Abstract
Pinus radiata and eucalypts are fast-grown species, well suited to plantation forestry in New Zealand and elsewhere, and for the manufacture of a wide range of solid wood and reconstituted wood products, including pulp and paper.
This paper examines the variation and end-use potential of the individual-tree kraft fibre and handsheet properties of 25 trees of 13-year-old P. radiata and 29 trees of 15-year-old Eucalyptus nitens. Individual-tree fibre property differences are assessed with reference to the fibre quality requirements of a range of wood-free paper grades. Strategies and procedures are also described which will enable parent trees with desired fibre properties to be identified, propagated and mass produced.
In selecting fibre types for different paper and pulp grades, the apparent density of “unrefined” pulps(500 PFI mill rev) is the base against which other “unrefined” handsheet properties are compared. Apparent density is a direct measure of fibre packing density and arrangements in handsheets, and is determined by fibre length and cross-section dimensions, and the related morphological configurations of collapse and straightness. Although the individual-tree pulps of both species can normally be refined to the same tensile index, apparent density values can be very different depending on their fibre properties. Thus, minimal pulp refining is preferred for comparing individual-tree pulps for trees election.
Apparent density is best predicted by the kraft fibre property combination of the fibre width/thickness ratio and length. The combination of chip basic density and kraft fibre length is also a good predictor of handsheet apparent density but not necessarily of the best fibres for the manufacture of particular products. Wood density is a measure of the ratio of wood substances to void space in each individual-tree chip sample and is not indicative of the numbers of fibers which make up a unit volume.
Kraft handsheet propeties varied widely among trees for both species and were well-predicted by kraft-fibre dimensions. The high broad-sense heritabilities shown for these traits in P. radiata mean that clonal forestry could provide pulpwood of uniform and predictable pulping performance from monoclonal forest blocks. The high narrow-sense heritabilities shown so far for wood properties in P. rafiata (and for some wood properties in E. nitens) indicate that planting control-pollinated families of known characteristics could have a similar though less uniform result.
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