Alpine peatlands are valuable but vulnerable ecosystems with diverse hydrological and biogeochemical functions, and they provide habitat for rare and endangered species. Therefore, their characterization requires non-destructive investigation techniques. Furthermore, due to alpine terrain conditions, only light-weighted and robust equipment can be used. We studied two adjacent alpine peatlands of similar size, altitude, and climatic conditions, but with differing topographic and geologic settings resulting in contrasting ecohydrological functioning. The first one is a rainwater-fed bog, the second one is a fen fed by lateral inflow of shallow groundwater from the surrounding slopes. Two simple geoelectrical techniques were applied to obtain rapid geophysical fingerprints of these peatlands: vertical electrical sounding (VES) and self-potential (SP). The clearly contrasting results agree with conceptual understandings of bogs and fens.
The bog VES displays a high-resistivity near-surface layer, corresponding to lowly-mineralized water in the organic soil that originates directly from rainwater. Resistivity in the near-surface layers of the fen is two orders of magnitude lower due to more highly-mineralized groundwater influenced by water-rock interaction. The SP profile of the bog indicates radially-divergent drainage, corresponding to a convex water table, i.e., recharge in the center of the bog and drainage towards the edges. The SP profile of the fen points to lateral inflow from adjacent slopes, corresponding to a convex water table; the fen drains via swallow holes at its northern edge.
The paired-peatland approach made it possible to isolate and identify the effects of ecohydrological functioning on geophysical properties, while eliminating possible differences due to climate, size or altitude. This study also shows that few and simple geophysical measurements can produce relevant insights into the properties of peatlands, which is especially useful for high alpine locations.