Wattle silviculture and pulping studies

• Chinese Academy of Forestry, China
• Research Institute of Chemical Processing and Utilisation of Forest Products, China

China has a great need for tannin (for leather and adhesive manufacture) as well as for timber, firewood, poles and paper pulp. An earlier ACIAR project (8458) made good progress in introducing new genetic resources of black wattle (Acacia mearnsii) into China, through provenance and progeny trials. It included research on the ultrafiltration and stiasny analyses of tannin extracts, climatic analysis and floral biology. Project findings formed the basis of a book in Chinese on black wattle and its utilisation.

This replacement project consolidates and continues that work, although the Australian component of the tannin research will be scaled down. It now incorporates pulping studies in both countries, using A. mearnsii and other promising acacias.

There are six subprojects. In the first subproject, the scientists will maintain and measure the existing provenance trials of A. mearnsii in southern China and identify superior provenances. They will plant additional breeding populations to produce improved seed, and establish trials of additional bipinnate and cold-tolerant acacias. Seed for pilot plantations and seed-production areas will be collected in Australia.

The second subproject will investigate the heritability of frost resistance in A. mearnsii, together with variation within and between provenances. Glasshouse experiments in Australia will use seed from each of two provenances in New South Wales, and results will be compared with data from provenance and progeny trials in China.

Australian studies of reproduction biology will involve controlled cross- and self-pollinations in both A. mearnsii and A. melanoxylon. The team will establish beehives in a natural population near Bungendore, NSW. Anatomical studies will check the growth of pollen tubes in self- and outcrossed pollinations and the parentage of the seed produced.

Climatic analyses of frost occurrences in China and Australia comprise the fourth silvicultural subproject, in which the Australian and Chinese scientists will develop interpolation surfaces for minimum temperatures in the two countries, using average monthly and absolute data.

Assessment of pulpwood quality of Acacia species will cover both natural and cultivated stands in each country, and also material currently stored at the CSIRO Clayton Laboratories. The scientists will develop a classification system for pulp and pulpwood and prepare a detailed manual for pulpwood quality assessment.

In China, laboratory tests on wattle tannin adhesives will use Chinese and South African tannins. They will investigate the effects of differing pH, the amount and type of aldehyde donor, fortifiers, fillers etc., and wood-substrate and gluing conditions such as wood moisture content, glue loading, assembly times, pressing temperature and pressure. Later tests simulating factory conditions will seek to optimise adhesive formulations and gluing conditions.

Apart from its direct relevance to China's current program of expanding A. mearnsii plantations in southern China, the research will identify and supply high-quality seed for more productive and better adapted plantations. It will characterise the pulping qualities of a wide range of Australian acacias - not previously attempted on this scale - which has potential importance for future plantations in Australia and elsewhere. The proposed work on climatic interpolation surfaces will also have wide applicability in both the forestry and agricultural sectors.