Brittany B. Elliott’s research while affiliated with Queensland University of Technology and other places

Climate change threatens long‐term soil health because of increased severity and frequency of drought periods. Applying biochar to soils before a drought can increase non‐biochar soil carbon (C) and water storage over the long term and sustain crop yield. However, the on‐farm benefit of buried solid biochar and applied liquid biochar at low rates remains uncertain. This study examined the effects of two novel biochar‐based soil amendments on soil C, water storage and crop yield. The biochar‐based amendments included a biochar reactive barrier (RB) made by layering wood‐based biochar, straw mulch and cow manure into a series of open surface trenches, and a liquid biochar mineral complex (BMC) applied twice, at low rate (200 kg ha⁻¹) to one side of RB (fertilised area), while the other side of RB received no treatments (non‐fertilised area). Moisture concentration within the RB ranged from 6.76% up to 56.68% after large rainfall, more than double the surrounding soils and gradually started migrating from the RB outwards. Soil within 50 cm distance of the RB showed a 24.5% increase in non‐biochar soil C compared with soil at 600 cm distance of the RB, 2.54% versus 2.04%, respectively, in the non‐fertilised area, which was supported with lowering soil microbial activity. Pasture yield increase was associated with liquid BMC fertiliser rather than proximity to the RB. Pasture yield was 44% higher in the fertilised area compared with the non‐fertilised area 27.89 t ha⁻¹ versus 19.31 t ha⁻¹. Approximately 158 kg CO2e was removed from the atmosphere for each cubic meter of RB and an annual removal of 150 kg CO2e ha⁻¹ was estimated by liquid BMC application. Income earned by increased yield was still profitable even though applied liquid BMC could cost between USD 400–520 ha⁻¹ including shipping costs. Overall, our study suggested biochar‐based RB and BMC fertilisers can effectively increase soil moisture retention while building non‐biochar soil C storage in the surrounding soil. The adoption of biochar‐based techniques has the potential to improve drought resilience while increasing soil C in wide range of non‐irrigated cropping systems.

Human impacts on ecosystems often transcend ecosystem boundaries and environmental realms, complicating ecosystem assessment, conservation, and management. Whether and how different impacts affect ecosystems in distinct but adjacent domains remains untested in many settings, and is rarely tested concurrently at the same spatial scales. In this study, we quantified the effects of coastal urbanisation on the structure of terrestrial coastal vertebrate assemblages (including birds, reptiles and mammals using baited trail cameras) and marine surf zone fish assemblages (using baited underwater videography) at 100 sites along 50 km of beach in eastern Australia. Sites occurred along a gradient of intensities of urban land conversion in the hind dunes. While the effects of urbanisation on the species sampled were pervasive across both ecosystems, the area of urbanised land mattered more for the coastal vertebrates observed, while proximity to urbanised land was more important for the surf zone fish observed. Here, fewer individuals and species of coastal vertebrates were found at sites with a greater extent of urbanised land within 5 km. Conversely, fish assemblages were more diverse in the surf zones abutting urban areas and more abundant at sites approximately 150 m from urbanised land. The spatial properties of these landscapes, including proximity to headlands for coastal vertebrates and reefs for fish, modified the effects of urbanisation. Our findings suggest that urbanisation can have ecologically nuanced effects that are detectable across the land-sea boundary, and stress the importance of landscape context when assessing and conserving animal assemblages in and around coastal cities.

Insects and arachnids are abundant and diverse, respond to key human impacts and support a diversity of key ecological functions. They are therefore widely recognised as effective surrogates for ecosystem condition. Their efficacy as indicators and surrogates in coastal dunes has, however, rarely been quantified, but might be instructive in guiding management in these often highly impacted coastal ecosystems. In this study, we (1) tested the effects of spatial and habitat drivers on the abundance of key insect and arachnid groups, and (2) used these patterns to identify viable management surrogates for impacts and management actions. We surveyed insect, arachnid and plant assemblages in coastal dunes at 20 sites on the Sunshine Coast in central eastern Australia. We have identified indicators for habitat condition and indicators for impact, and taxa that could be used to measure restoration outcomes. Crucially, five indicator groups also met criteria for being umbrella species, as management actions that increase their abundance would confer benefits to most other insect and arachnid taxonomic groups. We identified seven indicator groups (five insect and two arachnid), and each were affected by multiple spatial and habitat metrics, with metrics quantifying the composition and structure of vegetation communities being the most important predictors of most indicator’s distributions. Implications for insect conservation: We highlight the importance of understanding subtleties in spatial patterns and the unique set of spatial and environmental conditions that each group requires when identifying suitable indicator taxa for use in the conservation and management of coastal dunes.

World tree nut production has increased rapidly by around 50 % in the past decade; however, nut defects cause losses. For example, we know that brown centres are a major internal discolouration defect in macadamia nuts and are linked to the storage of nut-in-shell under improper conditions at high temperature and humidity. However, key chemical changes in brown centre kernels have not been described. In this study, we compared brown centres and white kernels from: 1) samples that were “induced” in the laboratory by storing at high moisture concentration; and 2) samples that were dried immediately after harvest using industry best practice methods recommended by the Australian Macadamia Society (AMS). We measured the moisture concentration, sugar concentration, fatty acid concentration, peroxide value, nutrient concentration and volatile compounds of induced and AMS samples. Our results showed that storing nut-in-shell macadamia under wet and hot conditions increased brown centres compared with samples immediately dried using the AMS regime, 10.33 % vs 1.44 %, respectively. Induced brown centres had significantly higher moisture concentrations than induced white centres. Volatile compounds including nonanoic acid, octanoic acid and 2,3 butanediol were identified and associated with brown centre formation in macadamia kernels and the initiation of lipid oxidation. Our results suggest sugar hydrolysis and the Maillard reaction are associated with brown centres both in laboratory induced samples and those formed using industry best practice drying methods. Our study suggests improper drying and storage at high temperature and high humidity are likely to result in brown centre formation. We recommend brown centre losses can be reduced by appropriate drying and storage practices.

(1) Background: The oil stability of tree nuts during storage can be influenced by storage conditions such as temperature, humidity, and moisture concentration. However, few studies have assessed how the presence of testa and shell affects the oil stability of tree nuts during storage. We aimed to determine how storage conditions affect oil stability in almond and canarium, in particular, the presence of testa and storage time of nut-in-shell (NIS). (2) Methods: We measured peroxide value (PV), free fatty acid (FFA) and hexanal concentrations of almond and canarium (blanched vs. kernel-in-testa) stored at 45 °C for 24 days. We also measured PV, FFA and fatty acid composition of canarium samples at days 0 and 140 stored as NIS under ambient conditions. (3) Results: The presence of testa in almond and canarium decreased hexanal and PV concentrations at day 24 of incubation. Canarium PV and FFA concentrations increased over 140 days of storage in the shell compared to day 0. However, both PV and FFA concentrations remained within the acceptable threshold during storage. No changes in fatty acid composition were found during NIS storage. (4) Conclusions: Testa and shell could act as a natural coating, slowing down oxidation rates. Hence, long-term storage on nuts in testa or nuts in shell are recommended for tree nuts.

The extent, condition and connectedness of ecosystems has been significantly impacted by human activities globally, leading to a widespread appeal of and demand for ecological restoration. Maximising the ecological outcomes and cost effectiveness of restoration requires that plans be optimised by indexing the distribution, abundance and condition of habitat-forming species, and that target ecosystem conditions be developed in concert with restoration site attributes. This type of quantitative approach for creating malleable ecological targets which are informed by local environmental conditions is, however, uncommon. In this study, we surveyed the composition and coverage of understorey plants, and the composition and size of trees in coastal dunes at five transects at each of 20 sites (for n = 100) on the Sunshine Coast, central eastern Australia, and use this information to prioritise restoration sites and create optimised planting regimes for degraded sites. Each of the identified indicator species (six understorey and four tree species) had unique preferred conditions and was affected by multiple environmental and spatial variables at varying spatial scales, with most species affected by urbanisation. Species distribution models (SDMs) were used to identify target/reference ecosystems and optimal planting mixes for potential restoration sites given the site’s environmental attributes. Our approach of integrating data on the distribution, abundance and condition of habitat-forming species into multiple SDMs can be used to optimise planting regimes at restoration sites and provides a framework for setting dynamic restoration targets across landscapes.

Coastal wetlands are restored to regenerate lost ecosystem services. Accurate and frequent representations of the distribution and area of coastal wetland communities are critical for evaluating restoration success. Typically, such data are acquired through laborious, intensive and expensive field surveys or traditional remote sensing methods that can be erroneous. Recent advances in remote sensing techniques such as high-resolution sensors (<2 m resolution), object-based image analysis and shallow learning classifiers provide promising alternatives but have rarely been applied in a restoration context. We measured the changes to wetland communities at a 200 ha restoring coastal wetland in eastern Australia, using remotely sensed Worldview-2 imagery, object-based image analysis and random forest classification. Our approach used structural rasters (digital elevation and canopy height models) and a multi-temporal technique to distinguish between spectrally similar land cover. The accuracy of our land cover maps was high, with overall accuracies ranging between 91 and 95%, and this supported early detection of increases in the area of key ecosystems, including mixed she-oak and paperbark (10 ha), mangroves (0.91 ha) and saltmarsh (4.31 ha), over a 5-year monitoring period. Our approach provides coastal managers with an accurate and frequent method for quantifying early responses of coastal wetlands to restoration, which is essential for informing adaptive management in the regeneration of ecosystem services.

Honeybees (Apis mellifera) depend entirely on floral resources (pollen and nectar) in their surrounding landscape to satisfy their dietary needs. Honeybee diets in temperate areas have been well studied, and there is increasing evidence that floral diversity is critical for honeybee health. Tropical forests often contain high floral diversity but honeybee diets have been rarely studied in the tropics. We aim to compare the botanical sources in bee bread between landscapes with and without surrounding forest cover in the eastern highlands of Papua New Guinea. We collected bee bread from 24 hives across 8 sites over two years and examined floral sources, diversity measures and major plant groups using DNA metabarcoding. We identified a total of 89 taxa across 34 orders, 41 families, 84 genera and 61 species of botanical sources in bee bread. Bee bread from hives in sites with surrounding forest contained significantly greater species diversity (H’ Forest = 1.4, H’ No forest = 1.1) and species evenness (J Forest = 0.68, J No forest = 0.6). Trees were the most abundant source of bee bread, regardless of landscape, and constituted 52% of total abundance. Herbaceous plants, mostly introduced species, were the second most abundant floral sources at ∼ 26% of total bee bread abundance, particularly in forest landscapes. We found the most abundant sources such as introduced tree species Leucaena leucocephala (Fabaceae) and native tree species Syzigium unipunctatum (Myrtaceae) were foraged on in both landscapes; other common species included introduced species Hylodesmum nudifloram (Facbaceae) and Bidens pilosa (Asteraceae), and native food crop Entada phaseoloides (Fabaceae). Interestingly, many wind pollinated species were found in both landscapes including Araucaria (Araucariaceae), Pinus (Pinaceae), Nothofagaceae species and Poaceae species. Our work suggests that bees are seeking out floral tree resources even in landscapes where trees are scarce. Thus beekeeping in tropical environments would benefit from preserving remaining forest cover and incorporating more trees to existing, open landscapes to optimize the diversity in honeybee diets.

The decline of both managed and wild bee populations has been extensively reported for over a decade now, with growing concerns amongst the scientific community. Also, evidence is growing that both managed and feral honey bees may exacerbate threats to wild bees. In Australia, there are over 1600 native bee species and introduced European honey bees (Apis mellifera) have established throughout most landscapes. There is a major gap in knowledge of the interactions between honey bees and native bees in Australian landscapes, especially floral resource use. Here we report on the pollen diets of wild bees in protected areas of coastal heathland, an ecosystem characterised by mass flowering in late winter and spring. We sampled bees within three sites and DNA metabarcoding was used to compare the pollen diets of honey bees and native bees. We recorded 2, 772 bees in total, with 13 genera and 18 described species identified. Apis mellifera was the most common species across all locations, accounting for 42% of all bees collected. Native bee genera included eusocial Tetragonula (stingless bees) (37%), and semi-social Exoneura and Braunsapis (19.8% combined). Metabarcoding data revealed both Tetragonula and honey bees have wide foraging patterns, and the bipartite network overall was highly generalised (H2’ = 0.24). Individual honey bees carried pollen of 7–29 plant species, and significantly more species than all other bees. We found niche overlap in the diets of honey bees and native bees generally (0.42), and strongest overlap with stingless bees (0.70) and species of Braunsapis (0.62). A surprising finding was that many species carried pollen from Restionaceae and Cyperaceae, families generally considered to be predominantly wind-pollinated in Australia. Our study showed introduced honey bee use of resources overlaps with that of native bees in protected heathlands, but there are clear differences in their diet preferences.