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Harvard Forest Symposium Abstract 2019

  • Title: Carbon Budget of the Harvard Forest Long-Term Ecological Research Site: Pattern, Process and Response to Global Change
  • Primary Author: Audrey Barker Plotkin (Harvard Forest)
  • Additional Authors: John Aber (University of New Hampshire - Main Campus); Emery Boose (Harvard Forest); Eric Davidson (University of Maryland - Center for Environmental Science); Michael Dietze (Boston University); Aaron Ellison (Harvard Forest); Adrien Finzi (Boston University); David Foster (Harvard Forest); Serita Frey (University of New Hampshire - Main Campus); Marc-Andre Giasson (Boston University); Trevor Keenan (Harvard); Jerry Melillo (Marine Biological Laboratory); Knute Nadelhoffer (University of Michigan (all campuses)); Scott Ollinger (University of New Hampshire - Main Campus); David Orwig (Harvard Forest); Andrew Richardson (Northern Arizona University); Kathleen Savage (Woods Hole Research Center); Jim Tang (Marine Biological Laboratory); Jonathan Thompson (Harvard Forest); Christopher Williams (Clark University); Steven Wofsy (Harvard University)
  • Abstract:

    How, where, and why carbon (C) moves into and out of an ecosystem
    through time are long-standing questions in biogeochemistry. Here, we
    bring together hundreds of thousands of C-cycle observations at the
    Harvard Forest in central Massachusetts, USA, a mid-latitude landscape
    dominated by 80–120-year-old closed-canopy forests. These data
    answered six questions: (i) where and how much C is presently stored in
    dominant forest types; (ii) what are current rates of C accrual or loss;
    (iii) what biotic and abiotic factors contribute to variability in these rates;
    (iv) is climate change affecting the forest’s C cycle; (v) how do rates of C
    accrual from regrowth compare to C cycle modifications imposed by
    global change experiments; (vi) are C stocks and accrual rates at the
    Harvard Forest representative of the surrounding ecoregion? Harvard
    Forest is an active C sink resulting from forest regrowth following land
    abandonment. Soil and tree biomass comprise nearly equal portions of
    existing C stocks. Net primary production (NPP) averaged 750–970 g C
    m-2 yr-1; belowground NPP contributed 30–60% of the total. Inventory
    data suggest no change in soil-C pools; however, radiocarbon data
    suggest a small but persistent sink of 10–30 g C m-2 yr-1. Net ecosystem
    production (NEP) in hardwood stands averaged ~300 g C m-2 yr-1. NEP
    in hemlock-dominated forests averaged ~450 g C m-2 yr-1 prior to
    infestation by the hemlock woolly adelgid (HWA) in 2013, and then
    became a net C source. Stand dynamics and climate change in the last
    three decades enhanced the C sink in hardwood stands; NPP increased
    26% between 2000–2014 (p = 0.02) and NEP increased 93% between
    1992–2015 (p = 0.13). The C sink in regrowing biomass equaled or
    exceeded C cycle modifications imposed by global change experiments.
    Median forest biomass in the surrounding ecoregion was only 78% of
    that at the Harvard Forest due to higher timber harvesting rates across
    the region. Data and simulation models suggest that forests across the
    region are likely to accrue C for decades to come, but may be disrupted
    if the frequency or severity of disturbance increases.

  • Research Category: Soil Carbon and Nitrogen Dynamics; Large Experiments and Permanent Plot Studies; Forest-Atmosphere Exchange

  • Figures:
  • Figure1a.jpg