| | 6 | Despite the importance of soil as a large component of the terrestrial ecosystems, the soil compartments are not well represented in the Land Surface Models (LSMs). Indeed, soils in current LSMs are generally represented based on a very simplified schema that can induce a misrepresentation of the deep dynamics of soil carbon. Here, we present a new version of the Institut Pierre Simon Laplace (IPSL) Land Surface Model called ORCHIDEE-SOM (ORganizing Carbon and Hydrology in Dynamic EcosystEms - Soil Organic Matter), incorporating the 14C dynamic in the soil. ORCHIDEE-SOM first simulates soil carbon dynamics for different layers, down to 2 m depth. Second, concentration of dissolved organic carbon and its transport are modeled. Finally, soil organic carbon decomposition is considered taking into account the priming effect. |
| | 7 | After implementing 14C in the soil module of the model, we evaluated model outputs against observations of soil organic carbon and modern 14C fraction (F14C) for different sites with different characteristics. The model managed to reproduce the soil organic carbon stocks and the F14C along the vertical profiles for the sites examined. However, an overestimation of the total carbon stock was noted, primarily on the surface layer. Due to 14C, it is possible to probe carbon age in the soil, which was found to underestimated. Thereafter, two different tests on this new version have been established. The first was to increase carbon residence time of the passive pool and decrease the flux from the slow pool to the passive pool. The second was to establish an equation of diffusion, initially constant throughout the profile, making it vary exponentially as a function of depth. The first modifications did not improve the capacity of the model to reproduce observations whereas the second test improved both estimation of surface soil carbon stock as well as soil carbon age. This demonstrates that we should focus more on vertical variation of soil parameters as a function of depth, in order to upgrade the representation of global carbon cycle in LSMs, thereby helping to improve predictions of the of soil organic carbon to environmental changes. |
| 7 | | Despite the importance of soil as a large component of the terrestrial ecosystems, the soil compartments are not well represented in the Land Surface Models (LSMs). Indeed, current LSMs generally represent soils in a very simplified way that can induce a misrepresentation of the deep dynamics of soil carbon and thus, large uncertainties in predictions of soil carbon response to climate change. In this study, we will present a new version of the IPSL-Land Surface Model called ORCHIDEE-SOM, incorporating the 14C dynamic in the soil. ORCHIDEE-SOM, first, simulates carbon dynamics in the soil column down to 2 m-depth, partitioned in 11 layers. Second, the concentration of dissolved organic carbon (DOC) in each layer and transport between layers are modeled. Finally, soil organic carbon (SOC) decomposition is considered taking into account the amount of fresh organic matter as a way of accounting for the priming effect. |
| 8 | | After implementing the 14C in the soil module of the model, we evaluated model outputs against observations of soil organic carbon and 14C activity (F14C) from four sites with different vegetation covers. The model managed to reproduce the soil organic carbon stocks and the F14C along the vertical profiles at the four sites. However, an overestimation of the total carbon stock throughout the profile was noted, but was mostly marked on the surface. Then, thanks to the introduction of 14C, it has been possible to highlight an underestimation of the age of carbon in the soil. Thereafter, two different tests on this new version have been established. The first was to increase carbon residence time of the passive pool and decrease the flux from the slow pool to the passive pool. The second was to establish an equation of diffusion, initially constant throughout the profile, making it vary exponentially as a function of depth. The first modifications did not improve the capacity of the model to reproduce observations whereas the second test showed a diminution of the soil carbon stock overestimation, especially at the surface and an improvement of the estimates of the carbon age. This assumes that model improvements should focus more on a depth dependent parameterization, mainly for the diffusion, in order to improve the representation of the global carbon cycle in LSMs, thus helping to constrain the predictions of the future soil organic carbon response to global warming. |
| 18 | | * Information about DOI to come... |
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| | 19 | == Metadata == |
| | 20 | |
| | 21 | || DOI || [XXX] || |
| | 22 | || Creator || Bertrand Guenet || |
| | 23 | || Affiliation || LSCE, CNRS || |
| | 24 | || Title || The use of radiocarbon 14C to constrain carbon dynamics in the soil module of the land surface model ORCHIDEE (SVN r5165) || |
| | 25 | || Publisher || Institut Pierre Simon Laplace (IPSL) || |
| | 26 | || //PublicationYear// || 2018 || |
| | 27 | || //ResourceType// || Software || |
| | 28 | || //Rights// || This software is distributed under the CeCILL license || |
| | 29 | || //rightsURI // || http://www.cecill.info/ || |
| | 30 | || Subject || Land surface model, pixel-to-point comparison, biomass || |
| | 31 | || //DataManager// || Karim Ramage (IPSL) || |
| | 32 | || //DataCurator// || Josefine Ghattas (IPSL) || |
| | 33 | || //ContactPerson// || Bertrabd Guenet (LSCE/CNRS) || |
| | 34 | || //FundingReference// || ANR-14-CE01-0004 DeDyCAS,ANR 2010 BLAN 605 Agriped and the European Research Council Synergy grant ERC-2013-SyG-610028 IMBALANCE-P || |
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