Australian forest growers biennial national conference
John Millet, New Zealand Tree Grower May 2014.
This conference was held at Gympie in south-east Queensland in October 2013 along with a pre-conference bus tour from Brisbane north to Gympie. Travelling to sub-tropical northern New South Wales and southern Queensland for information may seem rather wide of the mark, even for a former eucalypt grower from Northland. But I particularly wanted to see E. microcorys (tallowwood) growing in its native state, having grown them successfully as infill on shaded moist and sweaty sites on my farm among other eucalypts and native regeneration.
My hosts ensured that I saw this many times over, although the best stand I saw was tallowwood coming up and almost level-pegging with flooded gum, E. grandis, in Ringtail State Forest in Tewantin National Park. Sub-tropical Australia is traditionally world renowned for growing high-density hardwood with good mechanical properties, high natural durability, good stability and attractive colour. To produce a broad range of construction and appearance timbers, poles, bridging girders, veneer and craft-wood in a strong market, but with a diminishing resource, has entailed Australian forest owners taking a good look at some other species.
Some of these species will be familiar to our more northern New Zealand members but others will not. For example on Fraser Island, the world’s largest sand island in Hervey Bay, are some of the largest E. pilularis I have ever seen. But at this same location Syncarpia hillii– a satiny, pale strawberry, lustrous fiddle-back timber when quarter sawn – were so big that only the smaller ones and coppice were easily viewed. They look similar to the S. glomulifera we can grow here.
Points that particularly caught my interest during our travels included the differences between native and plantation forests.
Native forest includes remnant and regrowth areas of mixed species originating from the old growth which is now long gone or locked up. Large areas are still very important for maintaining hardwood supplies with characteristics at least approaching traditional grading of the old growth species concerned. Native forest is also managed for wildlife and water conservation, erosion control and carbon sequestration.
Regrowth forest may be modified by treating such as thinning, weed control in the interest of a better crop in 60 to 70 years or grazing. High grading over a few generations is native forest’s worst enemy and was a practice common to subsistence farming in south-east Queensland after World War I. By taking out a crop every time anything reached marketable size, the remaining forest is so depleted genetically that the only remedy is to import and plant trees with superior potential, in other words convert to a plantation.
Plantations are man-made for efficiency, much as we do in New Zealand with exotic tree species. This approach generally works well on the better land and higher costs are compensated for by much shorter rotations, whatever the product. An example can be given from the conference paper of the young manager of Super Forest Plantations, Northern Rivers in New South Wales. His recipe is backed by over 100 permanent plots across 100 hectares of plantation and also his experience growing saw-logs since 1999. Species trialled for growth and form were −
- Gympie messmate E. cloeziana
- Tallowwood E. microcorys
- Spotted gum Corymbia citriodora subsp. variegata (not quite the same as our Corymbia maculata)
- Grey ironbark E. siderophloia
- Red mahogany E. resinifera
- Brush box Lophostemon confertus (slower)
- Grey gum E. propinqua
- Turpentine Syncarpia glomulifera.
These species are now considered worth persisting with and the fact that they are more durable ensures a higher variety of end uses.
Mixed species stands are now preferred as they minimise the risk of total devaluation from species specific pests or diseases. They may also take advantage of unidentified differences in soil characteristics or microclimatic conditions that favour one species over another. Plantation establishment has always been at a disadvantage compared with native regeneration where the seedlings grow favourably where they like it best. Because Super Forest Plantations use nothing but wild unimproved seed, initial stockings were at least 1,250 stems per hectare.
This made thinning very costly and so has been reduced to 833 stems per hectare. This should provide the required number of stems with acceptable form from which to choose a final crop of productive trees, perhaps 150 to 200 stems per hectare. Row orientation is across the contour to allow for safer and easier machinery use and felling up and down the slope. This did leave me wondering why they make this differentiation between plantation and native forests.
Speed versus slow growth
A number of research papers given over two days at the Gympie conference very properly dealt with Australia’s slow change from an ever-diminishing native hardwood resource to the greater commercial efficiency of plantations. Scientists were concerned to point out to hardwood manufacturers that any products from plantations will be different from those more slowly grown in nature and also possibly inferior in terms of wood properties.
Durability, strength and stiffness are reduced from that of the old growth species. Research is trying to demonstrate that manufacturers can easily measure this, such as by determining resonance and timing the frequency of an acoustic signal through the log. More valuable recoveries from plantation thinning at an earlier age of 10 to 12 years are important in bolstering plantation economics. Assuming that thinnings are of sufficient quality, straight with small to no knots, veneer recovery of 50 to 70 per cent can be achieved, using new small spindleless lathe technology. This is up to three times better than usual green sawn recoveries from small plantation hardwood logs of similar diameter.
Because Queensland’s best hardwood species start with such high mechanical properties, trials claim that veneer from eight to 15-year-old plantation thinning compares very favourably with mature radiata pine and Douglas fir saw logs. Overall veneer processes are considered better adapted to the sub-tropical and tropical hardwood plantations.
Special saws have been tested on temperate eucalypt plantation logs with a small end diameter more than 35 centimetres and found to have an economic recovery of only 30 per cent, producing narrow boards at risk of poor market acceptance. The wood industry is busy researching entirely new products linked to modern building specifications and better suited to using the new fibre from plantations, as opposed to the once more familiar native timber. Materials and structures under development include −
- Structural members used while round
- Steamed and arched round structural members
- Glue-laminated timber for long trusses needing superior strength to that of softwood
- Attractive and hard-wearing floor overlays emerging from thin sawing hardwood techniques
- Performance-enhancing composites of laminated veneer lumber and plywood I-beams where the advantages of all the natural fibres is exploited in mixtures.
High quality wood processing
Hurford Hardwood of South Lismore in New South Wales is a good example of enlightened and high quality wood processing going back through three generations of one family, with two generations attended the conference. They wereTree Grower of theYear, NSW 2011 and we lunched with them on the pre-conference bus tour at Kygle where they have a processing and drying facility employing 100 people as well as contractors. We admired some of the stunningly coloured finishes that sub-tropical hardwoods can provide. Species that New Zealanders would recognise include −
- Blackbutt – E. pilularis
- Flooded gum – E. grandis
- Forest red gum – E. teretecornis
- Red ironbark
- Spotted gum
- Sydney blue gum – E. saligna
- Tallow wood – E. microcorys
- Grey gum – E. propinqua
- Grey ironbark – E. paniculata
- Silver top stringybark – E. laevopinea
- Red mahogany – E. resinifera.
Hurford Hardwood obtain a proportion of their timber from private native forests with the balance from State Forestry which is certified under the Australian Forestry Standard/Chain of Custody AS4707-2006. With an eye on future supplies and the environment they have purchased over 5,000 hectares of land locally on which to establish 25,000 plantation eucalypts each year. They do this following strict environmental guidelines and a code of practice regulated by the New South Wales government.
Their plantation design incorporates riparian ribbons of local mixed species which will never be harvested but support existing, designated soil and water and native plant and animal habitats. Sustainable harvesting of the production plantations should begin within 25 years. An added bonus for Hurford’s new enterprise is that it should act as a marketing incentive for nervous green-minded customers buying their fine flooring and joinery. However, a challenge remains to duplicate all the species they use into plantation situations.
Roundwood and poles
The types of dry native forest regrowth commonly found in south-east Queensland and coastal New South Wales contain the richest natural expanse of preferred pole species in Australia and are mostly of exceptional quality. Power companies still prefer hardwood timber rather than any other material. It has a proven life of over 60 years and can be grown in 15 to 35 years, assuming the exacting state specifications can be met by the grower. These growers appear to be in a seller’s market for the foreseeable future.
|Durability class||Strength group 1||Strength group 2|
|Class 1||Ironbark||Tallow wood|
|Grey gum||White mahogany|
|Grey box||Gympie messmate|
|Class 2||Red mahogany|
The Australian Standard AS3818.11 sets out the limits of tolerance for standard and select poles covering size, straightness, knots, insect holes, spiral grain, pipes, gum veins, resin pockets, end splits, barrel checks, dry sides and mechanical damage. Poles are classified for durability and strength by species.
Power companies have their own pole specifications within the standard and this also differs by state. Sizes range from eight metres long up to 23 metres, with the very important strength factor measured at ground level in kilonewton (kN) units. In addition, 65 per cent of all pole demand is in the important range of 12.5 metres to 14 metres. Their availability can be improved by an innovative and engineered addition to strength group two, which has a three metre steel extension to the butt, and which uses two shorter lengths in less demand.
Log-making to maximise best value recoveries is an extremely skilled occupation, requiring the log-maker to discern if and when poles are useable, to have a good knowledge of specifications and to strike the right balance between light saw-logs and longer poles. This is also based around maintaining a regime to maximise pole production in a region particularly suited to it. For example, much of the land is depleted dry spotted gum farmland in need of restoration and where growing larger bole sizes is a struggle.
Pole production therefore probably pays the Queensland and New South Wales farm forester the best stumpage. For example, a key size pole one cubic metre in volume accurately identified, segregated and presented as a pole by a skilled contractor may have a stumpage value over two-and-a-half times the equivalent log stumpage value.
Two utility companies, Koppers and Ergon Energy, made presentations at the conference on the state of the Australasian pole industry. They were worried that demand for roundwood and poles would peak in less than 15 years at levels well in excess of present supply. Koppers wanted to help the problem by explaining the high potential profitability to growers, claiming little more than seven per cent slippage to pulp and lower value saw logs and veneers. They said growing this material was mostly a matter of education and skill. Ergon Energy, on the other hand, launched their sustainable pole supply project in 2007 aiming to be 50 per cent self-sufficient in supply by growing their own poles on their own land. However estimates of their future production remain less certain.
The burning question still appears to be that, when roundwood from well-managed pruned and thinned, plantation-grown eucalypt forest becomes available, will its strength mean grades will need to be re-assessed and pole specifications revised to compensate for loss of strength? Some strength problems may be solved by increasing diameter. However duplicating class 1 or class 2 durability, even in younger and softer hardwood plantation thinning, might be more of a problem owing to inadequate preservative penetration. To do so would be very costly, although the termite problem of lower durability class would be solved.
Another conference presentation was provided on this problem. Through-boring involves drilling a pattern of 12 millimetre holes through a less durable pole in the most critical zone 600 millimetres above and below the ground line.The hole pattern is designed to minimise effect on pole strength and create zones of treated
wood which fully protect the pole with preservative, even though its heart-wood penetration is limited to the immediate vicinity of the holes. A long-term field trial started a year earlier has produced data on the treatment characteristics, decay and termite durability and mechanical performance of four plantation sourced species in pole form – E. globulus, E. grandis x camaldulensis, E. dunnii and E. nitens.
Treating durable timber
The tour visited Dale and Myer’s Pole Mill out of Tiaro which also specialises in sawing, boring and edging cross-arms. It felt good seeing some of their products, strapped up and chalked, destined for Tauranga. The manager lives on the vast yard site which is surrounded by a bund to prevent any wood preservative run-off. The complete range of pole lengths come in from the loading ramps, having been de-barked by a barking bar located below the skidders blade, then measured and graded into heaps and surface sprayed against insect infection where necessary.
All the extensive range of hardwood products, from the longest of transmission poles to short strainers, piles and cross-arms are pressure tank-treated with chromated copper arsenate so they can be guaranteed durable for 50 years and be up to specification. Treatment takes care of any sapwood that might still cling to these durable hardwoods, preferably derived from private and state-owned native regrowth.
Coal seam gas extraction boom
Quantities of valuable gas are situated under large volumes of water, the water being classified as a regulated waste under the Environment Protection Act. Depending on the level of common salt or other sodium impurities, an opportunity exists using salt-resistant red river gum hybrids such as flooded gum, E. camaldulensis x E grandis, to absorb this waste water by distributing it in a plantation area. The gas company pays for the right to dispose of the water.
The gums have to grow well enough to keep the water table of the irrigated areas below the soil’s productive profile for at least the 30 to 50 year window of gas production. The forest can be either for timber or conservation, private or state-owned. In either case it is green infrastructure with gas extraction and would be the main economic reason for the plantation.
All this was explained when we stopped at the University of Southern Queensland at Toowoomba by Glenn Dale, the Managing Director of Tree Crop Technologies Pty Ltd. Since 2007 the company has worked with Coal Seam Gas and various mining companies to undertake feasibility studies into the use of waste water beneficially, with over 1,500 hectares of land involved. His colleague Neil Halpin is a dab hand at picking suitable land for these exacting trials, judging it by feel and its present vegetative cover.
Myrtle rust, an exotic strain of eucalypt rust, a pathogen long recognised as a threat to Australia’s native Myrtaceae, was first detected on the central coast of New South Wales in April 2010. Government attempts to confine it have failed and it now infects over 200 myrtle species in Victoria, New South Wales and Queensland. Symptoms are severe blighting of new shoots and expanding foliage and stem infection causing dieback. Reports from Brazil are that its greatest effect is in the nursery on new plantings or on coppice growth.
Scientists are now urgently trying to determine myrtle rust’s characteristics. Variation in susceptibility was observed between species and at a provenance and family level, indicating opportunities to select and breed for resistance. Programmes run in parallel with measuring any changes in the rust population itself, either from new incursions or mutations within the current strain. With information still limited, myrtle rust is a significant worry in determining what best to plant. Let us hope it does not get to New Zealand.
Clonal Solutions Australia Pty Ltd provided a comprehensive presentation based on 15 years of pioneering work with production and assessment of eucalypt clones. The difference between seed and clonal propagation was explained. Despite careful provenance selection when harvesting seed, wide genetic variability occurs but vegetative propagation of clonal material retains the same genetic character.
Genetic uniformity of the trees means the need for blanking is very low, thinning being less necessary. Stocking rates are also lower, as are planting costs, and sturdier plants are produced with less chance of a hockey-stick tap root when grown in well spaced root trainers. The company claims that these advantages more than make up for the higher cost of clones over seedlings.
Cuttings from controlled crosses cost about twice as much, and seedlings raised by tissue culture four times as much, because they require a high level of technical skill and highly capitalised laboratory facilities. Tissue culture is like cuttings in miniature and is in two stages. The first requires a lab able to provide a totally sterile environment under controlled environmental conditions to grow the culture and then a climatically controlled nursery in which to grow the propagules. Lead times, the time the planter allows between placing an order and delivery to him, also vary. For seedlings it is approximately 3 months, cuttings 6 to 9 months, and tissue culture 9 to 15 months.
Plantations of the future
The ability of a clone to be propagated determines the commercial viability of the clonal production system and can be represented by a propagation index unique to each individual clone. There are four aspects to a successful clonal plantation programme −
- Partnership between the breeders of elite clones and the propagating nursery
- Propagation index of the clone
- Adequate time between ordering and delivery scheduling
- Continuous production is much cheaper than large one-off orders.
Clonal Solutions conclude that clonal plantations are far more profitable than seedling plantations and are the plantations of the future. But I was disappointed that they were not impartial enough to mention any of the dangers. What if Australia’s future forests are to consist of vast areas of clonal single species plantations in which some resistance to a pest like myrtle rust has not been adequately provided for? The high risks and high gains of clonal short-cuts could be dramatically exposed. It means we might well be glad of the opportunity for genetic selection banked away in production or conservation native forests, old growth or regrowth.
I once asked Neil Barr if E. microcoys had a rival in excellence and he said, ‘Yes, there is, it is cloeziana, which doesn’t seem to have taken off in New Zealand. I don’t know why – it just hasn’t.’ Gympie messmate E. cloeziana grows to its very best in size and form around Gympie, preferring moderately deep sedimentary volcanic loams. Popular for super strong and durable poles from native regrowth, where close competition has kept the knot size small, it has one major drawback in that it does not abscise its branches well.They tear off, letting rot into the pith to form pipes running the length of the tree.
Pipes can vary from a neat two centimetre diameter hole, which does not matter much, to something more cavernous in older saw-logs. Pruning all the useful length of the tree is essential when growing messmate in plantations as the risk of pipe is greater and is very expensive if growing poles.
One useful identification feature I noticed while viewing the Bjelke-Petersen plantation in the Burnett region was that it produces its seed in dense clusters out on the ends of branches so they look like bird nests. Most impressive was a good look at some old-crop messmate near Kinkin. The best of these, known as the Doggrell tree after its 1950s protector, had a circumference of 7.80 metres, height 50 metres to crown and age 350 years. With help I used my tape to find that the diameter at breast height was two metres. Quite a thrill to see, but hard to photograph.
Take home messages
We should keep a close eye on all the research coming out of Australia as their forest scientists are forced to re-evaluate the changing characteristics of plantation-grown hardwood for the good of their future forest industry. In effect they may be becoming more like us with a focus on tailor-made plantations and less on native eucalypt forest. New Zealand needs to develop and assure specifications for its own plantation hardwood, but both countries could help one another in achieving this.
For northern growers try Queensland western white gum or Chinchilla white gum, E. argophloia. I would try a few if I had the room. It is a tall good-looking gum, the bark with some colour, heartwood deep red, hard, strong and durable and somewhat like E. bosistoana. Paul Millen is trying them and maybe also as a hybrid.
John Millet is a member of the Lower North Branch and has been involved with the branch and forestry matters since its formation in the 1950s. In the last year or so John has travelled to forest owner conferences in Australia and Chile.