Soils are composed of solid, liquid, and gaseous phases. The spatial organization and structure of the solid phase is referred to as the soil architecture and determines fluxes of the liquid and gaseous phases. Traditionally, soil architecture is assumed to be stable over timescales relevant to soil functions, such as carbon, nutrient, and water cycling. However, this assumption does not always hold, especially under changing land use and climate conditions. Dynamics of pore structure and soil aggregates and redistribution of soil material through mixing and erosion continuously reshape the soil architecture over short to long timescales, affecting the functions of soils. To comprehensively understand soil functionality in a changing world, it is imperative to view soils as dynamic, four-dimensional systems.

This special issue (SI) invites papers that study soil dynamics using numerical and statistical models. The focus will be on the development of model-based representations, or digital twins, of soil systems to study soil processes, dynamics, and functions from the pore to the landscape scale and from diurnal dynamics to millennial evolution. By bringing together modellers and models that work on different spatiotemporal scales, we aim at synergies between soil hydrology, soil physics, soil geography, and soil ecology to develop holistic models that consider soils and their functions as dynamic systems. This SI is an initiative of the International Soil Modeling Consortium (ISMC, https://soil-modeling.org/) and the 3-4D Soil models working group (https://dbges.de/en/commissions-and-working-groups/working-groups/wg-3-4d-soil-models), part of the German Soil Science Society.