Ecological adaptations in Douglas-fir (Pseudotsugamenziesii var. glauca) populations. III. Central Idaho

Abstract

Growth, phenology, and cold hardiness of seedlings from 74 populations of Douglas-fir (Pseudotsugamenziesii var. glauca (Beissn.) Franco) from central Idaho were compared in four contrasting environments. Analyses of 3-year-old seedlings revealed population differentiation for eight variables: bud burst, bud set, multiple flushing, height, deviation from regression of 3-year height on 2-year height, spring frost damage, fall frost damage, and winter injury. These analyses, as well as high intercorrelations among population means, suggested that adaptations result from a balance between selection for a high growth potential in mild environments and selection for cold hardiness in severe environments. Consequently, genetic variation among populations was closely related to the elevation, geography, and climate of the seed source.