Salvaging what we can – novel data on wind damage from the Rangipo Accelerator trial

Authors: Simeon J. Smaill, Jonathan Harrington, Sadeepa Jayathunga, David Pont and John Lee
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 2024, Issue N.Z.J.For. 69(1) 2024, pp Pages 25 - 31, May 2024
Publisher: New Zealand Institute of Forestry

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Abstract: Wind events are a well-known threat to planted forests in New Zealand and around the world, and the magnitude and frequency of these events is predicted to increase under future climate change. Past research has enabled the development of tools and management strategies that can reduce the risk of damage to New Zealand’s radiata pine estate, but the random nature of wind events means there are few datasets linking the incidence of wind damage, and even fewer comparing the performance of different genotypes during the same event. The damage caused to the Rangipo Accelerator trial in February 2023 by the wind event associated with Cyclone Gabrielle provided a rare opportunity to address some of these knowledge gaps. This trial contains multiple radiata pine genotypes of the same age, and has been assessed regularly since establishment in 2016, providing a considerable pre-event baseline dataset. Post-event assessment showed that 31.3% of the ~7000 trees in the trial sustained damage, with tree genotype significantly associated with the incidence of damage. Airborne LiDAR was suitable for rapidly identifying the variability in damage across the trial, but was not able to provide robust tree or plot level metrics, given the large number of leaning and damaged trees. Examination of wood properties of damaged and undamaged trees showed that trees with greater wood density sustained less damage. A small study of internal wood properties in standing bent trees revealed substantial internal damage that could markedly reduce the future value of the trees if they were retained within the stand. One option that forest growers could pursue to reduce the risk of damage is to select and deploy trees with traits that confer greater wood density, but it is acknowledged that such trees may also grow more slowly than other stock. Ongoing monitoring of the trees in the Rangipo Accelerator trial will provide more certainty around the longer-term effects of bending and other forms of wind damage on tree value, and given the rarity of such sites this is strongly recommended.

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