Early growth results of three Eucalyptus grandis x Eucalyptus nitens hybrid clonal trials and their response to snow events

摘要

Eucalyptus grandis x Eucalyptus nitens (GxN) hybrid clones are selected to combine complimentary characteristics of E. nitens and E. grandis. GxN hybrid clones also have the potential to increase growth rates and provide adaptability to a changing climate. A series of three trials planted across a range of high-productivity, mid-altitude sites in the KwaZulu-Natal midlands was established to test the suitability of a suite of GxN hybrid clones. Seven commercially available GxN clones together with two widely planted pure species controls, Eucalyptus dunnii and Eucalyptus smithii, were chosen for this study. The trials were set out in random complete block designs with nine treatments and four replications set out in square plots of 25 trees. The trials were measured for diameter at breast height at 23 months and monitored for snow damage over two winter seasons. Snow was noted at the Baynesfield site and subsequent snow damage assessments were performed. Basal area per hectare was calculated for each plot as a function of diameter at breast height and survival. Significant differences were observed between GxN hybrid clones in both growth and snow tolerance. The top-performing clones significantly outperformed both pure species controls in terms of growth and snow tolerance. Early results indicate that GxN hybrids may be better suited to high-potential, mid-altitude sites exposed to light snow risk than the currently recommended pure species.