|Exploration and the quantitative characterization of the spatial composition, the microarchitecture, the stability, and the properties of soil microaggregates with a unique combination of sophisticated high-resolution imaging and analytical techniques are the major obcectives of this Research Unit (RU).
The RU is organized in different projects that provide the complementary and specific elemental, chemical, physical, topographic and mechanical information on the soil microaggregates at the micron to submicron scale with overlapping scale ranges.
For this, the first mandatory prerequisite is to separate and isolate soil microaggregates not only according to their different size classes, but also with respect to their mechanical stability (against ultrasonic disruption energy).
The grand goals of this RU are to
gain a model-based mechanistic understanding of the formation, build-up, composition, properties and stability of these basic soil structures and
relate that to fundamental target functions of soil: the habitat function for microorganisms, the function as carbon sink and the water-storage function.
We expect that a major advancement of the mechanistic understanding of the target functions of soil will derive from the concomitant application of the above-mentioned techniques to both soil microaggregates isolated from a soil texture toposequence - in the second phase additionally a chronosequence - or collected from a so far unique multi-stable-isotope labeling microcosm experiment. The labeling experiment is designed to explore simultaneously the role of mineral and organic matter key components (57Fe for iron oxides, 29Si for phyllosilicate clay minerals, 13C for extracellular polymeric substances) and key "actors" (15N and 13C for bacteria) in the formation of soil microaggregates. To proof already existing and newly developed theories and to quantitatively analyze the data-based theoretical concepts of soil microaggregate formation, stability and turnover, an explicit continuum scale modeling approach is integrated to fuse the still largely isolated modeling approaches that focus either on flow and transport, biogeochemical cycling, carbon turnover, microstructure formation, or microbial activity. This will be based on the iterative refinement of the conceptual model on the formation of soil microaggregates acknowledging the co-evolution of properties and structure, both being identified as the major factors required to simulate the role of these basic soil structures for the functions of soil.
Research team during the kick-off meeting, Munic, Bavaria, October 2015