Abstract:
This thesis is concerned with developing techniques for identifying "superior" Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) parent trees based on seedling progeny evaluation. The growth responses of up to 14 open-pollinated families to shade, drought, and stand density were assessed in four experiments. A technique was developed to compare family height growth responses to
increasing stand density while accounting for genetic variation in growth rates. Family rankings based on seedling evaluation criteria were compared with 15-year growth records for an earlier cohort from the same parent trees. The significant findings of this study were: (1) fifteen-year field height rankings were related to differences
in budset date, height growth rate, and branchiness among seedlings grown with or without shade or drought stress; (2) seedling-field correlations were inversely
related to seedling-seed weight correlations; (3) seedling-field correlations improved with age in the field;
(L) family correlations between spaced-plant growth and closed-stand growth were low for measures of seedling size but high for measures of seedling shape, and; (5) there
was genetic variation in height growth responses to increasing stand density in single-family seedling plots.
