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June, 2015

Diverse Forests, Emerging Opportunities

Issue 4, June 2015

Partnership success!

We are pleased to announce that the new Ministry of Business, Innovation and Employment partnership programme has been approved, and look forward to the new research and collaborations now made possible. The partnership will focus on Douglas-fir, cypress species and a range of durable and non-durable eucalypt species, across the value chain from product to improved germplasm. It will concentrate on products with strength, durability and appearance properties that cannot be met with radiata pine. The partnership will be led by Future Forests Research and supported by a range of investors including processors, growers and tree breeders. It is a collaborative research effort between Scion, University of Canterbury and Marlborough Research Centre.

A large amount of research has been delivered during the last quarter. John Moore, Mark Kimberley, Melissa Evans, Jonathan Dash, Andrew Gordon and Sarah Orton have developed branching and wood den sity models for Douglas-fir, and implemented them in Forecaster.

Mari Suontama, Toby Stovold, Mark Miller, Kane Fleet and Russell McKinley have been measuring and testing E. nitens wood samples from the breeding population. Growth stress/strain, wood density, shrinkage and internal checking are being measured for selection of eucalypt trees with wood suited to the delivery of a solid-wood endproduct.

Charlie Low has been testing whether hybrid cypress crosses can be delivered directly to the field, rather than go through a cycle of clonal testing. This trial will be planted in winter.

Many thanks for your continued support, and we look forward to working with you under the new partnership.

Heidi Dungey and Patrick Milne

Research reports available at:


Forecaster models updated for New Zealand Douglas-fir

Wood density of New Zealand grown Douglas-fir

Early research has shown that branching and wood density are the two most important factors influencing timber stiffness in Douglas-fir. Therefore, for forest managers to achieve their targeted end-product outcomes, they need information on how wood density and branch characteristics are affected by site, silviculture and genetics. They also need sound knowledge of the variation in wood density between sites, between trees within a stand and within a tree.

While a large amount of this information has already been collated, it had not been systematically analysed to understand what contributes to the variation in wood density. As part of the Diverse Species, Emerging Opportunities programme, we undertook a study to develop models that estimate the variation in Douglas-fir wood density.

New models were developed using an extensive dataset of measurements from approximately 10,000 trees across multiple stands spanning 50 years. These models explain the variation in outerwood density between stands and between trees within a stand, and the radial and longitudinal variation in wood density within a tree.

Wood density was found to be strongly influenced by the environment, especially temperature. In particular, stands grown on cooler sites located at higher elevations in the South Island have lower density than those grown on warmer sites in the North Island. The resulting wood density models that were developed have now been incorporated within the Forecaster growth and yield simulator. This will allow forest managers to estimate different environmental factors on the distribution of wood density within different log products.

This study has presented the first comprehensive model for the prediction of Douglas-fir wood density across New Zealand. The most surprising find was the low influence of stand density on wood density. The study also raises several important questions that we will be pursuing in further work, including the influence of soils, genetics and Swiss needle cast on wood density, particularly for stands growing in the North Island. (Technical Note available at


Douglas-fir branch model

Forecaster is an important tool for estimating the yield of Douglas-fir stands by log grade. Log grades are primarily specified by size and quality, where quality is determined by branch SED (small end diameter) and log straightness.

We recently undertook a study to calibrate Forecaster’s existing BLOSSIM branching models and the generic forking models for four Douglas-fir log grades (CF+, CF-, DS and Pulp). Pre-harvest inventory data was compared with Forecaster predictions for the same stand. The prediction of stand quality and the mix of log grades produced at harvest were the key parameters for this study.

A total of 303 inventory populations (over 100,000 stems) were analysed, providing good correlation between Forecaster predictions and the pre-harvest inventory data. As a result, a new branch model has been implemented within Forecaster.

Results of this study will provide gr owers with greater confidence to use Forecaster to predict recoverable volume for these four log grades.

Extending this study to include domestic log grades, Stand Density Index (SDI) and Relative Density Index (RDI) would provide further information.



Douglas-fir controlled cross progeny trial site at Beaumont


Douglas-fir controlled cross progeny trial at Beaumont

A 16 year-old Douglas-fir controlled cross progeny trial in Beaumont was assessed by the Scion field crew in early May. The assessment was carried out to see if it was possible to do forward selections from a first-generation trial.

The trial was assessed for diameter, branching, malformation, straightness, acoustic velocity and acceptability, and cores for density were collected. Analysis confirmed that the heritability of traits was mostly moderate except for branching, which was low. Moderate heritabilities indicate that we can make good genetic progress for this population in the Douglas-fir breeding programme.


Ongoing efforts to control Eucalyptus tortoise beetle

Eucalypts have become an integral part of the New Zealand landscape, valued for their use as firewood, amenity, shade, shelter, wood, pulp and paper. Along with their establishment, however, has been the steady colonisation of their Australian insect pests. The most prevalent and destructive of these is the Eucalyptus tortoise beetle, Paropsis charybdis, commonly known as paropsis (shown above).

First found near Christchurch in 1916, it’s thought the beetle arrived via the port as eggs on seedlings, or hibernating adults on hardwood logs. Unchallenged by natural predators, it established rapidly and is now present throughout New Zealand.

Females can lay up to 4,000 eggs during their lifetime, with two new generations of beetles produced per year. This, along with their voracious appetite, has resulted in a rapid population expansion.

Repeated defoliation of eucalypts leads to crown dieback, coppicing, growth loss and eventually tree death. Historically, some outbreaks of paropsis have led to some plantations of Eucalyptus nitens being abandoned.

Efforts to control paropsis using its own natural predators and parasitoids (biological control), date back to 1932 and have been met with variable success.

The problem continues

Current biological control agents fail to control both larvae and adults. By the second generation of the year, beetle population density is high and inflicting considerable damage. For those forests that are Forest Stewardship Council certified, paropsis can be problematic as the only control measure involves spraying broad spectrum insecticides. These insecticides are costly, will also kill any biological control agents, and more importantly, require ongoing derogations from FSC for continued use.

Since 2012, Sustainable Farming Fund funding has been allocated to the FFA, with Scion’s entomolo gists and a project team, to investigate alternative biological control agents for paropsis. It has many natural enemies in its native Australia, and recent studies have identified the parasitoid wasp Eadya paropsidis as a likely candidate to attack larvae in New Zealand conditions (as shown below).

In collaboration with Dr Geoff Allen from the University of Tasmania, Scion is conducting ongoing research in our containment facilities to verify E. paropsidis’ suitability prior to its release in New Zealand.

Questions we will be asking include:

  • Can we rear E. paropsidis in the lab?
  • Once it emerges from the host, E. paropsidis spins a cocoon and undergoes an obligate pupal diapause for 10 months until the following summer. Is it possible to reduce this time?
  • What is the host range of E. paropsidis?
  • What are the risks to non-target insects?



Copyright 2015 NZ Forest Research Institute, trading as Scion. All rights reserved. Diverse Species News is published quarterly, and is also available in hard copy format.

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