Genetic and Spacing Effects on Loblolly Pine Plantation Development Through Age 17

Land, S. B., Jr., Roberts, S. D., and Duzan, H. W., Jr. IN: Proceedings of the 12th biennial southern silvicultural research conference, p. 413-419. USDA Forest Service, Southern Research Station, General Technical Report SRS-71. Kristina F. Connor, ed. 2004.

Abstract— Eight North Carolina families and a Mississippi-Alabama commercial check of loblolly pine (Pinus taeda L.) wereplanted at three spacings (5x5, 8x8, and 10x10 feet) in east Mississippi. Results for ages 5, 9, 13, and 17 years indicated that spacing effects occurred by age 5 for d.b.h. and height and by age 9 for survival, stand volume, and periodic annual incre-ment (PAI) in volume. D.b.h. decreased as spacing decreased. Height was temporarily stimulated as trees began to compete with each other. Density-related mortality began between ages 5 and 9 for the 5x5 and between ages 9 and 13 for the 8x8and 10x10. Peak PAI occurred during these same periods. The 5x5 spacing had the greatest stand volume at ages 9 and 13,but by age 17, the 8x8 and 5x5 spacings were similar. Family effects were detected by age 5 for d.b.h., height, stand volume,and PAI. Survival differences among families became significant by age 13. Family NC1 consistently ranked highest in stand volume at all ages, and it had 27 percent more volume per acre than the local check at age 17. The primary contributor to family differences for stand volume was survival. Family-by-spacing interactions were seldom significant.

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Author(s): Samuel B. Land, Jr., Scott D. Roberts, Howard W. Duzan, Jr.

Section: Genetics and Tree Improvement