Genetic evaluation of growth and wood properties in new Acacia mangium × A. auriculiformis hybrid clones at Ba Vi, Hanoi, Vietnam

Acacia mangium × A. auriculiformis hybrids are widely deployed in tropical plantation forestry due to their rapid growth and versatile wood properties. This study evaluated growth, stem form, and wood properties in a clonal trial of 40 Acacia hybrid clones established at Ba Vi, northern Vietnam, with the objectives of quantifying clonal variation, estimating clonal-mean broad-sense heritability, examining relationships among traits, and identifying superior clones for potential deployment. The trial was assessed at age five using a randomized complete block design with four replications. Growth traits (diameter at breast height and total height), stem form traits (stem straightness and branch size), and wood properties (basic wood density and dynamic modulus of elasticity, MoEd) were analysed using linear mixed-effects models with spatially correlated residuals. Significant clonal variation was detected for all traits. Clonal-mean heritability was moderate for height (H² = 0.36 ± 0.06) and basic wood density (H² = 0.25 ± 0.06), and lower for MoEd (H² = 0.16 ± 0.05) and stem form traits. Genetic correlations indicated a strong positive association between height and diameter (rg = 0.90 ± 0.03) and moderate negative correlations between growth traits and basic wood density, indicating a trade-off between rapid growth and denser wood. Several clones outperformed certified control clones for stem volume while maintaining acceptable wood properties and survival, demonstrating substantial scope for phenotypic clonal selection and deployment of Acacia hybrids under Vietnamese plantation conditions.