Official website of the New Zealand Farm Forestry Association


Natural durability: Correlation between extractive content and fungal assay

By Monika Sharma, Laurie Cookson and Clemens Altaner, May 2018.

Download SWP-T045 (pdf)

Executive summary

The main objective of this work was to validate if extractive content (EC) predicted by NIR spectroscopy correlated with mass-loss durability measurements. 7 year-old Eucalyptus bosistoana heartwood samples with known EC (NIR) grown in New Zealand on four sites were tested for durability (mass-loss) against two basidiomycete fungi, a brown-rot and white-rot.

  • The result suggested that high EC predicted by NIR identified samples with low mass-loss and can therefore be used to select durable genotypes. However, some samples with low mass-loss (i.e. durable) had a low EC (NIR) and therefore would have been missed. Note: this does not compromise the identification of the durable individuals.
  • The average mass loss for the 7 year-old E. bosistoana NZ grown unimproved trees met at least the performance of a class 1 (above-ground) rated species (Corymbia maculata) (AS 5604 2005).
  • Further, some 7 year-old E. bosistoana trees produced heartwood, which showed no significant (<3%) mass-loss.
  • Large variation was found between trees and between sites, highlighting the need to select durable genotypes as well as investigating site factors contributing to durability of heartwood.

It needs to be noted that the stratified sampling strategy optimised to aid the 1st objective (correlation between EC and mass-loss) amplified the extremes, i.e. more high and low EC samples than would be expected in a random sample.

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