Eucalypts (mainly E. camaldulensis) are widely planted in Thailand. They now occupy some 1000 km2, with most having been planted over the past 10 years. With logging of native forests now suspended, the plantation rate is likely to keep increasing to supply wood for domestic use and export. However, the rapid expansion of eucalypt planting has been accompanied by growing community concern about the possible deterioration of soils resulting in reduced tree productivity. Fast-growing plantations draw large quantities of nutrients from the soil, and significant amounts of these are removed in harvested biomass.

E. camaldulensis is also potentially important in Laos, but in that country plantation development has been slower. Nevertheless, development of wood-based industries is a government priority, and establishment of large-scale plantations with this eucalypt, and possibly other species, is expected.

The main aim of this project is to improve the productivity and sustainability of eucalypt plantations in Southeast Asia, using Thailand and Laos as representative countries, but with emphasis on Thailand. This will be done through breeding and through promoting more complete utilisation of plantation eucalypts, while ensuring that the long-term productive capacity of forest land is conserved.

ACIAR has commissioned the CSIRO Division of Forestry to lead the project. Its scientists will collaborate with counterparts in the Royal Forestry Department, Bangkok, Thailand, and the Department of Forestry and Environment, Vientiane, Laos. In Australia, the University of New South Wales and the Australian National University will also collaborate. Exchange visits will be made among scientists from the three countries.

The collaborators will enhance the economic returns from plantations by breeding to increase the yield of usable biomass and by developing and improving an additional product, eucalyptus oil. Vigour, stem form, disease resistance and oil yields will be the key traits for selection.

In Australia, scientists will attempt to identify early-age indications of later-age performance by relating field performance of families of E. camaldulensis to an index of water use efficiency determined by measuring stable carbon isotope ratios of seedlings of the same families. Another trial will relate field performance to the outcrossing rate of parental trees, determined by isozyme techniques on seedlings. If successful, these indicators could lead to laboratory-based selection of families for future breeding programs.

Using methodologies developed in Australia, the scientists will evaluate Thai plantations of E. camaldulensis for their potential to produce medicinal-grade eucalyptus oil. Since many of the plantations include E. camaldulensis originating from North Queensland, where high-oil-yielding genotypes have been identified, this is expected to produce positive results and be followed by the establishment of a pilot commercial distilling operation in Thailand.

Trials of eucalyptacacia mixtures will be the focus of work aimed at maintaining the productive capacity of land under intensive plantation management. The researchers will establish trials of eucalyptacacia mixtures in Thailand and evaluate sustainability and productivity. There is evidence that the yield from mixed plantations of eucalypts and nitrogen-fixing trees such as acacias is greater than that of a eucalypt monoculture. More importantly, such mixtures are likely to assist sustained production by increasing soil nitrogen status, and by mobilising soil reserves of slowly available phosphorus. Additional benefits may come from the understorey acacias suppressing weeds and providing a source of fuelwood and bee forage.

Trials in Laos will concentrate on developing seed orchards to provide improved seed, and on consolidating spillover effects of established ACIAR species trials in Thailand. The collaborators will conduct small field trials of the most promising eucalypts, acacias, casuarinas and fast-growing Lao native species.

Multiple benefits will stem from the project. The breeding program for tropical provenances of E. camaldulensis will ensure superior seed becomes available to forestry projects in Thailand and Laos, and eventually other countries. Research confirming the potential for oil production from E. camaldulensis could lead to a significant saving in foreign exchange through the development of a local eucalyptus oil industry in Thailand.

The successful use of acacias to maintain soil nitrogen availability will give benefits of sustained yield from plantations and savings on expensive nitrogen fertiliser, which would otherwise be needed to maintain productivity. Thai and Lao scientists will be trained in experimental design and analysis, gaining expertise in this important element of forest research. Australia will benefit through gaining new technologies for the development of appropriate management strategies for Australian eucalypt regrowth forests.

Vietnam has joined the project at a later date to test species of Melaleuca and some additional oil work flowing from research in Thailand. This will involve identification of Melaleuca species and provenances for wood and/or oil production in the Mekong Delta. Scientists will also have the opportunity to check the quality of Melaleuca oil and to assess any potential for Australian production.

The additional work will identify markets in Thailand and Vietnam for the Eucalyptus and Melaleuca oils that might be produced. This will also involve identification of essential oil agencies capable of testing the quality of oil produced and coordinating the marketing. Project participants will also design, build and test a low-cost still in Thailand.