@article{7af84d3f24074ad68cb2b40eb5e466f5,
title = "Carbon budget of the Harvard Forest Long-Term Ecological Research site: pattern, process, and response to global change",
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-yr-old closed-canopy forests. These data answered four questions: (1) where and how much C is presently stored in dominant forest types; (2) what are current rates of C accrual and loss; (3) what biotic and abiotic factors contribute to variability in these rates; and (4) how has climate change affected the forest{\textquoteright}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 was 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 increases.",
keywords = "belowground production, carbon cycling, climate change, disturbance, ecosystem ecology, eddy covariance, forest ecosystems, gross primary production, long-term ecological research, net primary production, permanent plots",
author = "Finzi, {Adrien C.} and Giasson, {Marc Andr{\'e}} and {Barker Plotkin}, {Audrey A.} and Aber, {John D.} and Boose, {Emery R.} and Davidson, {Eric A.} and Dietze, {Michael C.} and Ellison, {Aaron M.} and Frey, {Serita D.} and Evan Goldman and Keenan, {Trevor F.} and Melillo, {Jerry M.} and Munger, {J. William} and Nadelhoffer, {Knute J.} and Ollinger, {Scott V.} and Orwig, {David A.} and Neil Pederson and Richardson, {Andrew D.} and Kathleen Savage and Jianwu Tang and Thompson, {Jonathan R.} and Williams, {Christopher A.} and Wofsy, {Steven C.} and Zaixing Zhou and Foster, {David R.}",
note = "Funding Information: Adrien Finzi, Marc‐Andr{\'e} Giasson, and Audrey Barker Plotkin are co‐first authors of this paper; each contributed equally to the conceptualization of ideas, preparation of data, data analysis, and writing. This research was supported in part by the National Science Foundation Harvard Forest Long‐Term Ecological Research Program (since 1988; NSF‐DEB grant numbers 8811764, 9411975, 0080592, 0620443, and 1237491). Flux tower and associated plot measurements were additionally supported by the AmeriFlux Management Project with funding by the U.S. Department of Energy{\textquoteright}s Office of Science under Contract No. DE‐AC02‐05CH11231, and previously through the DOE NIGEC program. Collection of soil carbon data from the soil warming plots was supported by the NSF–Ecosystem Studies (DEB0447967) and the NSF Long‐Term Research in Environmental Biology (DEB1456610) Programs. Additional support for A. C. Finzi and M.‐A. Giasson was provided by the U.S. Department of Energy–Terrestrial Ecosystems Science (DE‐SC0006741). T. F. Keenan acknowledges support by the Director, Office of Science, Office of Biological and Environmental Research of the U.S. Department of Energy under Contract DE‐AC02‐05CH11231 as part of the RGCM RuBiSCo SFA. S. V. Ollinger and Z. Zhou acknowledge support from NSF grant number 1638688, NASA grant numbers NNX08AG14G, NNX14AJ18G, and NNX11AB88G, and USDA‐NIFA grant number 1006997. N. Pederson acknowledges support for the tree‐ring work from NSF EF‐1241930. C. A. Williams acknowledges financial support from NASA{\textquoteright}s Carbon Monitoring System program (NNH14ZDA001N‐CMS) under award NNX14AR39G. We thank Brett Butler for helping to coordinate access to FIA plot locations pursuant to a Memorandum of Understanding 09MU11242305123 between the U.S. Forest Service and Harvard University. Thanks to Elizabeth Nicoll for contributing to data compilation, and to Lo{\"i}c D{\textquoteright}Orangeville for providing the processed Hemlock Tower dendrometer band data. Finally, the authors appreciate the helpful suggestions from anonymous reviewers on a previous version of the manuscript. Funding Information: Adrien Finzi, Marc-Andr{\'e} Giasson, and Audrey Barker Plotkin are co-first authors of this paper; each contributed equally to the conceptualization of ideas, preparation of data, data analysis, and writing. This research was supported in part by the National Science Foundation Harvard Forest Long-Term Ecological Research Program (since 1988; NSF-DEB grant numbers 8811764, 9411975, 0080592, 0620443, and 1237491). Flux tower and associated plot measurements were additionally supported by the AmeriFlux Management Project with funding by the U.S. Department of Energy{\textquoteright}s Office of Science under Contract No. DE-AC02-05CH11231, and previously through the DOE NIGEC program. Collection of soil carbon data from the soil warming plots was supported by the NSF–Ecosystem Studies (DEB0447967) and the NSF Long-Term Research in Environmental Biology (DEB1456610) Programs. Additional support for A. C. Finzi and M.-A. Giasson was provided by the U.S. Department of Energy–Terrestrial Ecosystems Science (DE-SC0006741). T. F. Keenan acknowledges support by the Director, Office of Science, Office of Biological and Environmental Research of the U.S. Department of Energy under Contract DE-AC02-05CH11231 as part of the RGCM RuBiSCo SFA. S. V. Ollinger and Z. Zhou acknowledge support from NSF grant number 1638688, NASA grant numbers NNX08AG14G, NNX14AJ18G, and NNX11AB88G, and USDA-NIFA grant number 1006997. N. Pederson acknowledges support for the tree-ring work from NSF EF-1241930. C. A. Williams acknowledges financial support from NASA{\textquoteright}s Carbon Monitoring System program (NNH14ZDA001N-CMS) under award NNX14AR39G. We thank Brett Butler for helping to coordinate access to FIA plot locations pursuant to a Memorandum of Understanding 09MU11242305123 between the U.S. Forest Service and Harvard University. Thanks to Elizabeth Nicoll for contributing to data compilation, and to Lo{\"i}c D{\textquoteright}Orangeville for providing the processed Hemlock Tower dendrometer band data. Finally, the authors appreciate the helpful suggestions from anonymous reviewers on a previous version of the manuscript. Publisher Copyright: {\textcopyright} 2020 by the Ecological Society of America",
year = "2020",
month = nov,
day = "1",
doi = "10.1002/ecm.1423",
language = "English (US)",
volume = "90",
journal = "Ecological Monographs",
issn = "0012-9615",
publisher = "Ecological Society of America",
number = "4",
}