Browsing by Subject "210Pb dating"

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.