Peatland carbon cycling and the implications of permafrost thaw; a chronosequence study.

Wednesday, 16 December 2015: 17:30
2006 (Moscone West)
David Olefeldt, University of Alberta, Edmonton, AB, Canada, Nicolas Pelletier, University of Montreal, Montreal, QC, Canada, Julie Talbot, University of Montreal, Département de géographie & Geotop, Montreal, QC, Canada, Christian Blodau, University of Münster, Münster, Germany and Merritt R Turetsky, University of Guelph, Guelph, ON, Canada
Peatlands in the Mackenzie River valley initiated ~9000 years ago and have built up vast soil carbon stores since. Peatland development history in this region is characterized by several distinct stages, varying in nutrient status and permafrost conditions. Widespread permafrost thaw has recently occurred in response to warming, thus making large soil C stores available for microbial processes and mineralization. A crucial question to answer is whether these peatland become net sinks or sources of C following thaw. The net response to thaw will either be dominated by new peat C accumulation at the surface or by mineralization of old peat C released from permafrost. In order to address this question we cored peat plateaus and nearby thermokarst bogs near Fort Simpson, Northwest Territories, representing 4 chronosequences. The cores were analyzed for C content, radiocarbon dates, macrofossils, testate amoebas, peat humification degree, elemental analysis, and microbial lability through an incubation experiment. Together, these approaches reveal peatland development histories, both before and following permafrost thaw. It is clear from our findings that C cycling following permafrost thaw will be intrinsically dependent on the developmental history of the peatland.