Geoelectrical Fingerprinting of Two Contrasting Ecohydrological Peatland Types in the Alps

Abstract

Peatlands are valuable but fragile ecosystems with diverse biogeochemical and hydrological functions, so their characterization requires non-destructive investigation. We studied adjacent alpine peatlands of similar size, at the same altitude, and exposed to identical climatic conditions, but with differing topographic and geologic settings producing contrasting ecohydrological functioning; one is a rainwater-fed bog, the other is a groundwater-fed fen. Two intentionally simple geoelectrical techniques were applied to obtain rapid geophysical fingerprints of these peatlands: vertical electrical sounding (VES) and self-potential (SP). Strongly contrasting results agree with conceptual understandings of bogs and fens. The bog VES displays a high-resistivity near-surface layer, corresponding to lowly-mineralized rainwater, while resistivity in the fen is two orders of magnitude lower due to more highly-mineralized groundwater. The SP profile of the bog indicates radially-divergent drainage, while the profile of the fen points to lateral groundwater inflow from adjacent slopes. The paired-peatland approach made possible identification and isolation of the effects of hydrological functioning on geophysical properties, while eliminating possible differences due to climate or altitude. Most importantly, this study shows that very few and simple geophysical measurements can produce critical near-real-time data on hydrologic properties of peatlands – which is especially important for inaccessible high alpine locations.