Effects of seed origin on drought resistance of Douglas-fir (Pseudotsuga menzisii ) (Mirb.) Franco

Douglas-fir seedlings from a number of seed origins were subjected to drought conditions in the greenhouse and laboratory. Interior mountain seedlings showed significantly greater drought resistance than seedlings from origins west of the Cascade Mountains. Differences were also found within each of these groupings. In the Corvallis, Oregon, area seedlings produced from seed on a south slope had more drought resistance than those from a short distance away on a north slope. Differences in drought resistance may involve either drought hardiness or drought avoidance, or both.