Aspect influences cone abundance within the crown of Pinus banksiana Lamb. trees at the limit of the species distribution in northern Quebec (Canada)

We studied the variability in cone and seed production and vegetative growth within the crown of jack pine trees (Pinus banksiana Lamb.) in a population al the limit of the species distribution in northern Quebec. Number of cones, number of fertile scales per cone, proportion of formed seeds per cone, and branch elongation were compared among heights and aspects for 15 trees, over a 4-year period. Cone number was generally greater in the south quadrant and in the upper part of the tree crown. Number of fertile scales per cone, proportion of formed seeds per cone, and branch elongation were also higher in the upper part of the tree crown, but did not vary much with aspect. Increased cone production in the south quadrant of the tree crown was thus not strictly related to higher branch growth and vigor, but appeared to result from direct and/or indirect effects of higher intercepted radiation on this part of the tree crown.