Impacts of soil redistribution on the transport and fate of organic carbon in loess soils

Soil erosion is an important environmental process leading to loss of topsoil including carbon (C) and nutrients, reducing soil quality and loss of biomass production. So far, the fate of soil organic carbon (SOC) in eroding landscapes is not yet fully understood and remains an important uncertainty in quantifying the global C cycle. The main objective of this research was to improve our understanding of the behavior and fate of different SOC pools in loess soils from Western Europe as affected by soil erosion, transport, and deposition processes. Erosion, transport, and deposition led to breakdown of aggregates, which altered the lateral redistribution of different SOC pools. Carbon mineralization at different slope positions was also affected resulting in C depletion at upslope positions and C accumulation at downslope positions. Most of the eroded C will be deposited downslope. Soil redistribution led to accumulation and stabilization of SOC in the depositional area due to the burial of C rich topsoil. The interplay between aggregation and the formation of mineral-associated SOC is one of the key issues to understand the stability of eroded SOC. However, a significant portion of eroded soil material with labile C in solid and dissolved phases will be transported by overland flow into aquatic environments, where it can be potentially mineralized. In eroding landscapes, CO2 emission is the predominant pathway of C losses. Additional research combining modelling approaches and field scale measurements is needed to further explore the role of soil redistribution in regional and global C budgets.