3D-organisation of the solid, pore and organic phases in soil microaggregates and its control on mechanical stability

• Applicant: Professor Dr. Stephan Peth
• Subject Area: Soil Sciences
• Term: from 2015 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 251268514

Soil structure is the expression of a complex spatial arrangement of solids (organic and inorganic matter) and pores, which are variably filled with water and gas. A plethora of soil functions such as the supply of nutrients and water, sequestration of carbon, transformation of pollutants or simply the functioning of soil as a habitat for soil organisms depend on soil structure. Despite of the importance of aggregates as building blocks that sustain soil structure related functions, initial aggregate formation is still poorly understood. In the frame of the research unit 2179 (Mad Soil: Microaggregate development in Soil) this subproject investigates physical key processes involved in soil aggregation to support the development of a mechanistic understanding of aggregate formation. We study the dynamics of soil micro-aggregate formation and turnover by applying modern experimental approaches and analytical tools such as X-ray tomography (University of Kassel), Synchrotron tomography (HASYLAB), quantitative 3D image analysis and physicochemical microsensing to obtain quantitative links between micro-aggregate architecture und its influence on biotic and abiotic processes leading to aggregate formation. In the first phase of the research unit we will focus on a toposequence (clay content gradient) and a multi-isotope labelled microcosm experiment. The main research question in this context is how soil structure evolves as a function of clay content and how this influences the interaction of physical (water and oxygen transport) with biological (microbial activity, EPS) processes and the resulting mechanical stability of micro-aggregates (e.g. by creating low entropy stable structures). The 3D images will be analyzed to obtain morphological and structural information. This will enable us to quantify not only the pore space, but also the spatial organization of pores and solid phases of these building blocks. The results will be correlated with physical properties obtained from microscale soil measurements (e.g. oxygen microdiffusion, SOM location, mechanical stability) which will enhance our understanding of the role of physical processes in aggregate formation and provide input data for the development of a mechanistic quantitative model of micro-aggregate formation (subproject PM).

• DFG Programme: Research Units
• Subproject of: FOR 2179: MAD Soil - Microaggregates: Formation and turnover of the structural building blocks of soils
• Co-Investigator: Dr. Daniel Uteau Puschmann