Evaluation of the pulpwood quality of 13 lesser-known eucalypt species

摘要

The kraft pulping and papermaking potential of 13 eucalypt species proposed for use in farm forestry production systems was assessed in relation to existing commercial pulpwood resources. Samples from 128 trees, representing 13 eucalypt species aged from 6 to 13 years, were collected across five sites in the eastern states of Australia. Wood basic density, kraft pulping properties and unbleached papermaking properties were measured and selected figures used to calculate an index of the suitability of different wood resources for export woodchips. Two of the sites in the Australian Capital Territory differed particularly in terms of rainfall, and by sampling the same genotypes at both sites, the effects of differences in growing conditions on wood quality were assessed. The slow-growing trees from the low-rainfall (450-500 mm) Kowen site had generally lower wood densities, lower pulp yields and poorer papermaking properties than samples of corresponding species from Uriarra, where mean annual rainfall was more than 200 mm higher. The species indicated by the pulpwood quality index as most suitable for chemical pulping were Corymbia maculata from Gympie, followed by Eucalyptus occidentalis from Timmering and E. dunnii from Coffs Harbour. E. smithii may also have promise as pulpwood, ranking above E. nitens (a commercially important species) at both Uriarra and Kowen. The two species least suitable for chemical pulping were E. benthamii and E. kartzoffiana, which both produced significantly lower quality wood than that available from the native forests of Tasmania, the largest source of woodchips available for export markets. The strong association found between low rainfall and poor pulpwood quality suggests that farmers planning to grow trees in dryland regions (<600 mm) may suffer more than reduced growth rates. The trees may also produce poorer quality and hence less marketable pulpwood.