Who is this report targeted at?
This report is intended for use by researchers, industry, and government agencies that are involved in the development of farm forestry and forestry in the Northern Territory (NT) and northern Australia.

Background
A recent analysis identified considerable potential for agroforestry in the NT. This analysis also indicated that genetic development and testing of key species was a major research priority to support the development of farm forestry in the region.

Previous tree evaluation research in the Northern Territory has only occurred sporadically since 1950. Some of that research provided early ‘best bet’ species recommendations, and locally adapted material for seed and clonal collections. The species and provenances selected for this project are likely to perform well on suitable sites in the NT as they were obtained from previous work undertaken in northern Australia by the Queensland Forestry Research Institute in collaboration with the CSIRO Australian Tree Seed Centre, and the Northern Territory Conservation Commission. Two of the four best bet species previously identified were red mahogany Eucalyptus pellita and African mahogany Khaya senegalensis, which were recommended for breeding and selection research to improve growth rates and profitability of plantations.

Eucalyptus pellita does not naturally occur in the NT but has performed well in trials planted on Melville Island in 1992 and 1989. As there are uncertainties about the long-term maintenance of the Melville Island plantings and those in north Queensland, there was a perceived need to develop a land race adapted to the Top End of the NT.

Aims and objectives
This project undertook to test the suitability of important genotypes of acacias, eucalypts and other potentially useful hardwood species for growing as plantation species in the Top End of the Northern Territory. The research also aimed to establish:

• a clonal seed orchard and a clonal conservation bank of Khaya senegalensis (dry zone mahogany) to enable gene conservation and genetic improvement of the population
• a Eucalyptus pellita provenance seedling seed orchard that aims to develop sources of seed and vegetative material suited to that particular environment.

The project is the first step in a logical, staged approach for rapid development of high-yielding forest tree varieties. The stages comprise: parallel testing of ‘best bet’ taxa (species, provenances and hybrids); development of commercial varieties from the superior taxa matched to sites; infusion of new genetic material including various locally-produced hybrids; and ongoing breeding for refinement of superior varieties. Following on from this project, the research intends to contribute to ongoing genetic development by establishing breeding facilities in a range of sites in the NT and by further development of improvement facilities in north Queensland.

Methods used
Four sub-projects were established:

• a dryland taxa trial near Berry Springs, Darwin River to assess and compare imported eucalypt hybrids, pure eucalypt species, ‘best bet’ local species, and dry zone exotic hardwoods for suitability to the 1000 – 1800 mm rainfall zone
• establishment of seed production areas (SPA) of genetically superior E. pellita collected from Melville Island provenance progeny trials and selected provenances from Papua New Guinea (PNG) for use in the NT
• clonal propagation of superior K. senegalensis provenances identified in the Gunn Point trials and other NT sources to establish a clonal seed orchard and clonal seed bank for the species.
• a second taxa trial planted at Howard Springs to replicate the first taxa trial at a different site and to determine the impact of lime on plant performance.

The dryland taxa trial near Berry Springs southwest of Darwin was planted and fertilised in December 2000 (2000-01 wet season). Measurements were taken in April of each year subsequent to planting.

In the same wet season, the Eucalyptus pellita provenance seedling seed orchard was established on crown land at Howard Springs, 20 km south east of Darwin. The composition of the E. pellita seed production area was made up of three provenances from natural stands in PNG and open pollinated bulked seed from phenotypically-superior trees selected in the Melville Island provenance-progeny trial.

The Khaya senegalensis (African mahogany) clonal seed orchard and clonal conservation bank were established in the 2001-02 wet season at Howard Springs and Berrimah Farm respectively.

The source of genetic material was the Gunn Point provenance trials that were established by CSIRO in the 1970-71 wet season. Within the three provenance trials that were screened for selection of superior trees, there were 20 provenances (18 from African countries and two from New Caledonia, ex Ivory Coast) included in the clonal seed orchard. Two additional trees from Berrimah Farm with outstanding characteristics, but of unknown origin, were included. Collection of suitable scion material began in July 2001 with the aim of selecting four trees per provenance.

From each tree (ortet) six clones (ramets) were taken to provide four clones for the clonal seed orchard and two for the clonal seed bank. The ‘top-cleft’ grafting method was chosen after trialling a range of grafting techniques. 850 grafts were made with an overall success rate of 85%. The clone sites were planted out in December 2001.

The second of the dryland taxa trials was established in December 2002 and January 2003 on government land at the Howard Springs site adjacent to the E. pellita seed production area. The aims of the other trials included assessment and comparison of ‘best bet’ species, and the evaluation of lime application to the growth or range of species.

Results/Key findings
This report presents the early results from four sub-projects:

• the three-year results for the dryland taxa trial near Berry Springs
• design and establishment of the Eucalyptus pellita provenance seedling seed orchard
• two years of results for the Khaya senegalensis clonal seed orchard and clonal conservation bank establishment
• the first year’s results for the second dryland taxa trial established at Howard Springs in the 2002-03 wet season.

In the dryland taxa trial near Berry Springs, after three years the best performing species included the fast growing exotic Pterocarpus macrocarpa, and the fast growing tropical Acacias and Eucalyptus camaldulensis from a Thailand seed orchard. The poorer performing entries (although few) were notable as their persistency was very low or non-existent after only 28 months and susceptibility to insect damage was evident.

The Eucalyptus pellita provenance seedling seed orchard was successful established, despite the difficulties in establishment due to rainfall distribution and the giant termite, Mastotermes darwinensis. Average survival at 27 months was 64.5%. It is anticipated that after the final culling of the poorer performing trees and the final thinning down to the recommended 200 trees per hectare, the seed production area can be expected to fulfil its planned function successfully.

The Khaya senegalensis (African mahogany) clonal seed orchard and clonal conservation bank were successfully established at Howard Springs and Berrimah Farm. This was the first time that genetic improvement facilities have been established for this species in northern Australia.

The establishment of both the clonal seed orchard and clonal conservation bank was very successful, and when the trees begin to set seed suitable for local plantings, seed will be available for farm forestry activities in the NT and possibly other regions in northern Australia. In addition there is a sound base from which to undertake a genetic improvement program.

In the second of the dryland taxa trials, plant survival at age four months was acceptable (83-100%) with the exception of the Corymbia complex treatment (67%) and E. argophloia (17%). Acacias displayed better growth in the un-limed treatment, and Pterocarpus spp. showed better performance in the limed treatment. As only the first year’s results are reported here, the results must be regarded as preliminary.

Implications for relevant stakeholders
Breeding and improvement facilities were successfully established within this project at Howard Springs, Berrimah Farm and a private property at Darwin River. As a result, the Northern Territory is now in a good position to become self sufficient in producing plantation tree species and provenances suited to the environment of the Top End.

The implications from each sub-project are as follows:

• The dryland taxa trials are a valuable resource for the ongoing evaluation of the better performing species for the Top End. Based on the preliminary results, there may be commercial interest in pursuing plantation establishment of some of these species in the future.
• Satisfactory survival within the E. pellita provenance seedling seed orchard indicated that the seed production area can be maintained for future seed collection. The Howard Springs site is more conveniently located than the Melville Island seed production area, and provides an alternative future seed source, as there is uncertainty that the Melville site will be maintained.
• The successful establishment of the K. senegalensis clonal seed orchard means that farm forestry and industry stakeholders in the NT can anticipate the ongoing availability of improved K. senegalensis seed. This seed will have a known, broad genetic base that will be suitable for local plantings; the clonal seed orchard could also be used as a basis for a genetic improvement program.