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Understanding the uncertainty in global forest carbon turnover

Pugh, Thomas A.M. LU ; Rademacher, Tim ; Shafer, Sarah L. ; Steinkamp, Jorg ; Barichivich, Jonathan ; Beckage, Brian ; Haverd, Vanessa ; Harper, Anna ; Heinke, Jens and Nishina, Kazuya , et al. (2020) In Biogeosciences 17(15). p.3961-3989
Abstract

The length of time that carbon remains in forest biomass is one of the largest uncertainties in the global carbon cycle, with both recent historical baselines and future responses to environmental change poorly constrained by available observations. In the absence of large-scale observations, models used for global assessments tend to fall back on simplified assumptions of the turnover rates of biomass and soil carbon pools. In this study, the biomass carbon turnover times calculated by an ensemble of contemporary terrestrial biosphere models (TBMs) are analysed to assess their current capability to accurately estimate biomass carbon turnover times in forests and how these times are anticipated to change in the future. Modelled baseline... (More)

The length of time that carbon remains in forest biomass is one of the largest uncertainties in the global carbon cycle, with both recent historical baselines and future responses to environmental change poorly constrained by available observations. In the absence of large-scale observations, models used for global assessments tend to fall back on simplified assumptions of the turnover rates of biomass and soil carbon pools. In this study, the biomass carbon turnover times calculated by an ensemble of contemporary terrestrial biosphere models (TBMs) are analysed to assess their current capability to accurately estimate biomass carbon turnover times in forests and how these times are anticipated to change in the future. Modelled baseline 1985-2014 global average forest biomass turnover times vary from 12.2 to 23.5 years between TBMs. TBM differences in phenological processes, which control allocation to, and turnover rate of, leaves and fine roots, are as important as tree mortality with regard to explaining the variation in total turnover among TBMs. The different governing mechanisms exhibited by each TBM result in a wide range of plausible turnover time projections for the end of the century. Based on these simulations, it is not possible to draw robust conclusions regarding likely future changes in turnover time, and thus biomass change, for different regions. Both spatial and temporal uncertainty in turnover time are strongly linked to model assumptions concerning plant functional type distributions and their controls. Thirteen model-based hypotheses of controls on turnover time are identified, along with recommendations for pragmatic steps to test them using existing and novel observations. Efforts to resolve uncertainty in turnover time, and thus its impacts on the future evolution of biomass carbon stocks across the world's forests, will need to address both mortality and establishment components of forest demography, as well as allocation of carbon to woody versus non-woody biomass growth.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Biogeosciences
volume
17
issue
15
pages
29 pages
publisher
Copernicus GmbH
external identifiers
  • scopus:85089708739
ISSN
1726-4170
DOI
10.5194/bg-17-3961-2020
language
English
LU publication?
yes
id
42a54d8c-eb22-4312-b6b0-93bc61694449
date added to LUP
2020-11-17 13:18:07
date last changed
2023-01-11 14:41:34
@article{42a54d8c-eb22-4312-b6b0-93bc61694449,
  abstract     = {{<p>The length of time that carbon remains in forest biomass is one of the largest uncertainties in the global carbon cycle, with both recent historical baselines and future responses to environmental change poorly constrained by available observations. In the absence of large-scale observations, models used for global assessments tend to fall back on simplified assumptions of the turnover rates of biomass and soil carbon pools. In this study, the biomass carbon turnover times calculated by an ensemble of contemporary terrestrial biosphere models (TBMs) are analysed to assess their current capability to accurately estimate biomass carbon turnover times in forests and how these times are anticipated to change in the future. Modelled baseline 1985-2014 global average forest biomass turnover times vary from 12.2 to 23.5 years between TBMs. TBM differences in phenological processes, which control allocation to, and turnover rate of, leaves and fine roots, are as important as tree mortality with regard to explaining the variation in total turnover among TBMs. The different governing mechanisms exhibited by each TBM result in a wide range of plausible turnover time projections for the end of the century. Based on these simulations, it is not possible to draw robust conclusions regarding likely future changes in turnover time, and thus biomass change, for different regions. Both spatial and temporal uncertainty in turnover time are strongly linked to model assumptions concerning plant functional type distributions and their controls. Thirteen model-based hypotheses of controls on turnover time are identified, along with recommendations for pragmatic steps to test them using existing and novel observations. Efforts to resolve uncertainty in turnover time, and thus its impacts on the future evolution of biomass carbon stocks across the world's forests, will need to address both mortality and establishment components of forest demography, as well as allocation of carbon to woody versus non-woody biomass growth.</p>}},
  author       = {{Pugh, Thomas A.M. and Rademacher, Tim and Shafer, Sarah L. and Steinkamp, Jorg and Barichivich, Jonathan and Beckage, Brian and Haverd, Vanessa and Harper, Anna and Heinke, Jens and Nishina, Kazuya and Rammig, Anja and Sato, Hisashi and Arneth, Almut and Hantson, Stijn and Hickler, Thomas and Kautz, Markus and Quesada, Benjamin and Smith, Benjamin and Thonicke, Kirsten}},
  issn         = {{1726-4170}},
  language     = {{eng}},
  month        = {{08}},
  number       = {{15}},
  pages        = {{3961--3989}},
  publisher    = {{Copernicus GmbH}},
  series       = {{Biogeosciences}},
  title        = {{Understanding the uncertainty in global forest carbon turnover}},
  url          = {{http://dx.doi.org/10.5194/bg-17-3961-2020}},
  doi          = {{10.5194/bg-17-3961-2020}},
  volume       = {{17}},
  year         = {{2020}},
}