School of Agriculture, Food and Ecosystem Sciences - Research Publications

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    Evaluation of Spectral Indices for Assessing Fire Severity in Australian Temperate Forests
    Tran, BN ; Tanase, MA ; Bennett, LT ; Aponte, C (MDPI AG, 2018)
    Spectral indices derived from optical remote sensing data have been widely used for fire-severity classification in forests from local to global scales. However, comparative analyses of multiple indices across diverse forest types are few. This represents an information gap for fire management agencies in areas like temperate south-eastern Australia, which is characterised by a diversity of natural forests that vary in structure, and in the fire-regeneration strategies of the dominant trees. We evaluate 10 spectral indices across eight areas burnt by wildfires in 1998, 2006, 2007, and 2009 in south-eastern Australia. These wildfire areas encompass 13 forest types, which represent 86% of the 7.9M ha region’s forest area. Forest types were aggregated into six forest groups based on their fire-regeneration strategies (seeders, resprouters) and structure (tree height and canopy cover). Index performance was evaluated for each forest type and forest group by examining its sensitivity to four fire-severity classes (unburnt, low, moderate, high) using three independent methods (anova, separability, and optimality). For the best-performing indices, we calculated index-specific thresholds (by forest types and groups) to separate between the four severity classes, and evaluated the accuracy of fire-severity classification on independent samples. Our results indicated that the best-performing indices of fire severity varied with forest type and group. Overall accuracy for the best-performing indices ranged from 0.50 to 0.78, and kappa values ranged from 0.33 (fair agreement) to 0.77 (substantial agreement), depending on the forest group and index. Fire severity in resprouter open forests and woodlands was most accurately mapped using the delta Normalised Burnt ratio (dNBR). In contrast, dNDVI (delta Normalised difference vegetation index) performed best for open forests with mixed fire responses (resprouters and seeders), and dNDWI (delta Normalised difference water index) was the most accurate for obligate seeder closed forests. Our analysis highlighted the low sensitivity of all indices to fire impacts in Rainforest. We conclude that the optimal spectral index for quantifying fire severity varies with forest type, but that there is scope to group forests by structure and fire-regeneration strategy to simplify fire-severity classification in heterogeneous forest landscapes.
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    Effects of mat composition and pressing time on citric acid-bonded ultra-low-density hemp hurd particleboard
    Fehrmann, J ; Belleville, B ; Ozarska, B ; Ismayati, M ; Dwianto, W (Elsevier, 2024-04-01)
    This study investigated the feasibility of using citric acid (CA) as a biobased and formaldehyde-free binder for producing ultra-low-density (320 to 338 kg/m3) hemp hurd particleboard (ULHPB). Mechanically decorticated hemp hurd chips were milled and then separated into fine (F), medium (M), and coarse (C) particle sizes. Three particle size mixes (PSM) were used to fabricate the panels: 100% C, 100% M, and a 50/50% mixture of CM. Each PSM was combined with low and high CA contents (20 and 30 wt%) and subjected to short and long pressing times (8 and 12 min) at 200 °C. Physico-mechanical characteristics were evaluated following Australian standard AS/NZS 1859.1 (2017) for reconstituted wood-based panels. Thermo-chemical analyses were performed to understand the properties of the raw hurd and to investigate the binding mechanisms in CA-ULHPB. The PSM had a significant impact on panel expansion (springback), internal bond strength (IB), water absorption (WA), and thickness swelling (TS) in most CA-ULHPB variants. PSM-C panels exhibited superior IB when pressed with 30 wt% CA for 12 min. The effect of PSMs diminished for WA and TS but CA content and pressing time remained highly significant. Py-GC/MS, FTIR spectroscopy and TGA indicated the formation of ester linkages with carbohydrate-derived OH-groups and the involvement of lignin moieties in the CA-ULHPB. This research identified optimal panel compositions and processing parameters for fabricating environmentally friendly composite panels using CA as a natural adhesive and hemp hurd as an agricultural by-product. The panels exhibited excellent properties and would be well suited as core layers in lightweight sandwich composites given their ultra-low-density range.
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    Lipase-catalyzed production of biodiesel: a critical review on feedstock, enzyme carrier and process factors
    Xia, S ; Lin, J ; Sayanjali, S ; Shen, C ; Cheong, L-Z (Wiley, 2024-01)
    Biodiesel is a green and renewable alternative energy source which can be produced through lipase-catalyzed transesterification process. Enzymatic biodiesel production has generated much interest owing to its environmentally friendly process, low wastewater treatment requirements and easy product separation. In this work, we attempt to review some of the recent patents and state-of-the-art technology in lipase-catalyzed transesterification for biodiesel production including feedstock, lipases, novel carriers and process factors. This work will provide useful guidance for researchers to develop cost efficient process for production of biodiesels.
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    Growth performance and feed utilisation of Australian hybrid abalone (Haliotis rubra × Haliotis laevigata) fed increasing dietary protein levels at three water temperatures.
    Hassan, ALI ; Mock, TS ; Searle, K ; Rocker, MM ; Turchini, GM ; Francis, DS (Cambridge University Press (CUP), 2024-03-28)
    Determining the macronutrient requirements for commercially valuable aquaculture species remains crucial for maximising production efficiency. Yet, such information is lacking for Australian hybrid abalone (Haliotis rubra × Haliotis laevigata), particularly with respect to life stage and water temperatures. The present study aimed to evaluate the effect of dietary protein inclusion level on the growth performance, nutrient utilisation and nutritional quality of juvenile (3·3 g) Australian hybrid abalone reared at three different temperatures representative of winter (12°C), average annual (17°C) and summer (22°C) grow-out periods and fed five diets containing graded dietary protein levels of 35, 38, 41, 44 and 47 %. Abalone growth increased with increasing water temperature with weight gains of approximately 100, 280 and 380 % of their initial weight at 12, 17 and 22°C, respectively. Furthermore, the present study clearly demonstrated that higher dietary protein inclusion levels (41 %) than those currently used commercially (35 %) would significantly improve the growth performance when water temperatures are ≥17°C without any adverse impacts on nutrient utilisation, nutrient deposition or nutritional quality of the abalone soft tissue. For example, at 22°C abalone fed a diet containing 41 % protein obtained a significantly higher weight gain percentage (421 %) compared with those fed a diet containing 35 % protein (356 %). Lastly, it is suggested that maintaining a dietary protein inclusion level of 35 % or implementing a 'least cost' feeding approach during cooler seasons, or where water temperatures are ∼12°C, may be beneficial, considering only marginal growth improvements were observed during these periods of slow growth.
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    Body composition changes and their relationship with obstructive sleep apnoea symptoms, severity: The Sleeping Well Trial
    Day, K ; Nguo, K ; Edwards, BA ; O'Driscoll, DM ; Haines, TP ; Hamilton, GS ; Ghazi, L ; Bristow, C ; Truby, H (CHURCHILL LIVINGSTONE, 2023-09)
    BACKGROUND & AIMS: Obstructive sleep apnoea (OSA) and obesity share a complex bi-directional relationship as location of body fat and changes in regional body composition may be more important for OSA improvement than changes in total body weight only. The aim of this study was to evaluate the impact of a 6-month weight loss intervention for adults newly diagnosed with moderate-severe OSA and obesity on regional body composition. The secondary aims evaluated the relationship between changes in OSA symptoms and severity and anthropometry and regional body composition during the first 12-months after commencing CPAP and explored differences in outcomes between males and females. METHODS: Participants (n = 59) received CPAP overnight at home alongside a 6-month modified fasting intervention with 12-months follow up. Regional body composition was measured by Dual X-ray absorptiometry, (DXA) and anthropometry before and after the lifestyle intervention. OSA severity was measured using the apnoea hypopnea index via overnight polysomnography and OSA symptoms were measured using the Epworth Sleepiness scale. RESULTS: Forty-seven adults (74% male) had complete measures available with a mean age of 50.0 y (SD 11.0) and BMI 34.1 kg/m2 (SD 5.0). Following the intervention average fat mass changed by -5.27 kg (5.36), p < 0.001) and visceral adipose tissue (-0.63 kg (0.67), p < 0.001) significantly decreased in males only with a maintenance of fat-free mass (mean -0.41 kg (1.80), p = 0.18). Females (n = 12) had significant decreases in waist circumference (mean -3.36 cm (3.18) p < 0.01), android lean (-0.12 kg (0.04), p < 0.05) and android total mass (-0.28 kg (0.39), p < 0.05) only. Regional body composition changes in males were positively associated with improvements in OSA severity (p < 0.01) but not OSA symptoms. CONCLUSION: Improvements in regional body composition were seen in males only which were related to improvements in OSA severity but not OSA symptoms. Females may exhibit different OSA pathophysiology and may require different treatment approaches. TRIAL REGISTRATION: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=369975&isReview=trueAACTRN12616000203459 ACTRN12616000203459.
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    Precipitation change affects forest soil carbon inputs and pools: A global meta-analysis.
    Xu, S ; Wang, J ; Sayer, EJ ; Lam, SK ; Lai, DYF (Elsevier BV, 2024-01-15)
    The impacts of precipitation change on forest carbon (C) storage will have global consequences, as forests play a major role in sequestering anthropogenic CO2. Although forest soils are one of the largest terrestrial C pools, there is great uncertainty around the response of forest soil organic carbon (SOC) to precipitation change, which limits our ability to predict future forest C storage. To address this, we conducted a meta-analysis to determine the effect of drought and irrigation experiments on SOC pools, plant C inputs and the soil environment based on 161 studies across 139 forest sites worldwide. Overall, forest SOC content was not affected by precipitation change, but both drought and irrigation altered plant C inputs and soil properties associated with SOC formation and storage. Drought may enhance SOC stability by altering soil aggregate fractions, but the effect of irrigation on SOC fractions remains unexplored. The apparent insensitivity of SOC to precipitation change can be explained by the short duration of most experiments and by biome-specific responses of C inputs and pools to drought or irrigation. Importantly, we demonstrate that SOC content is more likely to decline under irrigation at drier temperate sites, but that dry forests are currently underrepresented across experimental studies. Thus, our meta-analysis advances research into the impacts of precipitation change in forests by revealing important differences among forest biomes, which are likely linked to plant adaptation to extant conditions. We further demonstrate important knowledge gaps around how precipitation change will affect SOC stability, as too few studies currently consider distinct soil C pools. To accurately predict future SOC storage in forests, there is an urgent need for coordinated studies of different soil C pools and fractions across existing sites, as well as new experiments in underrepresented forest types.
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    Molecular Basis for Lysine Specificity in the Yeast Ubiquitin-Conjugating Enzyme Cdc34
    Sadowski, M ; Suryadinata, R ; Lai, X ; Heierhorst, J ; Sarcevic, B (AMER SOC MICROBIOLOGY, 2010-05-15)
    Ubiquitin (Ub)-conjugating enzymes (E2s) and ubiquitin ligases (E3s) catalyze the attachment of Ub to lysine residues in substrates and Ub during monoubiquitination and polyubiquitination. Lysine selection is important for the generation of diverse substrate-Ub structures, which provides versatility to this pathway in the targeting of proteins to different fates. The mechanisms of lysine selection remain poorly understood, with previous studies suggesting that the ubiquitination site(s) is selected by the E2/E3-mediated positioning of a lysine(s) toward the E2/E3 active site. By studying the polyubiquitination of Sic1 by the E2 protein Cdc34 and the RING E3 Skp1/Cul1/F-box (SCF) protein, we now demonstrate that in addition to E2/E3-mediated positioning, proximal amino acids surrounding the lysine residues in Sic1 and Ub are critical for ubiquitination. This mechanism is linked to key residues composing the catalytic core of Cdc34 and independent of SCF. Changes to these core residues altered the lysine preference of Cdc34 and specified whether this enzyme monoubiquitinated or polyubiquitinated Sic1. These new findings indicate that compatibility between amino acids surrounding acceptor lysine residues and key amino acids in the catalytic core of ubiquitin-conjugating enzymes is an important mechanism for lysine selection during ubiquitination.
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    Causes, Responses, and Implications of Anthropogenic versus Natural Flow Intermittence in River Networks
    Datry, T ; Truchy, A ; Olden, JD ; Busch, MH ; Stubbington, R ; Dodds, WK ; Zipper, S ; Yu, S ; Messager, ML ; Tonkin, JD ; Kaiser, KE ; Hammond, JC ; Moody, EK ; Burrows, RM ; Sarremejane, R ; DelVecchia, AG ; Fork, ML ; Little, CJ ; Walker, RH ; Walters, AW ; Allen, D (OXFORD UNIV PRESS, 2023-01-11)
    Abstract Rivers that do not flow year-round are the predominant type of running waters on Earth. Despite a burgeoning literature on natural flow intermittence (NFI), knowledge about the hydrological causes and ecological effects of human-induced, anthropogenic flow intermittence (AFI) remains limited. NFI and AFI could generate contrasting hydrological and biological responses in rivers because of distinct underlying causes of drying and evolutionary adaptations of their biota. We first review the causes of AFI and show how different anthropogenic drivers alter the timing, frequency and duration of drying, compared with NFI. Second, we evaluate the possible differences in biodiversity responses, ecological functions, and ecosystem services between NFI and AFI. Last, we outline knowledge gaps and management needs related to AFI. Because of the distinct hydrologic characteristics and ecological impacts of AFI, ignoring the distinction between NFI and AFI could undermine management of intermittent rivers and ephemeral streams and exacerbate risks to the ecosystems and societies downstream.
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