Résumé
Periodicity of shoot elongation in seedlings of Pinus contorta Dougl. ex Loud. was assessed during one growing season in two extremely different environments (Cowichan Lake, and Red Rock, British Columbia) for 109 provenances sampled range wide. Analysis of variance of total elongation and growth parameters showed significant differences among geographic regions and among provenances within each region. Our study also revealed tremendous genotype-by-environment interaction for growth and phenological traits. The response of growth to temperature of each provenance was assessed from their growth curve using an original methodology. The estimated temperature threshold of the provenance growth responses (i.e., the temperature for which the response reaches half of its maximum) varied between 4.1 and 6.5 deg C among regions. Threshold temperatures showed less variation than total elongation, and only the northern provenances showed thresholds significantly different from the other regions. Our results show that, across highly contrasting environments, relationship between phenology and growth may not be as important as the relationship between growth and number of internode priomordia. This tempers the results of studies, carried out in one or few similar environments, that have shown that phenological differences were important in determining total height growth in lodgepole pine. Lindgren, K., and Nilsson, J.E. 1992. Cold acclimation of Pinus sylvestris and Pinus contorta provenances as measured by freezing tolerance of detached needles. Scand. J. For. Res. 7: 309-315. Rehfeldt, G.E., Ying, C.C., Spittlehouse, D.L., and Hamilton, D.A. 1999. Genetic responses to climate for Pinus contorta in British Columbia: niche breadth, climate change and reforestation. Ecol. Monogr. 69: 375-407.