Soil Organic Carbon (SOC) Equilibrium and Model Initialisation Methods

an Application to the Rothamsted Carbon (RothC) Model

Nemo, K. Klumpp, K. Coleman, M. Dondini, K. Goulding, A. Hastings, Michael B. Jones, J. Leifeld, B. Osborne, M. Saunders, T. Scott, Y. A. Teh, P. Smith

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Carbon (C) emissions from anthropogenic land use have accelerated climate change. To reduce C emissions, dynamic models can be used to assess the impact of human drivers on terrestrial C sequestration. Model accuracy requires
correct initialisation, since incorrect initialisation can influence the results obtained. Therefore, we sought to improve the initialisation of a process-based SOC model, RothC, which can estimate the effect of climate and land-use change
on SOC. The most common initialisation involves running the model until equilibrium (‘spin-up run’), when the SOC pools stabilise (method 1). However, this method does not always produce realistic results. At our experimental sites, the observed SOC was not at equilibrium after 10 years, suggesting that the commonly used spin-up initialisation method assuming equilibrium might be improved. In addition to method 1, we tested two alternative initialisations for RothC that involved adjusting the total or individual SOC pool equilibrium
values by regulating the C input during the entire spin-up initialisation period (method 2) and initialising each SOC pool with recently measured SOC values obtained by SOC fractionation (method 3). Analysis of the simulation accuracy for each model initialisation, quantified using the root mean square error (RMSE), indicated that a variant of method 2 that involved adjusting the equilibrium total SOC to observed values (method 2-T) generally showed less variation in the
individual SOC pools and total SOC. Furthermore, as total SOC is the sum of all SOC pools, and because total SOC data are more readily available than the individual SOC pool data, we conclude that method 2-T is best for initialising RothC.
Original languageEnglish
Pages (from-to)215-229
Number of pages15
JournalEnvironmental Modeling & Assessment
Volume22
Issue number3
Early online date4 Nov 2016
DOIs
Publication statusPublished - Jun 2017

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organic carbon
carbon
soil
method
land use
carbon sequestration
fractionation
climate change

Keywords

  • SOC
  • RothC
  • model initialisation
  • agricultural management
  • ecosystem models
  • SOC fractionation

Cite this

Soil Organic Carbon (SOC) Equilibrium and Model Initialisation Methods : an Application to the Rothamsted Carbon (RothC) Model. / Nemo; Klumpp, K. ; Coleman, K.; Dondini, M.; Goulding, K.; Hastings, A.; Jones, Michael B.; Leifeld, J.; Osborne, B.; Saunders, M.; Scott, T.; Teh, Y. A.; Smith, P.

In: Environmental Modeling & Assessment, Vol. 22, No. 3, 06.2017, p. 215-229.

Research output: Contribution to journalArticle

Nemo ; Klumpp, K. ; Coleman, K. ; Dondini, M. ; Goulding, K. ; Hastings, A. ; Jones, Michael B. ; Leifeld, J. ; Osborne, B. ; Saunders, M. ; Scott, T. ; Teh, Y. A. ; Smith, P. / Soil Organic Carbon (SOC) Equilibrium and Model Initialisation Methods : an Application to the Rothamsted Carbon (RothC) Model. In: Environmental Modeling & Assessment. 2017 ; Vol. 22, No. 3. pp. 215-229.
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abstract = "Carbon (C) emissions from anthropogenic land use have accelerated climate change. To reduce C emissions, dynamic models can be used to assess the impact of human drivers on terrestrial C sequestration. Model accuracy requirescorrect initialisation, since incorrect initialisation can influence the results obtained. Therefore, we sought to improve the initialisation of a process-based SOC model, RothC, which can estimate the effect of climate and land-use changeon SOC. The most common initialisation involves running the model until equilibrium (‘spin-up run’), when the SOC pools stabilise (method 1). However, this method does not always produce realistic results. At our experimental sites, the observed SOC was not at equilibrium after 10 years, suggesting that the commonly used spin-up initialisation method assuming equilibrium might be improved. In addition to method 1, we tested two alternative initialisations for RothC that involved adjusting the total or individual SOC pool equilibriumvalues by regulating the C input during the entire spin-up initialisation period (method 2) and initialising each SOC pool with recently measured SOC values obtained by SOC fractionation (method 3). Analysis of the simulation accuracy for each model initialisation, quantified using the root mean square error (RMSE), indicated that a variant of method 2 that involved adjusting the equilibrium total SOC to observed values (method 2-T) generally showed less variation in theindividual SOC pools and total SOC. Furthermore, as total SOC is the sum of all SOC pools, and because total SOC data are more readily available than the individual SOC pool data, we conclude that method 2-T is best for initialising RothC.",
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