Early Growth of Acacia mangium × Acacia auriculiformis Hybrid Clonal Trials Established at Three Different Sites in Indonesia

Understanding how Acacia mangium × A. auriculiformis hybrid clones respond to different environments through a multi-site test is necessary. This study observed the early growth of the hybrids in clonal trials established in Central Java, Riau, and Jambi. The trials were laid out in a randomized complete block design: 20−44 clones (nine clones in common), 4−20 replications, tree spacing of 3 × 3m or 3 × 2m. Height, diameter at breast height and stem volume were assessed at two years of age. The results show that the growth rates of hybrid clonal trials in Riau and Jambi are higher than the rates in Central Java. Several significant differences were found among the clones for all traits with high clone repeatability (0.91−0.97) and ramet repeatability (0.49−0.69). Clone × site interaction was highly significant and affected a lower multi-site clone repeatability (0.30−0.70) and ramet repeatability (0.07−0.24). The top two clones and consistent ranking order across the three sites of clonal trial for volume were Clones 44 and Clone 42. The results implies the important strategies for deploying Acacia hybrid clones, but it will take more than two years for a clear pattern of differences between clones to emerge.