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Summary
Effects of spacing, family and spacing-by-family interaction on corewood and outerwood density, and annual latewood percentage from cambial age 2 to 21 years in radiata pine (Pinus radiata D.Don) were studied using 55 families planted at three spacings (1 × 1, 1 × 2 and 2 × 3 m). Significant family effects were observed for corewood and outerwood density, and latewood percentage, but spacing effects were significant only for outerwood density and latewood percentage. There was significant spacing-by-family interaction on corewood density (rB = 0.62). Closer spacing increased latewood percentage in both corewood and outerwood and reduced corewood proportion but it did not increase wood density in corewood significantly. It was also observed that closer spacing had no effect on outerwood length, but increased wood density in outerwood significantly. Closer spacing increased heritability for wood density (1.11 ± 0.27 vs 0.46 ± 0.15) and increased juvenile–mature genetic correlations for wood density while increasing the negative genetic correlations between diameter at breast height (DBH) and corewood density. There were positive genetic correlations between latewood percentage and density in both corewood and outerwood. The significant genotype-by-spacing interaction for corewood density may be used to increase wood density of corewood through breeding.
Acknowledgements
The experiment was planted and maintained on land originally belonging to Associated Forest Holdings Pty Ltd (part of Associated Pulp and Paper Mills, later Gunns Ltd). The paper was written when Dr Yuanzhen Lin and Dr Huixiao Yang were a visiting scholar and a joint PhD student, respectively, from South China Agricultural University under a CSIRO and China scholarship program. We thank Don Aurik from Timberlands Pacific Pty Ltd and David Spencer for assisting field sampling.