Towards a representation of priming on soil carbon decomposition in the global land biosphere model ORCHIDEE (version 1.9.5.2)

Abstract

Abstract. Priming of soil carbon decomposition encompasses different processes through which the decomposition of native (already present) soil organic matter is amplified through the addition of new organic matter, with new inputs typically being more labile than the native soil organic matter. Evidence for priming comes from laboratory and field experiments, but to date there is no estimate of its impact at global scale and under the current anthropogenic perturbation of the carbon cycle. Current soil carbon decomposition models do not include priming mechanisms, thereby introducing uncertainty when extrapolating short-term local observations to ecosystem and regional to global scale. In this study we present a simple conceptual model of decomposition priming, called PRIM, able to reproduce laboratory (incubation) and field (litter manipulation) priming experiments. Parameters for this model were first optimized against data from 20 soil incubation experiments using a Bayesian framework. The optimized parameter values were evaluated against another set of soil incubation data independent from the ones used for calibration and the PRIM model reproduced the soil incubations data better than the original, CENTURYtype soil decomposition model, whose decomposition equations are based only on first-order kinetics. We then compared the PRIM model and the standard first-order decay model incorporated into the global land biosphere model OR-CHIDEE (Organising Carbon and Hydrology In Dynamic Ecosystems). A test of both models was performed at ecosystem scale using litter manipulation experiments from five sites. Although both versions were equally able to reproduce observed decay rates of litter, only ORCHIDEE-PRIM could simulate the observed priming (R 2 = 0.54) in cases where litter was added or removed. This result suggests that a conceptually simple and numerically tractable representation of priming adapted to global models is able to capture the sign and magnitude of the priming of litter and soil organic matter.

High organic inputs explain shallow and deep SOC storage in a long-term agroforestry system – combining experimental and modeling approaches

“…Contrary to what was shown by Cardinael et al (2015c) in long-term bare fallows receiving contrasted organic amendments, the addition of another SOC pool could not surpass the inclusion of the priming effect in terms of model performance. Together with Wutzler and Reichstein (2013) and Guenet et al (2016), this study therefore suggests that implementing the priming effect into SOC models would improve model performances, especially when modeling deep SOC profiles.…”

ORCHIDEE-SOM: Modeling soil organic carbon (SOC) and dissolved organic carbon (DOC) dynamics along vertical soil profiles in Europe

“…Priming parameter for mineralization slow 194.03 (Guenet et al, 2016) priming_param ( Value within the range found in literature for fast pool of DOC (Boddy et al, 2008;Kalbitz et al, 2003;Qualls and Haines, 1992;Turgeon, 2008) Geosci. Model Dev.…”

“…The not-respired, recycled DOC (DOC Recycled ) coming from active, slow and passive SOC pools are redistributed in the different SOC pools following the same parameters as in the CENTURY model (Guenet et al, 2016;Parton et al, 1988): 20…”

“…Gjettermann, B., Styczen, M., Hansen, H. C. B., Vinther, F. P. and Hansen, S.: Challenges in modelling dissolved organic matter dynamics in agricultural soil using DAISY, Soil Biol. Biochem., 40(6) (Guenet et al, 2016) priming_param (c) slow (priming_param_islow)…”

“…This means that for the active carbon pool LOC is the litter and DOC, but for the slow carbon pool LOC is the sum of the litter, DOC and active SOC pools, and 20 finally, for the passive carbon pool LOC is the sum of litter, DOC, active and slow SOC pools. Finally, c is a parameter controlling the impact of the LOC pool on the SOC mineralization rate, i.e., the priming effect (Guenet et al, 2016, Table 1). The decomposition of the active SOC pool is further modified by a clay modifier , which considers that the SOC decomposition decreases when increasing the clay content:…”