Ecological adaptations in Douglas-fir (Pseudotsuga menziesii var. glauca ): A synthesis

Journal Article

Transfer Guideline: Recommendation

Measurements of 3rd-year height of 228 seedling populations, grown in four separate studies in two of the same common gardens, were used to summarize patterns of genetic variation for Douglas-fir across 250 000 km²of forested lands in Idaho and Montana, U.S.A. Because each study was conducted in different years with a different set of populations, measurements were transformed to standard deviates and then were scaled according to the performance of populations common between studies. Genetic variation in 3rd-year height was related to the elevation and geographic location of the seed source by a regression model that accounted for 87% of the variance among populations. In addition, 3rd-year height of 169 of the populations was strongly correlated (r = 0.80) to freezing injury observed in previous studies. Both variables showed that populations from elevationally or geographically mild sites were tall but had low freezing tolerance. Populations from harsh sites were short and cold hardy. In Douglas-fir, adaptation to heterogeneous environments can be viewed as physiological specialization for a relatively small portion of the environmental gradient; populations separated by a relatively short distance along the environmental gradient (e.g., 20 frost-free days) tend to be different genetically.