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Black spruce (Picea mariana (Mill) B. S. P.) first-year seedlings were exposed to 8-hr photoperiods and warm temperatures (26C maximum, 15C minimum) and tested weekly to determine bud dormancy status, frost hardiness, shoot moisture content, and the amount of damage caused. by a period of frozen storage ( - 3C). Bud dormancy status, frost hardiness, and shoot moisture content were all strongly correlated to the time of bud initiation. Frost hardiness was low ( - 5 to - 7.5C) during the period of needle primordia initiation until week 3 (3 weeks after 100% bud initiation), but bud dormancy decreased linearly over this period, from 37 days to budbreak for seedlings sampled at week - 1 (1 week before 100% of the seedlings had initiated terminal buds) and placed under conditions favoring shoot elongation, to 14 days to budbreak for seedlings sampled on week 3. From week 5 to week 8, there was a strong (r 2 > 0.999) linear correlation between frost hardiness and bud dormancy status. Shoot moisture content declined linearly from 84% on week - 1 to 74% on week 8 (r 2 = 0.97), and shoot moisture content was correlated with both frost hardiness (r 2 = 0.87) and the percentage of seedlings that suffered needle damage in frozen storage (r 2 = 0.85). Bud dormancy status, measured as number of days to 50% budbreak, was curvilinearly correlated with seedling damage following frozen storage, whereas linear relationships with damage in storage were found for dor- mancy release index (r 2 = 0.92) and frost hardiness (r 2 = 0.85). The ability of tree seedlings to endure frozen storage without damage has been empirically related to shoot frost hardiness, bud dormancy status, and shoot moisture content (Ritchie, 1984, 1986; Glerum, 1976; Rossvall-Ahnebrink, 1977), where seed- lings that are most dormant or have exceeded critical levels of frost hardiness or shoot moisture content exhibit the best stor- ability. These relationships have practical significance because they may enable the proper timing of tree seedling frozen stor- age to be predicted by the measurement of these variables. Ex- amples of the use of such attributes for predicting readiness for storage of various species have been given (Ritchie, 1984, 1986; Ritchie et al., 1985; Tinus et al., 1986). The levels of frost hardiness, bud dormancy, and shoot mois- ture content required for damage-free frozen storage have been shown to vary among species and for different provenances within a species (Ritchie, 1984, 1986; Ritchie et al., 1985; Rossvall-Ahnebrink, 1977). Therefore, it is important that the relationships between these variables and frozen storage be in- vestigated for new species before the implementation of storage programs. In Canada, nearly all container stock produced, ex- cept in British Columbia, is overwintered outside. There is growing interest in the use of frozen storage for overwintering container stock because of the advantages it gives in reducing losses due to shoot desiccation, root freezing, disease, and ro- dents. Further, seedlings held in storage possess high post-plant- ing stress resistance as a result of remaining dormant through the spring until planting. The purpose of this paper is to describe the relationships between shoot frost hardiness, bud dormancy status, shoot moisture content, and success of frozen storage for l-year-old black spruce seedlings.

Bud Dormancy Status, Frost Hardiness. Shoot Moisture Content, and Readiness of Black Spruce Container Seedlings for Frozen Storage