A modelling system for organic carbon dynamics in soil profiles during the holocene

Becker-Heidmann, P., Schipmann, R., Lehfeldt, R. (1995): A modelling system for organic carbon dynamics in soil profiles during the holocene. Abstracts of the First Science Conference of IGBP-GAIM, 25-29 September 1995, Garmisch-Partenkirchen, Germany: P-7.



During the last years, the dynamics of soil organic carbon has become a major research target also in climate change studies, because it may help to find the „missing sink“ of annually 2 Gt in the global carbon balance. Contrarily to the complexity of the subject, the modelling approaches have been rather simple so far. Soil organic carbon is still more or less a black box in global models.

Our modelling system is based on soil profiles with distinguished depth and horizon dependent processes and parameters, accounting not only for decomposition but also for vertical translocation processes. Main variables are carbon content, δ13C and 14C age of the soil layers. Output variables are also carbon, δ13C and 14C of gaseous emissions and percolation losses to the groundwater. The list of parameters contains texture (particle size distribution), pH, temperature and soil moisture and can easily be extended if necessary. The boundary conditions include δ13C and 14C of the carbon input. The system is programmed in C++ under Unix operating system and OSF/Motif with an interactive graphical user interface. Depth distributions of variables and parameters are visualized in interactive windows. For sensitivity analysis, the input data as well as the parameters and boundary conditions can be modified by drag and drop mouse actions. The system is designed as a module for a global „Community Terrestrial Biosphere Model“ which will be coupled to a global climate model, both developed within the common BMBF funded climate research project „Trace gas cycles“. Therefore, all intermediate modelling are logged into files which can be used by the other modules.

An extensive data base of thin layer-wise sampled soil profiles containing carbon, δ13C, 14C age, pH, texture and other data provides the test data for the different models and parameter sets. These soils have developed in Northern Germany after the last glaciation.

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