Breeding – getting the most from radiata pine
John Walker, New Zealand Tree Grower May 2010.
The best trees are tall, fat and straight – and in the best of all possible worlds they will be pruned and be at least 30 years old. This has been achieved in the last 80 years with perhaps a billion dollars of public money. Yet the best kept secret of the woods is that it is a cross-dressers’ nightclub.
They have all the attributes of pretty women, except the essential ones. Foresters have improved appearance but done little about wood quality and the sawmillers have learned to make do with what they get.
Losing less money
Conservatively, 20 per cent of all logs are of indifferent quality and will be processed at a loss. For example one sawmiller rationalised their finger-jointing recovery operation as a good way of losing less money than would otherwise be the case. New Zealand is not alone. In a review of UK sitka spruce in 2002 Macdonald and Hubert of Forest Research, Scotland, noted that low value pallets, packaging and fencing account for two-thirds of all production.
There is no relief in sight. The internal wood properties of radiata pine being planted today will be no better than that of the earliest mass plantings of the 1920s, and we will be milling this timber for another 40 years. Nevertheless there are opportunities. For example the FRST consortium is addressing this problem by sorting existing logs and timber into good or pro?table, and bad or marginal wood.
You can see the scale of the problem in a study by WQI, of three stands aged 8, 16 and 24, located in close proximity to one another, on similar soils and subject to the same management. One aspect of that study was to estimate the outer wood stiffness of trees in all three stands.
In each stand the trees were ranked and the average stiffness of the best and poorest noted. If we hypothesise that rankings do not change with age we can analyse the three stands like Russian dolls inside dolls. Looking inside the worst trees, their average stiffness would have been around 6.3 gigapascals at ring 24, 4.4 gigapascals at ring 16, and 2.6 gigapascals at ring eight.
We can generalise this study by saying that the outerwood of the worst trees in any stand is no better than the corewood of the best trees, and other data supports this. There is no way to identify the good and the bad trees just by looking. So one focus of the consortium is commercialising technology that rapidly and non-destructively probe the intrinsic qualities of sawn timber. This wide variation is an indication of the enormous potential for genetic improvement.
This brings up two important points. First, around the world in softwood plantations people are growing a proportion of wood that is pathetic. Some who might take offence will observe that their trees are different because they are being grown on long rotations. Therefore the poor wood is an increasingly smaller proportion of the tree, as in the Scandinavian option with a 60 year or more rotation. Another option is that their trees are planted with high stocking rates, suppressing the corewood zone, and thinned lightly and repeatedly − the Australian option and also that of some in New Zealand.
|Variation in the wood properties between trees within any stand|
|Age of stand||The real McCoy
Best 20 per cent of trees
Worst 20 per cent of trees
|24 years, equivalent to sapwood||11.0 GPa||6.3 GPa|
|16 years||8.0 GPa||4.4 GPa|
|8 years, equivalent to heartwood||6.5 GPa||2.6 GPa|
Second, some clarification may be necessary. The assumption is that if a tree is a loser at age eight it will be a loser at age 16 and again at age 24. The ranking between ages will experience drift, but this is unlikely to be serious matter.
This simplistic hypothesis has irritated tree breeders, especially when taken to extremes as we will argue below. Tree breeders prefer to delay their selections until around a third or even half of the rotation age. In addition their case is reinforced by the consensus that the best wood in the tree is the outer wood and that is where the most value is to be captured. They are delaying selections to get a better result in the outerwood of mature trees, but I disagree.
The first successful breeding programmes were mainly looking at visual characteristics and securing extra volume at the end of the rotation, with improved GF breeds for growth and form. It was therefore entirely logical to delay making selections, to take account of silviculture and to improve the robustness of growth model predictions. Breeders were chasing volume rather than quality, and they were well rewarded with trees of superior growth and form. However, today’s agenda should take improved growth and form for granted and seek new attributes to improve.
With regard to wood quality, the price differential is greater between the reject and utility grades than between utility and superior structural or board grades. In other words, poor corewood costs the grower or sawmiller more than can be gained in superior outerwood. Therefore the primary focus should be on improving corewood rather than on outerwood.
Delaying wood quality selections until a third or a half of the rotation age delays genetic turnover. In addition, the labour, cost and time involved in gathering material for tree improvement research and development increases dramatically with the age of material being studied – it becomes a self- defeating exercise.
Wild and unimproved
In contrast the new game is to screen radiata pine at age two rather than at age 10 or 15. You are therefore dealing with physically smaller piece sizes which are far cheaper to handle, can be analysed faster in minutes to weeks rather than months and years, and there is the ability to screen large populations. This means we do not get hung up on age/age correlations. If you are a winner at two you are a winner for life and you are focused on evaluating the worst wood in a tree. Finally, genetic gains can be deployed much faster.
Radiata pine is an unexceptional utilitarian species that would be greatly improved by cleaning out the runts or looking for elite trees. All New Zealand has achieved to date is to screen for growth and form, so that despite their good looks, our trees are wild and unimproved within. Huge gains in wood quality are readily achievable by mining our breeding populations.
This is a transformational opportunity. By screening at age two you can achieve the rapid genetic turnover in wood quality attributes equivalent to that achieved in the green revolution by Norman Borlaug in Mexico in the 1950's. Incidentally, Borlaug’s first degree was in forestry.
This dream was unachievable 10 years ago as the novel technologies and ideas to mass screen one to two-year-old wood had not been developed. It can take many years of patient development to achieve overnight success, and that is the prospect for the Radiata Pine Breeding Company as it begins testing his approach.
A game of statistics
Radiata pine has one singular advantage. Breeders have been assiduous in collecting material from land races and native populations – I believe we have some 3,000 families in New Zealand. Breeding is a game that uses statistics, ideally trawling through huge numbers to seek the very best. When you are looking to improve multiple traits, the larger the population you have, the better the result. It is equivalent to identifying individual pre-school children each with potential to be a good athlete, a good scholar and a good musician.
Up to now New Zealand has been unable to capitalise on this large genetic resource in radiata pine. Partly this is because of the sheer physical effort and partly the cost in trawling through 5, 10 and 15 year-old trials for wood quality traits was an impossible task. However when you look at younger material the costs fall dramatically and it merely becomes a daunting challenge.
Quick gains possible
There is a threat as well. Despite years of investment radiata pine remains unimproved with regard to wood properties and it comes out of the same starting gate alongside all other species. The same opportunities are available to them. Since genetic diversity is considerable in all tree species, significant gains can be made quickly and cheaply working with a relatively small number of families, perhaps around 100 families. Ironically, considerable improvements are as immediately achievable with a modest population of a little known species as can be achieved by well-recognised plantation species.
Hardwoods also have two advantages. First, they get off to a far better start in life with regard to wood quality. The wood in young hardwoods is superior to that of softwoods – but their wood is equally variable and so also amenable to further improvement. Secondly, hardwoods are better suited to producing good timber on short rotations than are softwoods, so commercial benefits can be realised in 12 to 16 years rather than 24 to 30 years.
Farm foresters will be delighted, but that is another story.
Long time problems
Pine breeders find themselves at the wrong end of a long temporal supply chain. There is at best a weak market pull from consumers, sawmillers and growers for something superior and innovative that will not reach its ultimate market for another 20 to 40 years. More immediately, breeders are confronting an unsophisticated industry unable to reconcile the conflicting desires of the bottom line and its long term economic sustainability.
If there is no additional payment for quality traits of seedlings, there is little incentive for breeders to improve quality. One approach might be to sell improved material at the same price as current planting stock but to register and take a royalty on the value of the final crop. If growers can trade in carbon, then it should be equally easy to own and trade in royalties – routine for the mining industry. A young Augustine would have approved.