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Rotation-age growth performance of 16 provenances and local growth superiority were assessed from a rotation- age reciprocal coastal Douglas-fir [Pseudotsuga menziesii var. menziesii (Mirb.) Franco] provenance test established in the Pacific Northwest of America. Provenance differences for total volume per plot were highly significant. Due to the significant provenance × site interaction effect, the best provenances varied across planting sites in terms of rotation-age volume growth. Local provenance trees exhibited superior volume growth at two of the six planting sites. At the remaining four sites, local provenances performed equally well as average non-local provenances. At the three low-elevation (< 460 m) sites, low-elevation provenances performed significantly better than high-elevation provenances. By contrast, high- and low-elevation provenances had similar growth at the two high-elevation (> 800 m) sites. Southern provenances generally grew faster than northern provenances at the Oregon sites, while northern provenances performed better than southern provenances at the sites in British Columbia. Regression analyses showed that although local growth superiority increased with the geographic distance between provenance’s origin and the test site in general (r=0.47, P The results suggested that breeding zones larger than the current second-cycle zones would lead to little loss of rotation-age total volume for coastal Douglas-fir in this region.

Measurements on growth traits up to 41 years of age from 68 progeny sites in eight first-generation breeding zones of coastal Douglas-fir (Pseudotsuga menziesii [MIRB.] FRANCO var. menziesii) in the US Pacific Northwest were used to investigate age trends of genetic parameters and to determine optimum age of selection. Heritabilities and age-age genetic correlations were estimated using univariate or bivariate mixed model analyses. Heritability estimates tended to increase with age for both total growth and growth increment traits. The estimates showed different age trends among breeding zones, but the differences were generally small. Age-age genetic correlations for total growth traits fitted Lambeth’s model surprisingly well, despite the data being collected from multiple breeding zones. Using rotation-age (i.e., 50yr) volume as the selection criterion, the greatest correlated gains per year were achieved by making family selection at juvenile ages (i.e., 9 for height, 13 for diameter, and 11 for volume). Similar results were obtained for within-family selection except that the optimum ages of selection were 2~4 years later than that from family selection, i.e., 11 for height, 15 for diameter and volume. Early selection on total height was always more efficient and had earlier optimum ages than on other growth traits. The optimum ages of early family selection on total growth were 4~11 years earlier than on the corresponding growth increment traits. It was also evident that the optimum ages of selection occurred later for slow-growth trials than for fast-growing trials.

Acoustic velocity (AV) data from 7,423 coastal Douglas-fir trees drawn from 347 wind-pollinated families on 14 sites, from four first-generation testing programs in the north Oregon Cascades, were analyzed. Families were measured on two or four sites at ages 23 to 41 years from seed using the Fakopp TreeSonic standingtree tool. Height (HT) and DBH data collected at ages 15 and 16 from seed, from all trees in the four programs (95,795 trees, 955 families), were used to calculate volume index (VOL = HT*DBH2) and stem taper (TAP = DBH/HT). All traits were analyzed using multivariate mixed model analyses. Across-site individual narrow-sense heritabilities for AV2 ranged from 0.24 to 0.40 among first-generation programs, compared to 0.12 to 0.23 for HT, 0.10 to 0.16 for DBH, 0.11 to 0.20 for VOL and 0.14 to 0.17 for TAP. Across-site type B correlations for AV2 ranged from 0.85 to 0.95, compared to 0.62 to 0.83 for HT, 0.60 to 0.74 for DBH, 0.67 to 0.78 for VOL and 0.66 to 0.79 for TAP. AV2 was negatively correlated with HT in three programs (rA = 0.17 to −0.28), and negatively correlated with DBH (−0.12 to −0.46), VOL (−0.05 to −0.44) and TAP (−0.09 to −0.40) in all four programs. Selecting the top 10% of the families sampled based on AV2 gave predicted gains of 4.4% to 9.6% for AV2 and −9.3% to 10.6% for VOL. The adverse genetic correlations between AV2 and growth, and the losses in gain in AV2 from selection based on growth, may be overestimated by suppression of slower-growing families in these older tests.

Realized gains for coastal Douglas-fir (Pseudotsuga menziesii var. menziesii) were evaluated using data collected from 15-year-old trees from five field trials planted in large block plots in the northern Oregon Cascades. Three populations with different genetic levels (elite - high predicted gain; intermediate - moderate predicted gain; and unimproved - wild seedlot) were compared at two planting spacings (1.8 × 1.8 m and 3.6 × 3.6 m). The realized gains at age 15 averaged over both the elite and intermediate progeny were 17.2% for stand volume per hectare, 3.5% for mean height, and 4.3% for diameter, compared to predicted genetic gains of 16.0% for volume, 5.4% for height, and 6.4% for diameter. Realized and predicted gains correlated well at the family level, with an average correlation coefficient close to 0.80. The improved populations also had higher survival rate and lower stem sinuosity than the unimproved population. Strong genetic level × planting spacing interaction effects were revealed for the growth traits at age 15 using mixed model analyses. Realized gains for stand per-hectare volume and mean growth rate were at least twice as large in the elite population as in the intermediate population at the close spacing. By contrast, both populations performed similarly at the wide spacing. This indicates that the selected genetic materials responded differently to the changes of competitive environment, and realized gain trials should closely mimic operational plantations in order to provide valid estimates of realized gains. Realized gains in per-hectare volume varied greatly among test sites. No significant genetic level x site interactions were found for any traits.

Variation in heritability and in genetic correlation estimates were evaluated for juvenile tree height and volume for six testing areas of loblolly pine (Pinus taeda L.) in the southeastern United States. Variance components and their functions (heritability and type B genetic correlations) were estimated from 265 six-parent disconnected diallel series, tested in almost 1000 trials (4 tests per diallel series). Original data were collected at age 6 years from about one million trees (265 diallel series x 30 crosses x 36 trees per cross/site x 4 sites) planted in field tests. Genetic tests were from the second cycle of breeding in the North Carolina State University - Industry Cooperative Tree Improvement Program. The overall unbiased individual-tree narrow-sense heritability for height was 0.19 and for volume was 0.16. The broad-sense heritabilities for height (0.24) and for volume (0.22) were higher than narrow-sense heritabilities due to the presence of non-additive genetic variance. There were moderate regional differences in these estimates, with tests in the Lower Gulf Coastal Plain tending to have the highest heritabilities for growth traits. There was very little association between site index and heritability, but heritabilities were higher on sites with the highest survival and highest test precision. Genotype x environment interactions were generally low both for half-sib and full-sib families, indicating that families can be operationally deployed to different sites with little concern about unpredictable performance.