Silvicultural treatments and associated growth rates, growth strains and wood properties in 12.5-year-oldEucalyptus grandis

Summary The effect of a number of silvicultural treatments on peripheral longitudinal growth strains and wood properties was examined at breast height (1.3 m) in 12.5-year-old plantation trees of Eucalyptus grandis (Hill) Maiden. These treatments included: untreated control (C); thinning (T); fertiliser and thinning (F); and fertiliser, weeding, insecticide and thinning (A). Strain was measured using electronic strain gauges glued to the outer xylem. Stem diameter was progressively greater and growth strain lower in treatments C, T, F and A respectively. Compared to treatment C, treatment A increased diameter at breast height by 190% and reduced longitudinal growth strain by 40%. However, within treatments, the level of growth strain was not related to growth rate. In silviculturally treated and fast grown trees, the reduced longitudinal growth strain gradient, along a radius from pith to outer xylem, would decrease splitting of wood during conversion. A positive relationship was found between growth strain and basic density within treatment A, the treatment with the fastest rate of growth. No other significant relationships were found between growth strain and basic density, fibre length, vessel diameter or ray width.