Comparative growth performance of different Australian provenances and local land races of Grevillea robusta at Lushoto and Ubiri in the West Usambara Mountains, Tanzania

Abstract

Growth of seven Grevillea robusta provenances from its natural habitat in northern New South Wales and southern Queensland, Australia, and five local land races were studied at two trial sites established in November 1998 at Lushoto and Ubiri in the West Usambara Mountains (WUM), North East Tanzania. The aim of the study was to compare the performance of natural provenances and progenies within provenances with local land races for subsequent management as seed production stands. Trees were assessed for survival, height, diameter at breast height, stem straightness, mean annual increment, branching, coppicing and flowering characteristics at 66 months. The experiment was a complete randomised block design, replicated three times in a 4 × 3 blocks design. The analysis of variance was done using SAS® software and means were compared using Duncan's multiple range test. Results indicated significant differences (P < 0.05) for stem straightness between the Australian provenances and land races at the Lushoto site. No significant differences (P > 0.05) were found for survival and the growth characteristics between the provenances and land races. The study provided indication for an opportunity to improve the species stem quality and consequent proportion of utilisable timber, whilst increasing the genetic base through introduction of some Australian provenances for planting in the highland areas of the WUM. Promising seed sources were recommended for pilot plantings while continuing with further observation to confirm the best-adapted provenances and land races for implementation in the WUM and similar agroecological zones. The study further recommended for establishment of multiplication stands from promising seed sources using at least 30 mother trees.