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Dynamics of forest carbon stocks, fires, and harvest under changing climatic conditions in the U.S. during the 20th century
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  • Andreas Magerl,
  • Simone Gingrich,
  • Sarah Matej,
  • Geoff Cunfer,
  • Matthew Forrest,
  • Christian Lauk,
  • Stefan Schlaffer,
  • Florian Weidinger,
  • Cody Yuskiw,
  • Karlheinz Erb
Andreas Magerl
University of Natural Resources and Life Sciences, Vienna

Corresponding Author:[email protected]

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Simone Gingrich
University of Natural Resources and Life Sciences, Vienna
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Sarah Matej
Institute of Social Ecology
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Geoff Cunfer
Department of History
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Matthew Forrest
Senckenberg Gesellschaft für Naturforschung
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Christian Lauk
University of Natural Resources and Life Sciences, Vienna
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Stefan Schlaffer
Vienna University of Technology
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Florian Weidinger
University of Natural Resources and Life Sciences, Vienna
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Cody Yuskiw
College of Law
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Karlheinz Erb
University of natural resources and life sciences Vienna
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Abstract

Wildfires and land use play a central role in the long-term carbon (C) dynamics of forested ecosystems of the United States. Important processes include fire suppression during the 20th century and a recent increase in fire activity, partly due to climatic extreme events. Although the historical fire narrative in the U.S. is well understood, its links to changes in forest biomass, resource use and consumption remain understudied. We reconstruct long-term trends in biomass burned, and biomass use by humans, integrating various data sources at different scales (national scale 1926-2017, regional level 1941-2017). We investigate the linear correlation of wildfires and forest biomass C stocks in comparison to forest uses, i.e., the extraction of woody biomass and forest grazing, and potential net primary production (NPPpot). During the 20th century, the reduction in burned biomass and increase in NPPpot coincide with forest regrowth in the Eastern U.S., allowing for increased wood harvest. Only in the Western U.S. these dynamics are less pronounced, indicating that forest fires and biomass harvest were less decisive factors for forest C stock developments in this section. In recent decades, linkages between forest change and wildfires are less straight-forward in all regions, indicating that past fire suppression levels are less efficient in present-day forests. Instead, the reduction of harvest in 3 of 4 regions was correlated to stock increase. We conclude that under changing climate, present-day fire and forest management practices might be unsuitable for ensuring both additional forest C sink potential and expanded wood use.