New Zealand Dryland Forests Innovation (NZDFI) is a collaborative tree breeding and forestry research project. It was established in 2008 and aims to select and improve drought-tolerant eucalypt tree species that produce high-quality ground-durable hardwood products. NZDFI’s vision is for New Zealand to be a world leader in breeding ground-durable eucalypts, and to be home to a sustainable multi-regional hardwood industry based on 100,000 ha of eucalypt forests by 2050.
Durable eucalypts are a group of eucalypt species (‘gum trees’, native to Australia). They produce heartwood (timber in the middle of their stem) which takes many years to decompose because of biochemical resistance to wood rot. This resistance to rot is called 'natural durability'. Naturally durable timbers can last for twenty years or more in contact with the ground with minimal rot. Durable timber does not need chemical treatment to prevent rot, unlike radiata pine.
Durable eucalypts are fast-growing and generally tolerant of dry environments. Some can tolerate rainfall of less than 600 mm/yr. Their timber is hard, strong and durable, and has many potential uses, both on-farm and in various high-value markets. Eucalypts store carbon, and support bees and native birds at times of year when other nectar and pollen supplies are scarce. They also coppice (regrow from a cut stump) so are good for soil conservation as their roots hold the soil in place even after harvest. Some durable species are highly adapted to New Zealand’s dry climates where they can produce very durable timber at a young age. Some species also thrive in higher rainfall areas where growth rates and production of durable timber can be very high.
There are a number of durable eucalypt species, and their site requirements vary. In general eucalypts will grow best on low altitude, fertile, relatively sheltered sites with good drainage and regular rainfall. However, NZDFI trials have confirmed that some species can tolerate very hot, dry, infertile and moderately exposed conditions. Suitable sites include low-productivity hill-country and ex-radiata pine cut-over sites. Fenced-off riparian sites are another option. Flat areas with frost exceeding minus 5 degrees can kill young trees. Also areas with poor drainage should be avoided. The NZDFI’s key target regions for durable eucalypts are NZ’s warmer eastern dryland regions: Gisborne/East Coast, Hawke’s Bay, Wairarapa, Marlborough, Nelson, North Canterbury and more recently, Northland. Our trial network is also demonstrating that there are some durable species which are well adapted to growing in regions with higher rainfall including the Central North Island and Taranaki regions.
Costs of establishment vary with site and grower objectives. The main cost elements are likely to include:
We recommend you consult a local regional council land management adviser, forestry consultant, or an experienced farm forester to discuss any ideas for new planting on your own property.
Form-pruning at age 1 or 2 years after planting is advised. This ensures the trees have one ‘leader’ (leading stem), giving them the potential to grow a single straight stem. Form-pruning can be done by with secateurs or loppers and is quick and easy. Clear-wood pruning (i.e. removing side-branches from stems to create a knot-free log) is likely to be needed only on edge trees or other trees receiving a lot of light. Trees within plantations generally self-prune.
Thinning is essential if crop trees are to grow to a marketable diameter. A minimum of two thinning operations is likely to be needed. The first, around age 4-6, should reduce tree numbers by about 50%. This operation gives the opportunity to select the best stems for the final crop. Second and any further thinnings will be needed as tree crowns begin to compete with each other. These operations may produce material which, on easily accessible sites, has potential e.g. for posts and poles, other fencing material or firewood.
This depends on the potential end use of the timber and the site's productivity. On most sites, by around age 15-18 the trees should be big enough, and have enough heartwood, for smaller products such as posts and poles/on-farm end uses such as for fencing material and on-farm joinery. If the target market is larger sawlogs, growers should anticipate a rotation of 25+ years.
Radiata pine is a versatile species which grows well on a wide range of site types. Durable eucalypts have greater drought tolerance, produce harder timber, and provide better biodiversity values. They can grow faster than radiata pine on some sites in their early years, sequestering more carbon and potentially accumulating more NZUs. Durable eucalypts tend to be more site-specific however, and it is important to get good advice about which species is best adapted to your site.
A key target New Zealand market for durable timber is posts and poles for vineyards, kiwifruit orchards and other horticultural crops with organic/sustainable production systems. The durable timber is an alternative to chemically treated (CCA-treated) radiata pine. Decking, flooring, joinery and electricity cross-arms are other potential end uses. Durable eucalypt timber is much higher strength than radiata pine: work is also underway to test durable eucalypt veneer as a component of engineered wood products such as laminated veneer lumber (LVL). High-strength engineered wood products are in demand world-wide for new modular and high-rise building construction.
Other high-value domestic and export markets include those where richly-coloured eucalypt timbers could replace very high-value markets for (often illegally harvested) tropical hardwoods such as teak and rosewood.
It’s a ‘chicken and egg’ situation at the moment. The amount of durable eucalypt timber available in NZ is very limited, so we can’t put a lot of effort into developing markets until the resource is there to supply them. However, we are very confident that market potential exists. The NZDFI's strategic focus is on developing regional hardwood industries which will produce durable hardwood and engineered wood products aligned with local, national and international demands.
There are few, if any, mature plantations of any scale of NZDFI species. The NZDFI team has developed early growth models for selected durable eucalypt species, based on permanent sample plots (PSPs) in two contrasting sites (low and high productivity). These will be updated over time as more data from our trials become available. The data is reported in our Strategic Plan (Section 5).
Because of the lack of market information, investment analysis of durable eucalypt plantings cannot be done in the same way as a grower might assess a potential radiata pine planting. Using a different approach, we have modelled financial scenarios for different growing regimes under high and low productivity conditions. See our economic information for more details.
NZDFI has received significant financial and in-kind support from government, landowners, industry and others, all of whom have confidence in the vision of a sustainable multi-regional hardwood forest industry in the future.
There are a number of unknowns and risks associated with growing durable eucalypts, which are still an emerging species group in New Zealand. These include:
The NZDFI’s research team is working hard on many of these aspects, and collaborating with international partners to fill important knowledge gaps and mitigate the main risks to New Zealand growers and the environment.
There is a wide range of information about the work of the NZDFI, and durable eucalypts in general, on the NZDFI website: www.nzdfi.org.nz You are also welcome to contact Paul Millen, NZDFI’s project manager, with any specific queries: p.millen@xtra.co.nz
C/- Marlborough Research Centre Trust, PO Box 875, Blenheim 7201