A near‐annual palaeohydrological study based on testate amoebae from a sub‐alpine mire: surface wetness and the role of climate during the instrumental period

Abstract

We present the first testate amoeba-based palaeohydrological reconstruction from the Swiss Alps, and the first depth to the water table (DWT) calibration dataset for this region. Compared to existing models, our new calibration dataset performs well (RMSEP ¼ 4.88), despite the length of the water table gradient covered (53 cm). The present-day topography and vegetation of the study mire Mauntschas suggest 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 surrounding area. 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 northwestern 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 subalpine mires is needed to understand the relationships between climate, testate amoebae and peatland development.

Fine-Scale Horizontal and Vertical Micro-distribution Patterns of Testate Amoebae Along a Narrow Fen/Bog Gradient

“…Indeed, the location and size of different microhabitats and related communities in Sphagnum peatlands are not stable over time [8] and this is clearly also true for testate amoeba assemblages as attested by the limited existing data on seasonal patterns [62] as well as the changes documented in numerous palaeoecological records [10]. Understanding environmental controls on testate amoebae communities at these finer spatial and temporal scales is key to improving our ability to interpret the highresolution fossil testate amoeba records in peatlands that is starting to being produced [31]. This will require both further detailed descriptive studies as well as manipulative experiments using biotic (phenols) and abiotic data and aiming to determine which factors influence testate amoebae and what the mechanisms are.…”

Comparing regional and supra-regional transfer functions for palaeohydrological reconstruction from Holocene peatlands

“…However in practice, microsieving makes analysis more efficient particularly when processing large numbers of samples often encountered in palaeoclimate studies and remains routinely employed (e.g. Elliott et al, in press;Lamentowicz et al, 2010;Payne, 2011;van der Knaap et al, 2011). Due to the large number of samples and the need to improve slide clarity for samples with minerogenic material present, the fine sieve stage was included for both contemporary and palaeo sample preparation to retain consistency.…”

“…Booth, 2008;Charman, 1997;Lamentowicz et al, 2009;Lamentowicz et al, 2010;Langdon and Barber, 2005;Mitchell et al, 2001;Payne et al, 2006;Swindles et al, 2010). The hydrology of ombrotrophic ('rain-fed') peatlands is strongly linked to effective precipitation (precipitation -evapotranspiration), especially during the deficit period (Charman, 2007).…”

“…Although there are a number of peat-based hydrological proxies, such as plant macrofossils and peat humification, testate amoebae have become increasingly favoured by many researchers over the last two decades as transfer functions can be used for quantitative reconstruction of palaeo-water tables (e.g. Charman et al, 2007;Charman and Warner, 1992;Lamentowicz et al, 2010;Payne and Mitchell, 2007;Swindles et al, 2010;Wilmshurst et al, 2003;Woodland et al, 1998).…”

The performance of single- and multi-proxy transfer functions (testate amoebae, bryophytes, vascular plants) for reconstructing mire surface wetness and pH

“…Combining different proxies in a synthetic way (e.g., in a single transfer function) is an alternative option. This option may be especially pertinent where proxies differ slightly in their response (Lamentowicz et al, 2010b) or are useful for different parts of a gradient (Gehrels et al, 2001). Previous studies have examined the combined use of testate amoebae, diatoms, and foraminifera (Gehrels et al, 2001) and diatoms and foraminifera (Kemp et al, 2009) for reconstructing past sea-level changes, and of chironomids, diatoms, and chrysophytes for reconstructing alkalinity, DIC, altitude, pH and dissolved CO 2 in mountain lakes (Thompson et al, 2008).…”