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Harvard Forest REU Symposium Abstract 2015

  • Title: Bounding Error for Total Carbon Stock Estimates in Harvard Forest Organic Soil
  • Author: Forrest Lewis (Harvard College (Harvard University))
  • Abstract:

    The terrestrial biosphere serves a fundamental role in the global carbon cycle by releasing and absorbing greenhouse gases. At the Harvard Forest, a deciduous forest in Central Massachusetts, biometric measurements have quantified above-ground organic carbon mass, but soil carbon has been less studied. In June-July 2015, I randomly selected 7 of 34 biometric plots from the footprint of the Environmental Measurement Station (EMS) Tower based on tree species variability to sample for soil organic matter (SOM). The cores, which were paired with samples from the 2014 summer survey to minimize spatial variability, were dried, sieved, root picked, ground, and ashed to determine SOM. The organic layer is defined as greater than 40% SOM and is traditionally isolated by separating cores at the point of color and textural change that indicates the mineral layer. Due to difficulty in delineating the organic and mineral layers, previous studies appear to underestimate the total soil carbon stock at the Harvard Forest. The 2014 summer survey estimated 36.70 MgC/ha in the organic layer, but my collocated measurements found 42.03 ± 1.04 MgC/ha. Using updated methods that allow for a more precise delineation as well as upper and lower bounds, changes over 1.04 MgC/ha can be detected on yearly and decadal time scales. By repeating this more precise way of constraining total carbon values, we can ascertain interannual variability in the organic layer carbon stock, which could shed light into the global carbon budget.

  • Research Category: Soil Carbon and Nitrogen Dynamics

  • Figures:
  • Total Carbon Error Bounds Per Core.pdf