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Urban warming affects many millions of city dwellers worldwide. The current study evaluated the extent to which trees reduce air and surface temperatures in urban settings across Greater Sydney, Australia. Summertime air and surface temperatures were measured directly in the shade of 470 individual trees planted in three contrasting contexts (parks, nature strips, asphalt) and compared with temperatures in paired adjacent areas receiving full sunlight. Differences between shade and sunlit temperatures were evaluated against measured morphological traits (leaf area index [LAI], clear stem height, crown depth, height and diameter at breast height) for all trees. On average, tree shade reduced mean and maximum air temperatures by 1.1 °C and 3.7 °C, respectively. Temperatures of standardised reference surfaces (black and white tiles and artificial grass) in tree shade were up to 45 °C lower compared to full-sun exposure, and were also lower in parks and nature strips compared to asphalt settings. The surface temperature of shaded natural grass was cooler compared to sunlit natural grass, although this difference did not vary between nature strip and park settings. The magnitude of air and surface temperature reductions due to tree shade was significantly, positively related to tree-level LAI and these relationships were stronger in asphalt and park contexts compared to nature strips. These findings can inform decisions made by urban managers and planners around the selection of tree characteristics to enhance cooling benefits in different contexts, as an important step towards more liveable and resilient cities. [ABSTRACT FROM AUTHOR]

Trees have been found to have significant cooling effect on outdoor thermal environment. This study explores the characteristics of a tree component (crown) that accounts for a large portion of the cooling effect. A field measurement was conducted in the Gold Coast, Australia, which has a subtropical climate (Cfa), according to the Köppen climate classification. The characteristics of the tree crown were indexed by its crown diameter, crown height, sky view factor (SVF), and leaf area index (LAI), based on which four new indicators that describe crown characteristics were proposed: gross canopy index (GCI), leaf layer index (LLI), crown volume index (CVI), and total canopy index (TCI). The former two are basic indicators and the latter two are sophisticated indicators. The results showed that the two sophisticated indicators were significantly associated with the mean radiant temperature beneath the tree crown and that increasing the value of each indicator by 10% could help reduce the mean radiant temperature by 0.67 °C (CVI) and 0.83 °C (TCI) respectively, if other predictors were fixed. Similarly, increasing the value of each basic indicator by 10% could help reduce the mean radiant temperature by 0.78 °C (GCI) and 0.066 °C (LLI) respectively, but their cooling effects were less significant than CVI and TCI. The thermal effect of the two sophisticated indicators was more significant than that of the two basic ones. Among all, TCI was found to be the best predictor of the outdoor thermal environment underneath the tree crown. This study proposes new effective indicators to quantify the cooling effects of trees and provides a rationale for plant selection in tropical/subtropical climates to achieve a more comfortable outdoor thermal environment. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a novel approach for automatic segmentation and object detection of tree crowns in airborne images captured from a low-flying Unmanned Aerial Vehicle (UAV) in ecology monitoring applications. Cost effective monitoring in these applications necessitates the use of vision-band-only imaging on the UAV platform; the reduction in spectral resolution (compared to multi- or hyper-spectral imaging) is balanced by the high spatial resolution available (20cm/pixel) from the low-flying UAV, when compared to existing satellite or manned-aerial survey data. Our approach to object detection thus uses both geometry and appearance information (through the use of tree shape and shadow information) in addition to spectral information to help accurately distinguish tree crowns within our application. A predictive geometric template for tree detection is constructed using on-board UAV navigation data, sun lighting information and information about the geometry of the target crown. A two-stage detection algorithm is then used to segment tree crowns based on spectral (colour) information convolved with information from the predictive template. Results of our approach are presented using airborne image data collected from a fixed-wing UAV during a weed monitoring and mapping mission over farmland in West Queensland, Australia. [Copyright &y& Elsevier]

Old-growth forests provide many ecosystem services and benefits. However, they are becoming increasingly rare and thus are an urgent priority for conservation. Accurately mapping old-growth forests is a critical step in this process. Here, we used LiDAR, an improved individual tree crown delineation algorithm for broadleaved forests, Gaussian mixture modelling, and a rule-based classification key to map the extent and location of old-growth forests across a topographically and ecologically complex landscape of 337,548 ha in southeastern Australia. We found that variation in old growth extent was largely driven by the old growth definition, which is a human construct, rather than by uncertainty in the technical aspect of the work. Current regulations define a stand as old growth if it was recruited prior to 1900 (i.e., >120 years old) and is undisturbed (i.e., <10% regrowth canopy cover and no visible disturbance traces). Only 2.7% (95% confidence intervals ranging from 1.4 to 4.9%) of the forests in the study landscape met these criteria. However, this definition is overly restrictive as it leaves many multi-aged stands with ecologically mature elements (e.g., one or more legacy trees amid regrowth) unprotected. Removing the regrowth filter, an indicator of past disturbances, increased the proportion of old-growth forests from 2.7% to 15% of the landscape. Our analyses also revealed that 60% of giant trees (>250 cm in diameter at breast height) were located within 50 m of cool temperate rainforests and cool temperate mixed forests (i.e., streamlines). We discuss the implication of our findings for the conservation and management of high-conservation-value forests in the region. [ABSTRACT FROM AUTHOR]

Background: Knowledge of how fire regimes influence flammability, and its role in shaping future fire regimes, exists mostly at species composition and ecosystem levels. The effect of fire regimes on fuel at the chemical level is poorly known. Aim: We aimed to empirically investigate the association between recent fire history and forest foliage chemistry; and to explore potential implications for forest fuel flammability. Methods: Using an orthogonal study design, we investigated the effects of fire frequency and time since fire on the chemical composition of Eucalyptus pilularis leaves from forest canopies and surface litter in south-eastern Australia. Key results: We found high fire frequency (fire-return interval 10–13 years) was associated with higher C:N, C:P, and C:K ratios in E. pilularis surface litter, and higher C:P in canopy leaves. Conclusions: Nutrients including nitrogen and phosphorous reduce flammability of plant tissues, and hence, the observed differences in leaf nutrients between high and low fire frequency sites could have important implications for future flammability of these forests. Implications: Our study has demonstrated a relationship between fire frequency and leaf nutrient stoichiometry, which may act as a mechanism through which repeated fires could increase fuel flammability. This warrants further investigation in other environments. Knowledge of how past fires may influence the future flammability of ecosystems remains poorly resolved. Here, we report significant effects of past fire frequency on the chemical properties of canopy leaves and leaf litter in a coastal Eucalyptus forest, which may have important implications for future forest flammability. [ABSTRACT FROM AUTHOR]

This paper presents a review of recent developments in the assessment and monitoring of health in Australian eucalypt forests and plantations of pine and eucalypt species, with an emphasis on damage caused by herbivorous insects. The diverse range of interests and priorities amongst Australian stakeholders of native forests and plantations influences the scale, resolution and accuracy of results sought, and this in turn influences how the assessment data are collected, analysed and reported. The authors discuss sampling systems that include extensive ground-based surveys, permanent plots and airborne technologies being developed in Australia. In all cases, there is an appreciation that the assessment protocols should be objective, repeatable and cost effective. Significant progress has been made in the application of digital, remotely sensed imagery to detect and classify damaged forest canopies. The success of this approach depends, in part, on a sound understanding of the progression of symptoms at the leaf, tree crown and stand scale, especially those symptoms that influence spectral reflectance behaviour. [ABSTRACT FROM AUTHOR]

Full-waveform airborne laser scanning (ALS) is a powerful tool for characterizing and monitoring forest structure over large areas at the individual tree level. Most of the existing ALS-based algorithms for individual tree delineation from the point cloud are top-down, which are accurate for delineating cone-shaped conifers, but have lower delineation accuracies over more structurally complex broad-leaf forests. Therefore, in this study we developed a new bottom-up algorithm for detecting trunks and delineating individual trees with complex shapes, such as eucalypts. Experiments were conducted in the largest river red gum forest in the world, located in the south-east of Australia, that experienced severe dieback over the past six decades. For detection of individual tree trunks, we used a novel approach based on conditional Euclidean distance clustering that takes advantage of spacing between laser returns. Overall, the algorithm developed in our study was able to detect up to 67% of field-measured trees with diameter larger than or equal to 13 cm. By filtering ALS based on the intensity, return number and returned pulse width values, we were able to differentiate between woody and leaf tree components, thus improving the accuracy of tree trunk detections by 5% as compared to non-filtered ALS. The detected trunks were used to seed random walks on graph algorithm for tree crown delineation. The accuracy of tree crown delineation for different ALS point cloud densities was assessed in terms of tree height and crown width and resulted in up to 68% of field-measured trees being correctly delineated. The double increase in point density from ~ 12 points/m 2 to ~ 24 points/m 2 resulted in tree trunk detection increase of 11% (from 56% to 67%) and percentage of correctly delineated crowns increase of 13% (from 55% to 68%). Our results confirm an algorithm that can be used to accurately delineate individual trees with complex structures (e.g. eucalypts and other broadleaves) and highlight the importance of full-waveform ALS for individual tree delineation. [ABSTRACT FROM AUTHOR]

We quantitatively assessed edge effects associated with elevated abundance of a hyper aggressive bird species, the noisy miner Manorina melanocephala , in fragmented eucalypt forest adjoining developed land. Long-term data from Toohey Forest, subtropical Australia, show that noisy miner colonies intensively occupy a zone of 20 m from the forest edge, with frequent use occurring up to 100 m from the edge, but little beyond 200 m. Within noisy miner colonies, the abundance and species richness of other birds were both about half those recorded at nearby transects which were outside the colonies' main activity area. Bird species smaller than noisy miners, which are also those with similar diets, were collectively 20–25 times more abundant, and their species richness tenfold greater, outside miner colonies than within them, whereas larger species, which have less dietary overlap, did not differ. Exclusion of small insectivorous birds has been hypothesised to cause elevated insect herbivore density, but we found no difference between tree crown defoliation or dieback rates within versus outside miner colonies. Aggression by noisy miners can be viewed as a mechanism of interspecific competition, since miners have a relatively large body size for their diet and are hence able to exclude virtually all potential competitors at relatively little cost. We examine evidence indicating that reduced bird diversity in eucalypt forest fragments of eastern Australia is often simply the effect of noisy miner occupancy of edges, acting directly on the densities of other species through their aggressive behaviour. With an edge effect 200 m deep, a remnant 10 ha in size is likely to become entirely occupied by noisy miners, and this is a size threshold that has been commonly reported in association with area-standardised avian diversity reductions. Convergent patterns of species loss from small forest fragments in different continents are the result of different underlying... [ABSTRACT FROM AUTHOR]

Accurate pre-harvest yield forecasting of mango is essential to the industry as it supports better decision making around harvesting logistics and forward selling, thus optimizing productivity and reducing food waste. Current methods for yield forecasting such as manually counting 2–3% of the orchard can be accurate but are very time inefficient and labour intensive. More recent evaluations of technological solutions such as remote (satellite) and proximal (on ground) sensing have provided very encouraging results, but they still require infield in-season sampling for calibration, the technology comes at a significant cost, and commercial availability is limited, especially for vehicle-mounted sensors. This study presents the first evaluation of a "time series"—based remote sensing method for yield forecasting of mango, a method that does not require infield fruit counts and utilizes freely available satellite imagery. Historic yield data from 2015 to 2022 were sourced from 51 individual orchard blocks from two farms (AH and MK) in the Northern Territory of Australia. Time series measures of the canopy reflectance properties of the blocks were obtained from Landsat 7 and 8 satellite data for the 2015–2022 growing seasons. From the imagery, the following vegetation indices (VIs) were derived: EVI, GNDVI, NDVI, and LSWI, whilst corresponding weather variables (rainfall (Prec), temperature (Tmin/Tmax), evapotranspiration (ETo), solar radiation (Rad), and vapor pressure deficit (vpd)) were also sourced from SILO data. To determine the relationships among weather and remotely sensed measures of canopy throughout the growing season and the yield achieved (at the block level and the farm level), six machine learning (ML) algorithms, namely random forest (RF), support vector regression (SVR), eXtreme gradient boosting (XGBOOST), RIDGE, LASSO and partial least square regression (PLSR), were trialed. The EVI/GNDVI and Prec/Tmin were found to be the best RS and weather predictors, respectively. The block-level combined RS/weather-based RF model for 2021 produced the best result (MAE = 2.9 t/ha), marginally better than the RS only RF model (MAE = 3.4 t/ha). The farm-level model error (FLEM) was generally lower than the block-level model error, for both the combined RS/weather-based RF model (farm = 3.7%, block (NMAE) = 33.6% for 2021) and the RS-based model (farm = 4.3%, block = 38.4% for 2021). Further testing of the RS/weather-based RF models over six additional orchards (other than AH and MK) produced errors ranging between 24% and 39% from 2016 to 2020. Although accuracies of prediction did vary at both the block level and the farm level, this preliminary study demonstrates the potential of a "time series" RS method for predicting mango yields. The benefits to the mango industry are that it utilizes freely available imagery, requires no infield calibration, and provides predictions several months before the commercial harvest. Therefore, this outcome not only presents a more adoptable option for the industry, but also better supports automation and scalability in terms of block-, farm-, regional, and national level forecasting. [ABSTRACT FROM AUTHOR]

This study analysed the characteristics of the recent (2018–2019) wildfires that occurred in the USA, Brazil, and Australia using Moderate Resolution Imaging Spectroradiometer (MODIS) active fires (AF), fire radiative power (FRP, MW) and burned area (BA) products. Meteorological and environmental parameters were also analysed. The study found various patterns in the spatial distribution of fires, FRP and BA at the three sites, associated with various vegetation compositions, prevailing meteorological and environmental conditions and anthropogenic activities. We found significant fire clusters along the western and eastern coasts of the USA and Australia, respectively, while vastly distributed clusters were found in Brazil. Across all sites, significant fire intensity was recorded over forest cover (FC) and shrublands (SL), attributed to highly combustible tree crown fuel load characterised by leafy canopies and thin branches. In agreement, BA over FC was the highest in the USA and Australia, while Brazil was dominated by the burning of SL, characteristic of fire-tolerant Cerrado. The relatively lower BA over FC in Brazil can be attributed to fuel availability and proximity to highly flammable cover types such as cropland, SL and grasslands rather than fuel flammability. Overall, this study contributes to a better understanding of wildfires in various regions and the underlying environmental and meteorological causal factors, towards better wildfire disaster management strategies and habitat-specific firefighting. [ABSTRACT FROM AUTHOR]

Increased demand for sustainable timber products has resulted in large investments in agroforestry in Australia, with plantations growing various Pinus species, selected to suit a plantation's environment. Juvenile Pinus species have a low fire tolerance. With Australia's history of wildfires and the likelihood of climate change exacerbating that risk, the potential for a total loss of invested capital is high unless cost-effective targeted risk minimisation is part of forest management plans. Based on the belief that the understory profiles within the juvenile plantations are a major factor determining fuel hazard risks, an accurate assessment of these profiles is required to effectively mitigate those risks. At present, assessment protocols are largely reliant on ground-based observations, which are labour-intensive, time consuming, and expensive. This research project investigates the effectiveness of using geospatial analysis of drone-derived photographic data collected in the commercial pine plantations of south-eastern Queensland as a cost-saving alternative to current fuel hazard risk assessment practices. Understory composition was determined using the supervised classification of orthomosaic images together with derivations of canopy height models (CHMs). The CHMs were subjected to marker-controlled watershed segmentation (MCWS) analysis, isolating and removing the plantation pine trees, enabling the quantification of understory fuel profiles. The method used proved highly applicable to immature forest environments with minimal canopy closure, but became less reliable for close canopied older plantations. [ABSTRACT FROM AUTHOR]

The frequency and intensity of forest disturbances, such as drought and fire, are increasing globally, with an increased likelihood of multiple disturbance events occurring in short succession. Disturbances layered over one another may influence the likelihood or intensity of subsequent events (a linked disturbance) or impact response and recovery trajectories (a compound disturbance), with substantial implications for ecological spatiotemporal vulnerability. This study evaluates evidence for disturbance interactions of drought followed by wildfire in a resprouting eucalypt‐dominated forest (the Northern Jarrah Forest) in southwestern Australia. Sites were stratified by drought (high, low), from previous modeling and ground validation, and fire severity (high, moderate, unburnt), via remote sensing using the relative difference normalized burn ratio (RdNBR). Evidence of a linked disturbance was assessed via fine fuel consumption and fire severity. Compound disturbance effects were quantified at stand scale (canopy height, quadratic mean diameter, stem density) and stem scale (mortality). There was no evidence of prior drought influencing fine fuel consumption or fire severity and, hence, no evidence of a linked disturbance. However, compound disturbance effects were evident; stands previously affected by drought experienced smaller shifts in canopy height, quadratic mean diameter, and stem density than stands without prior drought impact. At the stem scale, size and fire severity were the strongest determinants of stem survival. Proportional resprouting height was greater in high drought sites than in low drought sites (p < 0.01), meaning, structurally, the low drought stands decreased in height more than the high drought stands. Thus, a legacy of the drought was evident after the wildfire. Although these resprouting eucalypt forests have been regarded as particularly resilient, this study illustrates how multiple disturbances can overwhelm the larger tree component and promote an abundance of smaller stems. We suggest that this is early evidence of a structural destabilization of these forests under a more fire‐prone, hotter, and drier future climate. [ABSTRACT FROM AUTHOR]

The fire-tolerant eucalypt forests of south eastern Australia are assumed to fully recover from even the most intense fires; however, surprisingly, very few studies have quantitatively assessed that recovery. The accurate assessment of horizontal and vertical attributes of tree crowns after fire is essential to understand the fire's legacy effects on tree growth and on forest structure. In this study, we quantitatively assessed individual tree crowns 8.5 years after a 2009 wildfire that burnt extensive areas of eucalypt forest in temperate Australia. We used airborne LiDAR data validated with field measurements to estimate multiple metrics that quantified the cover, density, and vertical distribution of individual-tree crowns in 51 plots of 0.05 ha in fire-tolerant eucalypt forest across four wildfire severity types (unburnt, low, moderate, high). Significant differences in the field-assessed mean height of fire scarring as a proportion of tree height and in the proportions of trees with epicormic (stem) resprouts were consistent with the gradation in fire severity. Linear mixed-effects models indicated persistent effects of both moderate and high-severity wildfire on tree crown architecture. Trees at high-severity sites had significantly less crown projection area and live crown width as a proportion of total crown width than those at unburnt and low-severity sites. Significant differences in LiDAR -based metrics (crown cover, evenness, leaf area density profiles) indicated that tree crowns at moderate and high-severity sites were comparatively narrow and more evenly distributed down the tree stem. These conical-shaped crowns contrasted sharply with the rounded crowns of trees at unburnt and low-severity sites and likely influenced both tree productivity and the accuracy of biomass allometric equations for nearly a decade after the fire. Our data provide a clear example of the utility of airborne LiDAR data for quantifying the impacts of disturbances at the scale of individual trees. Quantified effects of contrasting fire severities on the structure of resprouter tree crowns provide a strong basis for interpreting post-fire patterns in forest canopies and vegetation profiles in Light Detection and Ranging (LiDAR) and other remotely-sensed data at larger scales. [ABSTRACT FROM AUTHOR]

Predictive vegetation mapping is an essential tool for managing and conserving high conservation-value forests. Cool temperate rainforests (Rainforest) and cool temperate mixed forests (Mixed Forest, i.e., rainforest spp. overtopped by large remnant Eucalyptus trees) are threatened forest types in the Central Highlands of Victoria. Logging of these forest types is prohibited; however, the surrounding native Eucalyptus forests can be logged in some areas of the landscape. This requires accurate mapping and delineation of these vegetation types. In this study, we combine niche modelling, multispectral imagery, and LiDAR data to improve predictive vegetation mapping of these two threatened ecosystems in southeast Australia. We used a dataset of 1586 plots partitioned into four distinct forest types that occur in close proximity in the Central Highlands: Eucalyptus, Tree fern, Mixed Forest, and Rainforest. We calibrated our model on a training dataset and validated it on a spatially distinct testing dataset. To avoid overfitting, we used Bayesian regularized multinomial regression to relate predictors to our four forest types. We found that multispectral predictors were able to distinguish Rainforest from Eucalyptus forests due to differences in their spectral signatures. LiDAR-derived predictors were effective at discriminating Mixed Forest from Rainforest based on forest structure, particularly LiDAR predictors based on existing domain knowledge of the system. For example, the best predictor of Mixed Forest was the presence of Rainforest-type understorey overtopped by large Eucalyptus crowns, which is effectively aligned with the regulatory definition of Mixed Forest. Environmental predictors improved model performance marginally, but helped discriminate riparian forests from Rainforest. However, the best model for classifying forest types was the model that included all three classes of predictors (i.e., spectral, structural, and environmental). Using multiple data sources with differing strengths improved classification accuracy and successfully predicted the identity of 88% of the plots. Our study demonstrated that multi-source methods are important for capturing different properties of the data that discriminate ecosystems. In addition, the multi-source approach facilitated adding custom metrics based on domain knowledge which in turn improved the mapping of high conservation-value forest. [ABSTRACT FROM AUTHOR]

To understand the potential of forests to adapt to wildfire, we studied the genetic architecture of fire-related structural, damage and recovery traits in a globally important Australian forest tree species, Eucalyptus globulus. Fourteen traits were evaluated in an outcrossed F2 population in a field trial in Tasmania, Australia, which was burnt by a wildfire 14 years after planting. The trial also included open-pollinated families of the grandparental dwarf and tall ecotypes used to produce the F2 population. We studied the phenotypic correlations within the F2 population and performed quantitative trait loci (QTL) analyses using a linkage map comprised of 472 markers. Ecotype comparisons revealed that almost all traits were under genetic control, with trees of the dwarf ecotype significantly more damaged and mainly recovering from lignotubers, whereas tall ecotype trees mainly recovered from epicormic resprouts extending for a variable height up the stem. Within the F2, tree size was negatively correlated with fire damage and positively correlated with recovery. Genetic control of fire-related traits was confirmed by the detection of 38 QTL in the F2 population. These QTL accounted for 4 to 43% of the phenotypic variation in these traits. Several QTL co-located and likely reflect pleiotropic effects. However, many independent QTL were detected, including QTL for crown consumption and trunk scorch, epicormic resprouting, resprout herbivory, and seedling establishment. The QTL detected argue that many genetically controlled mechanisms are responsible for variation in fire damage and recovery. [ABSTRACT FROM AUTHOR]

Increasing water abstraction is severely degrading the world’s wetlands, which is frequently reflected in the condition of flood dependent organisms. Understanding minimum requirements under which thresholds are crossed from desired to undesired states can improve managing for resilience and avoid catastrophic ecological consequences. The Macquarie Marshes, a Ramsar-listed wetland in eastern Australia is located in a catchment with a long history of water resource development. It is also a catchment in which there has been a strong focus on wetland recovery using environmental flows. We investigated changes in the condition of 212 river red gum trees ( Eucalyptus camaldulensis ), a long-lived flood dependent species, at 17 sites, over 18 years (1993–2011). Four variables were measured for each tree: crown density, crown size, dead branches and epicormic growth. More than half (56.13%, 119) of the healthy trees first measured in 1993, showed no signs of life by 2011. Using historic inundation mapping, we identified that condition declined with reduced flooding. The probability of inundation in the previous five years had the strongest explanatory power, with strong increasing threshold responses of persistence and recovery associated with probabilities of flooding exceeding 5 years in the previous 10 years. We extended our modelling to the river red gum forests of the Macquarie Marshes floodplain, showing that 37% of the area had a predicted survival probability lower than P = 0.6 while similar probabilities were present in only 12% of the area within the Macquarie Marshes Nature Reserve. The condition of river red gum forests, using the relationships identified, provide a useful measure of ecosystem health, particularly if extended to understanding of reproduction, germination and recruitment in relation to different scenarios for environmental flows. Embedding such a monitoring strategy in an adaptive management framework provides considerable promise for ongoing learning and improvement of management, not just for river red gums but also other indicators. There is a possibility that the current poor ecological condition of the Macquarie Marshes can be redressed with increased environmental flows restoring some of the river red gum forests that are a key characteristic of the wetland. [ABSTRACT FROM AUTHOR]

The spatial extent of terrestrial vegetation types reliant on groundwater in arid Australia is poorly known, largely because they are located in remote areas that are expensive to survey. In previous attempts, the use of traditional remote sensing approaches failed to discriminate vegetation using groundwater from surrounding vegetation. Difficulties in discerning vegetation groundwater use by remote sensing may be exacerbated by the unpredictable rainfall patterns and lack of annual wet and dry seasons common in arid Australia. This study presents a novel approach to mapping terrestrial groundwater‐dependent ecosystems (GDEs) by applying singular value decomposition (SVD) to time‐series of vegetation indices derived from Landsat‐8 data, to isolate the temporal and spatial sources of variation associated with groundwater use. In‐situ data from 442 sites were used to supervise and validate logistic regression models and neural networks, to determine whether sites could be correctly classified as GDEs using components obtained from the SVD. These results were used to produce a probability map of GDE occurrence across a 557 000 ha study area. Overall accuracy of the final classification map was 79%, with 72% of sites correctly identified as GDEs (true positives) and 16% incorrectly classified as GDEs (false positives). The approach is broadly applicable in arid regions globally, and is easily validated if general background knowledge of regional vegetation exists. Globally, and going forward, increased water extraction is expected to severely limit water available for GDEs. Successfully mapping GDEs in arid environments is a critical step towards their sustainable management, and the human and natural systems reliant upon them. [ABSTRACT FROM AUTHOR]

The assessment of forest health is an essential part of the monitoring of ecological sustainability in managed native forests. In Australia, unfortunately, very limited quantitative information on forest health is actually obtained for management and reporting purposes. In this article, we summarize current approaches used in Australia to assess native forest health and some recent developments in the application of remotely acquired digital imagery for classifying canopy health. In a recent study examining Bell miner associated dieback (BMAD), high-resolution airborne imagery was successfully manipulated to present severity categories for BMAD affected canopy. The potential of remotely sensed imagery lies not in map production but in the statistical modelling capacity of this spatial information, particularly when added to climatic and terrain-based spatial data sets. There are several statistical approaches to modelling these spatial datasets and in this article, we discuss our approach to producing a preliminary BMAD model. The importance of ground-based assessments is also emphasized and we recommend tree crown condition as a key health attribute for the spatial modelling of forests. Although significant progress has been made in the application of remote sensing technologies, the structural complexity of native forests means that there are still technical issues that require resolving before this approach becomes operationally routine. [ABSTRACT FROM AUTHOR]

Abstract: A conceptual model describing the response of two Australian floodplain eucalypts, river red gum (Eucalyptus camaldulensis) and black box (Eucalyptus largiflorens), to changes in water availability was developed based on field observations. This model was incorporated into a percentage based visual method estimating two tree crown parameters, crown extent and density. Extent is the amount of foliage at the periphery of the assessable crown; density is the density of assessable crown foliage. Polychoric correlation was used to determine the level of agreement between two experienced observers assessing river red gum and black box trees using a simple percentage scale and a percentage scale supported by the conceptual model. Trees were evaluated using the model by determining their position on a trajectory of water stress related decline and response. In both cases observer estimates of crown extent and density were significantly correlated. With the exception of red gum crown density the correlation coefficients were higher for the model supported scale. Using a conceptual model of tree response to water availability improved observer agreement. Supporting subjective assessment systems with a conceptual model is recommended to improve observer agreement in cases where a distinct model of the dominant stressor can be defined. [Copyright &y& Elsevier]

Abstract: Within Australia, the discrimination and mapping of forest communities has traditionally been undertaken at the stand scale using stereo aerial photography. Focusing on mixed species forests in central south-east Queensland, this paper outlines an approach for the generation of tree species maps at the tree crown/cluster level using 1 m spatial resolution Compact Airborne Spectrographic Imager (CASI; 445.8 nm–837.7 nm wavelength) and the use of these to generate stand-level assessments of community composition. Following automated delineation of tree crowns/crown clusters, spectral reflectance from pixels representing maxima or mean-lit averages of channel reflectance or band ratios were extracted for a range of species including Acacia, Angophora, Callitris and Eucalyptus. Based on stepwise discriminant analysis, classification accuracies of dominant species were greatest (87% and 76% for training and testing datasets; n =398) when the mean-lit spectra associated with a ratio of the reflectance (ρ) at 742 nm (ρ 742) and 714 nm (ρ 714) were used. The integration of 2.6 m HyMap (446.1 nm–2477.8 nm) spectra increased the accuracy of classification for some species, largely because of the inclusion of shortwave infrared wavebands. Similar increases in accuracy were achieved when classifications of field spectra resampled to CASI and HyMap wavebands were compared. The discriminant functions were applied subsequently to classify crowns within each image and produce maps of tree species distributions which were equivalent or better than those generated through aerial photograph interpretation. The research provides a new approach to tree species mapping, although some a priori knowledge of the occurrence of broad species groups is required. The tree maps have application to biodiversity assessment in Australian forests. [Copyright &y& Elsevier]

The ecology of floodplain ecosystems evolved according to the historical frequency and extent of inundation. In many dryland rivers, inundation frequency has reduced due to regulation, competition for water resources and climate change. In some rivers infrastructure has been constructed to enable temporary rises in water level and more frequent floodplain inundation, delivering environmental water to ecosystems that are dependent on surface water. During such events, the release of dissolved organic carbon (DOC) from inundated plant material may result in depletion of dissolved oxygen (DO). If the rate of DO depletion exceeds re‐aeration, hypoxic conditions can occur. Models have been developed to represent these processes, however, there is a wide range of chemical and biological interactions, and hence model parameters, involved. The aim of this research was: (1) identify the dominant parameters through sensitivity analysis, (2) design and implement a field monitoring program to quantify the inherent variability in those parameters, and (3) translate that input variability into the modelled DO, ultimately to support risk management decisions when planning delivery of environmental water. The results indicated that the mass of organic matter on a floodplain had the greatest impact on the modelled DO concentrations. Based on the field monitoring results, the steady state load of organic matter, that is, when the accumulation and decay rates are equal, was estimated, and vegetation mapping used to apply the field monitoring results across the floodplain for a 206 km reach of river of the River Murray, Australia. The model results from multiple, cumulative, operations identified one particular high‐risk operational site. The results are useful to prioritize monitoring effort to focus on the most sensitive model parameters and indicate that the likelihood of hypoxic conditions can be reduced through slower rates of inundation and timing events to coincide with periods with lower water temperature. The methodology developed can be transferred to other sites where hypoxic conditions are a potential outcome associated with delivery of environmental water. [ABSTRACT FROM AUTHOR]

Context: Vegetation patterns in hummock grasslands of Australia's arid interior can be very complex. Additionally, the grasslands are interspersed with variable amounts of trees and shrubs. Objectives: To better understand the spatial arrangement of this vegetation structure, and in particular the unvegetated bare-soil gaps, we analyzed the scale-dependent patterns of gaps, trees, and shrubs. Methods: We focused on two size categories of grassland gaps, large gaps ≥ 4 m2 known as fairy circles (FCs) and small gaps 1 to < 4 m2, and on trees and shrubs. We mapped four 200 m × 200 m study plots located east of the town of Newman in Western Australia, using drone-based aerial images and LiDAR. The RGB images were converted into binary images and the gaps and woody plants were automatically segmented. The spatial patterns of the four vegetation components were analyzed, as well as the shape properties of the vegetation gaps. Results: The most striking result was that small gaps appeared consistently at about 5 m distance away from the FCs, which are known as the most water-depleted locations in the grassland. The FCs were also rounder than the small gaps and this symmetry underlines their function as an extra source of water for the surrounding matrix vegetation. Trees and shrubs had spatial patterns that were unrelated to FCs, which likely results from their water uptake in deeper sub-soil layers. Conclusions: The consistent distance of small gaps to FCs is further support that the Australian fairy circles are a self-organized vegetation pattern that results from ecohydrological feedbacks. [ABSTRACT FROM AUTHOR]

Rapid decline and death of rural Eucalypts trees of all ages and species have been reported in the farmscapes of regional Australia due to various environmental and farming management related factors. The identification of existing farm tree species is important for long term management strategies to provide ecosystem stability in the region. This study explored the feasibility of structural attributes of LiDAR and spectral and spatial characteristics of high resolution remote sensing data to identify and map Eucalyptus tree species. An object based image segmentation and rule-based classification algorithm were developed to delineate tree boundaries and species classification. The integration of two datasets improved the classification accuracy (65%) against their separate classification (52% and 41%, respectively). The identification of tree species will help in getting first-hand information on existing farm trees, which may be used in assessing tree condition in time series related to management practices and complex dieback problem. [ABSTRACT FROM AUTHOR]

Herbivore foraging decisions are closely related to plant nutritional quality. For arboreal folivores with specialized diets, such as the vulnerable greater glider (Petauroides volans), the abundance of suitable forage trees can influence habitat suitability and species occurrence. The ability to model and map foliar nitrogen would therefore enhance our understanding of folivore habitat use at finer scales. We tested whether high‐resolution multispectral imagery, collected by a lightweight and low‐cost commercial unoccupied aerial vehicle (UAV), could be used to predict total and digestible foliar nitrogen (N and digN) at the tree canopy level and forest stand‐scale from leaf‐scale chemistry measurements across a gradient of mixed‐species Eucalyptus forests in southeastern Australia. We surveyed temperate Eucalyptus forests across an elevational and topographic gradient from sea level to high elevation (50–1200 m a.s.l.) for forest structure, leaf chemistry, and greater glider occurrence. Using measures of multispectral leaf reflectance and spectral indices, we estimated N and digN and mapped N and favorable feeding habitat using machine learning algorithms. Our surveys covered 17 Eucalyptus species ranging in foliar N from 0.63% to 1.92% dry matter (DM) and digN from 0.45% to 1.73% DM. Both multispectral leaf reflectance and spectral indices were strong predictors for N and digN in model cross‐validation. At the tree level, 79% of variability between observed and predicted measures of nitrogen was explained. A spatial supervised classification model correctly identified 80% of canopy pixels associated with high N concentrations (≥1% DM). We developed a successful method for estimating foliar nitrogen of a range of temperate Eucalyptus species using UAV multispectral imagery at the tree canopy level and stand scale. The ability to spatially quantify feeding habitat using UAV imagery allows remote assessments of greater glider habitat at a scale relevant to support ground surveys, management, and conservation for the vulnerable greater glider across southeastern Australia. [ABSTRACT FROM AUTHOR]

Overcoming low breeding success is a major challenge for reversing population decline in threatened species. High nest predation rates are a common cause of low productivity in birds, but implementing evidence‐based management actions to reduce nest predation is challenging. Targeted breeding management requires a good understanding of where threatened species breed, the identity and distribution of nest predator species and the impact of these nest predators on breeding success. For rare and nomadic species, this information is hard to come by. The breeding success of regent honeyeater Anthochaera phrygia has declined over recent decades, and nest predation is the primary cause of breeding failure. We conducted point‐count surveys of nine avian and three mammalian nest predator species across 80% of the regent honeyeater's contemporary breeding area in south eastern Australia. We used occupancy models to determine the presence of predator species at survey sites and spatial models to predict predator abundance and species richness across the breeding area. We incorporated predator predictions for regent honeyeater nest locations into nest fate and daily nest survival models. Predator abundance was correlated positively with tree hollow abundance and proximity to water and negatively with shrub cover. Regent honeyeater nest success showed no significant relationship with predator abundance or predator species richness. Given how abundant and widespread avian and mammalian nest predators were throughout the breeding area, improving regent honeyeater nest success is likely to require implementation of simultaneous nest protection measures to avoid potential compensatory nest predation. Further research is required to better understand the relationship between nest predator abundance and regent honeyeater nest success. [ABSTRACT FROM AUTHOR]

Vegetation complexity is an important predictor of animal species diversity. Specifically, taller vegetation should provide more potential ecological niches and thus harbor communities with higher species richness and functional diversity (FD). Resource use behavior is an especially important functional trait because it links species to their resource base with direct relevance to niche partitioning. However, it is unclear how exactly the diversity of resource use behavior changes with vegetation complexity. To address this question, we studied avian FD in relation to vegetation complexity along a continental‐scale vegetation gradient. We quantified foraging behavior of passerine birds in terms of foraging method and substrate use at 21 sites (63 transects) spanning 3,000 km of woodlands and forests in Australia. We also quantified vegetation structure on 630 sampling points at the same sites. Additionally, we measured morphological traits for all 111 observed species in museum collections. We calculated individual‐based, abundance‐weighted FD in morphology and foraging behavior and related it to species richness and vegetation complexity (indexed by canopy height) using structural equation modeling, rarefaction analyses, and distance‐based metrics. FD of morphology and foraging methods was best predicted by species richness. However, FD of substrate use was best predicted by canopy height (ranging 10–30 m), but only when substrates were categorized with fine resolution (17 categories), not when categorized coarsely (8 categories). These results suggest that, first, FD might increase with vegetation complexity independently of species richness, but whether it does so depends on the studied functional trait. Second, patterns found might be shaped by how finely we categorize functional traits. More complex vegetation provided larger "ecological space" with more resources, allowing the coexistence of more species with disproportionately more diverse foraging substrate use. We suggest that the latter pattern was driven by nonrandom accumulation of functionally distinct species with increasing canopy height. [ABSTRACT FROM AUTHOR]

• Frequent prescribed burning was applied over 45 years at a long running experiment. • Annual burning encouraged tree diameter growth rates. • Stand basal area had a negative influence on tree growth rates. • Triennial burning enhanced tree recruitment, resulting in higher tree densities. Frequent fire often has a negative impact of tree recruitment and growth. Tree growth rates, density and recruitment were compared among treatments of annual burning since 1952, triennial burning since 1973 and no burning (1946 to 1996) or single wildfire (1996 to 2018), in a dry sclerophyll eucalypt forest, south-eastern Queensland, Australia. Tree diameter (at breast height, DBH) growth rates were greater in the annually burnt treatment than in the triennially burn and single wildfire treatments over the period from 1974 to 2018, and these differences were also apparent pre-wildfire (period from 1974 to 1996). In the period from 1996 to 2018, the annually burnt treatment had greater DBH growth relative to the single wildfire treatment, but the triennial treatment had intermediate growth rates. Competitive interactions between trees (assessed using plot basal area) also had a negative impact on individual tree growth rates. The impacts of different fire regimes at this site on tree crown health were not apparent (P > 0.05) and there was only limited evidence that differences in growth rates were due to differences in soil nutrients (marginally higher topsoil phosphorus in the frequently burnt treatments, P = 0.075). Greater tree growth rates in the annually burnt treatment may be related to the lower density of understorey woody plants in this treatment and potentially reduced competition for soil moisture. The density of trees (DBH ≥ 10 cm) in 2018 was surprisingly higher in the triennially burnt treatment (381 stems/ha) relative to both the annually burnt (192 stems/ha) and single wildfire (234 stems/ha) treatments. This was largely due a higher level of recruitment over time and a higher density of stems 10–20 cm DBH in triennially burnt plots. Concerns regarding the impacts of frequent prescribed fire on tree recruitment and growth may be unwarranted in these remarkably resilient dry eucalypt forests. [ABSTRACT FROM AUTHOR]

Paropsis charybdis (Coleoptera: Chrysomelidae) has been a major pest of Eucalyptus spp. since invading New Zealand from Australia over 100 years ago. Here, we report on the phenology, egg parasitism and defoliation levels of P. charybdis at two Eucalyptus nitens plantations in the central North Island of New Zealand and assess the establishment prospects and potential impact of a new biological control agent, the larval parasitoid Eadya daenerys. Field monitoring found that 90–100% of first generation P. charybdis eggs emerged, showing that the existing egg parasitoids Enoggera nassaui (Hymenoptera: Braconidae) and Neopolycystus insectifurax (Hymenoptera: Pteromalidae) are ineffective at controlling this generation. Further field monitoring revealed effective control of second generation eggs by E. nassaui and N. insectifurax despite the presence of Baeoanusia albifunicle (Hymenoptera: Encyrtidae), a hyperparasitoid of E. nassaui. Phenology data show that first generation P. charybdis larvae will likely be synchronous with the adult emergence of E. daenerys (Hymenoptera: Braconidae) the new larval endoparasitoid proposed to be introduced from Australia. Climate matching predicts E. daenerys could establish in all areas of New Zealand where P. charybdisimpacted Eucalyptus spp. plantations are grown. The addition of a larval endoparasitoid could significantly contribute to the suppression of P. charybdis by decreasing first generation larval survival. [ABSTRACT FROM AUTHOR]

Two of Australia's most iconic ecosystems have recently sustained heavy damage related to climatic changes: the extensive eucalypt forests from catastrophic bushfires and the Great Barrier Reef from mass coral bleaching. Despite obvious differences, eucalypt trees and reef corals share some similarities in biology and ecology, particularly in relation to climate change impacts and adaptation. Both groups are the focus of an increasing research effort to characterize and respond to climate changes and here we examine how sharing research experiences can benefit both fields. Four key areas of research are considered: (a) modeling current distributions, (b) assessing impacts of climate change on future distributions, (c) using human‐assisted migration to improve survival, and (d) applying genetic enhancement to improve the species' survival. Examples of each research area are used to examine potential crossovers, limitations of the methods, and future requirements. We conclude that eucalypt and coral researchers, and indeed researchers for many other endangered taxa, can gain much by comparing experiences and methods, despite the apparent differences in their respective taxa. This article is categorized under: Assessing Impacts of Climate Change > Observed Impacts of Climate Change [ABSTRACT FROM AUTHOR]

Habitat fragmentation imperils the persistence of many functionally important species, with climate change a new threat to local persistence due to climate niche mismatching. Predicting the evolutionary trajectory of species essential to ecosystem function under future climates is challenging but necessary for prioritizing conservation investments. We use a combination of population genetics and niche suitability models to assess the trajectory of a functionally important, but highly fragmented, plant species from south‐eastern Australia (Banksia marginata, Proteaceae). We demonstrate significant genetic structuring among, and high level of relatedness within, fragmented remnant populations, highlighting imminent risks of inbreeding. Population simulations, controlling for effective population size (Ne), suggest that many remnant populations will suffer rapid declines in genetic diversity due to drift in the absence of intervention. Simulations were used to demonstrate how inbreeding and drift processes might be suppressed by assisted migration and population mixing approaches that enhance the size and connectivity of remnant populations. These analyses were complemented by niche suitability models that predicted substantial reductions of suitable habitat by 2080; ~30% of the current distribution of the species climate niche overlaps with the projected distribution of the species climate niche in the geographic region by the 2080s. Our study highlights the importance of conserving remnant populations and establishing new populations in areas likely to support B. marginata in the future, and adopting seed sourcing strategies that can help populations overcome the risks of inbreeding and maladaptation. We also argue that ecological replacement of B. marginata using climatically suited plant species might be needed in the future to maintain ecosystem processes where B. marginata cannot persist. We recommend the need for progressive revegetation policies and practices to prevent further deterioration of species such as B. marginata and the ecosystems they support. [ABSTRACT FROM AUTHOR]

In 2019/20 over 100 severe bushfires burned across the continent of Australia. The severity of these fires was exacerbated by many factors, including macroclimatic effects of global warming and, at the meso and micro scales, land management practices. The bushfire phenomenon cannot be stopped, however better management practices can help counter the increasing severity of fires. Hazard reduction burning is a method where certain vegetation is deliberately burned under controlled circumstances to thin the fuel to reduce the severity of bushfires. Fuel load is an important parameter to assess when hazard reduction burning, as the accumulation of vegetation in a forest profile affects the intensity of the burn. Conventional methods of measuring fuel load are time consuming and costly, and therefore it becomes increasingly important to investigate automated approaches for assessing fuel loads. This paper provides an overview of hazard reduction burning while explaining the methods to quantify fuel load. Then the paper presents our voxel approach in estimating the volume of fuel loads. The first results regarding different voxel resolutions are reported and analysed. This paper concludes with future steps and developments. [ABSTRACT FROM AUTHOR]

The expansion of rainforest pioneer trees into long‐unburnt open forests has become increasingly widespread across high rainfall regions of Australia. Increasing tree cover can limit resource availability for understorey plant communities and reduce understorey diversity. However, it remains unclear if sclerophyll and rainforest trees differ in their competitive exclusion of understory plant communities, which contain most of the floristic diversity of open forests. Here, we examine dry open forest across contrasting fire histories (burnt and unburnt) and levels of rainforest invasion (sclerophyll or rainforest midstorey) to hindcast changes in understorey plant density, richness and composition. The influence of these treatments and other site variables (midstorey structure, midstorey composition and soil parameters) on understorey plant communities were all examined. This study is the first to demonstrate significantly greater losses of understorey species richness, particularly of dry open‐forest specialists, under an invading rainforest midstorey compared to a typical sclerophyll midstorey. Rainforest pioneers displaced over half of the understorey plant species, and reduced ground cover and density of dry forest specialists by ~90%. Significant understorey declines also occurred with increased sclerophyll midstorey cover following fire exclusion, although losses were typically less than half that of rainforest‐invaded sites over the same period. Understorey declines were closely related to leaf area index and basal area of rainforest and wattle trees, suggesting competitive exclusion through shading and potentially belowground competition for water. Around 20% of displaced species lacked any capacity for population recovery, while transient seed banks or distance‐limited dispersal may hinder recovery for a further 68%. We conclude that rainforest invasion leads to significant declines in understorey plant diversity and cover in open forests. To avoid elimination of local native plant populations in open forests, fires should occur with sufficient frequency to prevent overstorey cover from reaching a level where shade‐intolerant species fail to thrive. [ABSTRACT FROM AUTHOR]

Ground-based visual assessment of crown condition is a cornerstone of tree condition assessment globally, and numerous condition assessment approaches have evolved to address the needs and perspectives of different users. In Australia's iconic Murray–Darling Basin (MDB), stands of floodplain eucalypts are increasingly vulnerable to a range of interacting stressors related to climate change and over-extraction of water for consumptive and agricultural use. A standardised approach developed in 2008 for assessing floodplain trees within the MDB provides extensive guidance to ensure field data is collected consistently. However, there is minimal instruction on how to interpret data, and consequently a range of evaluation approaches have evolved. The lack of a standardised reporting framework generated by these different approaches makes it difficult for floodplain managers and environmental water holders to make repeatable, robust decisions for prioritising water allocations across competing locations. To provide improved lines of evidence to support decision making, this paper describes a 'best-practise' approach to calculating a tree condition score from field data. Within, we document existing approaches in the southern Murray–Darling Basin, and recommend a method that meets the needs of floodplain managers as a pragmatic reporting, communication and decision support tool that does not require statistical analysis. Case studies and a revised conceptual model of tree decline and recovery are provided to demonstrate the validity of the recommended approach. [ABSTRACT FROM AUTHOR]

One of the major questions in ecology is how species share their ecological space and what enables them to coexist. Partitioning of foraging niches should facilitate local coexistence. Thus, detailed data on foraging ecology are needed to provide insight into the assembly of communities. To this end, we quantified foraging behaviour of songbirds (Passeriformes) on 21 sites in woodlands and open forests of eastern Australia along a 3000 km long latitudinal transect spanning from the tropics to southern temperate regions. We obtained 5894 prey attacks by 2624 individuals from 112 species. Birds foraged mostly by gleaning (53.4% of attacks) on leaves (51.3%) in the outer part of crown (41.4%) and in medium foliage density (40.8%). Birds foraged along the whole vertical extent of vegetation, but individual species concentrated their foraging into particular strata. In the 41 best sampled species (minimum of 30 attacks recorded), we identified foraging guilds defined first by the foraging substrate and then by the foraging method. Specialisation on foraging substrate was positively correlated with specialisation on method. The organisation of guilds, patterns of substrate and method used across species, and species specialisation were similar to previous local-scale studies from eucalypt woodlands and forests, and from forests in northern temperate regions in Europe and North America. Thus, using our own data and comparisons with previous studies, we confirm a general pattern of foraging guild organisation of woodland and forest songbirds outside the tropics. [ABSTRACT FROM AUTHOR]

Background: Almond is an emerging crop due to the health benefits of almond consumption including nutritional, anti-inflammatory, and hypocholesterolaemia properties. Traditional almond producers were concentrated in California, Australia, and Mediterranean countries. However, almond is currently present in more than 50 countries due to breeding programs have modernized almond orchards by developing new varieties with improved traits related to late flowering (to reduce the risk of damage caused by late frosts) and tree architecture. Almond tree architecture and flowering are acquired and evaluated through intensive field labour for breeders. Flowering detection has traditionally been a very challenging objective. To our knowledge, there is no published information about monitoring of the tree flowering dynamics of a crop at the field scale by using color information from photogrammetric 3D point clouds and OBIA. As an alternative, a procedure based on the generation of colored photogrammetric point clouds using a low cost (RGB) camera on-board an unmanned aerial vehicle (UAV), and an semi-automatic object based image analysis (OBIA) algorithm was created for monitoring the flower density and flowering period of every almond tree in the framework of two almond phenotypic trials with different planting dates. Results: Our method was useful for detecting the phenotypic variability of every almond variety by mapping and quantifying every tree height and volume as well as the flowering dynamics and flower density. There was a high level of agreement among the tree height, flower density, and blooming calendar derived from our procedure on both fields with the ones created from on-ground measured data. Some of the almond varieties showed a significant linear fit between its crown volume and their yield. Conclusions: Our findings could help breeders and researchers to reduce the gap between phenomics and genomics by generating accurate almond tree information in an efficient, non-destructive, and inexpensive way. The method described is also useful for data mining to select the most promising accessions, making it possible to assess specific multi-criteria ranking varieties, which are one of the main tools for breeders. [ABSTRACT FROM AUTHOR]

Worldwide, extreme climatic events such as drought and heatwaves are associated with forest mortality. However, the precise drivers of tree mortality at individual and stand levels vary considerably, with substantial gaps in knowledge across studies in biomes and continents. In 2010–2011, a drought‐associated heatwave occurred in south‐western Australia and drove sudden and rapid forest canopy collapse. Working in the Northern Jarrah (Eucalyptus marginata) Forest, we quantified the response of key overstory (E. marginata, Corymbia calophylla) and midstory (Banksia grandis, Allocasuarina fraseriana) tree species to the extreme climate event. Using transects spanning a gradient of drought impacts (minimal (50–100 m), transitional (100–150 m) and severe (30–60 m)), tree species mortality in relation to stand characteristics (stand basal area and stem density) and edaphic factors (soil depth) was determined. We show differential mortality between the two overstory species and the two midstory species corresponding to the drought‐associated heatwave. The dominant overstory species, E. marginata, had significantly higher mortality (~19%) than C. calophylla (~7%) in the severe zone. The midstory species, B. grandis, demonstrated substantially higher mortality (~59%) than A. fraseriana (~4%) in the transitional zone. Banksia grandis exhibited a substantial shift in structure in response to the drought‐associated heatwave in relation to tree size, basal area and soil depth. This study illustrates the role of climate extremes in driving ecosystem change and highlights the critical need to identify and quantify the resulting impact to help predict future forest die‐off events and to underpin forest management and conservation. [ABSTRACT FROM AUTHOR]

Wildfire refugia (unburnt patches within large wildfires) are important for the persistence of fire‐sensitive species across forested landscapes globally. A key challenge is to identify the factors that determine the distribution of fire refugia across space and time. In particular, determining the relative influence of climatic and landscape factors is important in order to understand likely changes in the distribution of wildfire refugia under future climates. Here, we examine the relative effect of weather (i.e. fire weather, drought severity) and landscape features (i.e. topography, fuel age, vegetation type) on the occurrence of fire refugia across 26 large wildfires in south‐eastern Australia. Fire weather and drought severity were the primary drivers of the occurrence of fire refugia, moderating the effect of landscape attributes. Unburnt patches rarely occurred under 'severe' fire weather, irrespective of drought severity, topography, fuels or vegetation community. The influence of drought severity and landscape factors played out most strongly under 'moderate' fire weather. In mesic forests, fire refugia were linked to variables that affect fuel moisture, whereby the occurrence of unburnt patches decreased with increasing drought conditions and were associated with more mesic topographic locations (i.e. gullies, pole‐facing aspects) and vegetation communities (i.e. closed‐forest). In dry forest, the occurrence of refugia was responsive to fuel age, being associated with recently burnt areas (<5 years since fire). Overall, these results show that increased severity of fire weather and increased drought conditions, both predicted under future climate scenarios, are likely to lead to a reduction of wildfire refugia across forests of southern Australia. Protection of topographic areas able to provide long‐term fire refugia will be an important step towards maintaining the ecological integrity of forests under future climate change. [ABSTRACT FROM AUTHOR]

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Trait divergence between populations is considered an adaptive response to different environments, but to what extent this response is accompanied by genetic differentiation is less clear since it may be phenotypic plasticity. In this study, we analyzed phenotypic variation between two Banksia attenuata growth forms, lignotuberous (shrub) and epicormic resprouting (tree), in fire‐prone environments to identify the environmental factors that have driven this phenotypic divergence. We linked genotype with phenotype and traced candidate genes using differential gene expression analysis. Fire intervals determined the phenotypic divergence between growth forms in B. attenuata. A genome‐wide association study identified 69 single nucleotide polymorphisms, putatively associated with growth form, whereas no growth form‐ or phenotype‐specific genotypes were identified. Genomic differentiation between the two growth forms was low (Fst = 0.024). Differential gene expression analysis identified 37 genes/transcripts that were differentially expressed in the two growth forms. A small heat‐shock protein gene, associated with lignotuber presence, was differentially expressed in the two forms. We conclude that different fire regimes induce phenotypic polymorphism in B. attenuata, whereas phenotypic trait divergence involves the differential expression of a small fraction of genes that interact strongly with the disturbance regime. Thus, phenotypic plasticity among resprouters is the general strategy for surviving varying fire regimes. Banksia attenuata has tree and shrub growth forms in ecosystems with frequent fire as an ecological disturbance in southwestern Australia. The divergence in growth form is determined by fire frequency in their habitats and by the differential expression of a small number of genes that interact with the disturbance regime. [ABSTRACT FROM AUTHOR]

The effects of anthropogenic climate change on biodiversity are well known for some high‐profile Australian marine systems, including coral bleaching and kelp forest devastation. Less well‐published are the impacts of climate change being observed in terrestrial ecosystems, although ecological models have predicted substantial changes are likely. Detecting and attributing terrestrial changes to anthropogenic factors is difficult due to the ecological importance of extreme conditions, the noisy nature of short‐term data collected with limited resources, and complexities introduced by biotic interactions. Here, we provide a suite of case studies that have considered possible impacts of anthropogenic climate change on Australian terrestrial systems. Our intention is to provide a diverse collection of stories illustrating how Australian flora and fauna are likely responding to direct and indirect effects of anthropogenic climate change. We aim to raise awareness rather than be comprehensive. We include case studies covering canopy dieback in forests, compositional shifts in vegetation, positive feedbacks between climate, vegetation and disturbance regimes, local extinctions in plants, size changes in birds, phenological shifts in reproduction and shifting biotic interactions that threaten communities and endangered species. Some of these changes are direct and clear cut, others are indirect and less clearly connected to climate change; however, all are important in providing insights into the future state of terrestrial ecosystems. We also highlight some of the management issues relevant to conserving terrestrial communities and ecosystems in the face of anthropogenic climate change. [ABSTRACT FROM AUTHOR]

Aim Savanna biomes cover around 20% of land surfaces, yet the origins and processes that have shaped their biodiversity remain understudied. Here, we assess the timing of diversification and how patterns of genetic diversity vary along an aridity gradient in specialized saxicoline gecko clades ( Oedura spp.) from the tropical savannas of northern Australia. Location Australian Monsoonal Tropics ( AMT), Kimberley region (Western Australia). Methods We compiled mitochondrial and nuclear data for two Kimberley endemic lizard clades ( Oedura filicipoda/murrumanu and O. gracilis), and allied non-Kimberley taxa ( O. marmorata complex). Species delimitation methods were used to identify evolutionary lineages, Maximum-likelihood and Bayesian phylogenetic methods were employed to assess relationships and diversification timeframes, and rainfall data and range sizes were tested for correlations. Results Phylogenetic analyses of cryptic or recently discovered lineage diversity revealed late-Miocene to early-Pliocene crown ages. Microendemism and diversity were highest in high-rainfall regions, while the most widespread lineages occurred in the central and south-east Kimberley, and showed evidence of introgression with parapatric lineages. Main conclusions The initial diversification in both clades was broadly concordant with global climatic events linked to the expansion of savanna biomes in the lateMiocene. Higher endemism in mesic and refugial areas suggests long histories of localized persistence, while wider distributions and evidence of introgression suggest a dynamic history at the arid-monsoonal interface. [ABSTRACT FROM AUTHOR]

Over the past 100 years, Australia has experienced pronounced changes in rainfall patterns, which in south-western Australia (SWAU) has resulted in both a >50% decrease of runoff since 1975 and effects on vegetation health. Resolving the dynamics of vegetation and climate is a prerequisite for predicting the response of vegetation to future climates and carbon mitigation objectives. With multi-resource vegetation indices (VIs; normalized difference vegetation index and leaf area index) and gridded climate data, this paper examines vegetation dynamics and sensitivity to rainfall change on the Australian continent for the past long drought period (2002-2010). We found that rainfall and VIs declined across 90% and 80% of the whole continent, respectively, compared to the baseline period of 2000-2001. The most dramatic declines in VIs occurred in open shrublands near the center of Australia and in SWAU, coinciding with significant reductions in rainfall and soil moisture. Overall, a strong relationship between water (rainfall and soil moisture) and VIs was detected in places where rainfall declined dramatically (up to 5 mm/year since 1970). For five major vegetation types, croplands showed the highest sensitivity to water change, followed by grasslands and woody savanna. Moderate sensitivity of open shrublands to water change was found, while evergreen broadleaf forests only showed a slight sensitivity to soil moisture change. Although there was no consistent significant relationship between rainfall and VIs of evergreen broadleaf forests, forests in south-eastern Australia, where rainfall had declined since 1997, have become more sensitive to rainfall change than in SWAU. Our results provide evidence that, at this scale of assessment and with interpolated data sets, a lasting reduced rainfall pattern has been a key factor constraining vegetation growth over the Australian continent. [ABSTRACT FROM AUTHOR]

Globally, forests are facing an increasing risk of mass tree mortality events associated with extreme droughts and higher temperatures. Hydraulic dysfunction is considered a key mechanism of drought-triggered dieback. By leveraging the climate breadth of the Australian landscape and a national network of research sites (Terrestrial Ecosystem Research Network), we conducted a continental-scale study of physiological and hydraulic traits of 33 native tree species from contrasting environments to disentangle the complexities of plant response to drought across communities. We found strong relationships between key plant hydraulic traits and site aridity. Leaf turgor loss point and xylem embolism resistance were correlated with minimum water potential experienced by each species. Across the data set, there was a strong coordination between hydraulic traits, including those linked to hydraulic safety, stomatal regulation and the cost of carbon investment into woody tissue. These results illustrate that aridity has acted as a strong selective pressure, shaping hydraulic traits of tree species across the Australian landscape. Hydraulic safety margins were constrained across sites, with species from wetter sites tending to have smaller safety margin compared with species at drier sites, suggesting trees are operating close to their hydraulic thresholds and forest biomes across the spectrum may be susceptible to shifts in climate that result in the intensification of drought., (© 2021 John Wiley & Sons Ltd.)

There is a significant need to provide nationwide consistent information for land managers and scientists to assist with property planning, vegetation monitoring applications, risk assessment, and conservation activities at an appropriate spatial scale. We created maps of woody vegetation cover of Australia using a consistent method applied across the continent, and made them accessible. We classified pixels as woody or not woody, quantified their foliage projective cover, and classed them as forest or other wooded lands based on their cover density. The maps provide, for the first time, cover density estimates of Australian forests and other wooded lands with the spatial detail required for local-scale studies. The maps were created by linking field data, collected by a network of collaborators across the continent, to a time series of Landsat-5 TM and Landsat-7 ETM+ images for the period 2000-2010. The fractions of green vegetation cover, non-green vegetation cover, and bare ground were calculated for each pixel using a previously developed spectral unmixing approach. Time series statistics, for the green vegetation cover, were used to classify each pixel as either woody or not using a random forest classifier. An estimate of woody foliage projective cover was made by calibration with field measurements, and woody pixels classified as forest where the foliage cover was at least 0.1. Validation of the foliage projective cover with field measurements gave a coefficient of determination, R²,of 0.918 and root mean square error of 0.070. The user's and producer's accuracies for areas mapped as forest were high at 92.2% and 95.9%, respectively. The user's and producers's accuracies were lower for other wooded lands at 75.7% and 61.3%, respectively. Further research into methods to better separate areas with sparse woody vegetation from those without woody vegetation is needed. The maps provide information that will assist in gaining a better understanding of our natural environment. Applications range from the continental-scale activity of estimating national carbon stocks, to the local scale activities of assessing habitat suitability and property planning. [ABSTRACT FROM AUTHOR]

Spaceborne laser altimetry waveform estimates of canopy Gap Fraction (GF) vary with respect to discrete return airborne equivalents due to their greater sensitivity to reflectance differences between canopy and ground surfaces resulting from differences in footprint size, energy thresholding, noise characteristics and sampling geometry. Applying scaling factors to either the ground or canopy portions of waveforms has successfully circumvented this issue, but not at large scales. This study develops a method to scale spaceborne altimeter waveforms by identifying which remotely-sensed vegetation, terrain and environmental attributes are best suited to predicting scaling factors based on an independent measure of importance. The most important attributes were identified as: soil phosphorus and nitrogen contents, vegetation height, MODIS vegetation continuous fields product and terrain slope. Unscaled and scaled estimates of GF are compared to corresponding ALS data for all available data and an optimized subset, where the latter produced most encouraging results (R² = 0.89, RMSE = 0.10). This methodology shows potential for successfully refining estimates of GF at large scales and identifies the most suitable attributes for deriving appropriate scaling factors. Large-scale active sensor estimates of GF can establish a baseline from which future monitoring investigations can be initiated via upcoming Earth Observation missions. [ABSTRACT FROM AUTHOR]

Australia supports a high diversity of sequestrate (truffle-like) macrofungi. This has long been thought to be related to the predominantly or seasonally dry climate. The present study posits that if aridity were a key factor in the evolution of sequestrate fruit-bodies, most sequestrate species would have emerged in Australia only after it began to aridify, which occurred post-separation with Antarctica (c. 32 million years ago). Focusing on the high phylogenetic diversity of sequestrate taxa in the Agaricomycetes in Australia, dates of sequestrate nodes were compiled directly from published phylogenies (four lineages) or created using sequences available on GenBank that were processed in BEAST using a secondary calibration method (nine lineages). Although the morphologically diverse Hysterangiales was found to be the first group to become sequestrate, c. 83 million years ago, overall sequestration in Australia occurred more recently. Models were created and compared and support was found for an increased rate of sequestration in Australia at some point between 34 and 13 million years ago (during the Oligocene and Miocene). Although the rate of sequestration is shown to have increased in Australia after separation from Antarctica, the timing also overlaps with the radiation of potential mycorrhizal plant associates, and the emergence of specialised mycophagous marsupials. Although aridification is evidently not the sole driver of sequestration, it is still likely to have had a major influence on the diversity of sequestrate fungi in Australia. Comparisons with other regions of high sequestrate diversity will be informative. [ABSTRACT FROM AUTHOR]

We analysed the influence of weather, time since fire (TSF) and topography on the occurrence of crown fire, as mapped from satellite imagery, in 23 of the largest wildfires in dry sclerophyll forests in eastern Australia from 2002 to 2013. Fires were analysed both individually and as groups. Fire weather was the most important predictor of crown consumption. TSF (a surrogate for fuel accumulation) had complex nonlinear effects that varied among fires. Crown fire likelihood was low up to 4 years post-fire, peaked at, 10 years post-fire and then declined. There was no clear indication that recent burning became more or less effective as fire weather became more severe. Steeper slope reduced crown fire likelihood, contrary to the assumptions of common fire behaviour equations. More exposed areas (ridges and plains) had higher crown fire likelihood. Our results suggest prescribed burning to maintain an average of 10 years' TSF may actually increase crown fire likelihood, but burning much more frequently can be effective for risk reduction. Our results also suggest the effects of weather, TSF and slope are not adequately represented in the underlying equations of most fire behaviour models, potentially leading to poor prediction of fire spread and risk. [ABSTRACT FROM AUTHOR]

Population monitoring is fundamental to the conservation of threatened species. This study aimed to develop an effective approach for long-term monitoring of the yellow-bellied glider (Petaurus australis) in north-eastNewSouth Wales. We conducted repeat surveys to account for imperfect detection and used counts in abundance modelling to produce indices of abundance. We used simulations to explore refinements to our study design. Surveys over three consecutive years produced 195 detections with >95% of detections by call. The probability of detection varied across years and survey occasions, ranging from 0.22 to 0.71. Abundance estimates were remarkably constant across years, ranging from 2.3±0.5 to 2.4±0.6 individuals per site. Occupancy estimates were also constant across years (0.90-0.91). Simulations were run to investigate the influence of the number of surveys (2 or 3) and the number of survey sites (20, 40 or 50) on the probability of occupancy. The design that reduced bias and provided an adequate improvement to precision was that of three visits to 40 survey sites. This design should be adequate to detect a decline in population abundance. Further studies of this kind are needed to better understand the population dynamics of this species. [ABSTRACT FROM AUTHOR]

The spatial arrangement and vertical structure of vegetation in urban green spaces are key factors in determining the types of benefits that urban parks provide to people. This includes opportunities for recreation, spiritual fulfilment and biodiversity conservation. However, there has been little consideration of how the fine-scale spatial and vertical structure of vegetation is distributed in urban parks, primarily due to limitations in methods for doing so. We addressed this gap by developing a method using Light Detection and Ranging (LiDAR) data to map, at a fine resolution, tree cover, vegetation spatial arrangement, and vegetation vertical structure. We then applied this method to urban parks in Brisbane, Australia. We found that parks varied mainly in their amount of tree cover and its spatial arrangement, but also in vegetation vertical structure. Interestingly, the vertical structure of vegetation was largely independent of its cover and spatial arrangement. This suggests that vertical structure may be being managed independently to tree cover to provide different benefits across urban parks with different levels of tree cover. Finally, we were able to classify parks into three distinct classes that explicitly account for both the spatial and vertical structure of tree cover. Our approach for mapping the three-dimensional vegetation structure of urban green space provides a much more nuanced and functional description of urban parks than has previously been possible. Future research is now needed to quantify the relationships between vegetation structure and the actual benefits people derive from urban green space. [ABSTRACT FROM AUTHOR]