Tim Wardlaw

• PhD
• Principal Investigator at University of Tasmania

Global biodiversity gradients are generally expected to reflect greater species replacement closer to the equator. However, empirical validation of global biodiversity gradients largely relies on vertebrates, plants, and other less diverse taxa. Here we assess the temporal and spatial dynamics of global arthropod biodiversity dynamics using a beta-...

Global gradients in species biodiversity are expected to reflect tighter packing of species closer to the equator. Yet, empirical validation of these patterns has so far focused on less diverse taxa, with comparable assessments of mega-diverse groups historically constrained by the taxonomic impediment. Here we assess the temporal and spatial turno...

Aim: Global gradients in species biodiversity may or may not be associated with greater species replacement closer to the equator. Yet, empirical validation of these patterns has so far focused on less diverse taxa, with comparable assessments of mega-diverse groups historically constrained by the taxonomic impediment. Location: Global Time period:...

Deadwood is a large global carbon store with its store size partially determined by biotic decay. Microbial wood decay rates are known to respond to changing temperature and precipitation. Termites are also important decomposers in the tropics but are less well studied. An understanding of their climate sensitivities is needed to estimate climate c...

In 2020, the Australian and New Zealand flux research and monitoring network, OzFlux, celebrated its 20th anniversary by reflecting on the lessons learned through two decades of ecosystem studies on global change biology. OzFlux is a network not only for ecosystem researchers, but also for those ‘next users’ of the knowledge, information and data t...

Tasmania experienced a protracted warm spell in November 2017. Temperatures were lower than those usually characterising heatwaves. Nonetheless the warm spell represented an extreme anomaly based on the historical local climate. Eddy covariance measurements of fluxes in a Eucalyptus obliqua tall forest at Warra, southern Tasmania during the warm sp...

Animals, such as termites, have largely been overlooked as global-scale drivers of biogeochemical cycles 1,2 , despite site-specific findings 3,4 . Deadwood turnover, an important component of the carbon cycle, is driven by multiple decay agents. Studies have focused on temperate systems 5,6 , where microbes dominate decay ⁷ . Microbial decay is se...

The amount of carbon stored in deadwood is equivalent to about 8 per cent of the global forest carbon stocks1. The decomposition of deadwood is largely governed by climate2–5 with decomposer groups—such as microorganisms and insects—contributing to variations in the decomposition rates2,6,7. At the global scale, the contribution of insects to the d...

Tasmania, which has a cool temperate climate, experienced a protracted warm spell in November 2017. In absolute terms, temperatures during the warm spell were lower than those usually characterising heatwaves. Nonetheless the November 2017 warm spell represented an extreme anomaly based on the local historical climate. Eddy covariance measurements...

Gross primary productivity (GPP) of wooded ecosystems (forests and savannas) is central to the global carbon cycle, comprising 67%–75% of total global terrestrial GPP. Climate change may alter this flux by increasing the frequency of temperatures beyond the thermal optimum of GPP (Topt). We examined the relationship between GPP and air temperature...

Globally, forests are facing an increasing risk of mass tree mortality events associated with extreme droughts and higher temperatures. Hydraulic dysfunction is considered a key mechanism of drought‐triggered dieback. By leveraging the climate breadth of the Australian landscape and a national network of research sites (Terrestrial Ecosystem Resear...

Non-stand-replacing wildfires are the most common natural disturbance in the tall eucalypt forests of Tasmania, yet little is known about the conditions under which these fires burn and the effects they have on the forest. A dry lightning storm in January 2019 initiated the Riveaux Road fire. This fire burnt nearly 64,000 ha of land, including tall...

Vegetation foliage clumping significantly alters the radiation environment and affects vegetation growth as well as water, carbon cycles. The clumping index (CI) is useful in ecological and meteorological models because it provides new structural information in addition to the effective leaf area index. Previously generated CI maps using a diverse...

Bark stripping by the Bennett’s wallaby (Macropus rufogriseus (Desmarest) subsp. rufogriseus) from the lower stems of 3–6-year-old radiata pine (Pinus radiata D. Don) causes significant damage in Tasmanian plantations. The usual diet of this generalist herbivore is mainly grasses and broadleaved forbs. As the factors that attract a wallaby to suppl...

Bark stripping by the Bennett’s wallaby (Macropus rufogriseus rufogriseus) from the lower stems of 3–6-year-old radiata pine (Pinus radiata) causes significant damage in Tasmanian plantations. The usual diet of this generalist herbivore is mainly grasses and broadleaved forbs. As the factors that attract wallabies to supplement its diet by eating t...

The ratio of leaf intercellular to ambient CO2 (χ) is modulated by stomatal conductance (gs). These quantities link carbon (C) assimilation with transpiration, and along with photosynthetic capacities (Vcmax and Jmax) are required to model terrestrial C uptake. We use optimization criteria based on the growth environment to generate predicted value...

1.Plant species show considerable leaf trait variability that should be accounted for in dynamic global vegetation models (DGVMs). In particular, differences in the acclimation of leaf traits during periods more and less favourable to growth have rarely been examined. 2.We conducted a field study of leaf trait variation at seven sites spanning a r...

Pine wilt disease, caused by the Bursaphelenchus xylophilus (pinewood nematode), has caused extensive damage to Pinus forests where it has invaded countries with susceptible hosts and with co-occurring native species of the cerambycid beetle Monochamus. A pest risk analysis showed that there is a moderate likelihood of pinewood nematode and its pri...

A review of current forest health surveillance and biosecurity surveillance activities and programs in Australia was conducted, including a grower survey, followed by benchmarking against the New Zealand system. We define forest health surveillance (e.g. in plantations) as activities dealing with endemic or established non-indigenous pests, and bio...

The forest, wood and paper products industry is a significant contributor to the Australian economy, ranking as the eighth largest manufacturing sector, with gross value of sales in 2015–2016 in excess of $23 billion, and an industry value-add of $9 billion. As with other agricultural industries, forest, wood and paper production is under constant...

Forest health and biosecurity programs rarely capture sufficient data to enable thorough cost-benefit analyses to be done. One notable exception has been Forestry Tasmania’s research project to develop and use an Integrated Pest Management (IPM) program for the leaf beetle Paropsisterna bimaculata. For this project we were able to estimate all majo...

In disturbance-dependent forest ecosystems, species associated with mature forest may maintain their ranges both by persisting in patches of mature forest and by recolonising patches regenerating after fire, harvesting or other disturbances. The null hypotheses are that these processes are both independent of the intensity of disturbance in the lan...

Sirex noctilio (Sirex) is an exotic wood wasp and a pest of Pinus that has been in Australia for 65 years. Our study quantified expenditure on Sirex control between 1952 and 2014 through the National Sirex Control program, and costed the impact of three major outbreaks where large-scale tree mortality occurred. We estimate the combined cost of the...

Maintaining developmental heterogeneity of ecological communities within landscapes is crucial for sustainable native forest management. Consequently, methods to assess forest maturity (i.e. the degree to which the forest contains attributes and supports processes characteristic of late‐successional forests) are valuable for making management decis...

The Tasmanian leaf beetle Paropsisterna bimaculata is a species native to Tasmania that can cause severe defoliation of eucalypt plantations. High populations of P. bimaculata, capable of causing severe defoliation if unmanaged, can periodically occur through a substantial proportion of a plantation rotation. Some exotic insect pests not yet establ...

Acoustic recording units (ARUs) have recently been used in place of field observers to survey birds. To test whether data obtained from ARUs and from point counts by a field observer are directly comparable, we surveyed Tasmanian forest birds using these two methods at exactly the same times and places. Data derived from ARUs were similar to those...

Climatic changes are likely to alter the distribution and abundance of insect and fungal pests of Australia’s plantations, and consequently the frequency and severity of outbreaks and damage to the host. Using review and synthesis of published literature, we examined these risks in temperate eucalypt and radiata pine plantations in Australia from t...

As Tasmania’s wet forests transition from mixed forest (eucalypt overstory with a rainforest understory) to rainforest they can be expected to lose more than half their total (live + dead, standing + downed) bole wood volume and biomass. On average rainforest sites contained 205 Mg C ha⁻¹, or 708 m³ ha⁻¹ less wood (live + dead, standing + downed) t...

Variable retention (VR) is increasingly being used as an alternative to clearcutting in temperate and boreal forests. VR is an approach to harvesting and regeneration that aims to improve biodiversity and social outcomes over the subsequent rotation, while continuing to meet silvicultural and economic imperatives. Aggregated retention, a form of VR...

Fire and timber harvesting can diminish the extent of older forests in the near term. The amount and configuration of mature and regenerating forest in the landscape (landscape structure) influences habitat suitability for mature-forest-associated species. We applied spatial analysis to describe the landscape structure of three wet eucalypt forest...

As Tasmania's wet forests transition from mixed forest (eucalypt overstory with a rainforest understory) to rainforest they can be expected to lose more than half their total (live + dead, standing + downed) bole wood volume and biomass. On average rainforest sites contained 205 Mg C ha À1 , or 708 m 3 ha À1 less wood (live + dead, standing + downe...

The roles that functional traits and/or evolutionary history of species from co‐occurring trophic groups have in determining community recovery following disturbance are poorly understood. Functional traits help determine how species interact with their environment, thus functional traits are likely to change with time since logging. However, trait...

Well-drained, aerated soils are important sinks for atmospheric methane (CH4) via the process of CH4 oxidation by methane-oxidising bacteria (MOB). This terrestrial CH4 sink may contribute towards climate change mitigation, but the impact of changing soil moisture and temperature regimes on CH4 uptake is not well understood in all ecosystems. Soils...

Timber harvest can adversely affect forest biota. Recent research and application suggest that retention of mature forest elements (‘retention forestry’), including unharvested patches (or ‘aggregates’) within larger harvested units, can benefit biodiversity compared to clearcutting. However, it is unclear whether these benefits can be generalized...

A robust non-parametric framework, based on multiple Radial Basic Function (RBF) kernels, is proposed in this study, for detecting land/forest cover changes using Landsat 7 ETM+ images. One of the widely used frameworks is to find change vectors (difference image) and use a supervised classifier to differentiate between change and no-change. The Ba...

The effects of Teratosphaeria leaf disease (TLD) on Eucalyptus globulus are varied, and it is currently poorly understood whether infection by TLD can cause long-term growth effects. Such information would greatly assist disease management and pruning regimes on E. globulus plantation sites, resulting in both financial and ecological benefits. Two...

OzFlux is the regional Australian and New Zealand flux tower network that aims to provide a continental-scale national research facility to monitor and assess trends, and improve predictions, of Australia’s terrestrial biosphere and climate. This paper describes the evolution, design, and current status of OzFlux as well as provides an overview of...

Fungal diversity of Australian eucalypt forests remains underexplored. We investigated the ectomycorrhizal (EcM) fungal community characteristics of declining temperate eucalypt forests in Tasmania. Within this context, we explored the diversity of EcM fungi of two forest types in the northern highlands in the east and west of the island. We hypoth...

Well-drained, aerated soils are important sinks for atmospheric methane (CH4) via the process of CH4 oxidation by methane oxidising bacteria (MOB). This terrestrial CH4 sink may contribute towards climate change mitigation, but the impact of changing soil moisture and temperature regimes on CH4 uptake is not well understood in all ecosystems. Tempe...

With globalisation, the world’s native biotas are increasingly exposed to disease, parasitism, herbivory and competition from exotic organisms. The vulnerability of native biota to these exotic invasions is exacerbated by human disturbance and global climate change. Rust pathogens are some of the most important plant pathogens, including Puccinia p...

OzFlux is the regional Australian and New Zealand flux tower network that aims to provide a continental-scale national research facility to monitor and assess trends, and improve predictions, of Australia’s terrestrial biosphere and climate. This paper describes the evolution, design and current status of OzFlux as well as an overview of data proce...

Altitudinal shifts in the distribution and/or composition of species communities or assemblages are often portrayed as demonstrating early signals of climate change. Mountain-top assemblages are often suggested as being particularly good indicators, as well as being potentially among the most vulnerable since they may have nowhere to go if the clim...

Needle fungi have been extensively studied in conifers but rarely in Pinus radiata. Previous studies of P. radiata have been based on fungal isolation and not direct PCR detection from needles. This research was a component of a study examining factors linked to spring needle cast (SNC) in Tasmanian P. radiata plantations and aimed to identify as m...

Tree species are exposed to single and combined forms of stress capable of inducing severe changes in plant functioning and survival. Climate change and other human disturbance continue to introduce novel combinations of stressors in forest ecosystems that make predicting their impact exceedingly difficult. In this chapter, we examine the causes an...

Needle fungi in conifers have been extensively studied to explore their diversity, but environmental factors influencing the composition of fungal communities in Pinus radiata D.Don needles have received little attention. This study was conducted to examine the influence of the environment as defined by rainfall, elevation and temperature on the co...

Spring needle cast (SNC) in Tasmania is defined by the early casting of pine needles and appears in 6- to 7-year-old pine plantations after canopy closure. The severity of SNC can vary significantly among trees growing within the same plantation. Fungal communities were surveyed in a Pinus radiata family trial, using DNA extraction from needles, PC...

Disturbance associated with severe wildfires and wildfire simulating harvest operations can potentially alter soil methane (CH4 ) oxidation in well aerated forest soils due to the effect on soil properties linked to diffusivity, methanotrophic activity or changes in methanotrophic bacterial community structure. However, changes in soil CH4 flux rel...

Clumping index is the measure of foliage grouping relative to a random distribution of leaves in space. It is a key structural parameter of plant canopies that influences canopy radiation regimes and controls canopy photosynthesis and other land–atmosphere interactions. The Normalized Difference between Hotspot and Darkspot (NDHD) index has been pr...

Environmental stress can be viewed as the physical, chemical, and biological con-straints on the productivity and development of ecosystems. For plants, Grime (1977) hypothesized that stress is one of the three fundamental drivers shaping plant strategies and he defined stress as a set of external constraints limiting the rate of resource acquisiti...

In plant/herbivore systems, elucidating the hierarchical genetic correlations that exist between enemies to a host plant (e.g., in the magnitude of damage) and determining how stable these effects are across environments is crucial for our understanding of potential eco-evolutionary dynamics in these systems. This sort of information would allow us...

A major aim of sustainable forest management is the maintenance or recolonisation of harvested areas by species that were present pre-disturbance. Forest influence (a type of edge effect that focuses on the effect of mature forests on adjacent disturbed forest) is considered to be an important factor that contributes to the ability of mature forest...

Forest ecosystems represent the largest soil sink for the greenhouse gas methane based on the activity of methanotrophic bacteria under aerobic soil conditions. Soil moisture status and soil structure both regulate soil gas diffusivity and therefore the availability of the substrate – atmospheric methane – to the bacteria in the soil layers. Climat...

Soils in forests ecosystem represent the largest land based methane (CH4) sink and therefore provide an important ecosystem service. Fire can alter soil properties linked to soil CH4 uptake potential but this has rarely been studied to date. We measured soil CH4 flux at temperate eucalypt forest sites (Victoria, Australia) that had different planne...

Climate change and fire influence the methane uptake capacity in Australian eucalypt forest soils Soil methane (CH4) oxidation in forest ecosystems comprise the largest soil sink for this potent greenhouse gas and climate change as well as fire can have significant impacts on this important process. We present data from a number of long-term green...

Many species of birds are adversely affected by clearcutting of Australian eucalypt forests for timber. However, recolonisation of harvested areas may be enhanced if mature forest is retained nearby (forest influence). We test the benefits of proximity to mature Tasmanian wet eucalypt forest on birds in adjacent regenerating clearcuts. We hypothesi...

In increasingly fragmented landscapes, it is important to understand how mature forest affects adjacent secondary forest (forest influence). Forest influence on ecological succession of beetle communities is largely unknown. We investigated succession and forest influence using 235 m long transects across boundaries between mature and secondary for...

Forest managers around the world face the problem of coping with current climatic variability as well as developing strategies for future climate change adaptation. Using Australia as an example, we describe past forest management responses to climatic variability and discuss these in the context of future adaptation strategies to deal with increas...

Cyclaneusma Needle Cast is associated with the fungal pathogen Cyclaneusma minus. The disease has led to significant losses of Pinus radiata production in New Zealand, but the disease appears less serious in Australia. Two cultural morphotypes of C. minus have been discriminated in New Zealand, and isolates from Australia also correspond to these t...

Routine forest health surveillance of Eucalyptus nitens and E. globulus plantations in Tasmania has detected more frequent borer-related mortality in mid-rotation plantations in drier areas of the state. Damaging borer populations are not usually detected using traditional health surveillance techniques until mortality has occurred. Appropriately b...

Tall eucalypt forests are iconic ecosystems renowned for the great height, high biomass and rapid growth rates of the trees that grow within them. These forests are highly valued for their biodiversity, timber production and social values. In the past, these values have been threatened by land clearing for agriculture, but now the most threatening...

In Australia, eucalypt plantations require management to prevent economic damage by native chrysomelid leaf beetles, generally by aerially spraying a broad‐spectrum insecticide. These beetles also pose a serious threat to plantations in other countries. Various alternatives, both ‘landscape’ and ‘control’ options, for managing leaf beetles were rev...

Most silvicultural methods have been developed with the principal aim of ensuring adequate regeneration of commercial tree species after harvesting. Much less effort has been directed towards developing methods that benefit the re-establishment of all forest biodiversity. The concept of ‘forest influence’ relates the probability of species re-estab...

Eucalypt forest decline has a complex aetiology often linked to altered soil chemistry caused by environmental disturbances. Forest decline has also been linked to alterations in ectomycorrhizal (ECM) fungal communities, which are imperative for nutrient transfer and affect ecosystem productivity and health. Our aim was to determine the influence o...

Bark stripping in Pinus radiata plantations by Bennett’s wallaby (M. rufrogriseus subspecies rufrogriseus) triggers high rates of tree mortality and reduces crop productivity, causing significant economic losses to the Australian forest industry. Bark stripping shows a marked increase during winter which may be associated with concurrent increases...

The possible drivers and implications of an observed latitudinal cline in disease resistance of a host tree were examined. Mycosphaerella leaf disease (MLD) damage, caused by Teratosphaeria species, was assessed in five Eucalyptus globulus (Tasmanian blue gum) common garden trials containing open-pollinated progeny from 13 native-forest populations...

Background/Question/Methods Retention forestry practices were initially developed in the PNW, and are now applied globally in place of clearcutting and other traditional silvicultural systems. A number of research studies have shown the value of small retained patches (aggregates) within harvesting units for maintaining species and structures ass...

Plantations of Eucalyptus globulus and E. nitens have been developed on Tasmanian State forest, with their combined area currently totalling 50,246 ha. The climatic envelope for this plantation estate was described by spatial interpolation of long-term climatic averages from an array of weather stations, using as parameters the mean minimum tempera...

Mammal browsing damage to Eucalyptus nitens and E. globulus seedlings in 23 eucalypt plantations throughout Tasmania was surveyed over time by repeated visits. All sites were planted with no initial browsing protection and monitored intensively. The levels of browsing damage overtime varied considerably among plantations, but more than half were da...

This paper investigates the diversity and ecology of the epigeous ectomycorrhizal (EcM) fungal assemblages of four plots in native Eucalyptus obliqua forest in Tasmania at different ages of regeneration since the natural disturbance of wildfire. From fortnightly visits to 1 ha of forest over a period of 14 months, 331 EcM species were documented. T...

The use of decay-class systems in characterising the state of decomposition of a forest’s complement of rotting logs is widespread. While most systems are based on an assessment of logs’ external characteristics, there is an implicit assumption that doing so captures important information on the underlying processes of internal decomposition. Howev...

The use of decay-class systems in characterising the state of decomposition of a forest’s complement of rotting logs is widespread. While most systems are based on an assessment of logs’ external characteristics, there is an implicit assumption that doing so captures important information on the underlying processes of internal decomposition. Howev...

Eucalyptus globulus is one of the best known examples of a heteroblastic plant. It exhibits a dramatic phase change from distinctive juvenile to adult leaves, but the timing of this transition varies markedly. We examined the genetic variation in the timing of heteroblastic transition using five large open-pollinated progeny trials established in n...

Two hundred thirteen potential sawlog trees from 22- to 34-year-old Eucalyptusregnans F. Muell. and Eucalyptusdelegatensis R.T. Baker regrowth forests from four sites in southern Tasmania were felled, dissected, and assessed for discolouration and decay. Of the aboveground origins, branches accounted for more than half of the discolouration and dec...

Litter in the tall, wet Eucalyptus obliqua forests of southern Tasmania supports rich and diverse macrofungal assemblages, with a total of 146 macrofungal species found fruiting in or on litter in a 1 ha area of native forest encompassing a range of fire histories. Of these, less than half (65 species) can be considered as preferring litter as a su...

The ecology and diversity of the macrofungal species assemblages associated with woody material in four plots with differing wildfire histories in a Tasmanian tall, wet, native Eucalyptus obliqua forest were investigated. The four woody substrata (CWD, other dead wood ODW, stags and living trees) supported substantially different macrofungal assemb...

This paper describes the wood-inhabiting fungi found in an intensive study of living Eucalyptus obliqua trees in Tasmania. Three hundred and twelve isolates of wood-inhabiting fungi were obtained from 18 trees, representing 91 species or operational taxonomic units (OTUs). A number of these were new records for Australia or for the living tree subs...

Assessment of crown condition is a useful tool for monitoring forest health and is used widely to assess tree dieback and decline. Multiple methods used to assess eucalypt crown condition are difficult to compare across studies. Furthermore, the relative effectiveness of the available methods has not been evaluated. The objective of this study was...

There are presently few tools available for estimating epidemic risks from forest pathogens, and hence informing pro-active disease management. In this study we demonstrated that a bioclimatic niche model can be used to examine questions of epidemic risk in temperate eucalypt plantations. The bioclimatic niche model, CLIMEX, was used to identify re...

In managed forest landscapes, understanding successional processes is critical to management for sustainable biodiversity. Coarse woody debris is a key substrate for forest biodiversity, particularly because it undergoes complex succession reflecting the effects of changes in both forest structure and substrate characteristics. The present study us...

In managed forest landscapes, understanding successional processes is critical to management for sustainable biodiversity. Coarse woody debris is a key substrate for forest biodiversity, particularly because it undergoes complex succession reflecting the effects of changes in both forest structure and substrate characteristics. The present study us...

• Artificial defoliation is often used to simulate defoliation by herbivory and is usually considered a good indication of a plant’s response to a given type of damage. However, the findings of studies directly comparing the two defoliation types are inconsistent. • Here, the short term effects of artificial and insect defoliation by larvae of Paro...

Over the past decade, considerable research has been done in Tasmania to better understand the ecological value of old eucalypts in temperate wet forests with respect to communities of wood-decay fungi and wood-inhabiting (saproxylic) beetles. Old eucalypts provide unique habitats for these organisms, and support a high species diversity and distin...

In the last 30 years there has been increasing recognition of the potential for dendrochronological studies on Tasmanian trees. This research is likely to provide information that can be used for historical, palaeoclimatic and palaeogeographical reconstructions. Research to date in Tasmania has focussed on the endemic conifers, in particular Lagaro...

Over the past decade, considerable research has been done in Tasmania to better understand the ecological value of old eucalypts in temperate wet forests with respect to communities of wood decay fungi and wood-inhabiting (saproxylic) beetles. Old eucalypts provide unique habitats for these organisms, and support a high species diversity and distin...

The responses of Eucalyptus globulus and E. nitens to pruning (removal of 0 or 60% of the green crown depth) in two lifts and nitrogen (N) fertiliser application (0 [N0], 100 [N1], 300 [N3] and 500 [N5] kg N ha-1) were compared at a site in south-east Tasmania under conditions where both species can be successfully grown. Pruning reduced growth of...