The genetics of stem volume, stem form, and branch characteristics in sapling noble fir

Genetic parameters for stem volume, stem form, and branching traits, along with the genetic interrelationships among these traits, were estimated from measurements on 60 open-pollinated families of noble fir (Abies procera RE HD.) planted on three progeny test sites in southwest Washington (U.S.). La rge family-by-site interactions were evident when all three sites were anal yzed together; consequently, data for the two low-elevation sites (<1200 m) were analyzed separately from the high-elevation site (1402 m). Significan t family variation was present in at least one environment for 10 of the 13 traits examined. Estimates of narrow-sense heritabilities were low to mode rate (0.09 to 0.49) for all traits. With the exception of branch number and stem sinuosity, genetic correlations among stem growth, stem form, and bra nch traits were weak or favorable, so that selection for stem growth should have few unfavorable effects. Amounts of genetic and phenotypic variation present indicate that moderate gains from selection and breeding programs a re possible for stem growth traits, while lesser gains can be achieved for stem form and branching traits.