The origin and extent of discolouration and decay in stems of young regrowth eucalypts in southern Tasmania
1996
Wardlaw, T.J.
Two hundred thirteen potential sawlog trees from 22- to 34-year-old Eucalyptus regnans F. Muell. and Eucalyptus delegatensis R.T. Baker regrowth forests from four sites in southern Tasmania were felled, dissected, and assessed for discolouration and decay. Of the aboveground origins, branches accounted for more than half of the discolouration and decay both in terms of incidence and volume. Stem-boring insects and branch crotches were the source of most of the remaining aboveground decay. Butt rots accounted for only 7% of the columns of discolouration and decay, but their incidence showed considerable local variation such that on some plots they accounted for more than 20% of the total volume of discolouration and decay in the bottom 6 m of the stem. Decay in individual trees was 0 to 17.5% of total volume, with a mean of 1.3%. Only 12% of the trees were completely free of discolouration and decay, while 25% of the trees had discolouration and decay in more than 1.5% of the total stem volume. Whilst both the incidence and percent volume of decay showed considerable, and often statistically significant, variation both among sites and locally, among plots within sites, the greatest proportion of the variation was tree to tree. Our ability to limit future timber losses resulting from decay will require that those site, stand, and most importantly, tree factors that influence the prevalence of, and susceptibility to, decay in eucalypts are identified.
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