I used to be terrified of pine forests. The tall, dark trees seemed to quiver with menace, fringing the roads as we drove along in our little car. I’d peer out the window and dare myself to look into the forest, half expecting to see a wild thing lurking between the trees.
Pinus radiata is New Zealand’s great timber tree. It covers 1.3 million hectares of land and forms the basis of a massive export industry. It was first introduced into New Zealand in 1859 and comprises 89% of the country’s plantation forests, including the massive Kaingaroa Forest on the central plateau of the North Island, the largest planted forest in the world.
Radiata pine was first introduced by European settlers in the late 1850s. Its excellent growth rate ensured it was a fantastic candidate for widespread planting, and thus a great quantity of seed was imported from California in the 1870s, for shelterbelts and woodlots. In the 1920s and 1930s, there came a forestry planting boom, and Pinus radiata was adopted as the species of choice. Versatile and hardy, it grew well throughout the coastal sands, heavy clays, gravels and volcanic ash deposits of Aotearoa.
A medium-density softwood, Radiata pine clearwood is one of the world’s best. It possesses the mighty ability to grow to a large diameter faster than almost any other tree species. The ideal climatic and soil conditions of New Zealand, coupled with superb forest management and genetic improvement schemes has rendered New Zealand radiata pine of the highest quality in the world. Despite being native to California, USA, radiata pine grows much faster in New Zealand than in its original home.
Uses for radiata pine
The uses for radiata pine are numerous and varied. It may be employed for both exterior and interior applications, domestic and commercial construction, furniture, panels (such as veneer, plywood, particleboard, fibreboard), landscaping and pulp and paper. Many of our chairs and tables are manufactured from New Zealand pine — your gluteus maximus may be comfortably settled within the embrace of radiata pine as we speak. Moreover, recent research has developed a treatment that can increase the hardness of pine wood to the level of wood such as oak or mahogany.
Genetic Improvement Programmes
In its original, undomesticated state, radiata pine was a coarse and highly variable tree, with numerous branches and a forked trunk. To quote a Scion publication, “with the intensive plantation forestry that has been developed here, and the scale on which it has been planted as an exotic, radiata pine has become one of the most domesticated of all forest tree species.”
A genetic research programme was started in Rotorua, in the 1950s to improve the quality of New Zealand radiata pine. At the Forest Research Institute, trees of superior growth and form were selected and propagated by grafting, a horticultural technique whereby tissues of plants are joined so as to continue their growth together. Led by Ib Thulin, the programme selected outstanding looking trees, which which were documented in detail, and had seed and grafts collected. These grafts were used for controlled crossing. A clonal seed orchard was established, and seed from the original trees and the controlled crosses made among the grafts was used for establishing progeny trials. Grafts of the very best-looking trees were used to establish the orchards, and were left to interpollinate. These orchards could be ‘rogued’ of the clones that failed in progeny tests to live up to their promise.” In order to prevent pollen contamination, the grafted pines were planted out at wide spacing in isolated seed orchards, far away from other plantations. The first improved radiata pines were planted in our forests in 1970.
Over time, the selection criteria for improvement programmes have become increasingly complex. Crossbreeding is one such technique, wherein closely (or distantly) related plants are interbred to produce new crop varieties or lines with desirable properties. Hybridization, the process of interbreeding between individuals of different species (interspecific hybridization) or genetically divergent individuals from the same species (intraspecific hybridization) is also employed. Plants actually hybridize much more frequently and successfully than animals do, as pollen from flowering plants disperses widely and may land on flowers of other species. However the only species with which Pinus radiata hybridises readily is knobcone pine (Pinus attenuata).
Moreover, chromosomal doubling (polyploidy) occurs more frequently in plants and facilitates the fertility of the hybrid offspring. Plant forms are also less rigorously controlled than animal forms, and thus the intermediate form of a plant hybrid is more likely to be physiologically successful. Advanced plant propagation techniques, coupled with the previous two techniques have enabled scientists to develop breeds of Pinus radiata that are adapted to particular climatic zones and soil types, produce wood that is stronger or more durable, and are resistant to foliage diseases such as dothistroma needle blight.
Pinus radiata is a fairly easy species to propagate vegetatively, as cuttings. In the 1960s, researchers tried to exploit this feature in order to capture both the superior tree form of adult material and the theoretically greater genetic gains and uniformity of clonal material. The effects of maturation, or physiological ageing, which made clones difficult to mass-propagate thwarted this goal however. Over time, the easy propagation of young seedlings was exploited by mass multiplying scarce seedlots of top genetic quality. In these seedlots, slight maturation may be exploited to improve tree form. True clonal forestry, wherein a limited number of intensively select and very well characterised clones are mass-propagated initially proved to be incredibly difficult, event with the assistance of in-vitro propagation systems. However these days, it has become an operationally feasible and commercialised venture.
Pine wood is like a fine whisky
Reading the descriptions of radiata pine wood on wood catalogues online reminds me of whiskey connoisseurs waxing lyrical about their favourite tipple. The veneer is “moderate-to-high lustre”, the wood is “creamy-coloured,” darkening over time with exposure to light, “even-textured”, and “easy to slice, peel, mould, turn, sand, plane, glue, stain and paint.” The medium density wood of Pinus radiata means that it is light, relatively soft and not very strong, easily penetrated by preservatives and pulped by chemical or mechanical processes.
However, it is not without its failings. Radiata pine wood is susceptible to insect borers and decay-causing fungi. It must be kept dry and protected by drying or chemical preservatives for permanent use. Prior to the 1940s, pine wood was treated with creosote, carbonaceous chemicals formed by the distillation of various tars and by pyrolysis of plant-derived material, such as wood or fossil fuel. The creosote process was then replaced by tanalising, a system of pressure treatment with water-borne copper, chrome and arsenic. Tanalising extends the life of the timber for decades.
Molecular biology and tree breeding
The development of molecular biology heralds a new era for tree breeding. Genetic fingerprinting has already been proved to be an excellent method for verifying genetic identity of material. It may even eliminate the need for controlled crossing. Genetic engineering is currently being pursued as a means of conferring “attributes that cannot readily be captured by conventional breeding.”
When I was eight years old, my family moved to a farm in Mangatangi. The rolling fields, dotted with cows were fringed with majestic pine trees. I would explore the belts of trees with my brothers and sisters, playing hide and seek and spotlight until dusk fell. The pine forest seethed with life, and I no longer was afraid of the towering pines.
This article was inspired by the Rowland D. Burdon’s wonderful piece “Breeding Radiata Pine – Historical Overview“, published in the NZ Journal of Forestry, February 2008 Vol. 52 No. 4.