Modelling how carbon affects soil structure

This paper presents a mechanistic model, named Struc-C, which describes how the soil organic carbon (SOC) influences the dynamics of soil structure, and consequently, soil physical behaviour. The model is partly inspired from the Rothamsed Carbon model, RothC-26.3, divided into three sub-models; the first describes SOC dynamics, followed by how aggregates can be created from the combination of the SOC with the soil clay, and finally, how this process influences soil porosity. Soil aggregates are regarded as the elementary bricks building soil structure, which comprise of organo-mineral associations that are subsequently bound together by more SOC to form the skeleton of larger aggregates. This is modelled by using two plant material pools from the RothC-26.3 model to create four new pools; three for increasing physical protection (or increasing aggregation), and one for the non-protected SOC (or non-aggregated). Struc-C has been tested over a simulated time of 200 years with input data from Rothamsted (England) and the Australian Capital Territory (Australia), and the output from the carbon model compared with RothC-26.3 outputs for both datasets. Although the model is still in its infancy, the simulations look promising when compared to RothC. Further improvements are also contemplated.