Biogeochemical and structural heterogeneity at the microscale govern the functional behavior of soil in many ways. Prominent examples are (i) the stabilization of soil organic matter due to reduced bioavailability in aggregated soil structure, (ii) the preferential transport of nutrients and contaminants along macropores, (iii) highly localized greenhouse gas emission/consumption (N20, CH4) around a few hotspots of microbial activity like particulate organic matter, (iv) the formation of the rhizosphere as complex system composed of plant roots, soil and associated microorganisms.
All of these processes have in common that the relevant mechanisms are fairly well understood in artificial systems like soil suspensions, micromodels and so on. However, it is a challenge to study these structure-mediated processes in undisturbed soils and sediments. Advances in the characterizations of microenvironments are possible along several lines:
1. Integration of imaging techniques for chemical mapping (SEM-EDX, SIMS) and microbial presence (FISH, fluorescence microscopy) with imaging of the 3D microstructure (CT, MRI) to embed biogeochemical information into a larger spatial context.
2. Experiments in structured soil (incubation experiments, transport experiments, etc.) in which bulk measurements (boundary fluxes, mass balances) are combined with micro-sensoric point measurements (gas sensors, moisture sensors) and imaging techniques that capture the inherent heterogeneity.
3. Spatially resolved, mechanistic modelling of process behavior can only be as good as the microscale input data and output data against which they are calibrated and validated. If these models prove to be useful they can help our understanding of the relevant processes through explorative modelling.
To meet these challenges requires an intensive dialog between modelers and experimentalists from different research disciplines in soil science, microbiology, geochemistry and computer science. This session aims at bringing scientists from different fields together to share their experience and visions about the characterization of microenvironments in soils and sediments