Carbon Budget Of The Harvard Forest Long‐Term Ecological Research Site: Pattern, Process, And Response To Global Change

  • Sites: US-Ha1, US-Ha2
  • Publication Type: EJOUR
  • Authors: Finzi, A. C.; Giasson, M.; Barker Plotkin, A. A.; Aber, J. D.; Boose, E. R.; Davidson, E. A.; Dietze, M. C.; Ellison, A. M.; Frey, S. D.; Goldman, E.; Keenan, T. F.; Melillo, J. M.; Munger, J. W.; Nadelhoffer, K. J.; Ollinger, S. V.; Orwig, D. A.; Pederson, N.; Richardson, A. D.; Savage, K.; Tang, J.; Thompson, J. R.; Williams, C. A.; Wofsy, S. C.; Zhou, Z.; Foster, D. R.

  • 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 four questions: (i) where and how much C is presently stored in dominant forest types; (ii) what are current rates of C accrual and loss; (iii) what biotic and abiotic factors contribute to variability in these rates; and (iv) how has climate change affected the forest’s C cycle? 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 680–750 g C m-2 yr-1; belowground NPP contributed 38–47% of the total, but with large uncertainty. Mineral soil C measured in the same inventory plots in 1992 and 2013 were too heterogeneous to detect 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 until infestation by the hemlock woolly adelgid turned these stands into a net C source. Since 2000, NPP has increased by 26%. For the period 1992–2015, NEP increased 93%. The increase in mean annual temperature and growing season length alone accounted for ~30% of the increase in productivity. Interannual variations in GPP and NEP were also correlated with increases in red oak biomass, forest leaf area, and canopy-scale light-use efficiency. Compared to long-term global change experiments at the Harvard Forest, the C sink in regrowing biomass equaled or exceeded C cycle modifications imposed by soil warming, N saturation, and hemlock removal. Results of this synthesis and comparison to 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 biotic and abiotic disturbances increase.


  • Journal: Ecological Monographs
  • Funding Agency: National Science Foundation, LTER; DOE, AmeriFlux Management Project
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  • Publication Year: 2020/08/04
  • DOI: 10.1002/ecm.1423
  • https://doi.org/10.1002/ecm.1423