South-eastern Australia Research Articles

Optimizing water management in young almond orchards with heavy clay soils in southeastern Australia using proximal and remote sensors

Optimizing water management in young almond orchards with heavy clay soils in southeastern Australia using proximal and remote sensors

3D seismic analysis of complex faulting patterns and fluid escape features and their relation to Late Cenozoic Magmatism in the Bass Basin, offshore SE Australia

Abstract Igneous intrusions in sedimentary petroleum basins are often perceived as having a negative impact on the elements of the petroleum system, though the impact of intrusion-related deformation features on petroleum systems and broader geoenergy applications is not well understood. In this study, we use 3D seismic reflection data to document a variety of deformation styles that are spatially and temporally associated late Cenozoic magmatic activity in the Bass Basin, offshore southeastern Australia; three types of normal fault systems (conjugate faults, concentric faults, radial faults) and fluid escape pipes. These deformation features occur in the overburden up to ∼600 m above underlying igneous intrusions, within the Eocene to Miocene Demons Bluff and Torquay formations. The conjugate faults bound graben and are interpreted to have formed in response to underlying dyke intrusions. The radial faults are interpreted to have formed in response to overburden uplift, though the link between these and associated igneous activity is less clear. We identify 101 fluid escape features that show variation in both the morphology of their surficial depressions and of the seismic reflection characteristics of their infilling deposits. These features are interpreted to be hydrothermal or volcanic vents with underlying pipe-like feeders, depending on their spatial association with adjacent or underlying igneous intrusions. The concentric fault systems are associated with surficial depressions, and quantitative analysis of reflection sags within these depressions suggest that they are a result of subsurface subsidence in response to formation of maar-craters. The intrusion-related deformation features documented in this study may have multiple effects on working petroleum systems, such as providing secondary fluid flow pathways that can either reduce seal integrity, or enabling migration of fluids into shallower reservoirs.

Wetland Plants and Aboriginal Paludiculture in North- and South-Eastern Australia

Aboriginal peoples in north- and south-eastern Australia practiced paludiculture, the cultivation of wetland plants for consumption, for many thousands of years before Europeans invaded them in the 1830s and 1840s. This article focuses on the yam daisy (Microseris spp.) in south-eastern Australia and the bulkuru sedge (Eleocharis dulcis) in north-eastern Australia in historical and recent accounts of wetlands in both regions. Aboriginal people in both places cultivated and harvested the tubers of both plants. Recent debates about Aboriginal peoples’ cultivation of native plants and whether they constitute agriculture apply the European value-laden yardstick of stages of human development with agriculture as the pinnacle of land use and constitute ‘hunting and gathering’ as lower in a hierarchy of value. They fail to appreciate not only the sophistication of the latter, but also that Aboriginal people cultivated grasses and grains on drylands (agriculture) and yams and sedges in wetlands (paludiculture).

Implications of Climate-Induced Localised Extinction of Bull Kelp (Durvillaea amatheiae) for Holdfast Macrofauna

Globally, work is being undertaken to preserve biodiversity and prevent further species extinctions. Yet, without adequate data about the presence of species within ecosystems, hidden extinctions can occur without our knowledge. Given that poleward range retractions are projected for bull kelp (Durvillaea amatheiae) in southeastern Australia, there is the potential for hidden extinctions to occur in associated macrofaunal species. However, this risk cannot be assessed due to the limited data on the invertebrate macrofauna associated with D. amatheiae. We documented macrofauna within D. amatheiae holdfasts, with the objective of establishing a first analysis of the holdfast fauna for this kelp and identifying, where possible, any host-specific taxa. Holdfasts were collected at six locations, spanning most of the range of D. amatheiae on the southeastern Australian mainland. Macrofauna were removed from holdfasts and identified to the lowest possible taxonomic level. Modelling was applied to determine factors correlated with patterns of assemblages among locations. Holdfast assemblages were found to vary significantly among locations and exhibited a latitudinal gradient in assemblage structure. The northernmost location (Aragunnu), which has the highest risk of D. amatheiae range retractions, was found to have distinct species assemblages and generally higher diversity and abundance than locations further south. However, no host-specific taxa were identified in samples, indicating that there is a low risk of multiple hidden species extinctions occurring in holdfast macrofauna, due to future range retractions of D. amatheiae. Rather, most of the macrofauna taxa in D. amatheiae holdfasts were found to also occur in association with the sympatric golden kelp Ecklonia radiata, which is not expected to undergo range retractions at the latitudes where losses of D. amatheiae are projected. Overall, there is an urgent need to develop strategies to combat projected future range retractions of D. amatheiae to reduce impacts on the species that rely on D. amatheiae for habitat.

Severe and Short Interval Fires Rearrange Dry Forest Fuel Arrays in South-Eastern Australia

Fire regimes have shaped extant vegetation communities, and subsequently fuel arrays, in fire-prone landscapes. Understanding how resilient fuel arrays are to fire regime attributes will be key for future fire management actions, given global fire regime shifts. We use a network of 63-field sites across the Sydney Basin Bioregion (Australia) to quantify how fire interval (short: last three fires <10 years apart, long: last two fires >10 years apart) and severity (low: understorey canopy scorched, high: understorey and overstorey canopy scorched), impacted fuel attribute values 2.5 years after Australia’s 2019–2020 Black Summer fires. Tree bark fuel hazard, herbaceous (near-surface fuels; grasses, sedges <50 cm height) fuel hazard, and ground litter (surface fuels) fuel cover and load were higher in areas burned by low- rather than high-severity fire. Conversely, midstorey (elevated fuels: shrubs, trees 50 cm–200 m in height) fuel cover and hazard were higher in areas burned by high- rather than low-severity fire. Elevated fuel cover, vertical connectivity, height and fuel hazard were also higher at long rather than short fire intervals. Our results provide strong evidence that fire regimes rearrange fuel arrays in the years following fire, which suggests that future fire regime shifts may alter fuel states, with important implications for fuel and fire management.

Yield response and water productivity of soybean (Glycine max L.) to deficit irrigation and sowing time in south-eastern Australia

The aim of this study was to investigate irrigation strategies and sowing dates that would maximise soybean yield and water productivity. It is based on field experiments conducted during two seasons and simulation modelling. Irrigation treatments were 33%, 66%, 66% plus 100% during pod development and pod-fill stages, and 100% of crop evapotranspiration (ETc). In the first season experiment, cvs. Bidgee and Snowy were sown on 15 Nov. In the second season, cv. Bidgee was sown on 15 Nov and 15 Dec. Five sowing dates (1, 15, 30 Nov and 15, 31 Dec) and eight irrigation scenarios were analysed in-silico using the crop model APSIM. For the simulations, the first four irrigation scenarios were set by applying 50%ETc during one of the four growth stages: vegetative stage, flowering stage, pod development and pod-filling stage, and maturity stage. The other five irrigation treatments were 0%ETc, 25%ETc, 50%ETc, 75%ETc, and 100%ETc throughout the growing season. Soil water content and above-ground dry matter were measured at regular time intervals. Seed yield, 100-seed weight, oil and protein contents were determined at harvest. Water deficit during pod development and pod-filling stage had significant effect on seed yield. The flowering stage was the next most sensitive stage for water deficit. During both cropping seasons, the 33% treatment yielded 51% of the fully irrigated reference. The latter had a significantly higher water productivity than all the deficit treatments. Early-sown soybean had higher yield than the late sown soybean. Sowing as late as early December was found to be still suitable for double cropping without significant yield loss. The result of this study is particularly useful for soybean farmers in water-scarce regions, such as south-eastern Australia, who practice double cropping with a tight cropping calendar.

Climate change exacerbates the compounding of heat stress and flooding in the mid‐latitudes

AbstractHeat stress and flood impacts have been extensively studied separately because of their significant societal and economic impacts, albeit apart from each other. Here we show that heat stress can trigger floods across large areas of North and South America, southern Africa, Asia and eastern Australia. We also show that the compounding of heat stress and floods is projected to worsen under climate change. This effect is magnified as we move from the Shared Socioeconomic Pathways (SSPs) 1–2.6 to 5–8.5. Moreover, in the future, the compounding between heat stress and floods is projected to extend to Europe and Russia, two areas where it has not been identified as relevant in the past. Moreover, by intersecting our results with future projections of the population of urban agglomerations, we find that heat stress/flood compound can pose a serious risk to a large portion of the world population. These results highlight the need towards improved preparation and mitigation measures that account for the compound nature of heat stress and flooding, and how the compounding is expected to be exacerbated because of climate change.

Estimating fine fuel loads in Eucalypt forests using forest inventory data and a modelling approach

Eucalypt forests are vital for biodiversity and fire dynamics, with fine fuels serving as the primary ignition source and critical factors in determining fire intensity. Accurate measurement of fine fuel via destructive field methods is location and time-restricted, hindering the tracking of their dynamic variations across diverse landscapes. In response, this study utilised forest inventory data collected by the Victorian Forest Monitoring Program (VFMP) in Victoria, southeastern Australia, along with allometric models, to estimate fine fuel loads across four vertical layers (surface, near-surface, elevated, and canopy). The average total fine fuel load in Victorian Eucalypt forests was estimated at 18.45 t ha−1 (ranging from 2.23 to 39.54 t ha−1), with surface litter contributing 58.2% of this total, followed by canopy (22.1%), near-surface (13.4%), and elevated (6.6%) fine fuels. We also conducted a comprehensive investigation and found distinct variations in fine fuel loads across different bioregions, forest covers, and vegetation types. Furthermore, stepwise multiple regression was employed to develop predictive models for estimating fine fuel loads from forest structural and environmental variables. Results show that total and canopy fine fuels can be reasonably explained by forest height, density, and climate-related variables (with R2 = 0.38 and 0.51, respectively). However, the explanatory power of these models diminished when applied to elevated, near-surface, and surface fine fuels. This study underscores the intricacies of fine fuel distribution in Eucalypt forests, emphasising the necessity for comprehensive factors in fire management planning. Further research is needed to better comprehend the relationship between forest characteristics and fine fuel dynamics to enhance wildfire risk assessment and mitigation strategies.

Early Pliocene Ostracoda from the Jemmys Point Formation, Gippsland Basin, southeastern Australia: nearshore and offshore origins of biodiversity

Early Pliocene ostracod faunas of the Jemmys Point Formation, onshore Gippsland Basin, yield a rich and well-preserved marine ostracod fauna of mixed shallow marine and deep marine origins. The ostracod faunas evidence a marine continental shelf palaeoenvironment that, during the deposition of one stratigraphic interval, was influenced by a strong, persistent upwelling current. This upwelling current allowed the migration of deep-sea Ostracoda (Philoneptunus sp.) onto the continental shelf. The deeper marine aspect of this early Pliocene fauna, and of modern ostracod faunas from the Bass Strait region, evidence the adaptation of deep shelf taxonomic clades to shallow cool temperate shelf environments and highlights one unusual evolutionary mechanism that has contributed to modern Bass Strait shallow marine biodiversity. Four species are newly described: Neonesidea chapminuta sp. nov., Tasmanocypris salaputia sp. nov., Oculocytheropteron jemmyensis sp. nov., and Philoneptunus plutonis sp. nov. Abbey P. McDonald* [a.mcdonald@deakin.edu.au], School of Life and Environmental Sciences, Deakin University, Burwood, Victoria 3125, Australia; Elizabeth A. Weldon [l.weldon@deakin.edu.au], School of Life and Environmental Sciences and Deakin Marine Research and Innovation Centre, Deakin University, Burwood, Victoria 3125, Australia; Mark T. Warne [mark.warne@deakin.edu.au], School of Life and Environmental Sciences and Deakin Marine Research and Innovation Centre, Deakin University, Burwood, Victoria 3125, Australia, and Museums Victoria, GPO Box 666, Melbourne, Victoria 3001, Australia.

Recruitment of a threatened foundation oyster species varies with large and small spatial scales.

Understanding how habitat attributes (e.g., patch area and sizes, connectivity) control recruitment and how this is modified by processes operating at larger spatial scales is fundamental to understanding population sustainability and developing successful long-term restoration strategies for marine foundation species-including for globally threatened reef-forming oysters. In two experiments, we assessed the recruitment and energy reserves of oyster recruits onto remnant reefs of the oyster Saccostrea glomerata in estuaries spanning 550 km of coastline in southeastern Australia. In the first experiment, we determined whether recruitment of oysters to settlement plates in three estuaries was correlated with reef attributes within patches (distances to patch edges and surface elevation), whole-patch attributes (shape and size of patches), and landscape attributes (connectivity). We also determined whether environmental factors (e.g., sedimentation and water temperature) explained the differences among recruitment plates. We also tested whether differences in energy reserves of recruits could explain the differences between two of the estuaries (one high- and one low-sedimentation estuary). In the second experiment, across six estuaries (three with nominally high and three with nominally low sedimentation rates), we tested the hypothesis that, at the estuary scale, recruitment and survival were negatively correlated to sedimentation. Overall, total oyster recruitment varied mostly at the scale of estuaries rather than with reef attributes and was negatively correlated with sedimentation. Percentage recruit survival was, however, similar among estuaries, although energy reserves and condition of recruits were lower at a high- compared to a low-sediment estuary. Within each estuary, total oyster recruitment increased with patch area and decreased with increasing tidal height. Our results showed that differences among estuaries have the largest influence on oyster recruitment and recruit health and this may be explained by environmental processes operating at the same scale. While survival was high across all estuaries, growth and reproduction of oysters on remnant reefs may be affected by sublethal effects on the health of recruits in high-sediment estuaries. Thus, restoration programs should consider lethal and sublethal effects of whole-estuary environmental processes when selecting sites and include environmental mitigation actions to maximize recruitment success.

A landscape scale model to predict post-fire debris flow impact zones

Post-fire debris flows pose a significant hazard in mountainous regions, but accurate assessment of the associated risk at large scales, particularly in the context of mega-fires, is limited. Although numerous models exist, few are functional at the landscape scale, and none integrate assessments of downstream effects with the likelihood of flow initiation to define both the frequency and magnitude of potential flows. The aim of this work, therefore, was to develop a post-fire debris flow model that could characterise both the occurrence frequency and associated runout of debris flow events and which could be rapidly applied to fire events at the landscape scale. We achieve this using a model integration approach that included the development of a reduced-complexity debris flow runout model, which was calibrated and independently tested for its application at large scales with a dataset of 1377 individual post-fire flows across south-eastern Australia. This model was then integrated with previously published methods determining debris flow source areas and likelihood of initiation specific to our study area. The developed model is intentionally designed for rapid response hazard management. Therefore, it predominantly incorporates only the fundamental, lowest parameter form drivers of debris flow initiation and runout termination, thus minimising computational complexity while ensuring prediction accuracy sufficient for hazard assessment even at application scales as large as mega-fires. Accounting for debris flows initiated from single headwaters and cases where flows simultaneously converge from multiple initiation points, our integrated model effectively characterises debris flow hazard across a geomorphologically diverse landscape encompassing >200,000km2 (capturing ~640,000 potential debris flow initiation locations across Victoria, Australia). Model testing using an independent validation dataset resulted in debris flow runout predictions with root mean square error (RMSE) of 176 and 308 m for non-convergent and convergent flows respectively. Crucially, these predictions can be computed rapidly for large (up to landscape scale) fire events with minimal input requirements and the use of a remotely-sensed observation dataset for domain calibration. As such, the model provides a critical means of addressing the capacity gap in assessments of post-fire debris flow hazard by efficiently integrating measures of occurrence frequency and runout for functional application at large scales. This new work empowers land managers to rapidly predict the hazard arising from post-fire erosion processes and represents an important applied step towards better understanding and mitigating the impacts of wildfire-induced debris flows.

Prolonged drought moderates flood effects on soil nutrient pools across a rainfall gradient

Climate change is manifesting through increased intensity and frequency of extreme events such as droughts and floods. Drought causes significant stress by limiting water availability, resulting in reduced plant growth and belowground carbon (C) inputs as well as plant nutrient uptake and microbial activity, thus impacting C and nutrient cycling. Severe floods can increase leaching of nutrients, which affect nutrient availability for plants and microorganisms potentially compounding drought-induced effects on C and nutrient cycles. However, few studies have assessed the interactions between drought and floods, constraining our ability to predict ecosystem-level effects of projected climate shifts toward fewer but larger rainfall events with longer dry spells between events. We conducted a study to assess how long-term drought moderates the effect of flooding on soil C, nitrogen (N) and phosphorus (P) pools across a rainfall gradient in south-eastern Australia. We collected soil monoliths from field rainfall manipulation facilities with a 5–7 years history of simulated reduced rainfall at three sites representing a rainfall gradient (∼200–800 mm) and exposed them to a 1-in-100-year flood event under laboratory conditions. We assessed nutrients and C in soil and microbial pools before and after the flood and in flood-induced leachates. The results showed that flooding caused significantly greater losses of N in leachates, with greater effect sizes in the drought treatments compared to ambient rainfall. This response was particularly pronounced for nitrate (152 % increase on average), especially at the site with the highest mean annual precipitation (>25-fold increase). This suggest that drought may significantly reduce the capacity of ecosystems to retain N following flood events, particularly in mesic ecosystems where C and nutrient pools are greater.

Distinct geographical and seasonal signals in two tree-ring based streamflow reconstructions from Tasmania, southeastern Australia

Study region Western Tasmania, southeastern Australia.Study focus We present two new tree-ring based inflow reconstructions from western Tasmania in southeastern Australia.The warm season reconstruction (Dec–Feb) extends from 1030–2007 CE and explains up to 42% of the variance in instrumental flow, while the cool season (JA) extends from 1550–2007 CE and explains 27% of instrumental flow variance. Key features include an extended pluvial period in the 11th Century and a protracted dry period in ∼1500CE, neither of which are represented in the DJF instrumental record. Decreasing JA flow since the 19th Century is consistent with a local sediment-based hydroclimate record.New hydrological insights for the region The reconstructions confirm that the instrumental data do not capture how protracted past low or high flow periods have been. It is therefore important to consider pre-instrumental flow data when planning for the future. The reconstructions provide new insights into regional variability through their association with the Subtropical Ridge (STR) and the Southern Annular Mode (SAM). Differing spatial signatures of the seasonal reconstructions, and their associations with season-specific impacts of STR and SAM, highlight the need for caution when considering the use of remote hydroclimate proxy records with strong seasonal signatures. The reconstructions suggest that extrapolation of seasonally defined reconstructions to represent annual flow for regions beyond the extent of their spatial footprint may be problematic.

Habitat loss and degradation reduce the abundance of the glossy grass skink, Pseudemoia rawlinsoni

Context Habitat loss and degradation are major drivers of biodiversity loss worldwide. In particular, wetland environments are being removed and degraded faster than any other terrestrial habitat on earth. The loss and degradation of wetlands has been particularly pronounced in south-eastern Australia. Aims Here we investigated the impact of habitat loss and degradation on the Data Deficient glossy grass skink (Pseudemoia rawlinsoni), a species that predominantly favours wetland vegetation in south-eastern Australia. Methods We established artificial cover-object (roofing tiles) survey grids in paired remnant and disturbed sites at six locations across Victoria, Australia, and surveyed for skinks between November 2021 and April 2022. Key results Sites at which glossy grass skinks occur are characterised by tall dense vegetation, with a high cover of matted biomass. Thermal profiles within these complex vegetation structures remain much cooler during hot days, and warmer during cold nights, than external temperatures. Nearby disturbed sites (i.e. grazed or mowed areas within dispersal distance of remnant sites) are generally devoid of skinks, have very low and structurally simple (open) vegetation, and have thermal regimes that offer lizards no respite from high summer temperatures. We found that roofing tiles are an effective way to survey for glossy grass skinks; even on cool cloudy days, the temperature of tiles, and the lizards sheltering beneath them, are often much higher than ambient temperatures. Conclusions These findings implicate habitat loss and degradation as having a substantial negative impact on glossy grass skink presence and abundance; skinks largely avoid disturbed areas, even at sites immediately adjacent to remnant habitat. This may be driven not simply by the removal of tall and dense vegetation structures, but the consequent loss of the optimal thermal buffer afforded by such structures. Implications Our study emphasises the threat that habitat loss and degradation pose to wetland species in Australia, and throughout the world.

Modelling changes in vegetation productivity and carbon balance under future climate scenarios in southeastern Australia

Australia, characterized by extensive and heterogeneous terrestrial ecosystems, plays a critical role in the global carbon cycle and in efforts to mitigate climate change. Prior research has quantified vegetation productivity and carbon balance within the Australian context over preceding decades. Nonetheless, the responses of vegetation and carbon dynamics to the evolving phenomena of climate change and escalating concentrations of atmospheric carbon dioxide remain ambiguous within the Australian landscape. Here, we used LPJ-GUESS model to assess the impacts of climate change on Gross Primary Productivity (GPP) and Net Biome Productivity (NBP) of carbon for the state of New South Wales (NSW) in southeastern Australia. LPJ-GUESS simulations were driven by an ensemble of 27 global climate models under different emission scenarios. We investigated the change of GPP for different vegetation types and whether NSW ecosystems will be a net sink or source of carbon under climate change. We found that LPJ-GUESS successfully simulated GPP for the period 2003–2021, demonstrating a comparative performance with GPP derived from upscaled eddy covariance fluxes (R2 = 0.58, nRMSE = 14.2 %). The simulated NBP showed a larger interannual variation compared with flux data and other inversion products but could capture the timing of rainfall-driven carbon sink and source variations in 2015–2020. GPP would increase by 10.3–19.5 % under a medium emission scenario and 19.7–46.8 % under a high emission scenario. The mean probability of NSW acting as a carbon sink in the future showed a small decrease with a large uncertainty with >8 of the 27 climate models indicating an increased potential for carbon sink. These findings emphasize the significance of emission scenarios in shaping future carbon dynamics but also highlight considerable uncertainties stemming from different climate projections. Our study represents a baseline for understanding natural ecosystem dynamics and their key role in governing land carbon uptake and storage in Australia.

Incorporating burn heterogeneity with fuel load estimates may improve fire behaviour predictions in south-east Australian eucalypt forest

Background Simulations of fire spread are vital for operational fire management and strategic risk planning. Aims To quantify burn heterogeneity effects on post-fire fuel loads, and test whether modifying fuel load estimates based on the fire severity and patchiness of the last fire improves the accuracy of simulations of subsequent fires. Methods We (1) measured fine fuels in eucalypt forests in south-eastern Australia following fires of differing severity; (2) modified post-fire fuel accumulation estimates based on our results; and (3) ran different fire simulations for a case-study area which was subject to a planned hazard reduction burn followed by a wildfire shortly thereafter. Key results Increasing fire severity resulted in increased reduction in bark fuels. In contrast, surface and elevated fuels were reduced by similar amounts following both low-moderate and high-extreme fire severity. Accounting for burn heterogeneity, and fire severity effects on bark, improved the accuracy of fire spread for a case study fire. Conclusions Integration of burn heterogeneity into post-burn fuel load estimates may substantially improve fire behaviour predictions. Implications Without accounting for burn heterogeneity, patchy burns of low severity may mean that risk estimations are incorrect. This has implications for evaluating the cost-effectiveness of planned burn programmes.

Grain Yield and Quality Losses Caused by Tan Spot in Wheat Cultivars in Australia

Tan spot (TS), known in Australia as yellow leaf spot, is caused by the fungal pathogen Pyrenophora tritici-repentis, a major foliar disease of wheat. Four experiments were conducted between 2016 and 2017 in two different climatic zones of southeastern Australia to determine the impact of TS on grain yield and quality in six wheat cultivars with different resistance ratings. In each experiment, high and low TS disease scenarios were applied to each cultivar. Disease severity was assessed as either whole-plot percentage leaf area affected (%LAA) or top three leaf (flag to flag-2) %LAA. Whole-plot %LAA was analyzed using both repeated measurements and area under the disease progress curve (AUDPC). For whole-plot %LAA, the repeated measurements identified differences in epidemic progression at key growth stages not identified through AUDPC. Both AUDPC and end-of-season flag to flag-2 %LAA were negatively correlated with grain yield and screenings. Increased rainfall impacting disease development and number of rain days above 5 mm increased TS severity across both climatic zones. Cultivar resistance ratings influenced grain yield loss, with moderately resistant, moderately susceptible, and susceptible cultivars losing up to 6, 18, and 24% grain yield, respectively. High disease significantly increased screenings by up to 1, 3, and 5% for moderately resistant, moderately susceptible, and susceptible cultivars, respectively. This study demonstrated that TS can cause significant grain yield losses in southeastern Australia, and a minimum cultivar rating of moderate resistance to moderate susceptibility was required to prevent severe TS and associated grain yield and quality losses. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

The marine hydroids of south-eastern Australia (Cnidaria: Hydrozoa)

The marine hydroids (Cnidaria: Hydrozoa) of south-eastern Australia are reviewed and commonly-encountered species are described and illustrated. A brief introduction to hydroid morphology, ecology and study methods is also provided, along with an account of early investigations into hydroids and a brief history of Australian hydroid studies.

Correlated environmental DNA and electrofished estimates of relative biomass for golden perch, Macquaria ambigua

In response to the need to augment electrofishing surveys of golden perch, Macquaria ambigua (an important endemic freshwater fish in southeastern Australia), with other non-lethal survey methods, the utility of environmental DNA (eDNA) as an index of relative fish abundance/biomass was investigated. From three adjacent rivers, five sites in each were sampled for eDNA immediately before electrofishing during sequential years. Up to six individuals or 10 kg of electrofished golden perch (200–548 mm total length) were caught or observed site−1. Analyses of concurrent eDNA concentrations revealed no significant relationship with the relative abundance of golden perch, but there was with relative biomass—manifesting as increasing eDNA concentrations between 1.1 and approximately 5.5 kg biomass site−1, after which concentrations stabilized at greater biomasses. Future research warrants assessing the viability of sampling eDNA for spatio-temporally monitoring rivers where low biomasses of golden perch (1–5 kg site−1) are likely to occur.

Moisture thresholds for ignition vary between types of eucalypt forests across an aridity gradient

ContextQuantifying spatial and temporal variations in landscape flammability is important for implementing ecologically desirable prescribed burns and gauging the level of fire risk across a landscape. Yet there is a paucity of models that provide adequate spatial detail about landscape flammability for these purposes.ObjectivesOur aim was to quantify spatial and temporal variations in ignitability across a forested landscape. We asked: (1) How do fuel moisture and meteorological variables interact to affect ignitability? (2) Do fuel moisture thresholds for ignition vary across a gradient of forest types? (3) How does the spatial connectivity of ignitable fuel vary over time? (4) How could an ignitability model be used to inform fire management decision-making?MethodsWe conducted field-based ignition tests with flaming firebrands over three fire seasons. Ignitions were attempted across a range of moisture and meteorological conditions at 15 sites in eucalypt forest in south-eastern Australia. Structural equation modelling and generalized linear models were used to quantify relationships between ignitability, aridity, fuel moisture and weather.ResultsThe strongest predictors of ignitability were the moisture content of dead near surface fine fuel and in-forest vapour pressure deficit. Ignition thresholds for both varied across an aridity gradient. Dense forests (i.e., wet and damp eucalypt forests) needed drier fuel and drier in-forest atmospheric conditions to ignite than sparser forests (i.e., shrubby foothill forest).ConclusionOur modelling of ignitability could inform fire planning in south-eastern Australia and the methodology could be applied elsewhere to develop similar models for other regions. Days with consistently high ignitability across the landscape are more conducive to the development of large wildfires whereas days when ignitability is spatially variable are more suitable for prescribed burning.