Growth and quality of Grevillea robusta provenances in Ruhande Arboretum, Butare, Rwanda

Abstract

Exotic hardwood tree species are very important in Rwandan plantation forestry. They are the primary source of energy, which makes about 97% of total national energy consumption. They are used as sawn timber for furniture industry, for construction and packaging. They are essential components of agroforestry systems where they play a significant role in conservation, species and product diversification to mention but a few. A trial on Grevillea robusta seed sources comprising of seven Queensland (Australia) provenances and one land race on an oxisol at Ruhande Arboretum, Butare, Rwanda was carried out. The species is the commonest on farm tree species in Rwandan agroecosystems and serves many functions. Wood productivity has been observed to decline when tree germplasm used is collected from landrace populations of exotic species. This study intends to evaluate the performance of seven provenances and one landrace of G. robusta in terms of wood yield and quality. Although the outstanding provenances reported elsewhere are not represented in the Rwandan trial which is very small and with a design that is not very well designed, useful results were obtained. Significant differences were observed in tree height and branching pattern at 13 years. All traits indicated strong juvenile-mature correlations. Trait-trait phenotypic correlation was also found to be strong in all traits. The correlations were observed to increase consistently with age, indicating the possibility of predicting yield at maturity by using early tree dimensions. High value germplasm may be produced from seed production areas using the best provenances from the species’ natural range. Conservation stands are suggested for further breeding and for seed production using seed from natural Australian sources.

Key words: Grevillea robusta, land race, provenance, agroecosystems, germplasm, conservation, seed production areas