Performance of eight eucalypt species and interspecific hybrid combinations at three sites in northern New South Wales, Australia

Abstract

Summary Eight eucalypt taxa, represented by six seedlots and nine clones (two seedlots of Corymbia citriodora subsp. variegata (CCV), one seedlot each of Eucalyptus cloeziana, E. dunnii and E. pilularis, one seedlot and two clones of E. grandis, one clone of E. saligna, three clones of the interspecific hybrid E. grandis × E. camaldulensis and five clones of the hybrid E. urophylla × E. grandis) were tested in taxa trials on three sites in northern New South Wales, Australia. Significant differences between sites and between taxa in survival, growth, stem form and attack by stem-boring insect larvae were demonstrated. All taxa grew best on the Convery site that had the highest mean annual rainfall, 1400 mm, on a Red Ferrosol soil derived from volcanic parent material; E. dunnii and E. pilularis grew to a mean dominant height of 17 m in 6 y, E. cloeziana to 15 m, C. citriodora subsp. variegata and E. saligna to 14 m. Fewer than 2% of trees of all taxa at this site were attacked by insects. The other two sites had Brown Dermosol soils and were drier, the Muller site receiving 1200 mm y−1 and the Ironbolt site 1100 mm y−1. Height and diameter growth of all taxa was slower at these sites, with E. pilularis and E. cloeziana showing the greatest reduction in growth while E. grandis × E. camaldulensis showed the least reduction. Overall survival at age 6 y was acceptable at all three sites, being highest at Convery site (86%) followed by Muller (77%) and Ironbolt (74%). While C. citriodora subsp. variegata and E. cloeziana had minimal damage at Mueller and Ironbolt, the other taxa had from 9% to 100% of stems affected by borers, with E. grandis, the E. saligna clone and E. urophylla × E. grandis proving particularly susceptible on these sites.