Invasive exotic plant species change biotic plant-soil feedback but the effects on abiotic plant-soil feedback is less well understood. This study investigates biotic and abiotic legacies along an invasion gradient on germination and growth of several native and one exotic species in a Temperate Native Grassland. Topsoil cores were extracted from inter-tussock spaces in seven grassland sites varying in exotic plant species richness. Half the cores were sterilised, and to half the live- and half the sterile-cores, a microbial wash was added. Five native forbs and one invasive exotic grass were sown apart in each core. Non-destructive and destructive measurements were made. Removal of soil biota by sterilisation improved germination of two native forbs and the microbial wash influenced germination of two species but not seedling growth of any species. Growth of native forbs in sterile cores increased along the invasion gradient, whereas growth of native forbs in live cores was the same along the gradient. In the live cores the increases in the abiotic plant-soil feedback were offset by reduction in the biotic plant-soil feedback. Biotic plant-soil feedback negatively and similarly affected growth of the invasive grass species at all sites. This study demonstrates that both biotic and abiotic plant-soil feedback in native grassland continue to be changed by ongoing invasion and the changes have a minor influence on germination and a consistent but opposing influence on growth of native species.

Abstract Nitrogen (N) availability regulates the productivity of terrestrial plants and the ecological services they provide. There is evidence for both increasing and decreasing plant N availability in different biomes, but the data are fragmentary. How plant N availability responds to climate change, N deposition and increasing atmospheric CO2 concentration remains a major uncertainty in the projection of the terrestrial carbon sink. The foliar N stable isotope ratio (δ15N) is an indicator of plant N availability but its usefulness to infer long-term global patterns has been limited by data scarcity. Combining ground-based δ15N and Landsat spectra, we derived annual global maps of Landsat-based foliar δ15N as estimates of plant N availability during 1984-2022. We found significant decreases in plant N availability for 44% and increases in 16% of vegetated Earth’s surface with large spatial heterogeneity. Plant N availability declined in woody-dominated ecosystems but increased in herbaceous-dominated ones. These δ15N trends were consistently and negatively correlated with the trends of Normalised-Difference-Vegetation-Index as they varied across ecosystems, suggesting increasing plant cover could have led to decreasing plant N availability. Our results indicate possible future reductions in plant N availability in many terrestrial ecosystems and provide a useful way to monitor those changes globally.

Context Kandosol soils are widely distributed in Australia and are frequently used for irrigated cropping. However, under intensive irrigated cropping they can degrade due to poor structural stability where surface soil aggregates break down as a result of slaking and dispersion; the slaking is associated with low soil organic carbon levels (<1.0 g/100 g) on these frequently cultivated soils, and the dispersion is related to the moderate level of exchangeable sodium percentage (ESP) combined with low electrical conductivity (EC) levels in the soil solution. Aims To investigate the effects of applied gypsum (0, 2 and 10 t/ha), irrigation with water of low EC (0.5 dS/m) and low sodium adsorption ratio (≤2), and two tillage practices, i.e. conventional tillage (CT) and reduced tillage (RT), on the structure of a marginally sodic (ESP 6) Yellow Kandosol soil. Methods The experiment was conducted at Carnarvon, Western Australia. Key results After 2 years the soil EC (1:5) and ESP levels were significantly reduced on all plots at the three gypsum rates. The three gypsum rates also significantly affected exchangeable calcium (Ca) and magnesium (Mg) and soluble Ca and Mg levels, as well as pH and dispersion values. Micromorphological examination indicated less dispersed clay with gypsum application. Conclusions The EC results indicated that the soil will require frequent re-application of gypsum to maintain electrolyte levels and prevent dispersion. With some of the variables, RT compared to CT demonstrated greater through-flow, which was attributed to the presence of more macropores in RT. Implications A change in management from semi-arid chenopod shrublands used for grazing to intensely cultivated horticulture will require careful consideration of factors causing soil structural instability.

The extent and abundance of Rytidosperma Steud. species in mixed woodland, forest and derived grassland was examined over a 15-year period following removal of long-term sheep grazing. Ground-layer vegetation in 73 permanent plots was surveyed five times between 2005 and 2020 in a 50-ha paddock on the southern tablelands of New South Wales. Sites were stratified over the slope positions and micro-habitats represented at the site. Of the 12 Rytidosperma species recorded, only R. pallidum was morphologically and ecologically distinct in the field. The remaining 11 species, termed `cryptic Rytidosperma', were assessed using a novel sampling method developed for this group. Rytidosperma pallida was the only species strongly associated with sclerophyll forest habitat. The 11 other species varied in their habitat preferences but, as a group, were most dominant and persistent on upper slopes. Over the 15 years, the relative abundance of R. pilosum, R. erianthum, R. monticola, R. carphoides and R. caespitosum declined as annual exotics, native sub-shrubs and low-palatability graminoids became more dominant. But only one species (R. pilosum) significantly declined in overall frequency of presence (constancy) in the plots. The changes observed suggest that when pastoral land is converted to conservation management, reduced grazing pressure could affect the abundance of Rytidosperma species important to other species, such as the threatened moth Synemon plana.

Summary A long‐term study of disease dynamics caused by the rust Uromyces valerianae in 31 discrete populations of Valeriana salina provides a rare opportunity to explore extended temporal patterns in the epidemiology of a natural host–pathogen metapopulation. Over a 28‐year period, pathogen population dynamics varied across the metapopulation with disease incidence (presence/absence), prevalence (% plants infected) and severity (% leaf area covered by lesions) all showing strong population and year effects, indicative of heterogeneity among years and host populations in the suitability of conditions for the pathogen. Disease incidence within individual host populations was significantly affected by host population size, disease prevalence the previous year and the proximity of neighbouring populations infected in the current year. After accounting for these variables there was still a marked temporal component with winter sea level having a significant effect; as did summer rainfall in the second part of the study period (1997–2011). Disease prevalence was also effected by host population size and disease prevalence in the previous year. However, it was less affected by spatial aspects of disease spread than was disease incidence. Winter sea level and June rainfall significantly affected disease prevalence. Assessment of disease impact on plant performance found strong variation in disease severity associated with the aspect and positioning of host populations. Plants growing in lower disease environments produced significantly more seeds than those growing in high disease sites. Significant variation in reaction to infection by U. valerianae was detected among plants within four populations and between these different populations. Synthesis. The epidemiology of Uromyces valerianae was highly influenced by host population size, previous disease and distance. After accounting for these factors, there was a clear temporal signal of change in disease incidence linked to winter sea level and summer rainfall. These patterns reinforce the importance of considering interactions in multiple populations over long periods of time in order to obtain a clear picture of the variability in disease‐induced selection pressures across time and space. The behaviour of the pathogen fitted that predicted for a metapopulation with considerable asynchrony in epidemiological patterns among demes.

In Figure 6 (page 2583), panel A is incorrect. The corrected panel is shown below; panels B and C were correct in the original paper. Australian milk fat—Seasonal and regional variation of melting propertiesJournal of Dairy ScienceVol. 99Issue 4PreviewThe solid fat content and dropping point of milk fat obtained over 2 yr and from 19 bulk milk production sites across Australia were characterized. Solid fat content at 5°C and 20°C, respectively, ranged between 49.9 and 66.1% and between 14.6 and 29.6% across all sites. Dropping point ranged between 30.5 and 35.4°C. The dropping point did not correlate with solid fat content at lower temperatures across several sites, indicating that it is not an accurate or useful measure of functionality at temperatures of 15°C or below. Full-Text PDF Open Archive

The solid fat content and dropping point of milk fat obtained over 2 yr and from 19 bulk milk production sites across Australia were characterized. Solid fat content at 5 °C and 20 °C, respectively, ranged between 49.9 and 66.1% and between 14.6 and 29.6% across all sites. Dropping point ranged between 30.5 and 35.4 °C. The dropping point did not correlate with solid fat content at lower temperatures across several sites, indicating that it is not an accurate or useful measure of functionality at temperatures of 15 °C or below. Although at times, considerable variation was observed in milk fat melting properties between sites located in similar geographic regions, statistical analysis by means of boxplots and multidimensional scaling revealed broad similarities within regions over the 24 mo. Multidimensional scaling also revealed similarities between some quite distant and diverse regions (e.g., Queensland and South Australia with constant and seasonal production, respectively). These analyses were used to make 5 groups from the 19 sites to describe seasonal melting properties. The groups with sites in west Victoria, southeast Victoria, and Tasmania showed the largest seasonal variation and range of values, with peaks and lows in southeast Victoria and Tasmania occurring up to 3 mo later than in west Victoria. The group with sites in New South Wales, Queensland, and South Australia had the least variation and range of values, which were relatively high throughout. The group with Western Australian sites showed medium levels of variation but distinct seasonal patterns, with solids fats typically below and dropping points higher than the national average. The Victorian group's lows in dropping point occurred about 2 mo later than did the low values of solid fat content. No single factor stood out as determining the variation in melting properties.

Humans are rapidly altering thermal landscapes, so a central challenge to organismal ecologists is to better understand the thermal niches of ectotherms. However, there is much disagreement over how we should go about this. Some ecologists assume that a statistical model of abundance as a function of habitat temperature provides a sufficient approximation of the thermal niche, but ecophysiologists have shown that the relationship between fitness and temperature can be complicated, and have stressed the need to elucidate the causal mechanisms underlying the response of species to thermal change. Towards this end, we studied the distribution of two crayfishes, Euastacus woiwuru and Euastacus armatus, along an altitudinal gradient, and for both species conducted experiments to determine the temperature-dependence of: (1) aerobic scope (the difference between maximum and basal metabolic rate; purported to be a proxy of the thermal niche); and (2) burst locomotor performance (primarily fuelled using anaerobic pathways). E. woiwuru occupied cooler habitats than E. armatus, but we found no difference in aerobic scope between these species. In contrast, locomotor performance curves differed significantly and strongly between species, with peak locomotor performances of E. woiwuru and E. armatus occurring at ~10 and ~18 °C, respectively. Crayfish from different thermal landscapes may have similar aerobic thermal performance curves but different anaerobic thermal performance curves. Our results support a growing body of literature implying different components of ectotherm fitness have different thermal performance curves, and further challenge our understanding of the ecology and evolution of thermal niches.

Agricultural landscapes can be characterized as a mosaic of habitat patches interspersed with hostile matrix, or as a gradient of patches ranging from suitable to unsuitable for different species. Arthropods moving through these landscapes encounter a range of edges, with different permeability. Patches of native vegetation in these landscapes may support natural enemies of crop pests by providing alternate hosts for parasitic wasps and/or acting as a source for predatory insects. We test this by quantifying species interactions and measuring movement across different edge-types. A high diversity of parasitoid species used hosts in the native vegetation patches, however we recorded few instances of the same parasitoid species using hosts in both the native vegetation and the crop (canola). However, we did find overall greater densities of parasitoids moving from native vegetation into the crop. Of the parasitoid groups examined, parasitoids of aphids (Braconidae: Aphidiinae) frequently moved from native vegetation into canola. In contrast, parasitoids of caterpillars (Braconidae: Microgastrinae) moved commonly from cereal fields into canola. Late season samples showed both aphids and parasitoids moving frequently out of native vegetation, in contrast predators moved less commonly from native vegetation (across the whole season). The season-long net advantage or disadvantage of native vegetation for pest control services is therefore difficult to evaluate. It appears that the different edge-types alter movement patterns of natural enemies more so than herbivorous pest species, and this may impact pest control services.

A study of the cholesterol content and fatty acid composition of fresh retail Australian pork was undertaken to determine whether new breeding, feeding and processing methods had resulted in any compositional changes in fresh pork in the market place since surveys undertaken in previous decades. Samples of 13 popular pork cuts were purchased from randomly selected supermarkets and butchers’ stores in urban areas across the socioeconomic scale in three States of Australia, and analysed, separable fat and separable lean, in late 2005 and early 2006. Variability was low across States for saturated and monounsaturated fatty acids, but more pronounced for polyunsaturated acids. The separable lean portions of all pork cuts contained levels of n-3 fatty acids and conjugated linoleic acid (C18:1c9t11) in measurable but not nutritionally claimable amounts, whilst total trans fatty acid levels were very low. There appeared to be some differences in fatty acid composition across States that may have resulted from feeding method. Cholesterol contents were similar to levels in the 80s and 90s for separable lean pork tissue, but presently are lower for separable fat tissue than for separable lean.

We measure the performance improvement that force feedback can provide in a virtual environment, through three experiments with, and without the assistance of haptic guidance. Performance measurements were undertaken with haptic, visual and auditory feedback alternatives. The first task investigated the use of haptic guidance mimicking reality, in the form of a simulated touchable surface of an object. The second investigated haptic guidance which waxed and waned as the user violated program rules by varying amounts. The third experiment investigated whether this latter artificial guidance would inhibit the user's free will by taking control out of their hands. The results showed that a significant improvement in both accuracy and speed was achieved by the introduction of haptics in all experiments. It also found that the haptic guidance did not take control away from the user and that they had significantly more control than with conventional warning methods. These experiments were not aimed at learning, or retention of skill, but on using haptics as an aid to improve performance during a task.

Survival in an experimental disease challenge test or to natural disease challenge is utilised by aquaculture breeding programs as the selection trait for disease resistance. However, these trials are expensive and do not offer the ability to retest animals. The aim of this study was therefore to estimate genetic parameters for resistance to amoebic gill disease (AGD) measured by a categorical scale of gross gill signs (“gill score”) and survival in a field challenge in order to establish whether gill score provides adequate measurement of genetic variation for AGD resistance compared to an AGD challenge survival. A total of 1504 Atlantic salmon smolt, representing 140 full-sib families, was transferred to a marine site in SE Tasmania. The gills were assessed by gill score prior to freshwater bathing on the first two rounds of infection, and then the disease was allowed to develop until mortalities began. Gill score was reassessed after 50days and mortality was allowed to continue until it had reached a plateau at 100days. The overall survival rate was 32.3% but varied from 0% to 69% between families. Estimated narrow sense heritability for AGD resistance assessed by gill score varied between 0.23 and 0.48 over the three rounds of infection. Heritability of AGD survival challenge was 0.40 to 0.49 on the observed scale using binary and longitudinal measures. Gill score and survival showed a weak (−0.19) to strong (−0.96) negative genetic correlation which improved when assessed closer to the survival challenge. Estimated genetic gains by selection of the top one hundred estimated breeding values for gill score indicated that up to 82% of the expected gain in survival can be achieved when compared to estimated gain by selection upon survival (days to death), thus minimising selection costs and improving fish welfare whilst allowing repeat measures to be made. The results show that genetic variation of gill score at the early onset of losses closely compares with survival results if the disease is allowed to progress without subsequent freshwater bathing. Gill score may therefore be utilised as a nondestructive and repeatable selection trait for breeding Atlantic salmon with greater resistance to AGD.

A study of the nutrient composition of Australian pork was undertaken to determine whether new breeding, feeding and processing methods had resulted in any changes in pork samples in the market place since surveys undertaken in previous decades. Samples of 13 popular pork cuts were purchased from randomly selected supermarkets and butchers’ stores in urban areas across the socioeconomic scale in three States of Australia, and analysed, raw and cooked, separable fat and separable lean, for nutrient composition (proximate components, minerals, vitamins) in late 2005 and early 2006. Results showed that present-day pork separable lean tissue continues to be low in fat, in line with stated objectives of practices implemented by the industry in Australia. Pork remains a good source of protein and of thiamin and other water-soluble vitamins, the latter being detected at nutritionally significant levels in fat tissue as well as lean; folate was detected in most samples, lean and fat portions. Iron content appeared to be slightly lower than in previous decades.

Amoebic gill disease (AGD) of Atlantic salmon in Tasmania is proactively treated by freshwater bathing when gross gill assessment (‘gill score’) indicates a moderate level of disease in a cage population. This generally ensures that few fish are exposed to severe disease symptoms and that few die, but also means that a proportion of the population shows little gross evidence of AGD. Individuals exhibiting few AGD symptoms at bath may be more resistant, or simply reflect an uneven spread of the disease through the population. This study had three main aims, firstly, to determine whether all fish in a cage population eventually require freshwater treatment after first infection; secondly, to ascertain whether there is any evidence of development of resistance to AGD; and thirdly, to see if there is a relationship between the level of proliferative gill reaction to the parasite, assessed by gill score, and time to mortality when the disease is left untreated. These aims were achieved by following gill score trajectories of individual fish through three rounds of natural AGD infection and relating these to the eventual fate of the fish in a natural AGD survival challenge after the second freshwater bath. There was no evidence of complete innate resistance to AGD as each fish eventually required a first freshwater bath. There was no relationship between the rate of first infection and the ultimate survival of each fish. For the second and third exposures, significant differences (P<0.001) were observed between the surviving fish and those that died in the challenge. Individual gill scores at the latter measurements were suggestive of development of resistance to AGD. Mortality during a natural summer AGD challenge in an un-bathed population of fish, that had two previous treated exposures to the disease, was 67.7% and gill symptoms at the onset of losses accurately predicted the rate of mortality.

Food information databases are an everyday reality in the working life of the nutritionist. In research, the public service or the food industry the work of obtaining analytical data or compiling data for a database will generally fall to the nutritionist (or dietitian) as the question of content is likely to lie outside the qualifications or experience of the information technology personnel engaged in database development or maintenance. A recent study of the nutrient composition of Australian pork provides an opportunity to discuss the areas which have to be covered in an analytical program to provide nutrient data that satisfy criteria for inclusion in a national food composition database or a product endorsement program such as the National Heart Foundation's Tick Program.

In arid and semiarid Australia fossorial vertebrates have been a major component of the soil biota mediating many fundamental landscape processes. However, many species such as the burrowing bettong (Bettongia lesueur) have become seriously depleted following European pastoral settlement. As 'landscape engineers', they were responsible for creating and maintaining a high degree of surface heterogeneity that promoted a diverse and productive herbaceous understorey, particularly in 'hard-red' communities dominated by mulga (Acacia aneura). While their regional extinction has had major impacts by contributing to desertification and loss of biodiversity, relict warrens 'engineered' by B. lesueur still remain in certain ecosystems and despite continual weathering, contribute significantly to herbage productivity and species diversity. This paper details the results obtained from a number of field studies aimed at determining the distribution of relict warrens at contrasting scales and their influence on landscape patch dynamics resulting from their impacts on soil nutrients, herbage composition and herbivory. Finally, the conservation implications following the continental extinction of this species and the resulting loss of fundamental ecosystem services, as well as cultural values, are discussed in the context of future re-introduction efforts.

ABSTRACTThis paper examines the role of fire in mediating the relative abundance of two of the world's major ecologically dominant ant genera, Iridomyrmex and Oecophylla, where they coexist across the tropical savanna landscapes of northern Australia. These taxa have contrasting biogeographical histories, which are predicted to lead to contrasting responses to fire. Iridomyrmex is an autochthonous Australian genus that has radiated primarily in the arid zone; as such, its abundance is predicted to be promoted by frequent fire because this maintains an open habitat. In contrast, Oecophylla is a genus of leaf‐nesting ants occurring in the canopies of Old World tropical rainforest, and is a recent arrival to Australia in geological time; the abundance of these ants is predicted to decline under frequent fire. We test these predictions using results from a landscape‐scale fire experiment, where three experimental fire regimes (including no fire) were applied to replicated subcatchments over a 5‐year period. Using sweep nets, ants were sampled in the grass layer (the habitat layer of greatest overlap between Iridomyrmex and Oecophylla) in eucalypt woodland (canopy cover < 30%) and open eucalypt forest (canopy cover about 50%) habitats. A total of 27 species from 11 genera were collected during the study; eight were common enough for statistical analysis, and the abundances of four of these were significantly affected by fire treatment. As predicted, the abundance of Iridomyrmex was promoted by fire, whereas that of Oecophylla declined. These changes occurred only under late‐season (relatively high intensity) fires, and for Oecophylla occurred only in open forest (not woodland) habitat. This fire‐mediated relationship between Iridomyrmex and Oecophylla mirrors the much broader, ecosystem‐wide dynamic between eucalypt‐dominated savanna and rainforest in tropical Australia, with savannas dominated by fire‐resistant sclerophyll elements of Australian origin, and rainforest dominated by fire‐sensitive mesophyll elements of South‐East Asian origin.

Alpine grazing reduces blazing' is a widely and strongly held view concerning the effects of livestock grazing on fuels, and therefore fire behaviour and impact, in Australia's high country landscapes. As a test of this hypothesis, we examined the patterns of burning across the alpine (treeless) landscapes of the Bogong High Plains in Victoria, following the extensive fires of January 2003. Data were collected from multiple transects, each 3-5 km long, with survey points located randomly at either 50, 200 or 500 m intervals. The transects traversed the major regions of the Bogong High Plains, both grazed and ungrazed. At each point, we recorded whether the point was burnt or unburnt, the vegetation type (closed-heath, open-heath, grassland or herbfield), the estimated prefire shrub cover, slope, aspect, and a GPS location. At burnt heathland sites, we recorded the minimum twig diameter (an a posteriori measure of fire severity) in a sample of common shrubs. In total, there were 108 km of transect lines, 419 survey points and 4050 twig measurements, with sample points equally distributed across grazed and ungrazed country. The occurrence of fire (i.e. burnt or unburnt) in grazed and ungrazed areas was analysed by logistic regression; the variation in twig diameters by anova. Approximately half of all points were burnt. There was no statistically significant difference between grazed and ungrazed areas in the proportion of points burnt. Fire occurrence was determined primarily by vegetation type, with the proportion burnt being 0.87 for closed-heath, 0.59 for open-heath, and 0.13 for grassland and all snow-patch herbfield points unburnt. In both closed-heath and open-heath, grazing did not significantly lower the severity of fire, as measured by the diameter of burnt twigs. We interpret the lack of a grazing effect in terms of shrub dynamics (little or no grazing effect on long-term cover of taller shrubs), diet and behaviour of cattle (herbs and dwarf shrubs eaten; tall shrubs not eaten and closed-heath vegetation generally avoided), and fuel flammability (shrubs more flammable than grass).Whatever effects livestock grazing may have on vegetation cover, and therefore fuels in alpine landscapes, they are likely to be highly localized, with such effects unlikely to translate into landscape-scale reduction of fire occurrence or severity. The use of livestock grazing in Australian alpine environments as a fire abatement practice is not justified on scientific grounds.