Visiting dark sides of model simulation of carbon stocks in European temperate agricultural soils: allometric function and model initialization

A - Papers appearing in refereed journals

Taghizadeh-Toosi, A., Cong, W-F., Eriksen, J., Mayer, J., Olesen, J. E., Keel, S. G., Glendining, M. J., Katterer, T. and Christensen, B. T. 2020. Visiting dark sides of model simulation of carbon stocks in European temperate agricultural soils: allometric function and model initialization. Plant and Soil.

AuthorsTaghizadeh-Toosi, A., Cong, W-F., Eriksen, J., Mayer, J., Olesen, J. E., Keel, S. G., Glendining, M. J., Katterer, T. and Christensen, B. T.
Abstract

Aims
Predictions of medium to long-term changes in soil organic carbon (SOC) stocks involve simulation models with plant carbon (C) inputs estimated from crop yields using crop harvest indices and allometric scaling involving fixed root-to-shoot ratios. The choice of allometric approach and initial distribution of SOC among model pools is crucial for model estimates.
Methods
We evaluated the impact of a modified allometric approach for grass leys and initial model set-up using the C-TOOL model. Four European agricultural long-term experiments were considered including three experiments with different frequency of grass leys in the crop rotation and one permanent grassland.
Results
The modified allometric function for ley relied on fixed below-ground C input regardless of mineral fertilizer inputs and modified pool initialization involved available site history. Including available, but insufficient, pre-experiment history to adjust the initial set-up of model SOC pools did not improve to the C-TOOL simulations. Changing the allometric approach for ley from fixed shoot-to-root ratios to fixed below-ground C input decreased the soil C input dramatically and improved the C-TOOL simulation of SOC stocks for fertilized treatments in all experiments when combined with standard model set-up. For unfertilized treatments, however, the efficiency of the standard allometric function was superior to the modified one.
Conclusions
Our results challenge the prevalent use of allometric approaches based on fixed root-to-shoot in SOC simulation models. The potential of modifying the initial distribution of SOC among model pools by accounting for historic land use remains in the dark.

KeywordsSoil organic carbon; Grassland; C-TOOL; Allometric functions; Model initialization
Year of Publication2020
JournalPlant and Soil
Digital Object Identifier (DOI)doi:10.1007/s11104-020-04500-9
Web address (URL)https://link.springer.com/article/10.1007/s11104-020-04500-9#Ack1
Open accessPublished as non-open access
FunderThe Danish Ministry of Climate, Energy and Building
The Danish Ministry of Environment and Food
Swedish Farmers’ Foundation for Agricultural Research
Biotechnology and Biological Sciences Research Council
Lawes Agricultural Trust
Funder project or codeThe Rothamsted Long Term Experiments [2017-2022]
Publication dates
Online02 Apr 2020
PublisherSpringer
ISSN0032-079X

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