Genetic Gains in Growth and Simulated Yield of Pinus monticola

Abstract

Abstract Between years 7 and 25, genetic variances for height and diameter have increased in 29 full-sib western white pine (Pinus monticola Dougl.) families planted on two sites. Family differences in height were statistically significant throughout most of the period, while differences in breast-high diameter were detected after year 13. Estimated heritabilities for height were relatively constant, averaging 0.11 and 0.33 for individuals and families, respectively; those for diameter have generally increased throughout the period and by year 25 had reached 0.14 for individuals and 0.43 for families. These heritabilities coupled with relatively large phenotypic variances suggest that programs of forward selection should provide genetic gains of about 7% in the height or 9% in the diameter of individual trees in year 25. Genetic correlations of height at various ages with stem volume in year 25 were high (>0.85), as were the correlations involving diameter and 25-yr volume after year 13. Correlated responses to selection suggested that year 7 would be the most efficient time to select, providing 85% of the maximum gain available in 25-yr volume. A stand simulation model was used to project the yields (volume per acre) expected from the progenies of selections made in year 7. Results of the simulations suggested that the amount of increase in yield depended on the density, rotation length, and manner by which genetic gains accrue beyond year 25. The results implied that relatively small gains in the attributes of 25-yr-old trees can result in either increased volumes per acre for a given rotation or decreases in the rotation to achieve a given volume. For. Sci. 37(1):326-342.