Modelling soil organic matter at long-time and landscape scales.

Abstract : Understanding and simulating the soil organic matter had become a key challenge to betterpredict the landscape dynamic and its evolution. Although numerical modelling developmentsalready integrate soil organic matter to improve agricultural practices at field or plot scales,additional work needs to be carried out to describe the landscape evolution over hundreds tothousands of years.We aim to identify and quantify the processes associated to organic matter cycle that take part inlandscape long-term evolution. We complete a reference sediment transport model designed forlarge scale evolution by adding some physical considerations relative to organic matter behaviour.The main developments concern: Organic matter productivity and its export to soils Organic matter evolution and degradation along soil profile and during transport Rock and regolith compartments with different lithologies and compositions Weathering and erosionIn this presentation, we explore the strengths and limits of this model designed to address a widevariety of questions in various settings. We also discuss the results and assess the validity of thisapproach considering availability of long-term sedimentary records