Executive summary
What the report is about
This report presents new data on growth of high value tropical timber species in southeastern and north Queensland, and discusses best-bet configurations for mixed-species plantations. The project measured key trial sites in southeastern and north Queensland, and used this and previous data to analyse species by site productivity, and mixed-species designs. The project presented these results and recommendations via a range of extension activities – the report summarises a series of workshops attended by growers, extension staff and researchers in north, central and southeastern Queensland and northern New South Wales.

Who is the report targeted at?
This report is for researchers, extension staff and tree growers and others interested in the growth performance and management of high value tropical timber mixed-species plantations in eastern Queensland and northern New South Wales.

Background
In tropical and sub-tropical eastern Australia, mixed-species timber plantations primarily involve the establishment of high-value, rainforest cabinetwood plantations, although there is also a growing number of plantations involving mixed eucalypts, bush-tucker species and sandalwood species and their hosts.

At present, the current technologies for growing mixed species plantations are highly complex and not well-known. Much of the available information is also fragmented between a large number of sources in this wide geographic region. This is further complicated by the large number of potential commercial timber species available to be planted on a particular site or across a particular region of interest.

Aims and objectives
The goal of this project was to rebuild, maintain and enhance communication networks with the main stakeholders involved with mixed-species plantations in Queensland and New South Wales. By working with these groups and individuals, information on the latest management practices was identified, collated and summarised. Combined with DPI&F resources, this information was communicated to interested growers and stakeholders to improve the understanding of mixed species plantation technologies throughout the region. The project objectives had three broad components: (1) species to site productivity assessment; (2) best-bet mixed-species configurations; and (3) extension of information.

Methods
Species to site productivity assessment was conducted for north and central Queensland by examining a number of key Queensland Department of Primary Industries & Fisheries (DPI&F) trials and over 110 growth plots in existing operational plantings. In southern Queensland, site productivity assessment was conducted through the establishment and monitoring of new growth plots in a number of existing private plantations managed by the two consultants, Jack Mitchell and John Steele.

In order to identify the latest best-bet mixed-species configurations across this region, various existing plantings were examined. These included a number of key DPI&F research trials and operational mixedspecies plantations established by the Community Rainforest Reforestation Program, private growers and consultants.

Communicating information about mixed-species technologies across tropical and sub-tropical eastern Australia was facilitated by establishing and maintaining communication networks between the wide range of stakeholders groups. Relevant, existing technical literature was identified (including JVAP publications). New technical and scientific summaries were produced based on the latest information and presented at a range of public seminars, community meetings, workshops and conferences.

Results
Trial assessment results identified a number of cabinetwood and eucalypt species with good productivity and potential for particular regions and particular site types. Species performance was ranked for 32 top species in northeastern and central Queensland, and measured for 17 species in southeast Queensland.

Two broad groups were identified: sun-loving fast growers and intermediate to slow growers with high value timber.

The range of plantations examined clearly demonstrated the gradual improvements in the understanding of inter-specific competition and operational factors such as harvest management. This evolution from random to quite complex designs, provided good information to guide the development of more effective and economic mixed-species plantation designs.

The project used field days, seminars, workshops and hard-copy and electronic publications to communicate generic recommendations on species selection and silvicultural management, to stakeholders throughout this diverse region. Thirteen workshops were conducted in eastern Queensland and northern New South Wales, attended by a total of approximately 400 people, primarily landowners with plantations or interest in planting. The project culminated in a final workshop where project outcomes and latest mixed-species plantation technologies were presented (attended by 45 people) The workshop participants provided information on their attitudes and motivations for planting mixed species plantations – most private landowners in tropical and sub-tropical eastern Australia prefer the concept of mixed-species plantations over monocultures. These designs best meet their expectations of commercial returns, personal satisfaction, conservation and sustainability values for their property.

Implications
Data showed variability in species growth across different site types, climatic conditions, management techniques and temporal variations; and often unpredictable inter-specific relationships which can affect growth on any specific site type. Nevertheless, the examination of a large range of operational plantings and research trials yielded some useful information on the most successful species across a range of site types. This has improved the capacity to recommend suitable species for planting.

It is hoped that the extension activities, the communication tools provided, and the momentum generated during the project have assisted researchers, extension providers, consultants and private landowners to implement more efficient and effective mixed-species plantations in this region. An important role of the workshops was to provide contact details for local extension support and consulting services, so that participants could continue to find information after the project and workshops finished.

Recommendations
Generic species recommendations and design configurations, such as those outlined in this project, need to be locally modified and adapted to suit each individual landowner’s situation and expectations, and the complexity of mixed species plantations.

The design of mixed-species plantation configurations must consider inter-specific competition and harvesting access. Tree species should be planted in rows to allow efficient harvest operations, and some strategic non-commercial thinning will be required to manage inter-tree competition. The mix of fastgrowing sun-loving species and the slower growing shade-tolerant species must also be considered.
 

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