EARLY SELECTION OF COASTAL DOUGLAS-FIR IN A FARM-FIELD TEST ENVIRONMENT

Farm-field tests are progeny tests established using intensive site pr eparation, close spacing and nearly complete weed control. Early growt h and wood density of coastal Douglas-fir in a farm-field environment up to 7 years from seed are compared with stem volume and wood density from 11 field sites at age 13 (20% to 25% of commercial rotation). Fa mily heritabilities are high for almost all traits in both the farm-fi eld and field sites. Breeding-value correlations of farm-field heights with field stem volume at age 13 increase from a low of 0.5 for farm- field age 1 and level off at about 0.7 by farm-field age 3. Farm-field diameter with field volume age 13 breeding-value correlations are ini tially lower than those for height, but increase to 0.82 by age 7. Woo d density breeding value correlations between field pilodyn assessment s at age 13 and farm-field stem sections at age 6 are 0.83. Maximum fa mily-selection efficiency per year (including a 5-year breeding delay) , relative to direct selection on field volume 13, reaches 162% using index selection on farm-field height and diameter at age 3. Within-fam ily selection efficiencies per year are highest at age 1 and decline q uickly. All selection in the farm-field test has a higher efficiency p er unit time than selection in field tests. It is concluded that corre ctly established farm-field tests will provide greater per year gains in stem yield and wood density traits than field sites.