Phenotypic Correlation among Branch and Upper-Crown Stem Attributes in Douglas-Fir

To provide a basis for developing objective branch-habit selection criteria for tree breeding, phenotypic correlations were made among several branch characteristics of 15- to 35-year-old Pseudotsuga menziesii (Mirb.) Franco var. menziesii . Correlation analyses indicate that: (1) branchangle is not significantly associated with any variable except average cross-sectional area of branch bases; (2) of trees of similar stem volume those with fewer branches tend to have larger diameter branches; (3) of trees of similar stem volume those with fewer branches tend to have longerbranches; (4) trees with fast height growth tend to have shorter branches when compared with slower growing trees of similar volume; (5) of trees of similar stem volume those growing faster in height tend to have smaller diameter branches; (6) tree age is not significantly correlated withany branch or stem characteristic; (7) stem volume is correlated with all measured variables except branch angle; (8) except for the close relationship between branch length and average cross-sectional area of branches, branch characteristics are generally very slightly associated. Path coefficientanalysis suggests that variations in the four branching characteristics are directly associated with approximately 62 percent of the variation in stem volume.