Articles | Volume 11, issue 3
Geosci. Model Dev., 11, 937–957, 2018
Geosci. Model Dev., 11, 937–957, 2018

Model description paper 15 Mar 2018

Model description paper | 15 Mar 2018

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

Marta Camino-Serrano1,2, Bertrand Guenet3, Sebastiaan Luyssaert4, Philippe Ciais3, Vladislav Bastrikov3, Bruno De Vos5, Bert Gielen6, Gerd Gleixner7, Albert Jornet-Puig3, Klaus Kaiser8, Dolly Kothawala9, Ronny Lauerwald10, Josep Peñuelas1,2, Marion Schrumpf7, Sara Vicca6, Nicolas Vuichard3, David Walmsley11, and Ivan A. Janssens6 Marta Camino-Serrano et al.
  • 1CREAF, Cerdanyola del Vallès, 08193, Catalonia, Spain
  • 2CSIC, Global Ecology Unit CREAF-CSIC-UAB, Bellaterra 08193, Catalonia, Spain
  • 3Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
  • 4Department of Ecological Sciences, Free University Amsterdam (VUAmsterdam), De Boelelaan 1085, 1081 HV Amsterdam, the Netherlands
  • 5INBO, Research Institute for Nature and Forest, Gaverstraat 4, 9500 Geraardsbergen, Belgium
  • 6Department of Biology, Research Group of Plant and Vegetation Ecology, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium
  • 7Max Planck Institute for Biogeochemistry, Hans-Knöll-Straße 10, 07745 Jena, Germany
  • 8Soil Science and Soil Protection, Martin Luther University Halle-Wittenberg, von-Seckendorff-Platz 3, 06120 Halle (Saale), Germany
  • 9Department of Limnology, Evolutionary Biology Centre, Norbyvägen 18D, Uppsala University, Uppsala, 75236, Sweden
  • 10Department of Mathematics, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QE, UK
  • 11Institute of Ecology, Faculty of Sustainability, Leuphana University of Lüneburg, Universitätsallee 1, 21335 Lüneburg, Germany

Abstract. Current land surface models (LSMs) typically represent soils in a very simplistic way, assuming soil organic carbon (SOC) as a bulk, and thus impeding a correct representation of deep soil carbon dynamics. Moreover, LSMs generally neglect the production and export of dissolved organic carbon (DOC) from soils to rivers, leading to overestimations of the potential carbon sequestration on land. This common oversimplified processing of SOC in LSMs is partly responsible for the large uncertainty in the predictions of the soil carbon response to climate change. In this study, we present a new soil carbon module called ORCHIDEE-SOM, embedded within the land surface model ORCHIDEE, which is able to reproduce the DOC and SOC dynamics in a vertically discretized soil to 2 m. The model includes processes of biological production and consumption of SOC and DOC, DOC adsorption on and desorption from soil minerals, diffusion of SOC and DOC, and DOC transport with water through and out of the soils to rivers. We evaluated ORCHIDEE-SOM against observations of DOC concentrations and SOC stocks from four European sites with different vegetation covers: a coniferous forest, a deciduous forest, a grassland, and a cropland. The model was able to reproduce the SOC stocks along their vertical profiles at the four sites and the DOC concentrations within the range of measurements, with the exception of the DOC concentrations in the upper soil horizon at the coniferous forest. However, the model was not able to fully capture the temporal dynamics of DOC concentrations. Further model improvements should focus on a plant- and depth-dependent parameterization of the new input model parameters, such as the turnover times of DOC and the microbial carbon use efficiency. We suggest that this new soil module, when parameterized for global simulations, will improve the representation of the global carbon cycle in LSMs, thus helping to constrain the predictions of the future SOC response to global warming.

Short summary
Global models generally oversimplify the representation of soil organic carbon (SOC), and thus its response to global warming remains uncertain. We present the new soil module ORCHIDEE-SOM, within the global model ORCHIDEE, that refines the representation of SOC dynamics and includes the dissolved organic carbon (DOC) processes. The model is able to reproduce SOC stocks and DOC concentrations in four different ecosystems, opening an opportunity for improved predictions of SOC in global models.