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Importance of vegetation dynamics for future terrestrial carbon cycling

Ahlström, Anders LU ; Xia, Jianyang; Arneth, Almut; Luo, Yiqi and Smith, Benjamin LU (2015) In Environmental Research Letters 10(5). p.054019-054019
Abstract
Terrestrial ecosystems currently sequester about one third of anthropogenic CO 2 emissions each year, an important ecosystem service that dampens climate change. The future fate of this net uptake of CO 2 by land based ecosystems is highly uncertain. Most ecosystem models used to predict the future terrestrial carbon cycle share a common architecture, whereby carbon that enters the system as net primary production (NPP) is distributed to plant compartments, transferred to litter and soil through vegetation turnover and then re-emitted to the atmosphere in conjunction with soil decomposition. However, while all models represent the processes of NPP and soil decomposition, they vary greatly in their representations of vegetation turnover and... (More)
Terrestrial ecosystems currently sequester about one third of anthropogenic CO 2 emissions each year, an important ecosystem service that dampens climate change. The future fate of this net uptake of CO 2 by land based ecosystems is highly uncertain. Most ecosystem models used to predict the future terrestrial carbon cycle share a common architecture, whereby carbon that enters the system as net primary production (NPP) is distributed to plant compartments, transferred to litter and soil through vegetation turnover and then re-emitted to the atmosphere in conjunction with soil decomposition. However, while all models represent the processes of NPP and soil decomposition, they vary greatly in their representations of vegetation turnover and the associated processes governing mortality, disturbance and biome shifts. Here we used a detailed second generation dynamic global vegetation model with advanced representation of vegetation growth and mortality, and the associated turnover. We apply an emulator that describes the carbon flows and pools exactly as in simulations with the full model. The emulator simulates ecosystem dynamics in response to 13 different climate or Earth system model simulations from the Coupled Model Intercomparison Project Phase 5 ensemble under RCP8.5 radiative forcing. By exchanging carbon cycle processes between these 13 simulations we quantified the relative roles of three main driving processes of the carbon cycle; (I) NPP, (II) vegetation dynamics and turnover and (III) soil decomposition, in terms of their contribution to future carbon (C) uptake uncertainties among the ensemble of climate change scenarios. We found that NPP, vegetation turnover (including structural shifts, wild fires and mortality) and soil decomposition rates explained 49%, 17% and 33%, respectively, of uncertainties in modelled global C-uptake. Uncertainty due to vegetation turnover was further partitioned into stand-clearing disturbances (16%), wild fires (0%), stand dynamics (7%), reproduction (10%) and biome shifts (67%) globally. We conclude that while NPP and soil decomposition rates jointly account for 83% of future climate induced C-uptake uncertainties, vegetation turnover and structure, dominated by biome shifts, represent a significant fraction globally and regionally (tropical forests: 40%), strongly motivating their representation and analysis in future C-cycle studies. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Environmental Research Letters
volume
10
issue
5
pages
054019 - 054019
publisher
IOP Publishing
external identifiers
  • wos:000355201800021
  • scopus:84930226901
ISSN
1748-9326
DOI
10.1088/1748-9326/10/5/054019
language
English
LU publication?
yes
id
243e6563-7960-42be-9a36-835404a75e63 (old id 5432989)
alternative location
http://stacks.iop.org/1748-9326/10/i=5/a=054019
date added to LUP
2015-05-27 14:58:56
date last changed
2017-10-22 04:11:53
@article{243e6563-7960-42be-9a36-835404a75e63,
  abstract     = {Terrestrial ecosystems currently sequester about one third of anthropogenic CO 2 emissions each year, an important ecosystem service that dampens climate change. The future fate of this net uptake of CO 2 by land based ecosystems is highly uncertain. Most ecosystem models used to predict the future terrestrial carbon cycle share a common architecture, whereby carbon that enters the system as net primary production (NPP) is distributed to plant compartments, transferred to litter and soil through vegetation turnover and then re-emitted to the atmosphere in conjunction with soil decomposition. However, while all models represent the processes of NPP and soil decomposition, they vary greatly in their representations of vegetation turnover and the associated processes governing mortality, disturbance and biome shifts. Here we used a detailed second generation dynamic global vegetation model with advanced representation of vegetation growth and mortality, and the associated turnover. We apply an emulator that describes the carbon flows and pools exactly as in simulations with the full model. The emulator simulates ecosystem dynamics in response to 13 different climate or Earth system model simulations from the Coupled Model Intercomparison Project Phase 5 ensemble under RCP8.5 radiative forcing. By exchanging carbon cycle processes between these 13 simulations we quantified the relative roles of three main driving processes of the carbon cycle; (I) NPP, (II) vegetation dynamics and turnover and (III) soil decomposition, in terms of their contribution to future carbon (C) uptake uncertainties among the ensemble of climate change scenarios. We found that NPP, vegetation turnover (including structural shifts, wild fires and mortality) and soil decomposition rates explained 49%, 17% and 33%, respectively, of uncertainties in modelled global C-uptake. Uncertainty due to vegetation turnover was further partitioned into stand-clearing disturbances (16%), wild fires (0%), stand dynamics (7%), reproduction (10%) and biome shifts (67%) globally. We conclude that while NPP and soil decomposition rates jointly account for 83% of future climate induced C-uptake uncertainties, vegetation turnover and structure, dominated by biome shifts, represent a significant fraction globally and regionally (tropical forests: 40%), strongly motivating their representation and analysis in future C-cycle studies.},
  author       = {Ahlström, Anders and Xia, Jianyang and Arneth, Almut and Luo, Yiqi and Smith, Benjamin},
  issn         = {1748-9326},
  language     = {eng},
  number       = {5},
  pages        = {054019--054019},
  publisher    = {IOP Publishing},
  series       = {Environmental Research Letters},
  title        = {Importance of vegetation dynamics for future terrestrial carbon cycling},
  url          = {http://dx.doi.org/10.1088/1748-9326/10/5/054019},
  volume       = {10},
  year         = {2015},
}