Mark A. Hunt

Thinning of forestry plantations is a common silviculture practice to increase growth rates and to produce larger dimension logs. The wood properties, basic density and stiffness, are key indicators of the suitability of timber for particular purposes and ultimately determine timber value. The impact of thinning operations on wood properties is, therefore, of considerable interest to forest growers and timber producers. To date, studies examining the impact of thinning on wood properties have produced variable results and understanding the consistency of the effects of thinning treatments across various sites for important plantation species is limited. Two non-destructive assessment techniques, drilling resistance and acoustic wave velocity, were used to examine the impact of thinning on basic density and stiffness in 19–21-year-old plantation grown Eucalyptus nitens across three sites. Commercial thinning to 300 trees ha⁻¹ decreased the stiffness of standing trees and this effect was consistent across the sites. Reduction in stiffness due to thinning ranged from 3.5% to 11.5%. There was no difference in wood properties between commercially and non-commercially thinned trees to 300 trees ha⁻¹ and no difference in wood properties when thinned to 500 trees ha⁻¹. Basic density was not affected by thinning. The site had significant effects on both basic density and stiffness, which were lowest at the highest precipitation and highest elevation site. The results indicate that wood properties are influenced both by silviculture and site environmental differences. This knowledge can be used for the better management of E. nitens resources for solid wood production.

A major challenge in ecological restoration is assessing the success of restoration plantings in producing habitats that provide the desired ecosystem functions and services. Forest structural complexity and biomass accumulation are key measures used to monitor restoration success and are important factors determining animal habitat availability and carbon sequestration. Monitoring their development through time using traditional field measurements can be costly and impractical, particularly at the landscape-scale, which is a common requirement in ecological restoration. We explored the application of proximal sensing technology as an alternative to traditional field surveys to capture the development of key forest structural traits in a restoration planting in the Midlands of Tasmania, Australia. We report the use of a hand-held laser scanner (ZEB1) to measure annual changes in structural traits at the tree-level, in a mixed species common-garden experiment from seven- to nine-years after planting. Using very dense point clouds, we derived estimates of multiple structural traits, including above ground biomass, tree height, stem diameter, crown dimensions, and crown properties. We detected annual increases in most LiDAR-derived traits, with individual crowns becoming increasingly interconnected. Time by species interaction were detected, and were associated with differences in productivity between species. We show the potential for remote sensing technology to monitor temporal changes in forest structural traits, as well as to provide base-line measures from which to assess the restoration trajectory towards a desired state.

Stiffness is considered one of the most important structural properties for sawn timber used in buildings and laminated structures including mass timber elements. There is great potential to use plantation Eucalyptus timber for structural applications, and the successful development of a plantation timber supply chain for structural products will depend on the accurate selection and grading of the resource. In this study we aimed to investigate the suitability of non-destructive testing (NDT) to improve selection and grading of sawn boards sourced from a young E. nitens plantation. We studied 268 sawn boards traced from the tree through to final processing stages. We found high and positive correlations between stiffness (measured as dynamic modulus of elasticity) tested at each board processing stage through acoustic wave velocity (AWV) and the static board modulus of elasticity measured through mechanical testing on dressed boards. Position of the board in the stem and sawn board processing treatment significantly impacted board modulus of elasticity, indicating that early selection of logs would allow larger yield of stiffer boards. We investigated the grading of boards through the traditional Australian Standards using a visual-grading system and through AWV, finding a classification error of 82.5% and 45.2%, respectively. We developed a linear model which was used to re-classify the boards, obtaining a smaller classification error, including fewer boards being over-graded. Our results demonstrate that AWV can be used as an early selection method for structural boards and can also be employed to satisfactorily grade E. nitens plantation boards to be used in building structures and as elements of mass timber.

Thermo-hydro mechanical (THM) treatments and thermo-treatments are used to improve the properties of wood species and enhance their uses without the application of chemicals. This work investigates and compares the effects of THM treatments on three timber species from Tasmania, Australia; plantation fibre-grown shining gum (Eucalyptus nitens H. Deane and Maiden), plantation saw-log radiata pine (Pinus radiata D. Don) and native-grown saw-log timber of the common name Tasmanian oak (which can be any of E. regnans F. Muell, E. obliqua L’Hér and E. delegatensis L’Hér). Thin lamellae were compressed by means of THM treatment from 8 mm to a target final thickness of 5 mm to investigate the suitability for using THM-treated lamellas in engineered wood products. The springback, mass loss, set-recovery after soaking, dimensional changes, mechanical properties, and Brinell hardness were used to evaluate the effects of the treatment on the properties of the species. The results show a marked increase in density for all three species, with the largest increase presented by E. nitens (+53%) and the smallest by Tasmanian oak (+41%). E. nitens displayed improvements both in stiffness and strength, while stiffness decreased in P. radiata samples and strength in Tasmanian oak samples. E. nitens also displayed the largest improvement in hardness (+94%) with respect to untreated samples. P. radiata presented the largest springback whilst having the least mass loss. E. nitens and Tasmanian oak showed similar dimensional changes, whilst P. radiata timber had the largest thickness swelling and set-recovery due to the high water absorption (99%). This study reported the effects of THM treatments in less-known and commercially important timber species, demonstrating that the wood properties of a fibre-grown timber can be improved through the treatments, potentially increasing the utilisation of E. nitens for structural and higher quality timber applications.

The stability of species and provenance performance across diverse environments is a major issue in restoration, particularly for assisted migration and climate‐adjusted provenancing strategies. This study examines how differences in species and provenance performance are affected by plant community composition in a dry sclerophyll forest restoration experiment. Five indices were measured over 6 years post‐establishment to evaluate the relative performance of community composition using 10 provenances of two focal eucalypts (Eucalyptus pauciflora and Eucalyptus tenuiramis) under six community treatments for E. pauciflora and five for E. tenuiramis. Community treatments varied according to the species planted as the immediate neighbor to the focal species, and included same species, same genus, or one of three different genera. Significant species and provenance differences were observed for all measured performance indices, with no evidence of interaction effects with community treatments. E. tenuiramis was more susceptible to insects and frost, and had poorer establishment but greater growth of the survivors than E. pauciflora. Generally, nonlocal provenances were more susceptible to insect herbivory and frost damage and had higher mortality than local provenances. At this early life‐stage there was no evidence that co‐planted species affected the relative performance of focal species or provenances, arguing transfer functions are likely stable across different planted communities. While species and provenance performance was not affected by community context, focal species differed in their response to upslope migration and any climate‐adjusted provenancing may require staged transfers to avoid maladaptation under contemporary growing conditions.

Background: Agroforestry systems can improve the provision of ecosystem services at the farm scale whilst improving agricultural productivity, thereby playing an important role in the sustainable intensification of agriculture. Natural capital accounting offers a framework for demonstrating the capacity of agroforestry systems to deliver sustained private benefits to farming enterprises, but traditionally is applied at larger scales than those at which farmers make decisions. Methods: Here we review the current state of knowledge on natural capital accounting and analyse how such an approach may be effectively applied to demonstrate the farm-scale value of agroforestry assets. We also discuss the merits of applying a natural capital approach to agroforestry decision-making and present an example of a conceptual model for valuation of agroforestry assets at the farm scale. Results: Our findings suggest that with further development of conceptual models to support existing tools and frameworks, a natural capital approach could be usefully applied to improve decision-making in agroforestry at the farm scale. Using this approach to demonstrate the private benefits of agroforestry systems could also encourage adoption of agroforestry, increasing public benefits such as biodiversity conservation and climate change mitigation. However, to apply this approach, improvements must be made in our ability to predict the types and amounts of services that agroforestry assets of varying condition provide at the farm or paddock scale.

Aim: To assess whether restoration of dry eucalypt‐dominated plant communities on ex‐pasture sites is constrained by soil characteristics.Location: Central Tasmania, Australia.Methods: We use nutrient status to test recovery trajectories of soils within eucalypt woodland restorations established on ex‐pasture sites. Eucalyptus trees within these sites have been successfully established but understorey plant communities have had negligible recovery. Soils from restoration sites, aged from 3 to 22 years, were contrasted with those from two reference ecotypes: established pastures and native eucalypt woodlands presumed to be similar to that originally replaced by the pastures. We hypothesized that (a) total soil carbon to nitrogen ratios (C:N) would be substantially higher in forest soils than in pasture soils; (b) soil nutrient levels would be lower in forest sites than within pasture sites; and (c) if restoration soils were recovering they should fit between these continuums according to age of planting.Results: Woodland and pasture reference soils were highly constrained in soil C:N and conformed to expectations. However, ex‐pasture restoration sites retained the characteristically low C:N and high nutrient levels of pasture soils, in particular total N. They also failed to demonstrate a transformational effect with age of planting.Conclusions: The results suggest that both restoration interventions and natural processes had not sufficiently disrupted existing below‐ground systems within the given time frame. Such an intractable stable state within the soil system highlights the need within restoration practice for an increased emphasis on soil ecological transformation. Improving and implementing practices aimed at driving soil change may assist a timelier reassembly of complex native ecosystems. This study also shows that soil C:N ratios may provide a cheap and simple means of identifying soil constraints on restoration.

Agroforestry (the integration of trees into agricultural landscapes) has been promoted, in Australia and elsewhere, as a way to increase farm productivity by providing a wide range of benefits. Despite this, adoption of agroforestry in Australian agricultural systems remains low. To implement agroforestry, farmers must be convinced the benefits of including trees outweigh the costs. This review evaluates the available quantitative data on shelter benefits with emphasis on Australian conditions, identifies key research gaps and determines if there is sufficient knowledge to make accurate predictions about impacts on farm productivity. Availability of quantitative data on windbreak shelter benefits was examined in five key areas; water use and evaporation, crop/pasture production, livestock mortality, livestock productivity and the capacity to model impacts of windbreaks on crop/livestock systems. Good quantitative data exists for many areas, particularly for changes in environmental conditions following tree establishment, however there were many gaps in key areas. Importantly, the ability to predict crop growth under spatially and temporally variable environmental conditions and the impact of windbreaks on livestock productivity is not yet able to be meaningfully quantified. Thus modelling the profitability of windbreaks is difficult and existing models require additional quantitative data to validate and improve them.