Preliminary studies on the ecology of palsa mounds in northern Ontario

• Published in: Canadian Journal of Botany
• Main Authors: Railton, J. B., Sparling, J. H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1973
• Subjects: Plant Science; Canada; Ice; ice core; palsa; palsas; permafrost; Subarctic
• Online Access: http://dx.doi.org/10.1139/b73-128; http://www.nrcresearchpress.com/doi/pdf/10.1139/b73-128

Peat mounds with frozen permafrost cores, or palsas, occur in areas with sporadic permafrost in subarctic and boreal parts of Canada. In northern Ontario, the surface vegetation of palsas is characterized by the presence of Cladonia alpestris, C. rangiferina, and C. sylvatica with occasional stunted Picea mariana which are surrounded by Ledum groenlandicum and Vaccinium vitis-idaea. From vegetational analysis, hummock and palsa morphology, and radiocarbon dating, evidence is given for a recent origin under climatic conditions similar to the present. The largest palsas appear to be about 200 years old. Details of energy exchange during July are given for mature, partially eroded, and collapsed palsas. The formation of palsas may be dependent on changes in surface albedo associated with vegetational change from Sphagnum fuscum to Cladonia spp. dominated communities where the albedo was found to increase from 13.8% to 21.3%. However, evidence is presented that decreased penetration of heat during summer associated with the drying of surface peat may be important in palsa formation. Lower thermal conductivity of the peat at this time would insulate the ice core from insolation. Collapse of palsas was attributed to surface and marginal erosion and higher heat penetration to the core associated with wetter peat conditions on the palsa.