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Trends in Genetic Parameters with Stand Development and Their Influence on Early Selection for Volume Growth in Loblolly Pine

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Analysis was conducted on data from a 15-year-old progeny test of 11 open-pollinated families of loblolly pine. Plots consisted of 49-tree blocks of single families, and measurements were taken annually for the first 8 years and at 10 and 15 years. Three types of analysis were used to explore early selection for a more mature trait. These analyses included: age-related trends in genetic and environmental variances, juvenile-mature genetic correlations, and indirect selection. The age-related trends varied by trait. The trends for additive genetic variance ranged from flat (survival) to exponential (total plot volume) or concave (live crown ratio). However, for all traits, additive genetic variance dipped around age 7 or 8, presumably due to intensifying competition at crown closure. Genetic correlations between early traits (juvenile) and more mature traits (15 years) were generally high. The correlations of height or total plot volume at age 15 with juvenile traits improved rapidly from age 1 to 5. Diameter at breast height, in which there was little or no increase from ages 3 to 5, was the one exception. When correlating earlier height with height or plot volume at age 15, the pattern of correlation coefficients took a noticeable dip at ages 7 or 8. With total plot volume at age 15 (TVOL15) as the goal of selection, response to indirect selection for height and survival at various ages was predicted. The predicted, indirect response was expressed as a ratio of response to direct selection for TVOL15 and termed relative efficiency. The relative efficiency of selection by ages 3, 4, or 5 was 81, 82, and 85%, respectively. Forest Sci. 32:944-959.

Keywords: Index selection; competition; genetic gain; heritability

Document Type: Journal Article

Affiliations: International Forest Seed Co., Box 290, Odenville, AL 35120

Publication date: 1986-12-01

More about this publication?
  • Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.
    Forest Science is published bimonthly in February, April, June, August, October, and December.

    2015 Impact Factor: 1.702
    Ranking: 16 of 66 in forestry

    Average time from submission to first decision: 62.5 days*
    June 1, 2016 to Feb. 28, 2017

    Also published by SAF:
    Journal of Forestry
    Other SAF Publications
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