Biogeosciences Discuss., 10, 7201-7256, 2013
www.biogeosciences-discuss.net/10/7201/2013/
doi:10.5194/bgd-10-7201-2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG.
The effect of vertically-resolved soil biogeochemistry and alternate soil C and N models on C dynamics of CLM4
C. D. Koven1, W. J. Riley1, Z. M. Subin1,*, J. Y. Tang1, M. S. Torn1, W. D. Collins1, G. B. Bonan2, D. M. Lawrence2, and S. C. Swenson2
1Lawrence Berkeley National Lab (LBNL), Berkeley, CA, USA
2National Center for Atmospheric Research (NCAR), Boulder, CO, USA
*now at: Princeton Environmental Institute, Princeton, USA

Abstract. Soils are a crucial component of the Earth System; they comprise a large portion of terrestrial carbon stocks, mediate the supply and demand of nutrients, and influence the overall response of terrestrial ecosystems to perturbations. In this paper, we develop a new soil biogeochemistry model for the Community Land Model, version 4 (CLM4). The new model includes a vertical dimension to carbon (C) and nitrogen (N) pools and transformations, a more realistic treatment of mineral N pools, flexible treatment of the dynamics of decomposing carbon, and a radiocarbon (14C) tracer. We describe the model structure, comparison against site-level and global observations, and overall effect of the revised soil model on CLM carbon dynamics. Site-level comparisons to radiocarbon and bulk soil C observations support the idea that soil C turnover is reduced at depth beyond what is expected from environmental controls by temperature, moisture, and oxygen that are considered in the model. The revised soil model predicts substantially more and older soil C, particularly at high latitudes, where it resolves a permafrost soil C pool, in better agreement with observations. In addition the 20th century C dynamics of the model are more realistic than the baseline model, with more terrestrial C uptake over the 20th century due to reduced N downregulation and longer turnover times of decomposing C.

Citation: Koven, C. D., Riley, W. J., Subin, Z. M., Tang, J. Y., Torn, M. S., Collins, W. D., Bonan, G. B., Lawrence, D. M., and Swenson, S. C.: The effect of vertically-resolved soil biogeochemistry and alternate soil C and N models on C dynamics of CLM4, Biogeosciences Discuss., 10, 7201-7256, doi:10.5194/bgd-10-7201-2013, 2013.
 
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