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• 1. [Article] Determination of relative economic weights for multitrait selection in coastal Douglas-fir

  Abstract: Relationships between tree traits and tree value for lumber production were investigated. For the purposes of estimating relative economic weights for use in multitrait selection in coastal Douglas-fir ...

  Citation × Citation Citation Abstract Copy Title: Determination of relative economic weights for multitrait selection in coastal Douglas-fir Author: Adams, W. T., Fahey, Thomas D., Aubry, Carol A. Abstract: Relationships between tree traits and tree value for lumber production were investigated. For the purposes of estimating relative economic weights for use in multitrait selection in coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii), tree height, diameter at breast height, and branch diameter were measured on 164 trees (ages 36–66 years). Increment cores from a subsample (92) of these trees were assayed by X-ray densitometry to determine wood density. Bole volume was derived by summing the log volumes of all logs from each tree. Value of lumber recovered from each tree was determined in a separate mill study using both visual and machine stress rated (MSR) grading rules. Multiple linear regression was used to relate tree value to the growth and wood quality traits. Stem volume and branch diameter significantly influenced tree value under visual grading, with relative economic weights of 0.06 dm3 and –5.22 cm, respectively. Wood density significantly influenced tree value under MSR grading (relative economic weights: 0.06 dm3, –6.69 cm, and 0.06 kg/m3, respectively), where lumber strength is measured more accurately. These regression coefficients can be used directly as economic weights in selection indices. Title: Determination of relative economic weights for multitrait selection in coastal Douglas-fir Author: Adams, W. T., Fahey, Thomas D., Aubry, Carol A. Abstract: Relationships between tree traits and tree value for lumber production were investigated. For the purposes of estimating relative economic weights for use in multitrait selection in coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii), tree height, diameter at breast height, and branch diameter were measured on 164 trees (ages 36–66 years). Increment cores from a subsample (92) of these trees were assayed by X-ray densitometry to determine wood density. Bole volume was derived by summing the log volumes of all logs from each tree. Value of lumber recovered from each tree was determined in a separate mill study using both visual and machine stress rated (MSR) grading rules. Multiple linear regression was used to relate tree value to the growth and wood quality traits. Stem volume and branch diameter significantly influenced tree value under visual grading, with relative economic weights of 0.06 dm3 and –5.22 cm, respectively. Wood density significantly influenced tree value under MSR grading (relative economic weights: 0.06 dm3, –6.69 cm, and 0.06 kg/m3, respectively), where lumber strength is measured more accurately. These regression coefficients can be used directly as economic weights in selection indices. Close

• 2. [Article] Multi-trait selection in coastal Douglas-fir

  Index selection provides an efficient means of conducting selection on multiple traits by combining information on economic value, heritability, and the genetic and phenotypic correlations between traits ...

  Citation × Citation Citation Abstract Copy Title: Multi-trait selection in coastal Douglas-fir Author: Aubry, Carol A. Index selection provides an efficient means of conducting selection on multiple traits by combining information on economic value, heritability, and the genetic and phenotypic correlations between traits to improve overall merit. The use of this method in forestry has been hampered by the lack of knowledge of the relative importance of individual traits in determining tree value. Data recently made available from a lumber recovery study made it possible to a) estimate relative economic weights for individual tree traits that are important in determining lumber value of coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) France var. menziesii) under two grading systems (visual and machine-stress-rated (MSR)) and b) test the implications of alternative weights under various multi-trait selection indices. Economic weights were derived by stepwise regression of total tree value, based on either visual or MSR grading of recovered lumber, on a variety of traits measured on 164 young-growth (ages 36-66 years) Douglas-fir trees in western Washington and Oregon. Two traits were found to have a significant influence on tree value under visual grading, stem volume and branch diameter, with relative economic weights 0.06 dm3 and -5.22 cm, respectively. In addition to volume and branch diameter, wood density also significantly influenced tree value under MSR grading (relative economic weights 0.06 dm3, -6.69 cm, and 0.06 kg/rn3, respectively), where lumber strength is measured directly. Selection indices and expected responses of volume, branch diameter, and wood density to index selection were examined utilizing progeny test data from 20-year old trees of 85 open-pollinated families replicated on three planting sites. The derived selection indices were quite different for the two lumber grading schemes, as were the expected responses in individual traits. Under visual grading, expected response in volume is large, but because wood density was not included in the index, a large negative (unfavorable) response in wood density is also expected. Using MSR grading, a positive response is expected in both volume and wood density, but the expected response in volume is less than when visual grading is used to determine economic weights. Little response in branch diameter is expected even though branch diameter was included as a trait in both indices. This is due to the low variability of branch diameter and its adverse genetic correlation with volume. Changes in genetic and phenotypic parameter estimates (tested by using only a portion of the progeny test data) resulted in different index coefficients and changes in expected responses of individual traits. These results emphasize the necessity of evaluating the implications of using a particular index prior to applying it to a breeding population. In one case, a desired gain index, with desired relative responses for volume and wood density equaling the MSR-based economic weights, was successful in predicting positive responses in both volume and wood density where a Smith-Hazel index had resulted in a negative response in volume. Thus, this type of restricted selection index provides a means of increasing overall merit while dictating the allowable changes in each trait. Title: Multi-trait selection in coastal Douglas-fir Author: Aubry, Carol A. Index selection provides an efficient means of conducting selection on multiple traits by combining information on economic value, heritability, and the genetic and phenotypic correlations between traits to improve overall merit. The use of this method in forestry has been hampered by the lack of knowledge of the relative importance of individual traits in determining tree value. Data recently made available from a lumber recovery study made it possible to a) estimate relative economic weights for individual tree traits that are important in determining lumber value of coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) France var. menziesii) under two grading systems (visual and machine-stress-rated (MSR)) and b) test the implications of alternative weights under various multi-trait selection indices. Economic weights were derived by stepwise regression of total tree value, based on either visual or MSR grading of recovered lumber, on a variety of traits measured on 164 young-growth (ages 36-66 years) Douglas-fir trees in western Washington and Oregon. Two traits were found to have a significant influence on tree value under visual grading, stem volume and branch diameter, with relative economic weights 0.06 dm3 and -5.22 cm, respectively. In addition to volume and branch diameter, wood density also significantly influenced tree value under MSR grading (relative economic weights 0.06 dm3, -6.69 cm, and 0.06 kg/rn3, respectively), where lumber strength is measured directly. Selection indices and expected responses of volume, branch diameter, and wood density to index selection were examined utilizing progeny test data from 20-year old trees of 85 open-pollinated families replicated on three planting sites. The derived selection indices were quite different for the two lumber grading schemes, as were the expected responses in individual traits. Under visual grading, expected response in volume is large, but because wood density was not included in the index, a large negative (unfavorable) response in wood density is also expected. Using MSR grading, a positive response is expected in both volume and wood density, but the expected response in volume is less than when visual grading is used to determine economic weights. Little response in branch diameter is expected even though branch diameter was included as a trait in both indices. This is due to the low variability of branch diameter and its adverse genetic correlation with volume. Changes in genetic and phenotypic parameter estimates (tested by using only a portion of the progeny test data) resulted in different index coefficients and changes in expected responses of individual traits. These results emphasize the necessity of evaluating the implications of using a particular index prior to applying it to a breeding population. In one case, a desired gain index, with desired relative responses for volume and wood density equaling the MSR-based economic weights, was successful in predicting positive responses in both volume and wood density where a Smith-Hazel index had resulted in a negative response in volume. Thus, this type of restricted selection index provides a means of increasing overall merit while dictating the allowable changes in each trait. Close