Process-oriented modelling to identify main drivers of erosion-induced carbon fluxes

Coupled modelling of soil erosion, carbon redistribution, and turnover has received great attentionover the last decades due to large uncertainties regarding erosion-induced carbon fluxes. For a process-orientedrepresentation of event dynamics, coupled soil–carbon erosion models have been developed. However, there arecurrently few models that represent tillage erosion, preferential water erosion, and transport of different carbonfractions (e.g. mineral bound carbon, carbon encapsulated by soil aggregates). We couple a process-orientedmulti-class sediment transport model with a carbon turnover model (MCST-C) to identify relevant redistributionprocesses for carbon dynamics. The model is applied for two arable catchments (3.7 and 7.8 ha) located in theTertiary Hills about 40 km north of Munich, Germany. Our findings indicate the following: (i) redistribution bytillage has a large effect on erosion-induced vertical carbon fluxes and has a large carbon sequestration potential;(ii) water erosion has a minor effect on vertical fluxes, but episodic soil organic carbon (SOC) delivery controlsthe long-term erosion-induced carbon balance; (iii) delivered sediments are highly enriched in SOC compared tothe parent soil, and sediment delivery is driven by event size and catchment connectivity; and (iv) soil aggregationenhances SOC deposition due to the transformation of highly mobile carbon-rich fine primary particles intorather immobile soil aggregates.