Erosion-induced Impact on Carbon Dynamics in the Crop-Rhizosphere Microbiome-Soil Organic Matter-Continuum (CropRhizoSOM)

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The magnitude and mechanistic impact of soil erosion on changes of soil carbon stocks are not resolved to date. Croplands can be considered as one important type of ecosystem to improve carbon sequestration, since they cover 14 million square kilometres of earth land surface, store one-tenth of the global soil organic carbon, and are continuously managed. An understanding of the mechanisms responsible for erosion impact on soil carbon dynamics and storage is a prerequisite for a quantification of the significance of erosion on the carbon source and sink functions of croplands. We aim for a substantial contribution to this unresolved topic. The proposed project will investigate the effect of mixing of different amounts of subsoil in a topsoil (Ap horizon) on key processes of carbon dynamics in a Crop-Rhizosphere Microbiota-Soil Organic Matter Continuum (CropRhizoSOM). The consortium will conduct 14C-tracer-based pot experiments with spring barley, in which a non-eroded Ap material from the experimental site CarboZALF-D (control, without Bt incorporation), a moderately eroded Ap material (with 20% Bt material) and strongly eroded Ap material (with 40% Bt material) will be comparatively analyzed. CropRhizoSOM will quantitatively determine and balance (I) carbon fluxes and allocation rates, (II) the functional adaption of the soil microbiota (gene markers, metagenomes, soil enzymes), and (III) the dynamics of organic carbon in various soil particle size fractions at different growth stages and in the following fallow period. Subsequently, we will identify which carbon pools were primarily accessed by the crop and the microbiota. On the basis of all results, a conceptual model considering flux rates and functional changes of the microbiota will be developed. Such a conceptual model will lay the foundations for subsequent experiments and adaptations in soil carbon models by future efforts.