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Plantation forests were originally established in South Africa to meet an increasing demand for solid wood products as there was a limited supply from native forests. The majority of the commercial softwood plantations were established with Mexican Pinus patula. Since growing conditions are known to impact tree growth, tree form, and wood quality of P. patula, sample plots were established over a cross-section of plantations in the Lowveld Escarpment and Highveld forestry regions of South Africa that covered an array of geologies and altitudes. Each sample plot was classified according to soil properties, rainfall, and temperature, and trees within the plots were measured for growth, form, and wood properties. Soil, growing days, and temperature were found to have little impact on tree form and wood properties. However, rainfall and specifically, spring rainfall, was found to have a highly significant impact on late wood formation, proportion of juvenile core, and wood density. In addition, tree height was found to be strongly correlated with maximum annual temperature.

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Mechanised harvesting operations are growing in popularity in South Africa, as motor-manual and manual harvesting operations pose significant health and safety risks to workers. Potential damage inflicted by singlegrip harvester feed rollers and delimbing knives on the log surface during debranching and debarking of eucalypts may affect chip size distributions during chip production. Chip size is important as it influences pulp quality and recovery in the kraft pulping process. The study investigated the influence of two mechanised debarking treatments in eucalypts (three feed roller passes and five feed roller passes along the stem surface) with feed-roller-induced log surface damage on pulp value recovery. The two mechanised treatments were compared against chips produced from manually debarked logs with no surface damage. In addition, the effect of two log drying periods (one week and two weeks) and three log classes (base, middle and top logs) on chip quality were also analysed. An economic evaluation was conducted to quantify potential recoverable pulp value losses associated with debarking treatments and log drying periods. Logs subject to manual debarking produced significantly less undesired sized chips than both three-pass and five-pass mechanically debarked logs and therefore had significantly greater pulp value recovery. Mechanically debarked logs had a projected pulp value recovery of R62, R86 and R123 less per bone dry tonne of chips produced from base, middle and top logs, respectively, when compared with manually debarked logs with no log surface damage after a one-week log drying period. Mechanically debarked logs also had a projected pulp value recovery of R77, R40 and R59 less per bone dry tonne of chips produced from base, middle and top logs, respectively, when compared with manually debarked logs with no log surface damage after a two-week log drying period. Logs dried for two weeks also produced significantly less under-sized chips than chips produced from one-week-dried logs and therefore had greater pulp value recovery. However, two-week-dried logs produced wood chips with significantly more over-thick chips than logs dried for one week. The volume of undesirable-sized chips produced during chipping increased with decreasing log size.