A near-annual palaeohydrological study based on testate amoeba from an Alpine mire: surface wetness and the role of climate during the instrumental period
We present the first testate amoeba-based palaeohydrological reconstruction from the Swiss Alps, and the first depth to the water table (DWT) calibration data-set for this region. Compared to existing models, our new calibration data set performs well (RMSEP=4.88), despite the length of the water-table gradient covered (53 cm). The present-day topography and vegetation of the study mire Mauntschas suggests that it is partly ombrotrophic (large Sphagnum fuscum hummocks, one of which was the coring site) but mostly under the minerotrophic influence of springs in the mire and runoff from the surroundings. Ombrotrophic Sphagnum fuscum hummocks developed at the sampling site only during the last 50 years, when testate amoebae indicate a shift towards dry and/or acid conditions. Prior to AD 1950 the water table was much higher, suggesting that the influence of the mineral-rich water prevented the development of ombrotrophic hummocks. The reconstructed DWT correlated with Pinus cembra pollen accumulation rates, suggesting that testate amoebae living on the mire and P. cembra growing outside of it partly respond to the same factor(s). Finally, temperature trends from the nearby meteorological station paralleled trends in reconstructed DWT. However, contrary to other studies made on raised bogs of NW Europe, the highest correlation was observed for winter temperature, despite the fact that testate amoebae would more logically respond to moisture conditions during the growing season. The observed correlation with winter temperature might reflect a control of winter severity on surface moisture during at least the first part of the growing season, through snow-melt and soil-frost phenomena influencing run-off. More ecohydrological work on sub-alpine mires is needed to understand the relationships between climate, testate amoebae, and peatland development.