Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
doi:10.5194/gmd-2016-304
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Model description paper
09 Jan 2017
Review status
This discussion paper is under review for the journal Geoscientific Model Development (GMD).
Carbon-nitrogen interactions in idealized simulations with JSBACH (version 3.10)
Daniel S. Goll1,2, Alexander J. Winkler3,4, Thomas Raddatz3, Ning Dong5,6, Ian Colin Prentice5,7, Philippe Ciais1, and Victor Brovkin3 1Le Laboratoire des Sciences du Climat et de l'Environnement, IPSL-LSCE CEA/CNRS/UVSQ Saclay, Gif sur Yvette, France
2also guest scientist at Max Planck Institute for Meteorology, Hamburg, Germany
3Max Planck Institute for Meteorology, Hamburg, Germany
4International Max Planck Research School on Earth System Modelling, Hamburg, Germany
5Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia
6Faculty of Agriculture and Environment, Department of Environmental Sciences, University of Sydney, NSW 2006, Australia
7AXA Chair in Biosphere and Climate Impacts, Department of Life Sciences, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot SL5 7PY, UK
Abstract. Recent advances in the representation of soil carbon decomposition (Goll et al., 2015) and carbon-nitrogen interactions (Parida, 2011; Goll et al., 2012) implemented previously into separate versions of the land surface scheme JSBACH are here combined in a single version which is set to be used in the upcoming 6th phase of coupled model intercomparison project (CMIP6) (Eyring et al., 2016).

Here we demonstrate that the new version of JSBACH is able to reproduce the spatial variability in the reactive nitrogen loss pathways as derived from a compilation of δ15N data (r=.63, RMSE=.26, Taylor score=.81). The inclusion of carbon-nitrogen interactions leads to a moderate reduction (−10 %) of the carbon-concentration feedback (βL) and has a negligible effect on the sensitivity of the land carbon cycle to warming (γL) compared to the same version of the model without carbon-nitrogen interactions in idealized simulations (1 % increase in atmospheric carbon dioxide per yr). In line with evidence from elevated carbon dioxide manipulation experiments (Shi et al., 2015; Liang et al., 2016), pronounced nitrogen scarcity is alleviated by (1) the accumulation of nitrogen due to enhanced nitrogen inputs by biological nitrogen fixation and reduced losses by leaching and volatilization as well as the (2) enhanced turnover of organic nitrogen.

The strengths of the land carbon feedbacks of the recent version of JSBACH, with βL=0.61 Pg ppm−1 and γL=−27.5 Pg °C−1, are 34 % and 53 % less than the averages of CMIP5 models (Arora et al., 2013), although the CMIP5 version of JSBACH simulated βL and γL which are 59 % and 42 % higher than multi-model average. These changes are primarily due to the new decomposition model, stressing the importance of getting the basics right (here: the decomposition of soil carbon) before increasing the complexity of the model (here: carbon-nitrogen interactions).


Citation: Goll, D. S., Winkler, A. J., Raddatz, T., Dong, N., Prentice, I. C., Ciais, P., and Brovkin, V.: Carbon-nitrogen interactions in idealized simulations with JSBACH (version 3.10), Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-304, in review, 2017.
Daniel S. Goll et al.
Daniel S. Goll et al.
Daniel S. Goll et al.

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Short summary
The response of soil organic carbon decomposition to warming and the interactions between nitrogen and carbon cycling are shown to affect the feedbacks between the land carbon cycle and the climate. We find in a model (JSBACH) that carbon-nitrogen interactions have only a small effect on the feedbacks whereas modifications of soil organic carbon decomposition have a large effect. The carbon cycle in the improved model is more resilient to climatic changes than in previous version of the model.
The response of soil organic carbon decomposition to warming and the interactions between...
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