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The soil system under global change: impacts on the biogeochemical cycles
Convener: Bas van Wesemael  | Co-Conveners: Carolina Boix-Fayos , Jan Vanderborght , Kristof Van Oost 
 / Tue, 14 Apr, 15:30–17:15
 / Attendance Tue, 14 Apr, 17:30–19:00

Human interventions on the soil system, mainly as a result of land use and land management, have now reached a level that soil forming processes are influenced on the decadal timescale. Soil erosion entrains lateral fluxes of C resulting in burial of C in colluvia and replacement of soil C on eroded hillslopes to such an extent that these lateral fluxes are now considered as a small but significant C sequestration in the global C cycle. Following deposition of the eroded soil, reactions between the fresh reactive mineral surfaces with organic matter have the potential to control C sequestration due to the strong influence of complexing cations and reactive soil minerals. Silica fluxes to the rivers are significantly lower in catchments under cropland compared to forested catchments but major gaps in the fundamental understanding of the silica cycle, particularly the effects of human activities, remain. Furthermore, the interaction between aforementioned effects and changes in climate are largely unknown. These examples demonstrate that soil forming processes have now reached such rates that they can no longer be considered to be in a steady state and that we need to include both dynamic soil properties and lateral fluxes for a better understanding of the role of soils in the biogeochemical cycles even at the scale of decades.

We would welcome contributions on the understanding and quantification of the feedbacks between the soil system and sediment, nutrient, water and carbon fluxes in response to anthropogenic forcings over timescales ranging from the decade to the millennium.