A genecological investigation of the annual rhythm of Pinus contorta Dougl. and a comparison with Pinus silvestris L.

In a material of 27 provenances of two-year-old Pinuss contorta it was found that the annual rhythm, illustrated by degree of lignification, colour of the bark on the terminal shoot, dry/fresh weight of needles, shoot extension, budsetting and electrical resistance, was related to the geographic and climatic parameters of seed source. Regression analyses showed that the rhythm was most closely correlated with the mean January daily temperature and latitude. The analyses also showed how latitude and altitude interact. Budsetting was found to have a pattern of geographic variation that was different from the other expressions of rhythm. A comparison between P. contorta and P, silvestris with reference to lignification, laboratory frost resistance and field hardiness, indicated that the Canadian pine, which withstands a Scandinavian climate far north of its seed source, presumably manages to do so in spite of a relatively low degree of winter adjustment in late September.