SYNOPSISA series of five composite trials of Eucalyptus grandis and E. saligna, planted in different areas of South Africa in 1983, was remeasured at the age of 7% years.At all locations E. grandis was superior to E. saligna in height, basal area and volume growth as well as stem form. Because of the higher density of E. saligna, the better seedlots of this species were as good wood mass producers as many of the E. grandis seedlots. The best E. grandis seedlots, however, were far superior to the best E. saligna seedlots.Within each species there were often major changes in the ranking of seedlots for growth variables between the ages of four years and 7% years. There were also indications of moderate genotype X environment interaction for E. grandis. It may therefore be unwise to select superior seedlots at a young age for tree breeding work either within climatic zones or for planting in other zones without testing all seedlots in all climatic zones for at least one-half the expected rotation age.Attempts to determine the best locations for future provenance selections for E. grandis for planting in the eastern Transvaal, South Africa's major E. grandis growing area, indicated that the climatic zones of Australia similar to that found at Coff's Harbour, N.S.W., should be preferred.
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