Long-term interactions between soil organic carbon dynamics, sediment redistribution and soil evolution
(2018)
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- Abstract
- Soils are a major reservoir for organic carbon storing more carbon (C) than vegetation and the atmosphere combined. Soil organic carbon (SOC) is regarded as a key soil property due to its effects on soil functions such as water retention or soil fertility. The removal of natural vegetation for agricultural purposes intensified soil redistribution processes and associated lateral SOC fluxes. There is now increasing acceptation that accelerated lateral SOC fluxes also alter the amount of carbon that is exchanged between soils and the atmosphere. Using a process-based, spatially-explicit modelling approach linking land cover change, soil redistribution, soil evolution and SOC cycling, this thesis highlights the strong temporal and spatial variability of the C budget at the catchment scale. Under soil erosion, SOC stock can reach a dynamic equilibrium at which the hillslope C export is compensated by the atmospheric replacement of the eroded C. The dynamic equilibrium follows a transient period of several decades in which the rate of C uptake from the atmosphere is steadily increasing. The SOC released from soils to the atmosphere quickly responded to anthropogenic land conversion while the erosion-induced C fluxes exhibited a very slow response time. Our model simulations suggest that, over the past millennium and for the environmental settings considered, the C sink could have almost offset the C losses related to land cover conversion. In addition, the long-term sustainability of the C sink and the establishment of a steady state regime are negatively affected by the impact of soil erosion on biomass productivity and soil resources. Using observations from a wide range of soil conditions, we showed that including biomass productivity evolution in the C budgeting improves the prediction of SOC losses and results in increased SOC losses and a reduced C sink intensity, relative to a scenario without soil erosion-productivity feedbacks. Finally, in contrast with environments characterized by deep soils, soil resources limitation prevents or limits the establishment of a steady-state regime due to the constraints exerted on the C sink. Together, this thesis provides an improved quantification of the long-term SOC budget under human impact.
- Affiliations
UCLouvain SST/ELI/ELIC - Earth & Climate
Citations
Bouchoms, S. (2018). Long-term interactions between soil organic carbon dynamics, sediment redistribution and soil evolution. https://hdl.handle.net/2078.5/104425