Long-term stability of permafrost in subarctic peat plateaus, west-central Canada

Abstract

Long-term vegetation succession and permafrost dynamics in subarctic peat plateaus of west-central Canada have been studied through detailed plant macrofossil analysis and extensive AMS radiocarbon dating of two peat profiles. Peatland inception at these sites occurred around 5800–5100 yr BP (6600–5900 cal. BP) as a result of paludification of upland forests. At the northern peat plateau site, located in the continuous permafrost zone, palaeobotanical evidence suggests that permafrost was already present under the forested upland prior to peatland development. Paludification was initiated by permafrost collapse, but re-aggradation of permafrost occurred soon after peatland inception. At the southern site, located in the discontinuous permafrost zone, the aggradation of permafrost occurred soon after peatland inception. In the peat plateaus, permafrost conditions have remained very stable until present. Sphagnum fuscum-dominated stages have alternated with more xerophytic communities characterized by ericaceous shrubs. Local peat fires have occurred, but most of these did not cause degradation of the permafrost. Starting from 2800–1100 yr BP (2900–1000 cal. BP) consistently dry surface conditions have prevailed, possibly related to continued frost heave or nearby polygon crack formation.

Peatland dynamics in a complex landscape: Development of a fen-bog complex in the Sporadic Discontinuous Permafrost zone of northern Alberta, Canada

“…Peatlands presently underlain by permafrost initiated mostly in permafrost-free environments, both in Canada (Zoltai & Tarnocai 1975;Sannel & Kuhry 2008) and in parts of the Russian Arctic (Oksanen et al 2001). In continental western Canada, basal peat ages range from 9000 to 3000 a BP, with the oldest dates in the Rocky Mountain foothills and northern Alberta, and the youngest dates in the southern Boreal Forest and Aspen Parkland (Halsey et al 1998).…”

“…However, there also appears to be considerable variability in vegetation-permafrost interactions. Not all permafrost peat profiles show collapse-aggradation cycles (Sannel & Kuhry 2008), and alternative pathways to peat plateau formation have been proposed (Oksanen et al 2001). Not all instances of permafrost collapse can be linked to fire (Kuhry 2008), and not all fires trigger permafrost collapse (Sannel & Kuhry 2008).…”

“…Not all permafrost peat profiles show collapse-aggradation cycles (Sannel & Kuhry 2008), and alternative pathways to peat plateau formation have been proposed (Oksanen et al 2001). Not all instances of permafrost collapse can be linked to fire (Kuhry 2008), and not all fires trigger permafrost collapse (Sannel & Kuhry 2008). Local and regional differences in peatland-permafrost interactions probably reflect differences in permafrost temperature and depth, different palaeoclimatic and palaeoenvironmental histories, and differences in available species pools.…”

“…Local and regional differences in peatland-permafrost interactions probably reflect differences in permafrost temperature and depth, different palaeoclimatic and palaeoenvironmental histories, and differences in available species pools. Further local studies are required (Sannel & Kuhry 2008), followed by broader syntheses to extract general patterns. Compared with other peat plateau regions, northwestern Alberta is characterized by relatively high mean temperatures and a thin, warm permafrost (Smith & Riseborough 2010).…”

From past to future: impact of climate change on range shifts and genetic diversity patterns of circumboreal plants

“…Macrofossils of this species from the Late Tertiary have been found in non-glaciated regions of Alaska (Matthews and Ovenden 1990) and in northern and northeastern Siberia (Nikitin 2006), from the end of the Wisconsin interglacial in Nova Scotia (Mott et al 1982), and in the Early Würm in Siberia (Laukhin et al 2007). Other studies have reported only Early, Middle, or Late Holocene macrofossils from North America, Europe, and Asia (Bhiry and Filion 1996;Booth and Jackson 2003;Booth et al 2004;Sannel and Kuhry 2008;Novenko et al 2009). The pollen and macrofossil records of the other two taxa, L. b ssp.…”