SP5

Soil organic matter (SOM) is heterogeneously distributed at different scales and stabilized in microaggregates, but the role of microaggregates¿ architecture for SOM storage and turnover time has eluded researchers. This project combines electron microprobe analyses mapping techniques (EPMA) and a three dimensional laser‐ablation isotope ratio monitoring (LA‐ICP‐MS and LA‐IRMS) to elucidate the spatio‐temporal patterns of SOM, its isotopic signature and adjacent other elements in microaggregates down to a size of 4‐20 μm. The subsequent data evaluation using pattern recognition and geostatistical tools will allow us to answer the following questions to which extent does the spatial pattern of SOM within microaggregates of different age and provenience (microcosm experiment, toposequence, chronosequence) follow a deterministic pattern, to which extent does turnover time and bioaccessibility of SOM within microaggregates affect spatial heterogeneity of C and N, and
how do pedogenic iron oxides and clay minerals control the accumulation and turnover of SOM in
microaggregates hot spots. We hypothesize that the older the microaggregates are, the less relevant are stochastic processes to explain the dynamics of SOM, thus providing a clue to the role of these microstructures for the biogeochemical cycling of nutrients and C turnover.