Chilling Requirements for Optimal Growth of Rocky Mountain Douglas-Fir Seedlings

摘要

One-year-old Douglas-fir (Pseudotsuga menziesii) seedlings from three contrasting interior provenances were chilled for periods ranging from 2 to 20 weeks. Chilling treatments were: a constant 4C, a fluctuating 4C night and 10C, and the outdoor environment. Analyses of six variables related to growth and phenology suggest that the chilling requirements of Rocky Mountain Douglas-fir seedlings were best satisfied by 17 weeks on constant 4C.