Juvenile/Mature Wood Transition in Loblolly Pine as Defined by Annual Ring Specific Gravity, Proportion of Latewood, and Microfibril Angle


  • Alexander Clark
  • Richard F. Daniels
  • Lewis Jordan


Juvenile/mature transition, <i>Pinus taeda</i> L, specific gravity, percent latewood, MFA


The length of juvenility or number of years a tree produces juvenile wood at a fixed height can be defined by the age of the wood at which properties change from juvenile to mature wood. This paper estimates the age of transition from juvenile to mature wood based on ring specific gravity (SG), proportion of annual ring in latewood, and ring average microfibril angle (MFA). The threshold method and the segmented modeling approach were used to estimate the age of transition. Twenty loblolly pine (Pinus taeda L.) plantations, 20-27 years old, were sampled across five physiographic regions in the southern United States. Increment cores were collected at 1.3 meters from 15 trees in each stand to determine ring specific gravity and proportion of latewood by X-ray densitometry and annual ring MFA by X-ray diffraction. Precisely determining the transition age between juvenile and mature wood was difficult because transition is gradual, not abrupt. The age of transition was found to differ by wood property because these properties mature at different rates due to genetic and environmental factors. Both the threshold and the segmented model approach showed that transition age varied among regions. Both approaches showed that length of juvenility based on ring SG was shorter in the South Atlantic and North Atlantic Coastal Plains (ranging from 5.5 to 7.9 years) compared to that in the Hilly Coastal Plain that ranged from 10.4 to 13.6 years. Using MFA to estimate the age of demarcation, both approaches showed the South Atlantic, Gulf Coastal, and Hilly Coastal Plains had shorter lengths of juvenility (ranging from 8.4 to 10.4 years) than the Piedmont and North Atlantic Coastal Plain (ranging from 10.5 to over 20 years).


Bendtsen, B. A. 1978. Properties of wood from improved and intensively managed trees. Forest Prod. J.28(10): 61- 72.nBendtsen, B. A., and J. F. Senft. 1986. Mechanical and anatomical properties in individual growth rings of plantation-grown eastern cottonwood and loblolly pine. Wood Fiber Sci.18(1):23-28.nClark III, A., and J. R. Saucier. 1989. Influence of initial planting density, geographic location, and species on juvenile wood formation in southern pine. Forest Prod J.39(7/8):42-48.nClark III, A., and M. B. Edwards. 1999. Effect of six sitepreparation treatments on Piedmont loblolly pine wood properties at age 15; Pages 316-320 in J. D. Haywood, ed. Proc. Tenth Biennial Southern Silvicultural Research Conference, Feb 16 - 18, 1999, Shreveport, LA. Gen Tech. Rep. SRS-30 Asheville, NC: USDA Forest Service, Southern Research Station.nClark III, A., R. F. Daniels, and J. H. Miller. 2005. Effect of controlling herbaceous and woody competing vegetation on wood quality of planted loblolly pine. Forest Prod. J (in press).nHodge, G. R., and R. C. Purnell. 1993. Genetic parameter estimates for wood density, transition age, and radial growth in slash pine. Can. J. For. Res.23:1881-1891.nJozsa, L. A. 1998. Basic wood properties of second-growth western hemlock. Special Publication No. SP-38. Forintek Canada Corporation, Vancouver, BC. 51 pp.nKrahmer, R. L. 1966. Variation in specific gravity of western hemlock trees. Tappi49(5):227-229.nLoo, J. A., C. G. Tauer, and R. W. McNew. 1985. Genetic variation in the time of transition from juvenile to mature wood in loblolly pine (Pinus taeda L.). Silvae Genet.34(1):14-19.nMegraw, R. A. 1986. Douglas-fir wood properties; Pages 81-96 in Douglas-fir Stand Management for the Future; Institute of Forest Resources Contribution No. 55, College of Forest Resources, University of Washington, Seattle, WA.nMora, C. R., R. F. Daniels, H.L. Allen, and A. Clark. 2005. Effects of early intensive silviculture on the juvenile-mature wood transition age and proportion of juvenile wood in loblolly pine trees. Forest Sci. (in-press).nPearson, R. G. and R. C. Gilmore. 1971. Characterization of the strength of juvenile wood of loblolly pine. Forest. Prod. J.21(1):23-31nPearson, R. G. and R. C. Gilmore. 1980. Effect of fast growth rate on the mechanical properties of loblolly pine. Forest Prod. J.30(5):47-54.nSAS Institute Inc., 2001 SAS/STAT User's Guide, release 8.02 edition. SAS Institute Inc., Cary, NC.nSauter, U. H. R., Mutz, and B. D. Munro. 1999. Determining juvenile-mature wood transition in Scots pine using latewood density. Wood Fiber Sci.31(4):416-425.nSenft, J. F., B. A. Bendtsen, and W. L. Galligan. 1985. Weak wood: Fast-grown trees make problem lumber. J. Forestry83(8):477-484.nSzymanski, M. B., and C. G. Tauer. 1991. Loblolly pine provenance variation in age of transition from juvenile to mature wood specific gravity. Forest Sci.37(1):160-174.nTasissa, G., and H. E. Burkhart. 1998. Juvenile-mature wood demarcation in loblolly pine trees. Wood Fiber Sci.30(2):119-127.nThomas, R. J., 1984. The characteristics of juvenile wood. Pages 40-52 in R. C. Kellison, ed. Proc. Symposium on Utilization of the Changing Wood Resources in the Southern United States. North Carolina State Univ., Raleigh, NC.nWareing, P. F. 1958. The physiology of cambial activity. J. Inst. Wood Sci. (1):34-42.nWear, D. N., and J. G. Greis. 2002. Southern forest resource assessment. Gen. Tech. Rep. SRS-53. Asheville, NC: USDA Forest Service, Southern Research Station. 635 pp.nZahner, R. 1963. Internal moisture content stress and wood formation in conifers. Forest Prod. J. (6):240-247.nZobel, B. J., and R. L. McElwee. 1958. Natural variation in wood specific gravity of loblolly pine, and an analysis of contributing factors. Tappi414(4):158-161.n






Research Contributions