Soil is the focal and connecting link between the information, matter and energy cycles of the hydrogeosphere and the atmosphere. Soil organic matter, clay sized particles and iron oxides are the most important reactants in soils building a complex physico-chemical interface. Beside the quality and quantity of the reactants, their spatial distribution and interaction affect the biogeochemical proc
esses which are the driving forces of key ecosystem functions including carbon cycling, plant productivity and water quality. These processes are active across many spatial scales ranging from the molecular level, taking place on nano- to micrometers, to the pedon and landscape level, acting on meters to kilometres. The major challenges are to identify the factors controlling the architecture of biogeochemical interfaces, to link the processes operative at the individual molecular and/or organism scale to the phenomena active at the aggregate scale in a general mechanistic framework. At the Chair of Soil Science we work on the general characterisation of soil organic matter and the identification and extraction of functional soil organic matter pools that are important for long term stabilisation of carbon in soils and at the same time are responsible for the formation of biogeochemical interfaces in aggregated soils. We use state-of-the-art techniques of SOM characterization by combining solid-state 13C NMR spectroscopy to analyse bulk SOM composition with chemolytic techniques and GC-MS for the analysis of major SOM compounds relevant for the soil C cycle, especially polysaccharides, lignin and cutin/suberin. Our results show that SOM structural chemical as well as spatial variability has to be considered in order to understand the sensitivity of SOM pools to degradation. For this we use nano-scale secondary ion mass spectrometry (NanoSIMS), allowing the simultaneous analysis of up to seven ion species with high sensitivity and resolution. It is an unprecedented tool for the analysis of biogeochemical processes and properties of soils, as it enables us to investigate the elemental and isotopic composition of soils at the submicron scale.
