Wood Color, Basic Density, and Decay Resistance in Heartwood of Fast-Grown Eucalyptus grandis Hill ex Maiden

Wood discs were cut at 4.5 ft. above ground level from plantation trees of Eucalyptus grandis, Hill ex Maiden, the plantings representing an age class series. Radial variation in quantitatively measured color, basic density and resistance to decay by Lenzites trabea (Pers.) G. H. Cunn. was studied on cores prepared from these discs. For trees 13 years of age or older, a change occurred from immature, decay susceptible heartwood near the pith to more mature, somewhat decay resistant wood at the sapwood/heartwood boundary. Radial variation in decay resistance and wood color both seem associated with position relative to the pith and with in situ ageing. The former is postulated to be controlled mainly by the deposition of polyphenols while the latter possibly results from polyphenolic polymerization. Decay resistance and color are very poorly correlated at most growth positions in trees of the various age classes. Basic density appears to have a strong indirect relationship with decay resistance. The need for basic chemistry research on wood color is discussed.