The soil carbon erosion paradox reconciled

Abstract

Abstract. The acceleration of erosion, transport and burial of soil organic carbon (C) in response to agricultural expansion represents a significant perturbation of the terrestrial C cycle. Recent model advances now enable improved representation of the relationships between sedimentary processes and C cycling and this has led to substantially revised assessments of changes in land C as a result of land cover and climate change. However, surprisingly a consensus on both the direction and magnitude of the erosion-induced land-atmosphere C exchange is still lacking. Here, we show that the apparent soil C erosion paradox, i.e., whether agricultural erosion results in a C sink or source, can be reconciled when comprehensively considering the range of temporal (from seconds to millennia) and spatial scales (from soil microaggregates to the Land Ocean Aquatic Continuum (LOAC)) at which erosional effects on the C cycle operate. Based on the currently available data (74 studies), we developed a framework that describes erosion-induced C sink and source terms across scales. Based on this framework, we conclude that erosion is a source for atmospheric CO2 when considering only small temporal and spatial scales, while both sinks and sources appear when multi-scaled approaches are used. We emphasize the need for erosion control for the benefits it brings for the delivery of ecosystem services, particularly in low-input systems, but our analysis clearly demonstrates that cross-scale approaches are essential to accurately represent erosion effects on the global C cycle.

The impact of natural closed depressions on soil organic carbon storage in eroded loess landscapes of East Poland

“…Kühn et al, 2017;Von Suchodoletz et al, 2019). Small Many studies emphasise, that waterlogging of soils at sediment depositional sites, reduces the soil microbial activity, stabilising SOC and limiting organic matter decomposition rates, affecting SOC resources (T. Li et al, 2019;Stallard, 1998;Świtoniak et al, 2015;Van Oost et al, 2007;Van Oost & Six, 2022;Zhang et al, 2016). Meersmans et al (2008) demonstrated that, in Flanders (Belgium), a higher SOC content coincides with soils of waterlogged areas (depressions areas) because of limitation of the SOC oxidation.…”

“…Burial of SOC in colluvial sediments at depositional sites enhances stabilisation and sequestration of SOC and reduces CO 2 fluxes from the soil to the atmosphere (Berhe et al, 2007;Borrelli et al, 2018;Chaopricha & Marin-Spiotta, 2014;Cheng et al, 2010;Lal & Pimentel, 2008;Stallard, 1998;Van Oost et al, 2007). The need to quantify which part of eroded SOC from soils is buried in sedimentary environments is emphasised in order to better assess terrestrial SOC dynamics and terrestrial carbon storage at large scales (Borrelli et al, 2018;Van Oost & Six, 2022).…”

Soil erosion on arable land: An unresolved global environmental threat

“…For example, some used soil-centred approaches, upscale results from plots or small catchments via parsimonious modelling approaches (Naipal et al, 2018; van Oost et al, 2007; Wang et al, 2017), while others uses sediment-centred approaches estimating erosion induced changes in C cycling from the sediment fluxes measured in macroscale river systems (Smith et al, 2001; Lal, 2003). Overall it can be concluded that an accurate global estimate it is currently not possible due to a lack in data to account for small scale dynamics of lateral soil fluxes and also a lack in process understanding while transporting carbon rich sediment from the hillslope into the oceans (Van Oost and Six, 2022).…”