Browsing by Subject "testate amoebae"
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(2019)Permafrost peatlands have the capacity to store significant amounts of carbon, and thus they act as important controllers of the climate. Approximately 14% of the world’s soil organic carbon pool is stored in permafrost peatlands, which are sensitive to climatic fluctuations due to their location in the high latitudes of the subarctic zone. Permafrost peatlands also act as a habitat for a large number of moisture-sensitive organisms, such as bryophytes and testate amoebae, which can be used to study how the hydrology of peatlands has changed and will continue to change throughout time, giving us an opportunity to predict the future of peatlands under a changing climate. In this Master’s Thesis I examined the testate amoebae composition and used these species as indicators to study hydrological fluctuations from three subarctic permafrost peatland cores extracted from Taavavuoma and Abisko in northern Sweden. The species compositions were combined with radiocarbon (14C) and lead (210Pb) dates to reconstruct the past water table levels for the late Holocene, spanning four climatic periods. The reconstructions were then compared to past studies on testate amoebae to understand how permafrost peatlands and their species assemblages respond to changes in the hydrology of the active layer of the peat. Out of the study sites only the Taavavuoma cores spanned the Dark Age Cold Period (DACP) and Medieval Climate Anomaly (MCA). Species compositions in both cores indicated fluctuating water tables during the DACP, but during the MCA the results began to contradict with one site showing a wetter, and the other a drier MCA. Two out of three study sites indicated a wetter Little Ice Age and a drier Post-Industrial Warming, supporting past studies indicating similar results, whereas one study site gave opposite results. The results indicated large variability in testate amoebae assemblages throughout time, indicating that the hydrology of peatlands can change very abruptly and vary considerably even on a local scale. Modelling is however complicated by the poorly known ecology of testate amoebae, which is why a multi-proxy approach is essential to reliably predict the future fate of permafrost peatlands.
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(2020)Northern peatlands have a major role in the global carbon cycle due to their carbon stocks and fluxes of carbon dioxide (CO2) and methane (CH4). Anthropogenic climate change may affect peatland carbon dynamics through changes in e.g. primary production, hydrology, and permafrost dynamics. It is uncertain whether these changes will lead to northern peatlands becoming significant sources of carbon to the atmosphere. Changes in moisture conditions especially can be an important factor in determining the carbon sink potential of northern peatlands. In this thesis I examine the palaeohydrology and peat accumulation over the past centuries in a permafrost peatland complex in Lovozero, Kola Peninsula, Russia. I used testate amoebae as a proxy of past changes in moisture conditions. Other study methods used here are detrended correspondence analysis (DCA) and 14C and 210Pb dating. The results were also supplemented with plant macrofossil and carbon accumulation data provided by other members of the research team. The results show varying responses of the peatland hydrology and peat accumulation to the past climatic shifts, suggesting that the changes have been driven more by autogenic factors rather than climate. However, all three sites indicated a drying trend and an increased peat accumulation for the last century. Yet, the last decade is charachterised by a wet shift. The wet shifts suggest that the peatlands may have crossed a threshold where increased evapotranspiration is exceeded by increased moisture due to thawing permfrost. The surface peat layers of all three sites were dominated by mixotrophic testate amoebae, which may have contributed to the high peat accumulation. The inconsistency of past successional pathways identified at Lovozero peatlands and the drying trend over the past century correspond to the previous studies from northern peatlands elsewhere. However, the most recent surface wetting during the last decade differs from what has been reported for the other northern sites. This suggests that the response mechanisms of peatlands to the anthropogenic climate change may not be uniform. Thus, further research is inevitably needed to increase our understanding of peatland-climate intercations.
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