Southern Forests: a Journal of Forest Science

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Are Eucalyptus clones advantageous for the pulp mill?

CRE Clarke


Eucalyptus clones, the ultimate exploitation of genetic variation, are perceived to be the ideal raw material for the pulp mill but is this really true? Their attributes include uniformity, superior pulp properties and faster growth while their only limitation is lack of the natural genetic variation which provides protection against adverse elements. This shortcoming, unless managed, is likely to have a dramatic impact on a mill. Commercial compartments of clones rarely exceed 100ha and are more commonly less than 50ha. The maximum that is planted to an individual clone in one year is 200ha. At an assumed production of 200t / ha this implies that parcels of up to 10, 000t of timber (but more often less) from a single genetic entity will arrive at the mill gate at the same time. Dramatic differences between clones are likely introduce more variation in the form 'slugs' than is experienced with seedlings where the variation is more of a continuous nature. The ten E. grandis hybrid clones used commercially by Sappi Forests have been evaluated for wood and dissolving pulp properties across a number of trial sites. Although wood and pulp properties varied between trees within clones, most of the variation was found to occur between clones and, as expected, clones were more uniform than seedlings. Dissolving pulp yield of clones varied from 43.8 to 45.6%, viscosity from 41.4 to 69.8cps and brightness from 43.7 to 50.7. Wood density was found to vary between clones from 460 to 570kg / m3, fibre diameter from 12.05 to 14.49:m and cell wall thickness from 2.40 to 2.64: m. Differences in wood and dissolving pulp properties between and within clones are compared here with E. grandis seedlings, the impacts on daily running of a dissolving pulp mill are discussed and suggestions are provided for management of clones in the mill to make best use of their unique properties.

Southern African Forestry Journal No.190 2001: 61-66

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