Holocene development and permafrost history in sub-arctic peatlands in Tavvavuoma, northern Sweden

Under changing climatic conditions permafrost peatlands can play an important role in the global carbon budget through permafrost carbon feedbacks and shifts in carbon assimilation. To better predict future dynamics in these ecosystems an increased understanding of their Holocene carbon and permafrost history is needed. In Tavvavuoma, northern Sweden, we have performed detailed analyses of vegetation succession and geochemical properties at six permafrost peatland sites. Peatland initiation took place around 10000 to 9600cal. a BP, soon after retreat of the Fennoscandian Ice Sheet, and the peatlands have remained permafrost-free fens throughout most of the Holocene. At the four sites that showed a continuous accumulation record during the late Holocene radiocarbon dating of the shift from wet fen to dry bog vegetation, characteristic of the present permafrost peatland surface, suggests that permafrost developed at around 600-100cal. a BP. At the other two sites peat accumulation was halted during the late Holocene, possibly due to abrasion, making it more difficult to imply the timing of permafrost aggradation. However also at these sites there are no indications of permafrost inception prior to the Little Ice Age. The mean long-term Holocene carbon accumulation rate at all six sites was 12.3 +/- 2.4 gC m(-2) a(-1) (+/- SD), and the mean soil organic carbon storage was 114 +/- 27kg m(-2).