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Tree improvement for important species is over 30 years old in the province of New Brunswick, Canada, and enough data have been accumulated to perform an economic analysis. In this study, we conducted a benefit-cost analysis of an ongoing, first generation, 6.5 ha white spruce clonal seed orchard, established in 1985-1987 in Lower Queensbury, New Brunswick. This seed orchard has provided seed for reforestation on Crown lands in the province since 1993. The analysis was undertaken by evaluating the present values of relative costs, benefits, and benefit/cost ratios (BCRs) associated with a plantation management strategy that uses the Lower Queensbury clonal seed orchard (LQ_CSO) versus one that uses wild stand (unselected) seeds. Cash flows were based on actual costs for the LQ_CSO (including orchard establishment and management, progeny test establishment and maintenance, and data analysis), and projected revenue increases from the genetic gains associated with the LQ_CSO relative to the unselected seedlot. Genetic gains at rotation ages were predicted using a growth and yield model that used 20-year old data collected from a realized gain test, and considered two rotation ages (40 and 50 years) along with two management scenarios (with vs. without commercial thinning). A number of discount rates (from 4 to 8 %) were also assessed. Findings indicated that the BCRs ranged from 12.5 to 0.4, depending on the scenario considered, with a majority being >1. BCRs increased when commercial thinning was applied, but declined marginally when the rotation age was extended from 40 to 50 years. Overall, the results demonstrated that the establishment of the LQ_CSO was an excellent investment for all scenarios when the discount rate was <6 %. [ABSTRACT FROM AUTHOR]

Height and diameter distributions between improved and unimproved (checklot) seedlots for white spruce [Picea glauca (Moench) Voss] and black spruce [Picea mariana (Mill.) BSP] were compared using the two-parameter Weibull function. Individual tree height at age 5-15 years and diameter at breast height at age 15 years that were collected from two series of large-plot realized gain tests were used for this purpose. For both species, improved seedlots did not significantly (α=0.05) change the shape parameter of the distributions relative to their checklots, suggesting that an overall shape value will be adequate to predict tree size distributions of various improved seedlots. The most important finding was that seedlot influenced the scale parameter (related to the range of the distribution) significantly, but from a practical viewpoint, only those scale values of the higher rated seedlots (i.e. seedlots collected from a rogued seed orchard or superior families) were significantly higher (α=0.05) than those of the respective unimproved seedlot. The changes in scale value of the alternative improved seedlots relative to the checklot (ΔScale) were comparable in magnitude to the respective realized genetic gains, suggesting that tree improvement effects on the scale value can be adjusted by realized genetic gains. The results also suggest that site and age significantly affected the scale value; in general, ΔScale became larger at earlier ages or on better sites. The findings reported here will be used in the development of yield functions for genetically improved white and black spruce in New Brunswick. [ABSTRACT FROM AUTHOR]