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Height and Diameter Relationships and Distributions in Loblolly Pine Stands of Enhanced Genetic Material

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The effect of genetic improvement on loblolly pine height-dbh relationships and height and dbh distributions was investigated using four loblolly pine genetic varieties, a half-sibling family, a full-sibling family, and two rooted-cutting clones, growing at two different levels of stand density. Height-dbh relationships were modeled using the Korf function and height and dbh distributions were described using sample moments of the distributions. The fixed effect of genetic variety on the height-dbh relationship was tested using likelihood ratio test and root mean square error statistics. Moments of height and dbh distributions were compared using analysis of variance techniques. The effect of genetic variety on the height-dbh relationship depended on stand density with differential effects being observed at higher stand density. Variance of the height-dbh regression line decreased with increased genetic uniformity among the trees in a stand; hence, vertical crown differentiation in a stand may decrease with genetic selection. Higher levels of genetic improvement resulted in an increase in the mean of the height distribution but had no effect on the mean of the dbh distribution, suggesting that genetic selection for faster height growth in loblolly pine may affect diameter and height development disproportionally. The effect of genetic improvement and planting of monoclonal stands on variance of height and dbh distributions depended on stand density with there being no effect at the lower density. However, variance of the distributions for nonclonal stands was greater at the higher density. There was no change in skewness of the distribution with genetic improvement or between clonal and nonclonal stands. Modeling effects of genetic improvement on loblolly pine height-dbh relationships and diameter and height distributions may require knowledge of the genetic mechanisms behind the differential responses of genetic varieties to stand density.

Keywords: Pinus taeda; clonal loblolly pine; modeling genetic improvement

Document Type: Research Article


Publication date: June 24, 2013

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  • 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

    Also published by SAF:
    Journal of Forestry
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