Feature The effect of growth rate and irrigation on the basic density and kraft pulp yield of Eucalyptus globulus and E. nitens
Geoff Downes , Dale Worledge , Laurie Schimleck , Chris Harwood , Jim French and Christopher Beadle
This study investigated the influence of growth rate and irrigation on basic density and kraft pulp yield of Eucalyptus globulus Labill. and E. nitens (Dean & Maiden) Maiden using both laboratory pulping and prediction of pulp yield and basic density by near-infrared spectroscopy (NIR). The comparison was made between 8-year-old trees grown under two experimental treatments at a dryland site in south-eastern Tasmania, Australia: irrigated to remove water as a factor limiting growth (irrigated, I), and regularly exposed to water stress (rainfed, R). A range of diameter classes was sampled within both treatments. Pulp yield and basic density were most affected by treatment (I,R), and to a lesser extent by species. Irrigated trees had significantly higher kraft pulp yield and lower basic density. There were no significant differences in pulp yield or density across diameter classes. Differences in seasonal growth patterns affecting the average chemical composition of annual wood growth appeared to be the main driver of the differences between irrigation treatments. Daily average growth measurements of neighbouring trees showed that the sub-annual patterns of growth were very consistent within treatments, but differed markedly between treatments, with the irrigated trees producing more late wood. Laboratory pulp yield and basic density measurements on multiple-tree bulked samples were used to construct NIR calibrations to predict individual tree values. This proved to be a cost-effective way of obtaining more detailed information on the patterns of variation in wood properties in the experiment. (no keywords)
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