Dr. Steffen Schweizer

Understanding organic matter storage in soils

Right under our feet, soils harbor vast amounts of organic matter thanks to various stabilization mechanisms. I am interested to disentangle specific biogeochemical properties that determine the fate of organic matter and its contained C and N in soils. To generate a fundamental understanding of how organic matter is stored, turned over and lost in soil systems, the formation of stable soil structures, the detection of potential carbon storage forms and the identification of interactions with soil minerals, plants and microbes form a central theme of my scientific approach.

Soil structure

When digging into a soil, its constituents never occur alone but bind together forming soil structures. Such aggregation processes determine which soil components get in close contact enabling biogeochemical interactions and what kind of pore space is left for the air and water cycle in between soil particles. The arrangement of soil structures provide a dynamic scaffolding which can induce physical and chemical barriers that are intertwined with organic matter storage and the terrestrial carbon cycle. Exploring soils from the perspective of complex structural units opens up new possibilities to research questions on their important role in organic C and N cycling.

The microscale perspective to resolve and better understand soil processes

Soil properties and functions differ tremendously when compared across landscapes. When zooming into soils, we also find a striking heterogeneity of their biogeochemical composition in space and time. At the microscale, a complex soil architecture creates dynamic landscapes at the scale of reactive fine-sized mineral particles, mineral-associated organic matter and soil microorganisms. In my research hypotheses, I address the compartmentalization of soil at the microscale into areas with distinct biogeochemical properties and functions. This is needed to systematically resolve the heterogeneity of mineral-microbial interactions and upscale the combined functionality of various compartments to soil as a whole. To analyze the soil at the microscale I take the advantage of a complementary range of spectromicroscopic techniques that provide the opportunity to observe microbes at work, probe highly active spheres and microenvironments around roots or detritus and follow the interactions of organic matter with mineral phases. Further information on our NanoSIMS and its possibilities to measure the distribution of various elements and isotopes can be found here. I aim to reveal spatial patterns that systematically explain the functioning of heterogeneous soil architecture at the microscale.

The global relevance of soils beyond temperate zones

I’m convinced that the investigation of agricultural practices in concert with innovative scientific expertise is critical for viable contributions to a better understanding of agroecosystems and their sustainable intensification. For all these reasons, I tackle scientific challenges based on interdisciplinary approaches, active science communication and cooperation across biogeochemical disciplines in my work.