| Summary: | Northern peatlands have accumulated ~500 Pg of carbon (C) over millennia, and contributed to a net climate cooling. However, the fate of peatland C pools and related climate-system feedbacks remain uncertain under scenarios of a changing climate and enhanced anthropogenic pressure. Here, Holocene C dynamics in the Hudson Bay Lowland, Canada (HBL) are examined at the landscape scale with respect to glacial isostatic adjustment (GIA), climate, and ecohydrology. Results confirm that the timing of peat initiation in the HBL is tightly coupled with GIA, while contemporary climate explains up to half of the spatial distribution of the total C mass. Temporal patterns in C accumulation rates (CARs) are related to peatland age, ecohydrology, and possibly paleoclimate, whereby CARs are greatest for younger, minerotrophic peatlands. Rapid and widespread peatland expansion in the HBL has given rise to a globally significant C pool, in excess of 30 Pg C and two-thirds of which is of late Holocene age. Yet, long-term decomposition of previously accrued peat has potentially resulted in some C losses, especially during the late Holocene when the landscape was occupied by an abundance of minerotrophic peatlands and climate was characterized by more precipitation and similar-to-colder temperatures than present. Model deconstruction of HBL C dynamics indicate that 85% of C losses occurred during the late Holocene, while spatio-temporal scaling of modern methane (CH4) emissions suggest a potential flux of 1 – 7 Pg CH4 to the late Holocene atmosphere, which provides evidence of a peatland contribution to the late Holocene CH4 rise recorded in ice cores. Although HBL peatlands may continue to function as a net C sink, conservative climate scenarios predict warmer and wetter conditions in the next century – beyond the HBL’s range of past climate variability, yet within the peatland climate domain – with implications for primary production and decomposition. Further investigation into controls on spatial-temporal C dynamics may reduce uncertainty concerning the HBL’s potential to remain a net C sink under future climate and resource management scenarios, and contribute to our understanding of global peatland C-climate dynamics. Ph.D.
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