Wood property maps showing wood variability in mature longleaf pine: does getting old change juvenile tendencies?
Established illustrations of juvenile wood in pines depict a central core of wood, varying little by diameter or cambial age, to be nested within mature wood tapering to the upper portion of the stem; alternative illustrations show greater complexity in attributing variability within this central core of wood to its proximity to the crown and/or the maturity of the tree when the wood was formed. The present study addresses the degree to which different representations of juvenile wood are applicable to a sampling of 70-yr-old longleaf pine (Pinus palustris Mill.) trees. Wood property maps were derived from X-ray densitometry data gathered from tree disks taken at every 61 cm along each tree bole. Unique to the wood property maps herein is that the two cardinal directions of the data (north and south) were preserved, thus providing true full-stem profiles. Compared with maps reported for younger southern pines, the central core of low-density wood extending the length of the tree boles was noticeably wider at the midheight than at the lower and higher relative heights. Another difference was that the higher ring specific gravity (SG) values, particularly at the lower heights, did not extend all the way to the wood closest to the bark. Narrower ring width and higher ring SG values above the 3Q height, normally being wood features associated with higher wood quality, can be attributed to thematurity of the study trees. Altogether, the wood property maps and data comparisons were consistent with an alternative juvenile wood illustration proposing that all the wood at the base of the tree, comprised of juvenile corewood and juvenile outerwood, as being different from the majority of the tree wood, upward from a one-quarter relative height.