DATING WITH CUSHION PLANTS - ESTABLISHMENT OF A SILENE-ACAULIS GROWTH CURVE IN THE CANADIAN ROCKIES

Average long-term growth rates of Silene acaulis cushions in four glacier forefields were used to construct a preliminary growth curve for use in relative dating of surfaces at alpine sites in the Canadian Rockies. Mean growth rates of 0.06 to 1.82 cm yr-1 were estimated from maximum diameters of 76 plants on 17- to 252-yr-old surfaces in the Kananaskis/Elk Lakes area of Alberta and British Columbia. A growth curve estimated from these data shows the growth rates are intermediate between data reported from the Swiss and Italian Alps, West Greenland, and Colorado. Further investigation is required to determine whether the sampling methodology and assumptions used to interpret cushion-diameter/substrate-age data are accurate. In the interim it is suggested that cushion-plant dating is best used in conjuction with independent dating techniques.