Black spruce breeding zones (BZs) in northwestern Ontario, Canada, were assessed for the feasibilities of expanding superior tree selection and orchard seed deployment across existing BZ boundaries under climate change. The assessment was based on performances of open-pollinated families in progeny tests established in four second-generation BZs. In these tests, families from outside BZs were tested alongside with families from within BZs. Results showed that trees grew faster with higher survival rates in southerly BZs than in northerly BZs. Within a BZ, families from southern BZs were taller, but with slightly lower survival rates in northerly BZs, while families from northern BZs were shorter with comparable survival in southern BZs. These patterns were consistent with results from provenance studies, suggesting potential benefits from deploying orchard seeds from southern BZs more northwardly, provided slightly lower survival rates not serious concerns. Genetic worth of breeding populations for the next generation could be improved by 4.6% in height when the top 100 genetically superior trees were selected with families within BZs. Allowing selection to include families from southerly BZs could lead to an average improvement of 4.9%. The implications for black spruce tree improvement programs are discussed.

Under a changing climate, tree improvement programs should revise breeding zones to improve climate change adaptation and program efficiency once information about adaptive capacity of breeding populations and genotype × environment (G × E) interaction becomes available. In this study, we evaluated the adaptation and growth, as well as G × E interactions, shown by white spruce (Picea glauca (Moench) Voss) open-pollinated (OP) families across two adjacent breeding zones (i.e., the BZ3300 and BZ4300, respectively) in northwestern Ontario using progeny test data, including 80 OP families (40 from each) that were cross-tested between the breeding zones. Results showed that the OP families from the southerly BZ4300 breeding zone averaged higher survival and significantly greater mean tree height growth than the local OP families in the more northern BZ3300 breeding zone at tree age of 14 years, with no notable difference in frost damage. Estimates of type-B genetic correlation from pairwise tests or combined-test analyses were almost all greater than 0.7, suggesting weak G × E interactions. Greater variation among families and higher heritability estimates in tree height were observed for families from the BZ3300 breeding zone or when families from the two breeding zones were combined. The weak G × E interactions, in addition to better survival and growth of the southerly families in the more northern breeding zone, suggested benefits from deploying seed from current seed orchard in the BZ4300 breeding zone to the BZ3300 breeding zone and merging the two breeding zones when starting the second generation breeding to increase tree improvement efficiency and likely higher genetic gain under future climate.

Growth and tree form characteristics of jack pine (Pinus banksiana Lamb.) rooted cuttings propagated from proliferated dwarf shoots (PDS) were compared with seedlings in two field trials 8 years after establishment. Results indicated that jack pine rooted cuttings from PDS can grow as well as seedlings and maintain acceptable tree form. Rooted cuttings of progeny from the 22 top-ranking open-pollinated families in a seedling seed orchard of jack pine were 4.2% taller and 10% larger in diameter at breast height than commercial seedlings tested on the same sites, which indicates that rooted cuttings have potential in realizing genetic gains in jack pine tree improvement programs. Rooted cuttings increased the proportion of trees with normal branching characteristics and reduced the percentage of trees with excessive heavy branches in the Sault St. Marie trial, which had larger tree sizes. However, longer term monitoring (20 to 25 years) is needed to determine stability of jack pine rooted cuttings planted on sandy soil where wind throw may become a problem as tree size increases.

Genetic parameters of growth traits were estimated for first-generation selections of black spruce (Picea mariana (Mill.) BSP) in northwestern Ontario from 720 open-pollinated families and more than 42 000 trees. Unbiased estimates of narrow-sense heritability for tree height growth averaged 0.19, 0.18, and 0.14 at ages 6, 11, and 19 years, respectively, from combined-site analyses compared with 0.25, 0.23, and 0.16 for the same ages from single-site analyses. Heritability estimates for diameter at breast height and stem volume were lower than that of height at age 19, suggesting that tree height is a more desirable trait for selection in black spruce. The moderately high estimates of type B genetic correlations implied limited operational importance of genotype x environment interactions. Estimates of age-age genetic correlation were high (> 0.88) among cumulative tree height growth at 6, 11, and 19 years but lower between height increments from different age intervals. Estimates of type B age-age genetic correlation were more than 0.2 lower than their type A counterparts, suggesting strong effects of common environments on the estimates of type A genetic correlations. Based on the relative selection efficiencies, selection on cumulative tree height between ages 6 and 11 was more efficient than at age 19.

To obtain a better understanding of the pattern of adaptive variation of Piceamariana (Mill.) B.S.P. from northwestern Ontario, a short-term provenance test was carried out for 75 seed sources collected east and west of Lake Nipigon. Provenances were grown in common environments at a greenhouse for two seasons (1990–1991) and a farm field and a forestry trial each for four growing seasons (1990–1993). Twenty-five growth and phenological variables were determined, including seedling height, needle flushing date, and the timing of shoot elongation. Significant levels of interprovenance variation were present for 18 of these variables. Graphic analysis of the pattern of variation indicated that sources from the southwestern portion of the collected area generally grew faster and flushed later than easterly sources near the north shore of Lake Superior. Superimposed on this general pattern were several irregularities caused by one or more provenances. Multiple regressions were run for each of the 18 variables against latitude, elevation, and 12 climatic variables interpolated for each of the seed sources by a geographic information system from 1951–1980 data obtained from 56 nearby weather stations. Large coefficients of variation (up to 0.57) were obtained for some variables. Combinations of climatic variables, including winter minimum and summer maximum temperatures together with precipitation and timing of the growing season, were excellent predictors of black spruce needle flushing dates, while summer temperature, precipitation, and elevation were moderately good predictors of height growth.