Wood properties and processing outcomes for plantation grown African mahogany (Khaya senegalensis) trees from Clare, Queensland (18 and 20 year-old trees) and Katherine, Northern Territory (14 year-old trees).

Khaya senegalensis, African mahogany, a high-value hardwood, was introduced in the Northern Territory (NT) in the 1950s; included in various trials there and at Weipa, Q in the 1960s-1970s; planted on ex mine sites at Weipa (160 ha) until 1985; revived in farm plantings in Queensland and in trials in the NT in the 1990s; adopted for large-scale, annual planting in the Douglas-Daly region, NT from 2006 and is to have the planted area in the NT extended to at least 20,000 ha. The recent serious interest from plantation growers, including Forest Enterprises Australia Ltd (FEA), has seen the establishment of some large scale commercial plantations. FEA initiated the current study to process relatively young plantation stands from both Northern Territory and Queensland plantations to investigate the sawn wood and veneer recovery and quality from trees ranging from 14 years (NT – 36 trees) to 18-20 years (North Queensland – 31 trees). Field measures of tree size and straightness were complemented with log end splitting assessment and cross-sectional disc sample collection for laboratory wood properties measurements including colour and shrinkage. End-splitting scores assessed on sawn logs were relatively low compared to fast grown plantation eucalypts and did not impact processing negatively. Heartwood proportion in individual trees ranged from 50% up to 92 % of butt cross-sectional disc area for the visually-assessed dark coloured central heartwood and lighter coloured transition wood combined. Dark central heartwood proportion was positively related to tree size (R2 = 0.57). Chemical tests failed to assist in determining heartwood – sapwood boundary. Mean basic density of whole disc samples was 658 kg/m3 and ranged among trees from 603 to 712 kg/m3. When freshly sawn, the heartwood of African mahogany was orange-red to red. Transition wood appeared to be pinkish and the sapwood was a pale yellow colour. Once air dried the heartwood colour generally darkens to pinkish-brown or orange-brown and the effect of prolonged time and sun exposure is to darken and change the heartwood to a red-brown colour. A portable colour measurement spectrophotometer was used to objectively assess colour variation in CIE L*, a* and b* values over time with drying and exposure to sunlight. Capacity to predict standard colour values accurately after varying periods of direct sunlight exposure using results obtained on initial air-dried surfaces decreased with increasing time to sun exposure. The predictions are more accurate for L* values which represent brightness than for variation in the a* values (red spectrum). Selection of superior breeding trees for colour is likely to be based on dried samples exposed to sunlight to reliably highlight wood colour differences. A generally low ratio between tangential and radial shrinkages was found, which was reflected in a low incidence of board distortion (particularly cupping) during drying. A preliminary experiment was carried out to investigate the quality of NIR models to predict shrinkage and density. NIR spectra correlated reasonably well with radial shrinkage and air dried density. When calibration models were applied to their validation sets, radial shrinkage was predicted to an accuracy of 76% with Standard Error of Prediction of 0.21%. There was also a strong predictive power for wood density. These are encouraging results suggesting that NIR spectroscopy has good potential to be used as a non-destructive method to predict shrinkage and wood density using 12mm diameter increment core samples. Average green off saw recovery was 49.5% (range 40 to 69%) for Burdekin Agricultural College (BAC) logs and 41.9% (range 20 to 61%) for Katherine (NT) logs. These figures are about 10% higher than compared to 30-year-old Khaya study by Armstrong et al. (2007) however they are inflated as the green boards were not docked to remove wane prior to being tallied. Of the recovered sawn, dried and dressed volume from the BAC logs, based on the cambial face of boards, 27% could potentially be used for select grade, 40% for medium feature grade and 26% for high feature grades. The heart faces had a slightly higher recovery of select (30%) and medium feature (43%) grade boards with a reduction in the volume of high feature (22%) and reject (6%) grade boards. Distribution of board grades for the NT site aged 14 years followed very similar trends to those of the BAC site boards with an average (between facial and cambial face) 27% could potentially be used for select grade, 42% for medium feature grade, 26% for high feature grade and 5% reject. Relatively to some other subtropical eucalypts, there was a low incidence of borer attack. The major grade limiting defects for both medium and high feature grade boards recovered from the BAC site were knots and wane. The presence of large knots may reflect both management practices and the nature of the genetic material at the site. This stand was not managed for timber production with a very late pruning implemented at about age 12 years. The large amount of wane affected boards is indicative of logs with a large taper and the presence of significant sweep. Wane, knots and skip were the major grade limiting defects for the NT site reflecting considerable amounts of sweep with large taper as might be expected in younger trees. The green veneer recovered from billets of seven Khaya trees rotary peeled on a spindleless lathe produced a recovery of 83% of green billet volume. Dried veneer recovery ranged from 40 to 74 % per billet with an average of 64%. All of the recovered grades were suitable for use in structural ply in accordance to AS/NZ 2269: 2008. The majority of veneer sheets recovered from all billets was C grade (27%) with 20% making D grade and 13% B grade. Total dry sliced veneer recovery from the logs of the two largest logs from each location was estimated to be 41.1%. Very positive results have been recorded in this small scale study. The amount of colour development observed and the very reasonable recoveries of both sawn and veneer products, with a good representation of higher grades in the product distribution, is encouraging. The prospects for significant improvement in these results from well managed and productive stands grown for high quality timber should be high. Additionally, the study has shown the utility of non-destructive evaluation techniques for use in tree improvement programs to improve the quality of future plantations. A few trees combined several of the traits desired of individuals for a first breeding population. Fortunately, the two most promising trees (32, 19) had already been selected for breeding on external traits, and grafts of them are established in the seed orchard.

Forest health guide: symptoms of insect and fungal damage on trees

The Forest health guide: symptoms of insect and fungal damage on trees is intended to help forestry and quarantine staff undertake tree health assessments, in both forest and urban environments. The guide is designed to be used as a quick reference to common symptoms of damage, not as an identification guide to particular insect pests and pathogens.

Forest and Wood Products Research and Development Corporation (FWPRDC) Cypress exatractives

Study to investigate the use of cypress pine extractives as a novel timber preservative.

High-value wood products from sub-tropical plantations

To refine the emerging silvicultural systems for sub-tropical eucalypt plantations to produce logs of acceptable dimensions and quality for processing into high-value solid and engineered wood products, while maintaining financial attractiveness for growers. The available resources are focussed primarily on sub-tropical Corymbia plantings.

Biological Control of Eucalypt Pests Overseas and Australia

This project aims to address the growing need for a coordinated approach to research into the biological control of Australian eucalypt insect pests by scoping the formation of a Centre in Australia which would (a) coordinate the evaluation and provision of biological control agents (initially to South Africa and Brazil, but in future years more widely), (b) research the role natural enemies play in pest population regulation in Australian eucalypt plantations and how this may be enhanced as a management tool, and (c) form a network focussed on forest biosecurity with an emphasis on eucalypt pests and pathogens.

An audit of forest biosecurity arrangements and preparedness in Australia.

Current biosecurity arrangements for plantation forestry are poorly defined, at least relative to other plant-based industries. Serious pest and disease outbreaks in forestry are relatively rare events. Preparedness for rare events is difficult. Part of the difficulty stems from the competing views of managers and stakeholders. This project sought to directly capture alternative views concerning the key objectives of plantation forest biosecurity, alternative strategies for achieving those objectives, and ultimately recommend preferred actions that might be broadly supported by stakeholders. The outcomes from the workshop were used as a basis to draft a list of strategic actions required to improve forest biosecurity in Australia and to be implemented over the next 2-5 years. Research priorities were identified as research to support cost benefit analyses; investigating the effects of changed environmental conditions on forest biosecurity; pathway analysis for functional pest guilds. Integration of this research within a CRC would also permit the effective development and extension of this research as well as providing training urgently required to maintain forest biosecurity and health expertise.

Evaluation of wood characteristics of tropical post-mid rotation plantation Eucalyptus cloeziana and E. pellita: Part (c) Wood quality and structural properties.

This study provides information about wood quality, structural properties, processing characterists and product suitability of wood harvested from fast-grown hardwood plantations. Wood quality attributes tested included density, extractive content, unit shrinkage, heartwood proportion and sapwood width. Structural properties tested included small clear and full section strength and stiffness, hardness, joint group, visual grade assessment and natural vibration-based grade assessment. The variation between the inner, intermediate and outer heartwood zones and the variation between provenances was also tested. Overall, the wood qualtiy attributes measured for 19 year-old E. cloeziana and 15 year-old E. pellita plantation material fall between those expected from the wood of mature, native forest trees and those found in younger plantation material of the same species.

Evaluation of wood characteristics of tropical post-mid rotation plantation Eucalyptus cloeziana and E. pellita: Part (d) Veneer and plywood potential.

Logs from two hardwood plantations in north Queensland were peeled to assess the veneer and plywood potential of fast-grown tropical plantation eucalypts. After visual grading and veneer recovery calculatios, selected veneers were assembled to produce plywood panels. These were tested for mechanical properties and glue bond strength to determine the suitability of young, fast-grown, tropical eucalytps for panel product applications.

Influence of Corymbia hybridisation on crown damage by three arthropod herbivores.

Three common pests (eucalypt tortoise beetle Paropsis atomaria, leaf blister sawfly Phylacteophaga froggatti and eriophyid mites) of commercial spotted gum plantations were assessed for their crown damage levels on parent and hybrid Corymbia taxa ( Corymbia torelliana, C. citriodora subsp. variegata and their hybrid) at three common-garden field sites. Damage levels differed significantly between sites for all three herbivore species, and between taxa for eriophyid mites and P. atomaria. However, herbivore response to hybridisation only differed for P. atomaria between sites, even where damage levels did not. Hybrids exhibited three common patterns of susceptibility relative to parent taxa, being most commonly intermediate to their parents for crown damage (additive resistance pattern), or no difference between parents and hybrids, or with one incidence of dominance for susceptibility.

The Queensland forest industry

An overview of the commercial growing, management and processing of forest products in Queensland.

Development of a productivity asessment toll for native spotted gum forest on private land based on estimates of forest growth on Crown land.

Reliable estimates of forest productivity are essential for improved predictions of timber yields for the private native spotted gum resource in southern Qld and northern NSW. The aim of this research was to estimate the potential productivity of native spotted gum forests on private land by making use of available inventory data collated from Qld and northern NSW for spotted gum forest on Crown land (i.e. state forests). We measured a range of site-related factors to determine their relative importance in predicting productivity of spotted gum forest. While measures such as stand height and height-diameter relationships are known to be useful predictors of productivity, we aimed to determine productivity for a site where this information was not available. Through estimation of stand growth rates we developed a spotted gum productivity assessment tool (SPAT) for use by landholders and extension officers. We aimed to develop a tool to allow private landholders to see the benefits of maintaining their timber resource. This paper summarises the information used to develop the SPAT with a particular focus on forest growth relationships.

Possible impacts of the invasive plant Rubus niveus on the native vegetation of the Scalesia Forest in the Galapagos Islands

Originally from Asia, Rubus niveus has become one of the most widespread invasive plant species in the Galapagos Islands. It has invaded open vegetation, shrubland and forest alike. It forms dense thickets up to 4 m high, appearing to displace native vegetation, and threaten the integrity of several native communities. This study used correlation analysis between a R. niveus cover gradient and a number of biotic (vascular plant species richness, cover and vegetation structure) and abiotic (light and soil properties) parameters to help understand possible impacts in one of the last remaining fragments of the Scalesia forest in Santa Cruz Island, Galapagos. Higher cover of R. niveus was associated with significantly lower native species richness and cover, and a different forest structure. Results illustrated that 60% R. niveus cover could be considered a threshold for these impacts. We suggest that a maximum of 40% R. niveus cover could be a suitable management target.

Diversity and abundance of fungivorous thrips (Thysanoptera) associated with leaf-litter and bark across forest types and two tree genera in subtropical Australia

Leaf-litter thrips were much more common and diverse in dry sclerophyll forest than in wetter forest types in subtropical southeast Queensland, Australia. In dry sclerophyll forest, the species composition of thrips in leaf-litter was strongly differentiated from the thrips fauna associated with bark of the trees Eucalyptus major and Acacia melanoxylon (4 of 34 species in common). The species composition of bark-dwelling thrips was similar across the two tree species and also across two eucalypts with different bark types, Eucalyptus major (flaky) and Eucalyptus siderophloia (rough). The diversity of thrips from the leaf-litter was not differentiated across all of these tree species. Virtually all thrips collected were Phlaeothripidae, subfamilies Idolothripinae and Phlaeothripinae. Idolothripinae were associated almost exclusively with leaf-litter, but Phlaeothripinae were in leaf-litter and bark. The association of fungal-feeding thrips with dry sclerophyll forest raises questions about their ecological requirements and the role they play in nutrient cycling. © 2012 Copyright Taylor and Francis Group, LLC.

Species-site matching in mixed species plantations of native trees in tropical Australia

Mixed species plantations using native trees are increasingly being considered for sustainable timber production. Successful application of mixed species forestry systems requires knowledge of the potential spatial interaction between species in order to minimise the chance of dominance and suppression and to maximise wood production. Here, we examined species performances across 52 experimental plots of tree mixtures established on cleared rainforest land to analyse relationships between the growth of component species and climate and soil conditions. We derived site index (SI) equations for ten priority species to evaluate performance and site preferences. Variation in SI of focus species demonstrated that there are strong species-specific responses to climate and soil variables. The best predictor of tree growth for rainforest species Elaeocarpus grandis and Flindersia brayleyana was soil type, as trees grew significantly better on well-draining than on poorly drained soil profiles. Both E. grandis and Eucalyptus pellita showed strong growth response to variation in mean rain days per month. Our study generates understanding of the relative performance of species in mixed species plantations in the Wet Tropics of Australia and improves our ability to predict species growth compatibilities at potential planting sites within the region. Given appropriate species selections and plantation design, mixed plantations of high-value native timber species are capable of sustaining relatively high productivity at a range of sites up to age 10 years, and may offer a feasible approach for large-scale reforestation.

The effect of long-term repeated burning and fire exclusion on above- and below-ground Blackbutt (Eucalyptus pilularis) forest vegetation assemblages

We used a long-term fire experiment in south-east Queensland, Australia, to determine the effects of frequent prescribed burning and fire exclusion on understorey vegetation (<7.5 m) richness and density in Eucalyptus pilularis forest. Our study provided a point in time assessment of the standing vegetation and soil-stored vegetation at two experimental sites with treatments of biennial burning, quadrennial burning since 19711972 and no burning since 1969. Vegetation composition, density and richness of certain plant groups in the standing and soil-stored vegetation were influenced by fire treatments. The density of resprouting plants <3 m in height was higher in the biennially burnt treatment than in the unburnt treatment, but resprouters 37.5 m in height were absent from the biennial burning treatment. Obligate seeder richness and density in the standing vegetation was not significantly influenced by the fire treatments, but richness of this plant group in the seed bank was higher in the quadrennial treatment at one site and in the long unburnt treatment at the other site. Long unburnt treatments had an understorey of rainforest species, while biennial burning at one site and quadrennial burning at the other site were associated with greater standing grass density relative to the unburnt treatment. This difference in vegetation composition due to fire regime potentially influences the flammability of the standing understorey vegetation. Significant interactions between fire regime and site, apparent in the standing and soil-stored vegetation, demonstrate the high degree of natural variability in vegetation community responses to fire regimes.