Taking a closer look: How spectromicroscopic imaging of organo-mineral associations leads to a novel perspective on interrelated soil functions

A wide range of image-based techniques revealed mounting evidence of a heterogeneous arrangement of mineral-associated organic matter (OM) in soils at the microscale and nanoscale. Spectromicroscopic approaches using such as NanoSIMS, STXM-NEXAFS, AFM, STEM-EELS, and others have provided insights about a patchy and piled-up arrangement of OM. This arrangement is determined by different local OM properties and mineral composition as well as OM-OM interactions. The emerging conceptual framework of the microscale arrangement of OM affects our understanding of soil functions: By compartmentalizing and decoupling local carbon sequestration in the mineral soil matrix, by localizing the mechanical stabilization of soil structure, by altering surface properties and re-distributing ion exchange sites, and by shaping distinct biotic microenvironments. After an overview on the spectromicroscopic evidence, this contribution will illustrate the emerging conceptual framework of localized soil functions, and highlight opportunities for research approaches based on the patchy and piled-up arrangement of OM at the microscale and nanoscale.