Erosion-induced carbon redistribution, burial and mineralisation — Is the episodic nature of erosion processes important?

Abstract

a b s t r a c tThere is still an ongoing scientific discussion regarding the importance of erosion-induced lateral soil organic carbon (SOC) redistribution for the burial and/or mineralisation of carbon and the resulting long-term C balance at the catchment scale. Especially the effects of the event driven nature of water erosion and the potentially associated enrichment of SOC in sediment delivery are still unclear. In general, two processes lead to enrichment of SOC: (i) enrichment due to selective interrill erosion at erosion sites, and (ii) enrichment due to selective depletion at deposition sites. In this study, the conceptual soil erosion and SOC turnover model SPEROS-C was adapted to integrate these processes and applied in a small arable catchment (4.2 ha) in Germany for a 57-year period. A total number of 901 model runs were performed with different realisations of frequency and magnitude of water erosion as well as realisations of enrichment and depletion ratios taken from literature and compared to a reference model run representing mean annual erosion without enrichment processes. In general, our modelling study indicates that ignoring temporal variability and enrichment processes may lead to a substantial misinterpretation of erosion-induced C fluxes. Especially the vertical C flux (difference between C inputs from plant assimilates and organic fertilizer and SOC mineralisation) at deposition sites strongly depends on the model parameterisation ranging from a maximum C source of −336 g C m −2 to a maximum C sink of 44 g C m −2 . In combination with a substantially higher C export due to enrichment processes, the overall C balance of the catchment potentially turns into a maximum C source of −44 g C m −2 at the end of the simulation period compared to a C source of −1 g C m −2 for the reference run.

Sediment-associated organic carbon and nitrogen inputs from erosion and irrigation to rice fields in a mountainous watershed in Northwest Vietnam

“…Nadeu et al (2012) point out the importance of sediment sources for OC cycling, as different erosion processes can result in sediments with different OC characteristics and thus different OC preservation patterns. Dlugoß et al (2012) and Fiener et al (2015) additionally emphasize the importance of the magnitude and frequency of erosion events, as they found few high-intensity events result in less OC loss. Similarly in our study site, direct runoff during large rainfall events contributed very little to the paddy OC inputs, even though these events brought in substantial sediment loads (Slaets et al 2015).…”

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

“…Agroecosystems in lower catchment areas may lose fertile sediments transported from upper landscape positions (Fiener, Dlugoß, & Van Oost, 2015).…”

“…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).…”

Modelling a century of soil redistribution processes and carbon delivery from small watersheds using a multi-class sediment transport model

“…Recently, spatially explicit models that combine erosion models with models of carbon dynamics have been developed (e.g. Changing Relief and Evolving Ecosystems Project (CREEP): Rosenbloom et al, 2001;Yoo et al, 2005; SPEROS-C: Van Oost et al, 2005a;Fiener et al, 2015). Both CREEP and the model presented by Yoo et al (2005) focus on long-term landscape development (i.e.…”

“…Second, carbon erosion simulation models need to consider relatively long timescales, i.e. several years to decades, as carbon erosion fluxes are relatively small when compared to rates of soil C turnover (Fiener et al, 2015). Current models addressing erosion (e.g.…”