which act as oxidizers in decomposition. Here, we examined Mn redox cycling across a moisture gradient in a temperate, deciduous forest soil, and related our findings to decomposition rates. We determined total Mn content, bioavailability, and Mn3+, 4+ content using chemical extractions on four soil horizons (litter, organic, A, and C horizons). We find that Mn3+ content, as a ratio of Mntotal, is positively correlated with soil moisture. This indicates that Mn redox cycling is more prominent in wetter soils, particularly in the organic and mineral layers. In a laboratory incubation study, we assessed the impact of redox cycles on decomposition by measuring respiration on soil cores amended with manganese oxides and subjected to wetting and drying cycles. The cores undergoing the wet/dry cycles had significantly larger decomposition rates than the continuously incubated cores. Current climate projections predict more intense precipitation events in the Northeast United States, rendering future soil moisture more variable. We would expect an increase in soil decomposition and a decrease in soil carbon storage with these precipitation changes.

  • Research Category: Soil Carbon and Nitrogen Dynamics

  • Figures:
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