CSIRO Land and Water

Abstract Large‐scale assessments of plant condition are needed in restored plant communities to evaluate if ecosystems are functioning similarly to natural reference systems. Remote sensing can yield information on plant condition in a more efficient way than current on‐ground physiological methods, which often require destructive sampling and are difficult to perform at large scales. In this study, we explore the use of near‐surface remote sensing approaches—leaf‐level thermography and hyperspectral reflectance—to estimate key physiological parameters and track seasonal change in a diverse group of plant species growing in a restored mine site of Western Australia. In this system, deviations from expected plant condition are mainly driven by water availability, which translates in various degrees of drought stress. We investigated the relationships between traditionally measured physiological variables and remotely sensed proxy indicators, with the following goals: (1) to assess the extent to which remotely sensed proxy indicators can reliably estimate key physiological variables in functionally diverse plant species, and (2) to explore a multivariate approach to track seasonal change in different species using a combination of remotely sensed proxy indicators. Our results indicate that univariate relationships between physiological variables and their remotely sensed proxy indicator for leaf water content and total chlorophyll concentration were accurately predicted for all species at the leaf level. This was not the case for fluorescence and stomatal conductance. Through multivariate analysis, we found that, when grouping samples through seasonal data centroids, three different data sets (physiological variables, all remotely sensed proxy indicators and remotely sensed proxy indicators from hyperspectral reflectance only) outlined very similar transitions across seasons in four out of the five studied species. This indicates that, when combined, remotely‐sensed proxy indicators generated through leaf hyperspectral reflectance have the potential to detect deviations in plant condition in a wide range of plant functional types. Using this approach to detect changes in levels of plant stress could enable early detection of potential issues in restoration and therefore may be used to inform adaptive management to improve long‐term restoration strategy and outcomes. Practical implication : through the multivariate approach based on remotely sensed proxy indicators that we present here, plant condition assessments can be conducted more efficiently in the context of ecological restoration.

Abstract Flower‐visiting flies are highly diverse and abundant in high‐elevation and latitude regions, where they can be important pollinators. However, the ecology of flower‐visiting Diptera is not well researched. We recorded flower interactions and quantified the pollen loads and diet of a locally abundant Lauxaniid fly, Incurviseta cf. maculifrons (Malloch, 1925), in Kosciuszko National Park, NSW, Australia. We described the mouthpart morphology of I. cf. maculifrons using scanning electron microscope (SEM) images in relation to its pollen diet. I. cf. maculifrons visited 23 plant species at sites above and below the treeline in the Australian alpine during 1500 total minutes of observation. Gut dissections ( n = 32) revealed large quantities of pollen (median = 4118, range = 56–18,296), typically belonging to only one or two plant species per individual fly (mean = 1.59, SD = 0.67). Most flies carried small pollen loads (range = 0–108 grains) on their bodies, made up mostly of pollen from a single plant species (median proportion = 0.7). I. cf. maculifrons had mouthpart features including ‘unfurled pseudotrachea’ and interpseudotracheal sensilla which possibly assist in the manipulation and sensing of pollen. The extent of flower visitation and pollen transport by I. cf. maculifrons suggests it is a potentially important montane Australian pollinator. Future studies should investigate the ecology and anthophilous habits of other Incurviseta species as well as the dual ecosystem services by other anthophilous Diptera and their larvae to better understand how disturbances to plant‐pollinator communities will impact ecosystem processes in high‐latitude and elevation regions.

Cyanogen chloride (NCCl) produced from the reaction of -CN with HOCl has previously been shown to afford activation of ribonucleotides. We now report that NCCl reacts with primary aliphatic amino acids to rapidly produce N-carbamoyl dipeptides in excellent yields (89-98%). Studies with l-alanine suggest that racemization of the amino acids does not occur significantly during the reaction. Quantum chemical (DFT) calculations predict that the mechanism proceeds via activated 2-amino-5(4H)-oxazolone intermediates, which undergo amino acid nucleophilic attack. NCCl can also be generated in situ from glycine and HOCl, enabling the "sacrificial activation" of glycine to form N-carbamoyl diglycine. At 70 °C, selective peptide bond hydrolysis yields N-carbamoyl glycine, which is a known peptide precursor. The findings herein build upon prior work involving NCCl in prebiotic ribonucleotide synthesis and activation, highlighting its potential as a general chemical activator for the prebiotic condensation of life's molecular building blocks.

Abstract Effective water and wetland management for waterbirds during nesting events benefits from knowledge of nesting timing, staging, duration, and associated foraging locations. Such information can inform managers about when, where, and for how long management actions such as environmental watering or predation protection are needed to support specific nesting stages. This is particularly relevant for species nesting in aggregations that are dependent on flooding of key sites to initiate and complete their nesting cycles, such as ibis and spoonbills. These species are frequently targeted for adaptive water and wetland management to support successful breeding events and can be bioindicators of wetland change. However, obtaining on-ground nesting data for highly mobile species in remote or inaccessible sites can be difficult. To solve this problem, we used GPS satellite telemetry to track nesting events for 3 species that frequently nest together in remote wetlands managed with environmental water: Threskiornis spinicollis (Straw-necked Ibis), T. molucca (Australian White Ibis), and Platalea regia (Royal Spoonbill). This is the first time that satellite telemetry for these highly mobile species has been used to analyze: (1) nest stages and nest attendance patterns; (2) distances travelled to forage during nesting; and (3) timing and duration of nesting events. We found both intra- and inter-species variation in nest attendance patterns and foraging distances. There were changes in nest attendance and foraging distance patterns corresponding with transitions between each of the 4 main nest stages: (1) nest establishment; (2) incubation; (3) immobile chicks; (4) mobile chicks. We discuss how this information can be used to implement strategic conservation management of waterbird populations and habitats including environmental watering, nest protection, and predator control.

Abstract Ants are often referred to as “the little things that rule the world” because of the critical roles they play as ecosystem engineers and through trophic and non‐trophic interactions. We describe an experimental test of the influence of ants on spiders and beetles in an Australian tropical savanna. We experimentally suppressed ant abundance through baiting in six plots, each matched with adjacent reference plots, across two sites (Territory Wildlife Park [TWP] and Tropical Ecosystem Research Centre [TERC]), and documented the impact on ground and arboreal spider and beetle communities. At the TWP site, ants were highly abundant and diverse, dominated by species of aggressive Iridomyrmex. Ant diversity was lower and Iridomyrmex low in abundance at the TERC site. At the TWP site, suppression treatment predominantly affected species of Iridomyrmex, reducing overall ant abundance on the ground by 52%–77%, but because few Iridomyrmex forgage arboreally, there was no change on vegetation. Suppression treatment had little effect on ant abundance on both the ground and vegetation at the TERC site. Despite marked ant suppression on the ground at TWP, we observed little response from either spiders or beetles after two years. Among spiders, the only response was a decrease (by 50%) in abundance of the ant‐associated family Prodidomidae. One beetle family (Scarabaeidae) also declined after ant suppression but was a suspected nontarget casualty of baiting. No spider or beetle family showed the increase in abundance that we predicted. Curiously, an increase was shown by the spider family Clubionidae at TERC despite minimal ant suppression. At both sites, experimental treatment had little influence on spiders and beetles on vegetation, consistent with the lack of suppression of ants on plants. The general lack of effect of ant suppression implies that there is surprisingly limited regulation of arthropod communities by ants in our study system. This contrasts with findings from other ant manipulation experiments and is particularly surprising as ant abundance is so high in Australian savannas. While our experiment involved ant suppression rather than elimination, our results suggest that Australian savannas are resilient to large reductions of a ubiquitous faunal group.

BackgroundThe ability to navigate is crucial to the survival of many flying animals. Though relatively much less is known about the navigational abilities of bats versus birds, recent progress has been made in understanding the navigational abilities of cave roosting bats, but little is known about those of arboreal roosting flying-foxes, despite their extreme mobility.MethodsWe use extremely high spatiotemporal resolution GPS tracking to examine the flight behaviour of 11 grey-headed flying-foxes (Pteropus poliocephalus) displaced 16.8 km from their roost. We examined flight metrics of the resulting high-resolution traces to understand whether the displaced animals were aware their location with respect to the roost of capture. We use 7 grey-headed flying-foxes tracked from the roost of capture—as part of a separate, concurrent study—to aid in this comparison.ResultsTen of 11 displaced individuals were detected at the roost of capture within four days of release, but all displaced individuals roosted for at least one night away from the roost of capture. Six individuals returned ‘home’ the next day, and four roosted away from ‘home’ for ≥ one further night. Prior to their return ‘home’, displaced individuals on average flew 2.7 times further and stopped 1.7 more times than reference individuals or displaced animals that had already returned ‘home’. This indicates that displaced individuals expended more effort each night than non-displaced individuals. This suggests that these individuals were attempting to return ‘home’, rather than choosing not to return due to a lack of motivation to home. Flight segments of displaced individuals were higher, less straight, and less likely to be oriented. Flight segments that ended in a point that an individual had previously visited were faster, higher, and straighter than those not known to end in a point previously visited.ConclusionsOur findings suggest that approximately half of the displaced animals were aware of where they were with respect to ‘home’ the night after release, whereas other individuals took at least a further night to orient themselves. While our results are consistent with previous work suggesting that non-echolocating bats may use a large-scale navigational map based on vision, sensory manipulations would be needed to confirm this.

Abstract Floods are recurring natural disasters worldwide, and they are causing increasing loss of life and property damage due to climate change and the occupation of flood-prone areas. In this context, flood modelling is an important tool to assess flood hazard and guide mitigation strategies. However, in situ hydro-climate observation networks required to provide reliable flood data are declining due to station closure, which jeopardizes the building of accurate flood models, particularly in low-latitude regions. This paper analyses an extreme flood event that occurred in eastern Australia in February 2022 which provides a point of reference for future floods in coastal catchments and humid sub-tropical climates, especially around the Pacific. This event combined some of the most extreme rainfall ever seen in Australia with initial soil water conditions close to saturation. It resulted in significantly lower peak time differences along river systems than in past historical events and led to the largest total insurance claim for a single flood event in Australia. The event is compared to a large dataset of observed floods across Australia from 1954 onwards to evaluate its “surprise” effect, or more precisely, how the inclusion of a single flood event can influence subsequent design flood calculations. The 2022 flood was found to be the event with the largest impact on the 1-in-100 years values (1% annual exceedance probability or AEP) for five- and ten-day total runoff. Including this single event increases these values by 13% averaged across 62 sites, respectively, with a maximum increase of up to 30% for certain sites. This impact is particularly significant considering the amount of hard infrastructure, such as roads and levees, that is built in reference to the 1% AEP level. Overall, the 2022 flood and the associated data collected for this paper presents an opportunity to use this event as reference for extreme flood scenarios in lower latitudes under combined riverine and coastal influence.

Groundwater denitrification studies require the careful quantification of excess N2 to determine that nitrate reduction has taken place. The measurement of corresponding noble gases Ne and Ar quantifies excess air N2 and in situ degassing. We compare, for the first time, measurement results from a high-precision quadrupole mass spectrometer (QMS) with a low-cost PlasmaDetek (plasma emission detector) GC add-on capable of analyzing all three gases (N2, Ne, Ar) from a single sample to obtain reliable data for denitrification calculations. Both methods can be used to accurately measure N2, Ne, and Ar concentrations that are reproducible and overlap within 2σ analytical uncertainty. Moreover, we discuss different groundwater headspace gas collection methods and show that Giggenbach bottles, while limited when storing samples for long-time periods (months or more), are reliable over shorter storage periods (up to 2 or 3 weeks), compared to cold-pressed copper tube collection methods, which are deemed stable over long timeframes (years). This novel plasma detector method will enable laboratories that do not have state-of-the-art noble gas facilities to undertake reliable measurement of dissolved groundwater gases (N2, Ne, and Ar) for groundwater denitrification studies, understand the implications of natural subsurface nitrate attenuation, and improve catchment nitrate budgets.