SP7

Aim of this subproject (SP7) is to investigate the development and dynamics of 3D architectures of soil microaggregates. The influence of clay content on the microstructure is examined in a toposequence and a central microcosm experiment where the role of soil aging on the initial formation and short term turnover of soil microaggregates is analyzed.
First, the generation of SMA by an alternative dry separation protocol is developed. By exerting a mechanical load in a loading frame macroaggregates crumble into microaggregates. In contrast to the commonly used wet separation approach this concept is considered be better mimic the aggregate separation under field conditions where tillage or mechanical loading with machines lead to the break up of macroaggregates down to microaggregate units. Another advantage of a dry separation technique is that re‐aggregation due to sample drying after wet separation is prevented.
By analyzing dry separated microaggregates with X‐ray computed tomography (XRCT) information about the 3D architecture of the pore and particle networks are obtained. Structural features, like contact area, coordination number, pore size distribution, channel width and connectivity, to mention a few, are worked out by complex image analysis algorithms.
By combining gas diffusion measurements on SMA and XRCT data transport processes are correlated with the pore network morphology and topology. Quantitative links between the spatial arrangement of pores and solid particles as well as physical processes in intra‐aggregate pore networks, like flow and distribution of oxygen and water are determined.