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Harvard Forest Symposium Abstract 2015

  • Title: The secret lives of roots: seasonality and partitioning of belowground C to three Harvard Forest stands
  • Primary Author: Rose Abramoff (Boston University)
  • Additional Authors: Adrien Finzi (Boston University)
  • Abstract:

    Fine roots are a seasonally dynamic carbon (C) pool that accounts for a large proportion of net primary production. Roots are the main conduit by which C is transported belowground and incorporated into soil organic matter. As such root growth, mortality and exudation are an important component of biogeochemical cycles, yet data on the timing and partitioning of C to these processes are rare. The objective of this study is to estimate the phenology and partitioning of C belowground across the growing season in stands dominated by red oak (Quercus rubra), white ash (Fraxinus americana), and eastern hemlock (Tsuga canadensis) on the Prospect Hill tract of Harvard Forest. We leveraged data from the Harvard Forest archive and used field sampling to estimate total belowground C flux (TBCF).



    Fine root growth and respiration were both positively correlated with temperature, but differed in their phenology. Root phenology was characterized by multiple flushes of growth and mortality, whereas root respiration was unimodal across the growing season. Of the three stands, white ash had the highest rate mass-specific fine root respiration, reflecting the high tissue [N] in ash roots. The fast rates of N cycling in ash stands is exacerbated by the invasive European earthworm (Lumbricus terrestris).



    Red oak stands allocated C belowground earlier in the season compared to eastern hemlock. TBCF was highest in the red oak stand, consistent with the observed increase in abundance of red oak at Harvard Forest over the past 30 years. TBCF was lowest in the eastern hemlock stand due to a decline in allocation to root production over the study period. This decline is coincident with the arrival and spread of the hemlock woolly adelgid in this stand. This study elucidates the seasonal partitioning of belowground C within the context of long-term stand dynamics.

  • Research Category: Soil Carbon and Nitrogen Dynamics