Growth potential of Eucalyptus cypellocarpa as an alternative species for the mid-altitude summer rainfall region of South Africa

Abstract

Eucalyptus grandis is predominantly cultivated in the humid, warmer temperate, subtropical regions in South Africa for pulp and paper production because of its rapid growth and desirable wood properties. With forestry expanding into mid-altitude drier and warmer, or drier and colder sites, the growth of E. grandis has been compromised by unsuitable growing conditions and, therefore, the search to identify reasonably well-performing species/provenances for such sites has extended to summer rainfall provenances of E. cypellocarpa for pulp and paper production. Seed collected from New South Wales, Australia, comprising provenances from Hanging Rock, Nullo Mountain, Wingello State Forests and Kaputar Mountain National Park was established in provenance/progeny trials on three sites in South Africa (Windy Gap, Petrusvlei and Speenkoppies). Trials were planted at 1 667 stems ha−1, in single-row plots of six trees, with four replications in one balanced and two unbalanced lattice designs. Commercial seed of other eucalypts and clones was used as controls. Diameter at breast height and height were measured at 96 months at Windy Gap, and 72 months at both Petrusvlei and Speenkoppies. Basal areas and volumes were derived from these measurements. There were distinct family and provenance differences for growth at the different sites, with the Hanging Rock provenance generally performing well across all sites. A genotype × environment interaction was present between two sites, as indicated by low Type B correlations of 0.47 and 0.53 for basal area and volume, respectively. This indicated that different populations of E. cypellocarpa should be developed for the cold and warm sites.