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

Abstract

Abstract. Coupled modelling of soil erosion, carbon redistribution, and turnover has received great attention over the last decades due to large uncertainties regarding erosion-induced carbon fluxes. For a process-oriented representation of event dynamics, coupled soil-carbon erosion models have been developed. However, there are currently few models that represent tillage erosion, preferential water erosion, and transport of different carbon fractions (e.g. mineral bound carbon, carbon encapsulated by soil aggregates). We couple a process-oriented multi-class sediment transport model with a carbon turnover model (MCST-C) to identify relevant redistribution processes for carbon dynamics. The model is applied for two arable catchments (3.7 and 7.8 ha) located in the Tertiary Hills about 40 km north of Munich, Germany. Our findings indicate the following: (i) redistribution by tillage 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 controls the long-term erosion-induced carbon balance; (iii) delivered sediments are highly enriched in SOC compared to the parent soil, and sediment delivery is driven by event size and catchment connectivity; and (iv) soil aggregation enhances SOC deposition due to the transformation of highly mobile carbon-rich fine primary particles into rather immobile soil aggregates.

Interdisciplinary Geo‐ecological Research across Time Scales in the Northeast German Lowland Observatory (TERENO‐NE)

“…For this purpose, the conceptual WaTEM/SEDEM model (Van Oost et al, 2000) as implemented in SPEROS‐C (Fiener et al, 2015) was used to simulate soil redistribution patterns in the kettle hole catchment from 1963 to 2016. To analyze process‐based effects of soil redistribution on SOC dynamics, a coupled process‐oriented and event‐based soil erosion and C turnover model was developed (MCST‐C; Wilken et al, 2017a, 2017b). The MCST‐C model was applied on a unique 100‐yr, high‐resolution rainfall dataset to analyze the effect of event size (Wilken et al, 2017a).…”

“…The MCST‐C model was applied on a unique 100‐yr, high‐resolution rainfall dataset to analyze the effect of event size (Wilken et al, 2017a). Subsequently, the model was used to compare the role of water erosion processes vs. tillage erosion on C dynamics (Wilken et al, 2017b).…”

“…The process‐oriented soil erosion and C turnover modeling studies using MCST‐C (Wilken et al, 2017a, 2017b) underlined (i) that event size is highly important due to the preferential transport of SOC and corresponding SOC enrichment processes in delivered sediments; (ii) the intra‐field catchment connectivity controls sediment delivery and corresponding SOC enrichment processes, as catchments with reduced sedimentological connectivity show enhanced SOC enrichment in delivered sediments; (iii) soil aggregation reduces sediment and SOC transport distances due to the encapsulation of highly mobile SOC‐rich fine particles; and (iv) in general, tillage erosion induced a substantial in‐field SOC sequestration compared with model runs without erosion.…”

Understanding the role of water and tillage erosion from <sup>239+240</sup>Pu tracer measurements using inverse modelling

“…There are only few models fusing both water and tillage erosion. Physically oriented models like MCST-C (Wilken et al, 2017b) and LandSoil (Ciampalini et al, 2012) work event based and are developed for process understanding, while conceptual USLE based models (WaTEM/SEDEM: Van Oost et al, 2000;Van Rompaey et al, 2001) aim at a robust prediction of long-term soil erosion rates (Alewell et al, 2019). For an inverse modelling approach to unravel tillage and water erosion based on radionuclide tracer, it is necessary to use a parsimonious approach with a limited parameter space and available input data over five to six decades, which suggests the use of conceptual models.…”

Characterising the biophysical, economic and social impacts of soil carbon sequestration as a greenhouse gas removal technology

“…Recent studies have attempted to couple USLE/RUSLE to simpler and more process-oriented soil-C models in order to describe erosion-caused losses of soil C (Wilken, Sommer, Oost, Bens, & Fiener, 2017). Modelling is complicated by (a) the episodic nature of erosion processes (Fiener et al, 2015); (b) feedback loops between SOC, stability of soil aggregates and soil erodibility (Ruis & Blanco-Canqui, 2017); and (c) small-scale heterogeneity of erosion processes (Panagos et al, 2016).…”