River Red Gum Research Articles

Republication: In That Case

A state government’s forestry department has approved logging of the country’s largest River Red Gum forest. Government officials maintained that if logging the wetlands had been prohibited then the physical, social and economic health and well being of local community towns would be placed at risk. Environmental organizations faced the problem of convincing citizens and the state to change their behaviours in the ways necessary to protect the forest and vulnerable non-human animal species. In its moral evaluation of forest protection a major environmental organization relied on a system of calculation that emphasised economic outcomes and behaviour. The group commissioned an independent economic analysis that showed that logging the wetland forest was economically unjustified. In considering the future trajectory of development, the data showed that the potential returns from using the forest for tourism activities could stimulate substantial economic returns. The decision to use economic consequences as the central measure of moral concern, and treat the environment as an economic resource divided the environmental community. A network of critics argued that its defence of the Red Gum forest and its value leaned too heavily on the economics of forests. Economic values should not, they contended, be confused with morality and moral argument; economic values were not sufficient to construct a normative system of ethics. So long as appeals were based on economic values—and the environment was treated as if it were a tradable good—the resulting ethic would be inadequate to guarantee long-term sustainability of non-sentient entities such as wetlands and forests. Indeed, the organization had closed the door on any positive valuation of the environment. Bioethical Inquiry (2009) 6:523 DOI 10.1007/s11673-009-9196-8

River red gum and white cypress forests in south-western New South Wales, Australia: Ecological history and implications for conservation of grassy woodlands

On the western rivers and plains of southern New South Wales, relatively small areas of forests remain in a semi-natural condition and conservation reserves are lacking. Severe drought stress in recent decades after two centuries of European management has raised issues about how best to manage these forests and, if necessary, restore them. The region was explored between 1817 and 1836. Settlers, foresters and ecologists described changes as Aboriginal culture was displaced, domestic stock, feral animals and exotic plants were introduced, rabbits were controlled, rivers were regulated, and grazing was reduced. The Aboriginal ecosystems were different to the new red gum ( Eucalyptus camaldulensis) and white cypress ( Callitris columellaris) forests which lack resilience. Trees, saplings, fallen timber, shrubs and parasitic plants have accumulated in recently ‘undisturbed’ sites and these features are now promoted as benchmarks for conservation. However, human activity including watering, thinning, firewood collection, grazing and/or burning may aid restoration whereas non-intervention may allow continuing degradation. This historical ecology and recent palaeoecology provide insights to conserving grassy woodlands globally.

Injection of fresh river water into a saline floodplain aquifer in an attempt to improve the condition of river red gum (Eucalyptus camaldulensis Dehnh.)

AbstractThe delivery of environmental flows to riverine floodplains is often constrained by water scarcity and infrastructure. This means that areas of floodplain are unable to receive environmental water through mechanisms like dam release, weir pool surcharge and artificial flooding of low lying areas. This study trials aquifer injection as a method of providing environmental flows to areas of stressed river red gum (Eucalyptus camaldulensis) on the floodplain of the lower River Murray. The objective was to inject fresh river water at the top of the saline alluvial aquifer to reduce root zone salinity and improve the condition of E. camaldulensis. Localized radial freshening of ∼10 m was observed at each of the five injection wells when 4·9 Ml (megalitres) of river water was injected into the aquifer over 45 days. Injection was abandoned after 45 days due to aquifer and well clogging, and increases in groundwater head, which caused four of the five wells to breach the confining clay layer. The trial resulted in localized and short‐lived freshening of the groundwater, which reduced salinity in the associated capillary fringe. This did not result in an improvement in the tree condition as they lay beyond the lateral extent of the freshening and were unable to access the water. Solutions to technical issues such as aquifer clogging and well breaching, as well as a need to increase the lateral extent of freshening, are required before shallow aquifer injection can be recommended as a method of delivering environmental flows. Copyright © 2009 John Wiley & Sons, Ltd.

Effect of groundwater freshening on riparian vegetation water balance

AbstractIn the floodplains of the lower River Murray (Australia), riparian open forests and woodlands dominated by River Red Gum (Eucalyptus camaldulensis Dehn.), Black Box (E. largiflorens F. Muell.) and River Cooba (Acacia stenophylla A. Cunn. Ex Benth.) have been severely impacted by salinization and drought. The ‘Bookpurnong Experiment’ was developed to test the hypothesis that watertable lowering combined with groundwater freshening would reduce tree water stress and improve floodplain vegetation health. Tree water use and water stress following groundwater freshening were examined using measurements of sapflow, pre‐dawn leaf water potentials and stable isotope composition of xylem water. Water use and water stress varied markedly across the floodplain. The open mixed forest lining the bank of the River Murray, with access to fresh groundwater, used five times more groundwater over the measurement period and maintained greater canopy vigour than the open mixed woodland at inland sites. The River Cooba trees approximately 80 m from the river responded to watertable lowering of 0·65 m and to groundwater freshening by increasing transpiration. Black Box trees at the same site experienced reduced plant water stress, with no increase in transpiration. However, at a third site, approximately 170 m from the river, where the saline watertable (total dissolved solids = 36 300 mg l−1) was lowered by 1 m, no change in plant water stress or pattern of plant water use was observed. These results indicate that groundwater lowering combined with groundwater freshening can provide an accessible water source for water‐stressed floodplain vegetation. Copyright © 2009 John Wiley & Sons, Ltd.

Effectiveness of artificial watering of a semi‐arid saline wetland for managing riparian vegetation health

AbstractEucalyptus camaldulensis Denh. (River Red Gum) and E. largiflorens F.Muell. (Black Box), the dominant riparian tree species that fringe the wetlands of the lower River Murray in south‐eastern Australia, are in severe decline. Artificial watering has been used as an emergency management measure in an effort to save these significant ecological assets. This study quantified the extent of lateral recharge and the tree response to artificial watering in a semi‐arid saline floodplain wetland. The extent of the vegetation response was linked to the extent of groundwater freshening from bank recharge, which was controlled by floodplain hydraulic conductivity. A two‐ to five‐fold increase in plant water potential and a three‐ to six‐fold increase in tree water use were observed in the 3 to 4 months after watering. Artificial watering is an effective floodplain management tool to preserve significant ecological assets during periods of low flow. It can be used to manage one‐third of E. camaldulensis communities on the Chowilla floodplain that grow within the estimated extent of bank recharge from wetland watering. However, water balance calculations indicate that the water stored as bank recharge would be discharged as evapotranspiration within three years, which means that regular artificial watering is required during periods of low flow to maintain high‐value floodplain sites. Copyright © 2009 John Wiley & Sons, Ltd.

Spatial Assessment of Water Use in an Environmentally Sensitive Wetland

Wetlands are among the most valuable ecosystems in the world and are crucial in supporting biodiversity. They also provide space for storing surface waters, where intense biological processing occurs that helps improve water quality. Human activities, particularly irrigated agriculture and urban developments instigating water diversions from rivers, have altered the hydrology of most wetlands. The Lower Murrumbidgee wetland, located in the Murrumbidgee River Catchment, is an example and is one of the significant wetlands across the Murray Darling Basin of Australia. Historic estimates show the volumes of water ranged from none in dry years to about 300 to 400 GL (1 GL = 10(9) L) in an average and wet year, respectively. The flows reaching the Lower Murrumbidgee wetland have been drastically reduced by at least 60% because of the upstream diversions introduced during the last century. These reductions have adversely affected the health of natural vegetation and agricultural crops in the Lower Murrumbidgee floodplain. This article presents the results of the quantification of total water consumption of various land uses in the Lower Murrumbidgee floodplain using the remote sensing-based Surface Energy Balance Algorithm for Land (SEBAL) modeling approach. The spatial analysis of actual evapotranspiration (ETa) shows that ETa rates are the highest (13-26%) for the red gum (Eucalyptus camaldulensis) forests both in summer and winter days. However, in terms of total ETa volume, lignum (Muehlenbeckia florulenta) constitutes the most significant part, which is around 14-30% of the total ETa volume for the area. Actual evapotranspiration from winter cereal cropping areas following the summer ponding is the third highest consumer of water after the river red gum and lignum. Actual evapotranspiration from the fallow land is also significant, representing 5-28% of total ETa from the region. In view of the extent of the unaccounted flows in the overall water balance of the system, there is a need to upgrade measuring and reporting infrastructure by strengthening the institutional and management arrangements to better gauge the efficiency of environmental and consumptive water use. The state-of-the-art technology of remote sensing-based SEBAL modeling proved to have potential for measuring actual water use with reliable accuracy and can be used for assessing the environmental and productive use of water from wetlands in other regions of Australia.

Greenhouse Gas Emissions Embodied in Reinforced Concrete and Timber Railway Sleepers

In Australia, there are currently two main materials used for railway sleepers: timber (river red gum, a species of eucalypt) and reinforced concrete. Within the state of Victoria alone, there are currently seven million railway sleepers that make up the rail network. It is estimated that around two million sleepers, or 29%, are presently required to replace timber sleepers and upgrade the entire network, for which there are significant environmental implications, such as the emission of greenhouse gases. These emissions are mainly as a result of the energy and other resources required or "embodied" through the sleeper manufacture, including those associated with harvesting timber and mining raw materials for manufacturing cement. Where alternatives are readily available, it is important that the environmental impacts of the various choices are assessed, ensuring that these impacts are minimized. This study aimed to assess the life cycle greenhouse gas emissions associated with timber and reinforced concrete railway sleepers and showed that the life cycle emissions of reinforced concrete sleepers were up to six times less than the emissions associated with timber sleepers. Taking the potential errors associated with this type of assessment into account, there appearsto be a significant advantage in using reinforced concrete sleepers, in terms of reducing the life cycle emissions associated with the provision of railway sleepers.

Decay state and inundation history control assemblage structure of log‐dwelling invertebrates in floodplain forests

AbstractFallen timber (logs, large boughs) is recognized as having high ecological significance on forest floors. In floodplain forests, fallen timber potentially has even higher value for supporting biodiversity than upland forests because distinct faunal elements use the timber in the flooded and unflooded conditions. Invertebrates were sampled in logs of the river red gum (Eucalyptus camaldulensis Dehnh.) that had been inundated 1 year earlier and compared with invertebrates in logs that had not been inundated for many years. The invertebrate fauna in river red gum logs was relatively depauperate, probably reflecting the variable, sub‐humid conditions on the floodplain. The abundance and taxon richness of invertebrates was highest in logs with greater structural complexity and heterogeneity due to extensive decay. Recent inundation slightly reduced taxon richness. The succession of log‐dwelling invertebrates was tracked though transitions between terrestrial fauna and aquatic fauna in a spring/summer flood cycle. Transition between the two faunae was rapid. Logs were colonized by aquatic invertebrates within 2 weeks of immersion by floodwaters and recolonized by terrestrial invertebrates within 4 weeks of emersion. This faunal dynamism highlights the need to consider the entire flood cycle in decisions about the management of fallen timber on floodplains for biodiversity. Copyright © 2009 John Wiley & Sons, Ltd.

An investigation of the hydrological requirements of River Red Gum (Eucalyptus camaldulensis) Forest, using Classification and Regression Tree modelling

AbstractRiver Red Gum (Eucalyptus camaldulensis) is widely distributed throughout many water courses and floodplains within inland Australia. In recent years, accelerated decline of River Red Gum condition has been observed in many locations, and field observations of the degradation are consistent with the reduction of flooding. However, there are few publications that quantitatively investigate the relationships between River Red Gum condition and flooding history. We applied Classification and Regression Tree (CART) to model the minimum flooding requirement of River Red Gum forest/woodland in Yanga National Park, located on the Lower Murrumbidgee Floodplain, southeast Australia, using crown conditions derived from historical aerial photographs spanning more than 40 years. The model produced has a moderate reliability with an overall accuracy of 64·1% and a Kappa index of 0·543. The model brings in important insights about the relationship between River Red Gum community type, flood frequency and flood duration. Our results demonstrated that (1) CART analysis is a simple yet powerful technique with significant potential for application in river and environmental flow management; (2) River Red Gum communities on the Lower Murrumbidgee Floodplain require periodic inundation (3–5 years) for a duration of up to 64 days to be in moderate to good conditions; (3) Although the crown conditions of different community types displayed similar degradation trends, they have distinct flooding requirements; and (4) The River Red Gum community in Yanga National Park may be managed as hydrological units given limited environmental water allocations. Copyright © 2009 John Wiley & Sons, Ltd.

Does wood type influence the colonisation of this habitat by macroinvertebrates in large lowland rivers?

Submerged woody habitat provides the major structure around which ecological processes operate in many lowland rivers. Colonisation by macroinvertebrates was measured in a south-eastern Australian river over a 32-day period in an experiment testing the hypothesis that wood type influences the invertebrate assemblage structure. The wood types were green wood, dry wood, and dry but previously waterlogged wood. All wood used was river red gum (Eucalyptus camaldulensis). Macroinvertebrates colonised previously waterlogged wood more rapidly than green or dry wood. The assemblage structure varied significantly over the sampling period, with copepods and cladocerans numerically dominating the assemblage during the first few days after the introduction of the wood. The assemblage became more diverse through time and was numerically dominated by dipterans, ephemeropterans and trichopterans. The results indicate that there was little difference in the time taken for macroinvertebrate colonisation after wood introduction when using either green or dry wood. This has implications for large-scale restoration projects, where green wood is likely to be a more readily available option for reintroduction than dry wood.

Utilizing airborne electromagnetic data to map groundwater salinity and salt store at Chowilla, SA

The Chowilla floodplain in South Australia is part of the Bookmark Biosphere Reserve with wetlands supporting a wide range of plants and animals, and has provided recreational opportunities to the general public (MDBC, 2006). However, the threats from saline groundwater and salt accumulation at the surface, combined with the overall low rainfall and the lack of natural flooding events in the recent past, have had a negative consequence for vegetation health, especially the river red gums. Information on the spatial patterns of groundwater salinity and the near surface (top 15 m) salt stores in the floodplain is integral to our understanding of floodplain hydrological processes that may be active in the Lower Murray Basin of Australia. This information can be used to help develop appropriate remedial activities for the management of ecologically important wetlands and in particular assist in the maintenance of a healthy vegetation community. A helicopter-borne electromagnetic (HEM) survey was conducted across the floodplain in conjunction with a validation drilling and borehole geophysical logging program. Based on the laboratory results from cored sediments and their pore fluids, we report on the salinity and salt store models calculated from the inverted HEM data.

Development of Marine Borer Natural Durability Classes for Timber in Australia

AbstractThe latest revision of Australian Standard 5604 on natural durability includes marine borer resistance ratings for many of its listed timbers. This paper describes the trials and reasoning behind the development of the marine borer resistance classes. Fundamental to this work was a small specimen test of 25 untreated hardwood timbers exposed at three marine sites:Port Stephens in NSWThe Victorian sites of Williamstown and Geelong Williamstown had greater marine borer hazard than Geelong, perhaps due to its calmer waters. The most durable species in the trial were turpentine (Syncarpia glomulifera), iroko (Chlorophora excelsa), grey gum (Eucalyptus propinqua), brush box (Lophostemon confertus), red ironbark (E. sideroxylon), New England blackbutt (E. andrewsii), white mahogany (E. acmenoides) and river red gum (E. camaldulensis). Pinus radiata treated to 2.4% m/m CCA was the best performing timber. Information for additional timbers was obtained from an earlier aquaria trial, and trials conducted i...

Short-term response of nutrients, carbon and planktonic microbial communities to floodplain wetland inundation

Environmental flows were released to the Macquarie Marshes (~210,000 ha) in north-west NSW of Australia between October and December 2005, inundating an estimated 24,600 ha of floodplain area. According to the flood pulse concept, the marsh floodplains would have stored large amounts of nutrients and carbon during dry antecedent conditions, which would be released into the overlaying flood water. Field studies were conducted in mid-December 2005 at two sites, one on open floodplain woodland with a sparse canopy of River Red Gum and ground cover dominated by saltbushes and the other on open floodplain with black roly-poly. At each site, nutrients, dissolved organic carbon (DOC), planktonic bacteria and phytoplankton were monitored daily for a 6-day period from the overlaying water of a floodplain inundated by the environmental water release. Those in mesocosms deployed in situ, containing marsh floodplain sediments that had been inundated artificially, were also monitored. The mesocosm results from both the sites showed that release of nitrogen was rapid, attaining mean concentrations of total nitrogen of 3.7–14.8 mg l−1, followed by more gradual increases in total phosphorus (mean concentrations 0.6–0.8 mg l−1) and DOC (26.1–50.2 mg l−1) within the 6-day experiment; planktonic microbial communities developed concomitantly with the increasing concentrations of nutrients and DOC, attaining mean densities of (6.0–6.9) × 106 cells ml−1 of planktonic bacteria and (80.7–81.4) × 103 cells ml−1 of phytoplankton; and for each site the overall measured condition of the mesocosm tended to approach that of the Marshes, over the course of the 6-day experiment. The present study (both observational and experimental) demonstrates that the floodplain sediments in the Marshes, which have been exposed to dry antecedent conditions, release nutrients and carbon to the overlaying flood water following inundation. These resources are thought to have been stored during the dry antecedent phase in accord with the flood pulse concept. Based on the mesocosm experiment, the released nutrients and carbon are in turn most likely to be used by microbial components, such as bacteria and algae, which develop within days of inundation of the floodplain sediments. Thus, environmental flow release provides potential for floodplains to attain a series of ecological responses including initial release of inorganic nutrients and dissolved organic matter and increase in planktonic bacteria and phytoplankton.

A comparison of phosphorus and DOC leachates from different types of leaf litter in an urban environment

Summary1. The leaching rates of filterable reactive phosphorus (FRP) and dissolved organic carbon (DOC) from five leaf litter types commonly occurring in urban environments in Mediterranean regions of Southern Australia were compared. The relative composition, bioavailability and oxygen demand of this DOC were also assessed. Four tree species were assessed, including the native river red gum (Eucalyptus camaldulensis) and three introduced deciduous species, the English elm (Ulmus procera), London plane (Platanus acerifolia) and white poplar (Populus alba). Grass cuttings (mixed species) were selected as a common garden waste.2. Except for English elm, the majority of FRP and DOC was released within the first 48 h. Grass cuttings released the highest amount of FRP with white poplar releasing the most DOC. Species that released relatively high amounts of DOC (white poplar, English elm, river red gum) released relatively low amounts of FRP. Conversely, species that released relatively low amounts of DOC (grass cuttings and London plane) tended to release relatively high amounts of FRP.3. Analysis of DOC composition, combined with the differing oxygen demand and DOC depletion curves, demonstrated that there were substantial differences in the DOC leached from the leaf litter of the different species. Biochemical oxygen demand and the biodegradability of the DOC was positively correlated with the proportion of hydrophilic and hydrophobic acids present in the leachate.4. These results demonstrate that simple measurements of nutrient release per gram of leaf litter would be insufficient to predict the ecological impact on receiving waters resulting from changes in dominant vegetation. Furthermore, the use of traps to prevent particulate leaf material from entering streams may have limited potential for reducing the load of dissolved nutrients. We conclude that any changes to vegetation type which substantially alter the timing of leaf fall or the composition of leaf leachates should be avoided.

DEFINING AND MANAGING ENVIRONMENTAL FLOWS: INPUTS FROM SOCIETY

Two key questions regarding the management of Australia's riverine environments are addressed: how much water should be allocated for environmental flows; and how should water entitlements for environmental flows be acquired and managed. First, an application of the choice modelling technique in the context of River Red Gum forests along the River Murray is used to demonstrate how the marginal values of water for the environment can be estimated for comparison against prices paid by extractive users of water. Second, mechanisms in the public and private sectors for the purchase of environmental water are contrasted.

Phenotype and gene flow in a marsupial (Antechinus flavipes) in contrasting habitats

Ecological factors are important drivers of phenotypic divergence, which may lead to incipient speciation. A variety of habitats should be preserved to maintain evolutionary potential. We used the marsupial, the yellow-footed antechinus (Antechinus flavipes) as a model species for investigating phenotypic differentiation between animals inhabiting two habitat types in south-eastern Australia: flood-plain river red gum and box–ironbark forests. All tested phenotypic characteristics varied between years at the same sites and therefore were not useful for investigating morphological specialization that may lead to speciation. Males generally were significantly heavier when antechinus densities were lower, but exceptions were found, possibly related to food availability. Teat-number variation recently has been shown to be associated with habitat specialization and incipient speciation within Antechinus agilis. We investigated genetic differentiation associated with this trait in A. flavipes. Population genetic analyses of microsatellite genotypes and mitochondrial DNA haplotypes revealed that sympatric 12-, 13- and 14-teat females in Chiltern forest were part of one freely interbreeding population. Our parentage analyses found two cases where 13-teat mothers produced 12-teat daughters. This suggests either plasticity or paternal genetic influence on the offspring's teat-number phenotype. Laboratory matings may be required to resolve the extent to which teat number is heritable in A. flavipes.

The role of seedbanks in restoration of floodplain woodlands

AbstractPlant communities on the River Murray floodplain, South Australia, are degraded by flow regulation and salinization, with up to 95% of eucalypt trees being dead or dying from water stress. This paper describes the floodplain seed bank and its capacity to respond to floods or managed ‘environmental flows’. The soil seed bank contained mainly annual native species, particularly chenopods, whereas the dominant trees, river red gum and black box (Myrtaceae: Eucalyptus camaldulensis, E. largiflorens), retained most of their seeds in a canopy seed bank (‘serotiny’). In healthy trees, seed release peaked in summer (December– February for river red gum, October–March for black box), but variable volumes suggested cyclical patterns in seed crops. Seed release, viability and germination rates did not appear to limit recruitment. In water‐stressed trees, however, seed release was up to nine‐fold less. Germination requires water from floods or local rainfall. Flow regulation has reduced flood frequencies and delayed timing, so that germination now is likely to be followed by relatively hot, dry conditions (summer). Following managed watering events, seeds accumulated in high‐water strandlines, where they germinated readily under a mulch of organic litter, but survival was limited. The importance of local rainfall as a complementary water source was demonstrated, and survival rates were higher for rain‐triggered germinants, compared to seedlings germinating in strandlines created by managed watering. Seedling survival would be greater if environmental flows were delivered to complement local rainfall or to extend the effect of short flood events. Copyright © 2008 John Wiley & Sons, Ltd.

Responses of a Carnivorous Marsupial (Antechinus flavipes) to Local Habitat Factors in Two Forest Types

Abstract Ecosystems around the world have been degraded or destroyed by human activities, including regulation of river flows, clearance of vegetation, and removal of fallen timber. In southeastern Australia much of the original vegetation was converted to farmland. Remaining forests such as hilly box–ironbark and floodplain river red gum (Eucalyptus camaldulensis) are mostly regrowth. The yellow-footed antechinus (Antechinus flavipes) inhabits both types of forests and is the only small, native, carnivorous mammal on most floodplains in southeastern Australia. In this region, frequency of flooding has been reduced by regulation of river flows, which has led to decline in conditions favorable for flood-adapted terrestrial and aquatic organisms. Here, we compared numbers of A. flavipes in box–ironbark forests, and in river red gum forests that were deprived of floods; partially inundated with environmental flows; flooded naturally; and watered in large, artificial floods. We found that abundance of A. flav...

Photodegradation, interaction with iron oxides and bioavailability of dissolved organic matter from forested floodplain sources

Photochemical degradation of dissolved organic matter (DOM) can influence food webs by altering the availability of carbon to microbial communities, and may be particularly important following periods of high DOM input (e.g. flooding of forested floodplains). Iron oxides can facilitate these reactions, but their influence on subsequent organic products is poorly understood. Degradation experiments with billabong (= oxbow lake) water and river red gum (Eucalyptus camaldulensis) leaf leachate were conducted to assess the importance of these reactions in floodplain systems. Photochemical degradation of DOM in sunlight-irradiated quartz tubes (with and without amorphous iron oxide) was studied using gas chromatography and UV-visible spectroscopy. Photochemical reactions generated gaseous products and small organic acids. Bioavailability of billabong DOM increased following irradiation, whereas that of leaf leachate was not significantly altered. Fluorescence excitation-emission spectra suggested that the humic component of billabong organic matter was particularly susceptible to degradation, and the source of DOM influenced the changes observed. The addition of amorphous iron oxide increased rates of photochemical degradation of leachate and billabong DOM. The importance of photochemical reactions to aquatic systems will depend on the source of the DOM and its starting bioavailability, whereas inputs of freshly formed iron oxides will accelerate the processes.

A survey of large forest owls in State Forests of south-western New South Wales, Australia

A survey of large forest owls was conducted at 261 survey points within State forests of south-western New South Wales, and an additional 10 sites within the Wagga Wagga Local Government Area in May-June 2004. A combination of listening, playback of recorded calls and spotlighting was used. Barking Owls Ninox connivens were recorded primarily from River Red Gum Eucalyptus camaldulensis vegetation associations (n = 8) and once from mixed Western Grey Box Eucalyptus microcarpa / River Red Gum association. No records of the Powerful Owl N. strenua or the Masked Owl Tyto novaehollandiae were obtained. Four other nocturnal bird species were recorded during the surveys: Southern Boobook N. novaeseelandiae (n = 74), Barn Owl T. alba (n = 61), Australian Owlet-nightjar Aegotheles cristatus (n = 46) and Tawny Frogmouth Podargus strigoides (n = 8). In light of the low frequency of Barking Owls recorded in this and other recent surveys, consideration needs to be given to upgrading the classification of the Barking O...