Development and testing of a process-based model (MOSES) for simulating soil processes, functions and ecosystem services

A novel process-based soil model (MOSES – Modelling Soil Ecosystem Services) is described and tested using field data. The model is designed to provide information about a soil profile at approximately 1-cm depth resolution, on a 1 min timestep. Conceptualisation of the model has targeted a set of soil ecosystem service-related functions, including carbon sequestration, water buffering and biomass productivity, with the model framework designed to allow inclusion of additional processes and functions over time. Processes implemented within the model include thermal conduction, water movement (using pedotransfer functions to determine hydraulic conductivity, matric potential and related parameters), organic matter pool dynamics and gas/solute diffusion. The organic matter status of the profile is initialised using iterative runs of the RothC model to determine partition sizes of Decomposable Plant Material, Resistant Plant Material and other carbon pools. The outputs of the model are used to evaluate soil ecosystem service provision. MOSES has been designed to allow the implementation of further soil processes in the future, with the intention of expanding the variety of soil ecosystem functions and services that can be modelled. Validation of the model against detailed time-series field measurements of CO₂ concentration and emission, temperature and water content of a freely draining podzolic soil in Ireland have shown it to be effective at simulating these specific parameters, with statistically significant association between measured and modelled values of temperature at all depths, for saturation at shallow depths and for CO₂ at all depths apart from the surface layer. Overall, the model was seen to perform better at shallow depth, with lower levels of accuracy in deeper layers. The model has also been shown capable of simulating soil functional provision, based on specific parameters and processes. The need to add additional processes to MOSES in order to improve the simulation of soil ecosystem service provision, multifunctionality and the effects of external drivers such as climate change and management is discussed.