Long-term impacts of harvest residue management on nutrition, growth and productivity of an exotic pine plantation of sub-tropical Australia

Residue retention is an important issue in evaluating the sustainability of production forestry. However, its long-term impacts have not been studied extensively, especially in sub-tropical environments. This study investigated the long-term impact of harvest residue retention on tree nutrition, growth and productivity of a F1 hybrid (Pinus elliottii var. elliottii × Pinus caribaea var. hondurensis) exotic pine plantation in sub-tropical Australia, under three harvest residue management regimes: (1) residue removal, RR0; (2) single residue retention, RR1; and (3) double residue retention, RR2. The experiment, established in 1996, is a randomised complete block design with 4 replicates. Tree growth measurements in this study were carried out at ages 2, 4, 6, 8 and 10 years, while foliar nutrient analyses were carried out at ages 2, 4, 6 and 10 years. Litter production and litter nitrogen (N) and phosphorus (P) measurements were carried out quarterly over a 15-month period between ages 9 and 10 years. Results showed that total tree growth was still greater in residue-retained treatments compared to the RR0 treatment. However, mean annual increments of diameter at breast height (MAID) and basal area (MAIB) declined significantly after age 4 years to about 68-78% at age 10 years. Declining foliar N and P concentrations accounted for 62% (p < 0.05) of the variation of growth rates after age 4 years, and foliar N and P concentrations were either marginal or below critical concentrations. In addition, litter production, and litter N and P contents were not significantly different among the treatments. This study suggests that the impact of residue retention on tree nutrition and growth rates might be limited over a longer period, and that the integration of alternative forest management practices is necessary to sustain the benefits of harvest residues until the end of the rotation.

Spatial model of site index based on Y-ray spectrometry and a digital elevation model for two Pinus species in Tuan Toolara State Forest, Queensland, Australia

Site index prediction models are an important aid for forest management and planning activities. This paper introduces a multiple regression model for spatially mapping and comparing site indices for two Pinus species (Pinus elliottii Engelm. and Queensland hybrid, a P. elliottii x Pinus caribaea Morelet hybrid) based on independent variables derived from two major sources: g-ray spectrometry (potassium (K), thorium (Th), and uranium (U)) and a digital elevation model (elevation, slope, curvature, hillshade, flow accumulation, and distance to streams). In addition, interpolated rainfall was tested. Species were coded as a dichotomous dummy variable; interaction effects between species and the g-ray spectrometric and geomorphologic variables were considered. The model explained up to 60% of the variance of site index and the standard error of estimate was 1.9 m. Uranium, elevation, distance to streams, thorium, and flow accumulation significantly correlate to the spatial variation of the site index of both species, and hillshade, curvature, elevation and slope accounted for the extra variability of one species over the other. The predicted site indices varied between 20.0 and 27.3 m for P. elliottii, and between 23.1 and 33.1 m for Queensland hybrid; the advantage of Queensland hybrid over P. elliottii ranged from 1.8 to 6.8 m, with the mean at 4.0 m. This compartment-based prediction and comparison study provides not only an overview of forest productivity of the whole plantation area studied but also a management tool at compartment scale.

Recruitment dynamics of invasive species in rainforest habitats following Cyclone Larry

In tropical forests, natural disturbance creates opportunities for species to claim previously utilized space and resources and is considered an important mechanism in the maintenance of species diversity. However, ecologists have long recognized that disturbance also promotes exotic plant invasions. Cyclones cause extensive defoliation, loss of major branches and multiple tree falls, resulting in a significantly more open canopy and increased light and heat levels in the understorey. The widespread and massive disturbance caused by cyclones provides ideal conditions for rapid recruitment and spread of invasive species. The ecological roles of invasive species in rainforest habitats following such a severe disturbance are poorly understood. Severe category 4 Cyclone Larry crossed the North Queensland coast in March 2006 causing massive disturbance to rainforest habitats from Tully to Cairns and west to the Atherton Tablelands. We established 10 plots in an area extensively damaged by this cyclone near El Arish in North Queensland. On each plot nine 2 × 2 m quadrats were established with three quadrats per plot in each of the following treatments: (i) complete debris removal down to the soil layer, (ii) removal of coarse woody debris only, and (iii) uncleared. We monitored recruitment, growth and mortality of all native and invasive species in the 90 quadrats every 3 months since the cyclone. Here we present the recruitment dynamics of invasive species across the study area in relation to the level of disturbance, the type of quadrat treatment, and the diversity and abundance of the native recruiting flora over the first 12 months post-cyclone. Our results suggest that invasive species will mostly comprise a transient component of the flora in the early stages of the successional response. However, some species may have longer-term effects on the successional trajectory of the rainforest and future forest composition and structure.

Forest health surveillance methodology in hardwood plantations in Queensland, Australia

Forest health surveillance (FHS) of hardwood plantations commenced in Queensland in 1997 as plantations expanded following a state government planting initiative arising from the national 2020 forest policy vision. The estate was initially characterised by a large number of small plantations (10-50 ha), although this has changed more recently with the concentration of larger plantations in the central coast and South Burnett regions. Due to the disparate nature of the resource, drive- and walkthrough surveys of subsets of plantations have been undertaken in preference to aerial surveys. FHS has been effective in detecting a number of new hardwood pests in Queensland including erinose mites (Rhombacus and Acalox spp.), western white gum plate galler (Ophelimus sp.), Creiis psyllid and bronzing bug (Thaumastocoris sp.), in evaluating their potential impact and assisting in focussing future research efforts. Since 2003 there has been an increased emphasis on training operational staff to take a greater role in identifying and reporting on forest health issues. This has increased their awareness of forest health issues, but their limited time to specifically survey and report on pests and diseases, and high rates of staff turnover, necessitate frequent ongoing training. Consequently, common and widespread problems such as quambalaria shoot blight (Quambalaria pitereka), chrysomelid leaf beetles (mainly Paropsis atomaria) and erinose mites may be under-reported or not reported, and absence data may often not be recorded at all. Comment is made on the future directions that FHS may take in hardwood plantations in Queensland.

Development of hazard site surveillance programs for forest invasive species: A case study from Brisbane, Australia

Hazard site surveillance is a system for post-border detection of new pest incursions, targeting sites that are considered potentially at high risk of such introductions. Globalisation, increased volumes of containerised freight and competition for space at domestic ports means that goods are increasingly being first opened at premises some distance from the port of entry, thus dispersing risk away from the main inspection point. Hazard site surveillance acts as a backstop to border control to ensure that new incursions are detected sufficiently early to allow the full range of management options, including eradication and containment, to be considered. This is particularly important for some of the more cryptic forest pests whose presence in a forest often is not discovered until populations are already high and the pest is well established. General requirements for a hazard site surveillance program are discussed using a program developed in Brisbane, Australia, in 2006 as a case study. Some early results from the Brisbane program are presented. In total 67 species and 5757 individuals of wood-boring beetles have been trapped and identified during the program to date. Scolytines are the most abundant taxa, making up 83% of the catch. No new exotics have been trapped but 19 of the species and 60% of all specimens caught are exotics that are already established in Australia.

Modelling predicts positive and negative interactions between three Australian tropical tree species in monoculture and binary mixture

Computer modelling promises to be an important tool for analysing and predicting interactions between trees within mixed species forest plantations. This study explored the use of an individual-based mechanistic model as a predictive tool for designing mixed species plantations of Australian tropical trees. The `spatially explicit individually based-forest simulator' (SeXI-FS) modelling system was used to describe the spatial interaction of individual tree crowns within a binary mixed-species experiment. The three-dimensional model was developed and verified with field data from three forest tree species grown in tropical Australia. The model predicted the interactions within monocultures and binary mixtures of Flindersia brayleyana, Eucalyptus pellita and Elaeocarpus grandis, accounting for an average of 42% of the growth variation exhibited by species in different treatments. The model requires only structural dimensions and shade tolerance as species parameters. By modelling interactions in existing tree mixtures, the model predicted both increases and reductions in the growth of mixtures (up to +/-50% of stem volume at 7 years) compared to monocultures. This modelling approach may be useful for designing mixed tree plantations.

Combined treatments of spinosad and chlorpyrifos-methyl for management of resistant psocid pests (Psocoptera: Liposcelididae) of stored grain

The combined efficacy of spinosad and chlorpyrifos-methyl was determined against four storage psocid pests belonging to genus Liposcelis. This research was undertaken because of the increasing importance of these psocids in stored grain and the problem of finding grain protectants to control resistant strains. Firstly, mortality and reproduction were determined for adults exposed to wheat freshly treated with either spinosad (0.5 and 1 mg kg-1) or chlorpyrifos-methyl (2.5, 5 and 10 mg kg-1) or combinations of spinosad and chlorpyrifos-methyl at 30°C and 70% RH. There were significant effects of application rate of spinosad and chlorpyrifos-methyl, both individually and in combination, on adult mortality and progeny reduction of all four psocids. Liposcelis bostrychophila Badonnel and L. decolor (Pearman) responded similarly, with incomplete control of adults and progeny at both doses of spinosad but complete control in all chlorpyrifos-methyl and combined treatments. In L. entomophila (Enderlein) and L. paeta Pearman, however, complete control of adults and progeny was only achieved in the combined treatments, with the exception of spinosad 0.5 mg kg-1 plus chlorpyrifos-methyl 2.5 mg kg-1 against L. entomophila. Next, combinations of spinosad (0.5 and 1 mg kg-1) and chlorpyrifos-methyl (2.5, 5 and 10 mg kg-1) in bioassays after 0, 1.5 and 3 months storage of treated wheat were evaluated. The best treatment was 1 mg kg -1 of spinosad plus 10 mg kg-1 of chlorpyrifos-methyl, providing up to 3 months of protection against infestations of all four Liposcelis spp. on wheat.

Achievements in forest tree genetic improvement in Australia and New Zealand 2: Development of Corymbia species and hybrids for plantations in eastern Australia

This paper describes the establishment of provenance seedling seed orchards of three spotted gums and cadaga (all species of Corymbia ex Eucalyptus). It also discusses the limitations of growing the spotted gums as pure species including: lack of mass flowering, susceptibility to a fungal shoot blight and low amenability to vegetative propagation. These limitations, together with observation of putative natural hybrids of the spotted gums with cadaga, and the early promise of manipulated hybrids, led to an intensive breeding and testing program. Many hybrid families have significant advantages in growth and tolerance to disease, insects and frost, and can be vegetatively propagated. They also exhibit broad environmental plasticity, allowing the best varieties to be planted across a wider range of sites than the spotted gums, resulting in more land being suitable for plantation development.

Variation in exotic and native seed arrival and recruitment of bird dispersed species in subtropical forest restoration and regrowth

Invasive bird-dispersed plants often share the same suite of dispersers as co-occurring native species, resulting in a complex management issue. Integrated management strategies could incorporate manipulation of dispersal or establishment processes. To improve our understanding of these processes, we quantified seed rain, recruit and seed bank density, and species richness for bird-dispersed invasive and native species in three early successional subtropical habitats in eastern Australia: tree regrowth, shrub regrowth and native restoration plantings. We investigated the effects of environmental factors (leaf area index (LAI), distance to edge, herbaceous ground cover and distance to nearest neighbour) on seed rain, seed bank and recruit abundance. Propagule availability was not always a good predictor of recruitment. For instance, although native tree seed rain density was similar, and species richness was higher, in native plantings, compared with tree regrowth, recruit density and species richness were lower. Native plantings also received lower densities of invasive tree seed rain than did tree regrowth habitats, but supported a similar density of invasive tree recruits. Invasive shrub seed rain was recorded in highest densities in shrub regrowth sites, but recruit density was similar between habitats. We discuss the role of microsite characteristics in influencing post-dispersal processes and recruit composition, and suggest ways of manipulating these processes as part of an integrated management strategy for bird-dispersed weeds in natural areas.

Sustainable native forest management. Case studies in managing private native forest in southeast Queensland.

The introduction describes productive forest in Queensland and summaries the principles of native forest management that achieve optimum productivity. Case study 1 deals with thinning an even-aged regrowth forest. It shows how thinning the stand actively manages the future composition and structure to improve productivity in the best stems and increase the commercial value of the next harvest. Case study 2 describes restoring productivity in a high-graded spotted gum - ironbark forest. It shows that defective and non-saleable trees should be removed so they do not repress the future stand; and that regeneration should be thinned, retaining the best trees in adequate growing space. Case study 3 discusses on-farm value adding for hardwood forests. It shows how long-term viability and maximum productivity and returns depend on the best management practices and knowing how to obtain the best returns from a range of forest products. Case study 4 examines integrated harvesting in a eucalypt forest. It shows how integrating the harvest enables the full range of timber products are harvested and sold for their maximum value while reducing the amount of waste.

Reduced efficacy of macrocyclic lactone treatments in controlling gastrointestinal nematode infections of weaner dairy calves in subtropical eastern Australia.

Faecal Egg Count Reduction Tests (FECRTs) for macrocyclic lactone (ML) and levamisole (LEV) drenches were conducted on two dairy farms in the subtropical, summer rainfall region of eastern Australia to determine if anthelmintic failure contributed to severe gastrointestinal nematode infections observed in weaner calves. Subtropical Cooperia spp. were the dominant nematodes on both farms although significant numbers of Haemonchus placei were also present on Farm 2. On Farm 1, moxidectin pour-on (MXD) drenched at 0.5 mg kg-1 liveweight (LW) reduced the overall Cooperia burden by 82% (95% confidence limits, 37-95%) at day 7 post-drench. As worm burdens increased rapidly in younger animals in the control group (n = 4), levamisole was used as a salvage drench and these calves withdrawn from the trial on animal welfare grounds after sample collection at day 7. Levamisole (LEV) dosed at 6.8 mg kg-1 LW reduced the worm burden in these calves by 100%, 7 days after drenching. On Farm 2, MXD given at 0.5 mg kg-1 LW reduced the faecal worm egg count of cooperioids at day 8 by 96% (71-99%), ivermectin oral (IVM) at 0.2 mg kg-1 LW by 1.6% (-224 to 70%) and LEV oral at 7.1 mg kg-1 LW by 100%. For H. placei the reductions were 98% (85-99.7%) for MXD, 0.7% (-226 to 70%) for IVM and 100% for LEV. This is the first report in Australia of the failure of macrocyclic lactone treatments to control subtropical Cooperia spp. and suspected failure to control H. placei in cattle.

The effect of initial spacing and thinning on wood quality and graded sawn recovery of mature Caribbean pine grown in Queensland.

A mature Caribbean pine (Pinus caribaea var. hondurensis) silviculture experiment provided initial square spacing treatments of 1.8 m2, 2.4 m2, 3.0 m2 and 3.6 m2 (equal to 3088, 1737, 1111 and 772 stems/ha) that were thinned at age 10 years to 600, 400 and 200 stems/ha, retaining an unthinned control for each initial spacing. The trial was destructively sampled at age of 28 years and discs taken along 8 various stem heights were analysed for variation in basic density and SilviScan wood properties. In addition, the logs from ten stocking × thinning treatments were processed in a sawing study. Results indicate thinning effects were generally more pronounced than initial spacing effects. Fast growing trees produced wood with significantly higher average wood densities and higher average stiffness values. Detailed SilviScan densitometry results obtained radially and at various stem heights enabled construction of tree maps for wood properties, providing insights into the variation in juvenile to mature wood proportion across the initial and post-thinning stocking treatments studied. Dried dressed recovery was strongly related to tree size, and log value decreased consistently from butt to top logs across all treatments. The estimated value per hectare was highest in unthinned plots due to values being multiplied by high stem numbers per hectare. However, a complete economic analysis considering all cost structures is required to investigate the optimal silviculture to maximise economic returns to growers and processors. Improved understanding of the relationship between initial spacing, post-thinning stocking and wood and end-product quality should help to customize future forest management strategies required to produce better quality wood and wood products.

Productivity of plantation hardwood tree species in north-eastern Australia: A report from the Forest Adaptation and Sequestration Alliance

The report summarises data from a large number of trials of species with potential for use by the plantation forest industry in north-eastern Australia and provides information aimed at improving the understanding of growth rates, pest and disease risks and carbon sequestration. Data is summarised and presented at a regional level as opposed to individual trial or plot level. As well, nutritional impediments to tree growth and impacts on forest health are also reported. This report is intended to contribute to policy deliberations about developing forestry opportunities that can that can be integrated into the landscape, with particular consideration given to lower rainfall regions. There are several examples in north-eastern Australia where production forests have developed sub-optimally; this has often been due to poor selection of tree species as little information has been available. This report helps address this deficiency.

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.