Changing dynamics of Alaskan peatlands in the continuous permafrost zone

Peatlands in the continuous permafrost region store globally important amounts of organic carbon, but the stability of this store is threatened by climate warming. Reconstructions from peatlands using sensitive indicators of environmental change, such as testate amoebae, offer insight into the way these ecosystems have responded to past climate changes throughout the late-Holocene. This thesis aims to use palaeoenvironmental reconstructions from two peatlands in the Alaskan North Slope, adjacent to Toolik Lake, to understand their recent past and predict future dynamics to projected warming. To do so, the ecology of testate amoebae from peatlands across the Alaskan North Slope was explored to identify the controlling variables in their distribution. Multivariate statistical analysis shows that pore water electrical conductivity (EC), a proxy for peatland trophic status, was the primary control on testate amoeba distribution, with water table depth (WTD) the secondary control. Two transfer functions were produced to reconstruct EC and WTD with good predictive power. Reconstructions identified that both peatlands at Toolik Lake were mostly moderately-wet, minerotrophic rich fens throughout the late-Holocene, but have undergone a rapid transition to dry, oligotrophic poor fens with post-1850 CE warming. Alongside this ecosystem state shift, there has also been a three-fold increase in carbon accumulation rate post-1850 CE. Overall, this thesis extends the utility of testate amoebae as hydrological indicators into continuous permafrost peatlands; and suggests that rapid ecosystem state shifts may have occurred with recent climatic warming, which may indicate increased rates of carbon sequestration in the future.