CGRG Bibliography of Canadian Geomorphology
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Author : Beilman, D.; and Yu, Z.
Date : 2007.
Title : Late Holocene permafrost-carbon dynamics in peatlands of Western Canada - A new multiproxy perspective from the southern limit.
Publication : 2007 Meeting of the American Association of Geographers, April 17-21 2007, San Francisco, California.
Issue :
Page(s) :
Abstract
The widespread thaw of discontinuous permafrost across the boreal plains of North America, including disappearance at its southernmost fringe, has resulted in changes to peatland vegetation and carbon cycling. The accepted regional model of peatland permafrost dynamics ascribes widespread formation to late Holocene cooling, and particularly to the onset and termination of 'Little Ice Age' cooling (LIA). However, detailed paleoenvironmental data in support of permafrost history and sensitivity have been lacking. Here we present a 9000 year high-resolution multi-proxy record of peatland history from a treeless thaw site at the southern limit of permafrost in Saskatchewan, Canada, using 11 AMS radiocarbon dates, plant macrofossils, carbon and nitrogen assays, and decomposition proxies. Minerotrophic conditions, first characterized by sedges and then by brown mosses, persisted until about 2500 years ago. Multi-proxy evidence suggests that permafrost developed before 700 years ago, associated with a sharp decrease in carbon accumulation. The age of a spruce needle layer at the transition between forest and post-thaw Sphagnum peat indicates that permafrost degraded between 300 and 500 years ago, followed by increase in carbon sequestration. These permafrost dynamics, which predate the LIA, are consistent with 1500-yr climate cycles evident in other Holocene records. The effect on modern vegetation of permafrost thaw at this site has persisted for hundreds of years.
Bibliography of Canadian Geomorphology