Cellular phenology of annual ring formation ofAbies balsameain the Quebec boreal forest (Canada)

Cell formation in growth rings of balsam fir (Abies balsamea (L.) Mill) in the boreal forest was studied to describe the timing of ring formation and the development patterns of earlywood and latewood. Wood micro-cores were extracted during the growing season from 1998 to 2000. The micro-cores were stained with cresyl fast violet to facilitate counting the number of cells in the radial enlargement, wall thickening phases, and mature cell phases. The periods required to complete these various phases were then estimated. Variations in the beginning of the growing season (May 7 – June 7), the earlywood–latewood transition (July 2 – July 19), and the end of the growing season ( August 20 – September 20) were observed. Short cell enlargement durations of less than a week for earlywood and 5–10 days for latewood were observed. Time required for cell wall thickening was about 20 days for earlywood and longer than 10–15 days for latewood. A certain flexibility was observed in the ring formation patterns and in the cell development rate, providing an advantage in the boreal forest where optimal growth conditions change from year to year. These findings on the spatial and temporal patterns of ring development may be useful for understanding tree relationships with climate or other environmental parameters.