Farm Forestry New ZealandAssessment of E. globoidea wood properties at Atkinson
By Lisa Nguyen, Ebenezer Iyiola, Monika Sharma and Clemens Altaner, February 2020.
Download SWP-T092 (pdf)
Executive summary
While growth characteristics of E. globoidea compare favourably to other eucalypt species in the NZDFI programme, its wood properties in particular natural durability (class 2), ease of drying and to some degree stiffness are good rather than exceptional. Therefore, wood properties should be considered in a tree breeding programme if ground durable solid wood products are envisioned as the future market.
144 families of E. globoidea were assessed at age 8 years old for heartwood quantity, extractive content (i.e. natural durability), drying defects (i.e. collapse) and stiffness (i.e. acoustic velocity). All traits were heritable and having a degree of variation enabling improvements through a breeding programme. The high heritability (h2 = 1.16) and large coefficient of genetic variation (CGV = 52%) of heartwood extractive content encourages selection for heartwood quality, as E. globoidea is in contrast to the other NZDFI species rated not class 1 but class 2 ground durable.
An unfavourable genetic correlation (-0.44; CI95 -0.62, -0.25) was found between heartwood quantity and extractive content, indicating the need for compromise between growth and natural durability. A favourable less strong genetic correlation (-0.27; CI95 -0.51, -0.02) was found between heartwood collapse and extractive content, indicating improvement in both if one is selected for. The other key traits were not correlated and therefore need to be selected for independently.
That data has been made available to the NZDFI partners to allow them to select superior genetics for commercial plant production.
Only 1 of 3 sites planted at the same time with the same genetics was assessed and environmental effects remain to be quantified.
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Post from Dean Satchell on May 20, 2021 at 8:37PM
I don't understand why heartwood quantity is measured as heartwood diameter (an absolute value) in this study. In my mind heartwood quantity is a relative value, i.e. proportion of the total diameter, usually expressed as a percentage.
This study shows that extractive content is negatively correlated with heartwood DIAMETER, but should I assume a negative correlation between extractive content and heartwood percentage?
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