Hydrogeophysical characterization of the soil along a floodplain-hillslope system in the High Fens
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- Peatlands are biotopes of interest because of the numerous ecosystem services they provide such as water purification, biodiversity and carbon storage. The latter is especially important as even though peatlands only cover 3% of global land surface, they are estimated to contain between 5% and 20% of the global soil carbon stock. In critical zone research, the integrated study of the subsurface on the landscape scale remains a key knowledge gap. This master thesis aims at addressing this problem by studying the subsurface of a hillslope-floodplain system in the High Fens peatlands with the use of hydrogeophysical methods: electromagnetic induction (EMI) and ground-penetrating radar (GPR). The EMI measurements revealed electrical conductivity values ranging from 8,0 to 15,0 mS/m across the study site and showed some contrast between wet and dry seasons. GPR and soil profiling allowed us to better understand the subsurface structure, which does not show a direct link with the observed soil bulk electrical conductivity. Indeed, soil profiles with comparable structures presented very different electrical conductivities. Measurements of the soil solution electrical conductivity have revealed low values ranging from 2,3 mS/m to 6,6 mS/m. These values explain the lower bulk electrical conductivities measured in saturated zones. The low soil water conductivity values, combined with the seasonal changes in measured bulk electrical conductivity, point to the fact that soil water content is the main contributor to the bulk electrical conductivity. This master thesis is a good starting point for comparison with future integrated peatland subsurface studies as well as the use of hydrogeophysical techniques in such environments.