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Forestry research

by  Margaret Richardson

From the beginnings of commercial forestry in New Zealand, researchers have been looking for ways to propagate, grow and process trees better and faster. They’ve also found ways to protect trees from pests and have developed new wood products, including biofuels.

The development of forest research

Early research

Pre-European Māori investigated the medicinal properties of New Zealand’s native trees, and their suitability as building materials. Later, European explorers and botanists also researched native forests.

Managing forest resources

In the early 20th century scientific research on how to manage New Zealand’s forests as a commercial resource began, including:

  • pulp and papermaking trials of native woods, carried out in the US
  • timber-strength testing at Auckland and Canterbury colleges
  • description of the taxonomy of native conifers at Victoria University College
  • investigation into forest insect pests by the Cawthron Institute, Nelson.

Researchers also began experimenting with fast-growing exotic tree species. Their aim was to establish exotic plantation forests instead of continuing to cut down native forests.

Pioneering research

A 1920 report to Parliament stated that to fully utilise native forests, improved management was needed. It recommended researching the pulping qualities of native timbers and investigating whether a cheap motor fuel could be created from the distillation of waste wood.

Forest research stations

In 1947 the Forest Experiment Station (later renamed the Forest Research Institute) was set up at Rotorua to coordinate Forest Service research. Nine years later the Forest and Range Experiment Station was established at Rangiora, Canterbury, to research South Island forestry issues.

Science reform

The Forest Service was disestablished in 1987 and its research resources became part of the new Ministry of Forestry. Further reform of the science sector led to the formation of Crown research institutes (CRIs) in 1992, and the Forest Research Institute (FRI) became a stand-alone business. Some staff, including scientists working on land protection and animal pests, transferred to CRI Landcare Research.

In 2005 FRI changed its name to Scion, having expanded its activities into the development of biomaterials (combining wood and other fibres with synthetics).

Reduced government funding for research, and the ‘user-pays’ philosophy, has meant that forestry scientists need to make their research commercially relevant.

Researching native forests

Native forest management

New Zealand’s native forests were once abundant, but logging had depleted them. Native trees are slow to grow to maturity and so, to meet the continuing demand for wood, fast-growing exotic forests were planted, mainly by the state.

Also, from the 1920s, to improve the management of native forests, the Forest Service set up research projects to study forest growth, regeneration and ecology.

National forest survey

To assess the amount of timber available in native forests the Forest Service began a national forestry survey in 1946. The survey also assessed the extent of natural regeneration and the effects of introduced animals.

The survey project was an enormous undertaking and fieldwork covered a huge area, including rugged mountain terrain.

The survey was completed in 1955, and was followed by further ecological and high-country surveys. Data collected in all of these surveys was also valuable for water catchment control and soil conservation.

Plotting a survey

The 1946 national forest survey involved measuring all saleable trees within sample plots. In the most intensively sampled areas there was a plot every quarter mile (0.4 kilometre), along grid lines one mile apart through the forest. In the least intensively sampled areas, plots were located every half mile, on lines four miles apart.

Selective logging research

Increasing concern for the environment led to protective legislation for native forests. Before 1975 it was legal to log native forest and convert the land to other uses. From 1975 to 1984, only selective logging (taking just some trees from a forest) was permitted.

Trials studied the impact of selective logging operations, with the aim of reducing damage to the remaining forest. Logging in North Island state native forests ceased in 1984, while it continued in the South Island until the early 2000s.

Growing more native trees

More recent research has emphasised forest ecology and rehabilitation. Crops of native tree species, including kauri, tōtara and beech, have been planted for timber production.

Studying exotic plantations

Experimenting with new species

As early as 1897, the state established plantations of exotic trees to provide for New Zealand’s future timber needs. To explore the growth rates of exotic species in New Zealand, there were experimental plantings at Whakarewarewa in the North Island and Hanmer in the South Island.

Eucalypts and redwoods were planted first, followed by a range of pines. By 1909, 5,140 hectares had been planted with more than 60 introduced species.

Radiata pine (Pinus radiata) was recognised as the best species for plantation forestry because it grew quickly and its timber was versatile. After the establishment of the State Forest Service in 1921, extensive exotic forests were planted, mainly in the central North Island.

Planting trees as crops

At first, little was known about how to grow trees as a crop. New Zealand researchers devised methods for propagation, planting and silviculture that influenced plantation forestry practices throughout the world.

The first challenge was to reduce the high cost of planting trees. Every detail, including the shape of the spade and the depth of the planting hole, became the subject of scientific research.

Pit planting

Foresters developed a pit planting technique to improve tree survival rates. This involved digging a pit into hard ground and making sure the tree’s roots were surrounded with loose soil, which could absorb and retain more moisture than compacted ground.

Nursery production

Young trees of uniform size and quality were needed to ensure high survival and maximum early growth rates. In the 1970s Forest Research Institute scientists developed a precision seed sower, a lateral root pruner and a seedling lifter that greatly improved mass production of seedlings.

Preparing planting sites

Preparing land for planting was hard labour, but in the 1970s machines for ripping and mounding the soil were developed. Improvements were also made in distributing fertiliser from aircraft.

Weed control

To ensure trees become properly established, shrubby weeds, such as broom, gorse and blackberry, must be controlled during the first few seasons of growth. Scientists conducted research on herbicides to find the safest, most cost-effective ways of controlling forest weeds.


In the 1970s and 1980s there were trial plantings of trees on farms, including the Tikitere trial near Rotorua, which was jointly established in 1973 by the Forestry Research Institute and the Ministry of Agriculture and Fisheries. Other trials were conducted at Whatawhata and Invermay research stations.

Trees were thinned to wider than normal spacings so that pasture could be grown between them. However, trees in fertile farmland often grew too fast, resulting in poorer wood quality. In addition, the spacing between trees meant branches were very large, further reducing the quality of the wood unless early pruning took place.

Although agroforestry seemed promising, and tree planting on farms was briefly popular, combining forestry with grazing has fallen out of favour.

Growth models

New Zealand researchers have developed models to predict how forests are likely to grow in a given place. Growth modelling uses data collected from a permanent sample plot system, established in New Zealand forests in the 1980s. Growth rates of different tree species are regularly measured at around 12,500 plot locations. With this information, planners are able to predict and regulate future wood production to take advantage of market movements.

Growing better trees

Tree breeding

Tree breeders began improving the quality of forests by selecting seed from trees with desirable characteristics. The first radiata pine seed orchards were established in the 1950s. Since then, there have also been tree improvement programmes for cypresses, eucalypts and Douglas fir.

Bigger or better?

Early genetic improvement of radiata pine focused on reducing the number and size of branches, and on producing a large, straight trunk. In recent years tree-breeding programmes have focused on improving wood quality and disease resistance.

Also in the 1950s, trials began to test coniferous trees from different parts of the northern hemisphere. The growth rates of different species were compared between various sites to find the best species for certain regions.

Mass-producing trees

When planting large areas, commercial growers wanted seedlings with uniform characteristics. Researchers experimented with vegetative propagation techniques, such as cuttings and tissue culture, to mass-produce trees without using seed.

Gene technologies

Since 1990 New Zealand scientists have identified trees with superior genetic makeup by examining their DNA. This screening process avoids lengthy and expensive testing.

In 2000 the first New Zealand field trial of genetically modified trees began in Rotorua, after being approved by the Environmental Risk Management Authority. Because of public controversy about genetic modification, it is unclear whether modified trees will ever be grown commercially. Nevertheless, New Zealand researchers are recognised as international leaders in this field.


One of the most important advances in New Zealand forestry research has been the development of planting, pruning and thinning systems for radiata pine to produce optimum growth and wood quality. For example, researchers established that early pruning of the lower branches from trees produces logs that are free from knots. The resulting ‘clearwood’ fetches a higher price from manufacturers of products such as furniture.

Food for thought

Trees, pasture and food crops all need fertiliser to replace elements consumed by the plants. In the case of forestry, fertiliser requirements are much lower.

Tree nutrition

When crucial nutrients are lacking in the soil, they need to be added for trees to grow well. By studying nutrients in the soil, forestry researchers have identified fertilisers to correct the deficiencies in most regions of New Zealand. These fertilisers are usually applied aerially at the time of planting, and then at 10-year intervals.

Leaf analysis techniques developed by New Zealand researchers were used in a 1980s national forest study to identify regions and sites where various trace elements were likely to be deficient.

Combating threats to forests

Forest health

With introduced trees came many new pests and diseases. From the 1920s the Forest Service was concerned that insect pests might come into the country on imported forest products, and lobbied for effective inspection and quarantine systems. It also initiated research on forest insects and diseases.

Insect pests

In the early 1900s it was discovered that a wood wasp, Sirex juvencus, laid its eggs inside the stems of pine trees. In 1929 researchers at the Cawthron Institute released the parasitic ichneumon wasp (Rhyssa persuasoria, which means ‘persuasive burglar’) to prey on the wood wasp. This was one of the first attempts at biological control in New Zealand, and it was successful. Biological control is now an important way of managing insect pests.

Forest entomologists identify insects from overseas that are likely to cause problems in New Zealand. These species are targeted by MAF Biosecurity New Zealand whenever they are found in the country. There were large, and controversial, eradication campaigns against insect pests in the 1990s and 2000s, including the painted apple moth in Auckland, and the Asian gypsy moth in Hamilton.

Well spotted

The 1996 discovery of the white-spotted tussock moth in Auckland prompted the first successful pest-eradication exercise ever undertaken in an urban area. The moth – which could have damaged ornamental and fruit trees, and native beech forest – was eradicated over large areas of residential Auckland through aerial and ground spraying.

Fungal disease

The first major disease of radiata pine was dothistroma needle blight, caused by the fungus Dothistroma pini. When it arrived in the 1960s the Forest Research Institute (FRI) urgently recruited forest pathology staff. There was intensive research on all aspects of the disease and trials refined techniques for spraying with copper, making it a cost-effective means of control. This treatment is still used.

Other common fungal diseases that have been made manageable by research include cyclaneusma needle cast (in pines), septoria leaf blight (in eucalypts) and Swiss needle cast (in Douglas firs).

Fungal fears

In 2004 New Zealand quarantine specialists discovered and destroyed pitch canker fungus – a serious threat to radiata pine – during a routine check of imported plant material. As a result, the importation of Douglas fir from the USA was restricted.

Animal pests

In 1956 the Forest Service became responsible for controlling animal pests in New Zealand forests, including possums, rats and goats. A research team at the FRI began studying the impact of pests on forestry, and methods of controlling them. This team later shifted to Landcare Research.

Forest fires

Before its disestablishment in 1987, the Forest Service was responsible for controlling fires in forests and rural areas, but this job has passed now to local authorities and individual forest owners. The study of fire behaviour in different kinds of forest is a small but important area of forestry research.

Identifying forest benefits

Soil fertility

Although plantation forests may exhaust soil nutrients, research in the South Island shows that the opposite can also be true. Exotic conifers have ectomycorrhizae (fungal associates) on their roots, which mobilise nutrients from organic matter deep in the soil, speeding up the rate at which these can be used by other plants. Some native species, such as beech and mānuka, have the same effect.

Soil stabilisation

Research shows that forests help stabilise soil in erosion-prone country. As a result forests have been planted on steep hills on the East Coast. Plantations have also been established on unstable coastal dunes that were threatening other land uses, such as farming, particularly on the west coast of the North Island from Northland to Manawatū.

Rain on the plain?

Do trees attract rain? This popular belief is not borne out by rainfall records from the central North Island. No increase in rainfall has been observed as a result of widespread forest planting there.


To research sustainable forestry management, plots were established throughout New Zealand in 2000 to test the impact of forestry practices on soil nutrition. Data will be used to manage plantation forests so they do not deplete the productive capacity of the land.

Water quality

Forests help stabilise land and protect waterways. Studies have shown that forested catchments have less erosion, produce less sediment and provide better aquatic habitats than pastoral catchments.

Forestry and the Kyoto Protocol

Under the Kyoto Protocol, New Zealand must reduce its greenhouse gas emissions to 1990 levels. Forestry can help achieve this goal because trees convert carbon dioxide in the atmosphere to carbon, which is stored in the form of wood and soil organic matter.

Climate change

Forests can absorb large amounts of carbon dioxide, so they can assist in balancing the greenhouse effect. Since New Zealand ratified the Kyoto Protocol in 2002, national monitoring systems have measured carbon flows across indigenous and plantation forests. This data is necessary for New Zealand to meet its reporting obligations.

Helping with the harvest

Inventory methods

Forest inventory methods refined over many years by Forest Research Institute researchers are now used by commercial forestry companies. Measurements of trees within a forest are collected to assess exactly how much wood is available, helping forest managers plan harvesting operations to be as profitable as possible.

Mechanised harvesting

Felling trees is heavy, dangerous and costly work, but using machinery makes the job safer and more efficient.

Most harvesting equipment developed overseas was unsuitable for New Zealand conditions. After conducting their own research into mechanised harvesting, Tokoroa engineering company Waratah began making machinery for local loggers. Waratah has since become a world market leader.

The high-viz vest

Harvesting researchers designed an item of clothing that has now become a Kiwi classic – the high-visibility vest. To make loggers more visible in the forest, coloured stripes were printed onto black singlets. These safety garments became so popular that the same style has been adopted by other industries.


High labour and transport costs make it difficult for New Zealand forest growers to compete internationally. To gain maximum value from every tree, researchers have identified logging methods that are efficient but minimise trunk damage, and the best ways of dividing each trunk into the log sizes to fetch the highest prices. This concept of gaining maximum value at the time of harvest has spread to other countries, where previously the main concern was to reduce harvest costs.


Since the early days of plantation forestry, researchers have tried to improve log-processing methods. Sawmillers have to work with variable log sizes, shapes and wood quality, and obtain the highest possible timber grades.

During the Second World War, state demonstration sawmills were set up at Waipā (near Rotorua) and Conical Hill (Otago). They were important in the development of sawing, grading, drying and wood preservation technologies for plantation timbers.

Wood processing possibilities

Timber engineering

Although radiata pine can be sawed, machined and treated more easily than other exotic woods, its properties vary from tree to tree, even when they are grown on the same site. Also, the wood within a single tree can vary markedly. Because of this, researchers have helped develop timber grading systems and building standards to ensure that the right wood is used for different purposes.

Timber drying

Because wood has a high moisture content, it must be dried in large kilns before use. Drying must be carefully controlled to prevent warping and bending of the timber. New Zealand research into the drying process leads the world. Breakthroughs include using high temperatures to dry wood as quickly as possible.

Wood treatment

Preservative treatments to protect wood from insect attack and decay have been developed by chemical companies working with researchers. But, because public opinion has swung away from chemical preservatives, other treatments have been sought.

Using swamp kauri

In the 1920s researchers tested whether swamp kauri was suitable for pulping, as the sodden wood dredged up from wetlands was seen as useless for anything else. The fibres were found to be unsuitable for paper, but swamp kauri is now one of the most valuable furniture timbers in New Zealand.

One alternative is to use heat to change the physical properties of the wood and make it unpalatable to insects and fungi. Another process, known as acetylation, modifies softwoods at a molecular level so they behave more like hardwoods, with more stable and durable wood.

Pulp and paper

New Zealand research into pulp and paper production initially focused on native species, before moving to exotics. Because most pulp and paper technologies originated in the northern hemisphere, using spruce and other European species, New Zealand research into pulping and processing radiata pine was needed so the local paper industry could develop.

Wood fuels

Methanol (also called wood alcohol) was the first fuel to be made from wood, but now researchers see ethanol as a more likely replacement for petroleum. It may also be possible to produce diesel fuel from wood.

Heat and power

New research aims to increase the production of renewable energy from wood. The forest industry often burns wood waste to produce heat for timber drying kilns. In large-scale commercial and industrial applications, such as sawmills, this energy can also be used to generate power.

Liquid biofuels

Rising oil prices in 1973 prompted forestry scientists to develop a technology to produce ethanol from wood. While pilot studies showed promise, motivation flagged when oil prices fell.

Due to concerns about climate change and rising oil prices, interest in biofuels has recently resurfaced, as they are seen as a carbon-neutral alternative to fossil fuels. New research in this field is underway in institutions and companies throughout New Zealand.

External links and sources

More suggestions and sources

How to cite this page: Margaret Richardson, 'Forestry research', Te Ara - the Encyclopedia of New Zealand, (accessed 18 July 2024)

Story by Margaret Richardson, published 24 November 2008