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The choice of planting density is a primary silvicultural decision in plantation management which considers the trade-off between individual tree size and total stand production, affecting the type, quantity and quality of products throughout the rotation. Trends in size and production with planting density are generally well known, however, less so is the interacting effect of site quality. Consequently, a case study in which basal area and basal area growth of Eucalyptus globulus Labill. plantations on five site qualities (122-435 m3·ha−1) planted at six densities (625 trees·ha−1, 4 m × 4 m; 833 trees·ha−1, 3 m × 4 m; 1000 trees·ha−1, 4 m × 2.5 m; 1250 trees·ha−1, 4 m × 2 m; 1667 trees·ha−1, 3 m × 2 m; and 2000 trees·ha−1, 3 m × 1.75 m) were used to investigate this interaction. As expected, both mean tree diameter of the whole stand and the basal area of the largest diameter 200 trees·ha−1 ( D200 trees) were higher at lower planting densities, whereas whole stand basal area was greater at higher planting densities. However, there were no significant ( P > 0.32) interactions between planting density and site quality for D200 or stand basal area, which contrasts with thinning responses in similar stands. This simplifies management considerations and suggests that trials at a given site quality may provide useful information about responses to planting density at other site qualities for the studied species. [ABSTRACT FROM AUTHOR]

The cost of harvesting short-rotation plantation eucalypts can be in excess of AU$2500·ha−1. Despite this high cost, the extent to which harvesting productivity is affected by tree genetics is not well understood. We address this issue in a study of two 10-year-old genetic field trials of Eucalyptus globulus Labill. in Australia. Standing-tree traits analysed were survival, diameter at breast height, basal area, and stem straightness and forking. Harvest traits analysed were volume, time, and productivity. Genetic group and within-group genetic variation (additive and dominance), stand-level family variation, phenotypic and genetic correlations, and the effects of inbreeding were estimated for these traits. The different scenarios studied showed that plantation harvest productivity was affected by tree genetics to some degree but was mainly affected through positive covariation with stem diameter. Harvest productivity is thus unlikely to have been adversely affected by past selection. Although no significant additive or dominance genetic variation in stem forking or straightness was detected, weak phenotypic correlations were consistent with harvest productivity being higher in straighter trees with no forking. High inbreeding depression was evident for growth and survival; however, in open-pollinated progeny, this resulted in only a slight reduction in harvest productivity (5.5%) compared with out-crossed progeny. [ABSTRACT FROM AUTHOR]