Contemporary fire regimes are recognized as a key threatening process for relatively immobile vertebrates and narrowly dispersing obligate seeder plant taxa in fire‐prone Australian savannas. Here, ...we assess the efficacy of proposed ecological performance threshold metrics for evaluating the current state of fire management for biodiversity conservation outcomes in Australia's premier, and best publicly funded savanna reserve, Kakadu National Park. The assessment draws on available data describing Landsat‐scale fire mapping over the period 1997–2015, habitat mapping, and mostly modeled responses of vegetation and faunal attributes. Despite conceptual and technical issues associated with various proposed performance thresholds and mapping products, the assessment demonstrates significant challenges with the current state of the reserve's fire management program. For example, by the end of 2015 it was observed that just 6% of woodland habitat in lowland and 23% in upland situations had remained unburnt for longer than three years and 98% of mapped fires in lowland and 87% in upland habitats were >1 km2 in extent. Of 14 assessed performance threshold metrics, two were within acceptable thresholds at the end of 2015, and none had improved materially over the decadal assessment period. Given substantial resources evidently required to deliver effective, seasonally intensive, fine‐grained adaptive fire management for biodiversity conservation outcomes in fire‐prone Australian savannas, we suggest that alternative resourcing opportunities through market‐based savanna burning greenhouse gas emissions abatement projects need to be explored.
ABSTRACT
BACKGROUND AND PURPOSE
Vestibular symptoms after concussion are common and associated with protracted recovery. The purpose of this study is to define resting‐state functional MRI (rs‐fMRI) ...brain connectivity alterations in patients with postconcussion vestibular dysfunction (PCVD) and correlations between rs‐fMRI connectivity and symptoms provoked during Vestibular/Ocular‐Motor Screening (VOMS) assessment.
METHODS
Prospective IRB approved study. Study group: 12 subjects with subacute PCVD (2‐10 weeks); control group: 10 age‐matched subjects without history of concussion or vestibular impairment. Both groups underwent clinical vestibular assessment. rs‐fMRI was acquired on 3.0T Siemens Trio with a 12‐channel head coil. rs‐fMRI data analysis included independent component analysis‐based functional connectivity group differences, graph theory analysis, and ROI‐to‐ROI connectivity correlation analysis with VOMS clinical derivatives. Group difference maps between resting‐state networks were calculated using dual regression method and corrected for multiple comparisons. Correlation analysis between ROI‐to‐ROI rs‐fMRI brain activation and VOMS assessment ratings was performed using Pearson correlation coefficient, with a significance threshold of P ≤ .05.
RESULTS
Compared to controls, PCVD group demonstrated significantly increased rs‐fMRI connectivity between the default‐mode network and right middle frontal gyrus and right postcentral gyrus; and between a vestibular‐sensorimotor network and right prefrontal cortex. Significant positive correlations were found between clinical derivative VOMS scores and components of the vestibular, visual networks, and multisensory processing cortical representations.
CONCLUSION
Altered rs‐fMRI brain connectivity with increased connectivity of visual input, multisensory processing, and spatial memory in PCVD is correlative with clinical derivative VOMS scores, suggesting maladaptive brain plasticity underlying vestibular symptomatology.
Aim Many tropical savannas are undergoing a trend of increasing woody biomass, or 'woody thickening'. Management to reduce fire frequency and intensity in savannas could substantially increase the ...amount of carbon stored in woody biomass. We addressed two questions: (1) are northern Australian savannas thickening; and (2) to what extent, and by what demographic processes, does fire affect woody biomass accumulation? Location Three large national parks, covering 24,000 km 2 , in monsoonal northern Australia. Methods We examined changes in woody biomass carbon stocks – inferred from tree basal area and the density of woody understorey plants – over a 10-year period in 136 savanna monitoring plots. We statistically assessed these changes in relation to fire frequency and severity. We used a meta-analysis to identify general trends in woody cover in Australian savannas over the last half-century. Results Woody biomass carbon stocks were relatively stable across the three national parks, but rates of change were statistically indistinguishable from earlier findings of a weak thickening trend. Change was negatively correlated with fire frequency, particularly the frequency of severe fires. High frequencies of severe fires decreased rates of accumulation of biomass by existing trees (through reductions in tree growth and death of individual stems), rather than whole-tree mortality and suppression of recruitment. However, across northern Australia, our meta-analysis identified a general, albeit weak, trend of woody thickening. Main conclusions The drivers of northern Australia's weak thickening trend are uncertain, but likely candidates include increasing atmospheric CO 2 concentration and water availability, and pastoral intensification. We demonstrate that changes to fire management have the potential to either increase or decrease rates of woody thickening relative to any underlying trend. Understanding how savanna fires affect woody biomass, and how fire effects are mediated by climate and CO 2 , are essential research priorities to predict the fate of savannas.
Ecologists have long sought to understand the factors controlling the structure of savanna vegetation. Using data from 2154 sites in savannas across Africa, Australia, and South America, we found ...that increasing moisture availability drives increases in fire and tree basal area, whereas fire reduces tree basal area. However, among continents, the magnitude of these effects varied substantially, so that a single model cannot adequately represent savanna woody biomass across these regions. Historical and environmental differences drive the regional variation in the functional relationships between woody vegetation, fire, and climate. These same differences will determine the regional responses of vegetation to future climates, with implications for global carbon stocks.
Savanna ecosystems comprise 22% of the global terrestrial surface and 25% of Australia (almost 1.9 million km²) and provide significant ecosystem services through carbon and water cycles and the ...maintenance of biodiversity. The current structure, composition and distribution of Australian savannas have coevolved with fire, yet remain driven by the dynamic constraints of their bioclimatic niche. Fire in Australian savannas influences both the biophysical and biogeochemical processes at multiple scales from leaf to landscape. Here, we present the latest emission estimates from Australian savanna biomass burning and their contribution to global greenhouse gas budgets. We then review our understanding of the impacts of fire on ecosystem function and local surface water and heat balances, which in turn influence regional climate. We show how savanna fires are coupled to the global climate through the carbon cycle and fire regimes. We present new research that climate change is likely to alter the structure and function of savannas through shifts in moisture availability and increases in atmospheric carbon dioxide, in turn altering fire regimes with further feedbacks to climate. We explore opportunities to reduce net greenhouse gas emissions from savanna ecosystems through changes in savanna fire management.
Inhibition of the SARS-CoV-2 main protease (Mpro) is a major focus of drug discovery efforts against COVID-19. Here we report a hit expansion of non-covalent inhibitors of Mpro. Starting from a ...recently discovered scaffold (The COVID Moonshot Consortium. Open Science Discovery of Oral Non-Covalent SARS-CoV-2 Main Protease Inhibitor Therapeutics. bioRxiv 2020.10.29.339317) represented by an isoquinoline series, we searched a database of over a billion compounds using a cheminformatics molecular fingerprinting approach. We identified and tested 48 compounds in enzyme inhibition assays, of which 21 exhibited inhibitory activity above 50% at 20 μM. Among these, four compounds with IC50 values around 1 μM were found. Interestingly, despite the large search space, the isoquinolone motif was conserved in each of these four strongest binders. Room-temperature X-ray structures of co-crystallized protein–inhibitor complexes were determined up to 1.9 Å resolution for two of these compounds as well as one of the stronger inhibitors in the original isoquinoline series, revealing essential interactions with the binding site and water molecules. Molecular dynamics simulations and quantum chemical calculations further elucidate the binding interactions as well as electrostatic effects on ligand binding. The results help explain the strength of this new non-covalent scaffold for Mpro inhibition and inform lead optimization efforts for this series, while demonstrating the effectiveness of a high-throughput computational approach to expanding a pharmacophore library.
Savanna sites are idealized as exhibiting a demographic “bottleneck” physiognomy comprising a lower stratum of abundant resprouting persistent “juveniles” (albeit of indeterminate age), a mid‐stratum ...comprising relatively few released “saplings,” and a canopy‐layer cohort of “adults.” The magnitude and frequency of disturbance is considered to influence the critical transition from juvenile into adult phases. Under fire‐prone Australian savanna conditions, an extensive suite of both observational and manipulative studies have explored the responses of tree recruitment to fire disturbances. These studies oftentimes have produced seemingly highly disparate responses, particularly with respect to the differential responses of relatively fast‐growing eucalypts versus non‐eucalypts under different fire regime, and overstory competition, conditions. This study contrasts the responses of tree recruitment height classes to (1) the effects of total canopy removal from severe Cyclone Monica in 2006 over a subsequent 10‐yr period, (2) with observations from long‐term monitoring sites under relatively stable overstory conditions at Litchfield National Park over a six‐year period, (3) under ambient, frequent fire occurrence (mean > 0.5 fires/yr) at both locales including relatively severe late dry season fires. Recruitment at both study sites was represented mostly by resprouting, clonally reproducing juvenile trees <2 m tall, around half of which died over respective assessment periods. At post‐cyclone assessment plots, there was substantial release of eucalypts, including within the first five years, into the >5 m height class, with negligible corresponding release of non‐eucalypts. At Litchfield plots, there was negligible release of both eucalypts and non‐eucalypts. In discussion, we contrast these results with findings from relevant regional studies. We contend that collective disparate observations feasibly can be reconciled as reflecting significant interactions between fire regime characteristics and variable site overstory competition effects, such that the rate of recruitment of fast‐growing savanna eucalypt individuals into the midstory is relatively independent of the fire regime, but is significantly regulated by resource competition interactions especially with the overstory, whereas recruitment of non‐eucalypts is relatively independent of overstory competitive effects, but is suppressed under fire regimes dominated by frequent, especially severe fires.
The Kere is a recurrent famine occurring in the south of Madagascar that emerged substantively in the 1930s. Each major event claims thousands of lives and keeps many in a cycle of impoverishment, ...despite the existence of various aid-based responses. This assessment presents qualitative research exploring two Kere-affected communities' experiences of the phenomenon. Through focus group discussions, we learn that the Kere is a complex social-ecological disaster, compounded by an intricate chain of causation and impacts. Seeking a deep understanding of affected peoples' perceptions and experience of the phenomenon, this paper challenges the idea that the Kere is a famine caused by recurring drought that can only be solved with provision of water and aid-based solutions. Based on community views and research literature, and the application of Ostrom's social-ecological systems framework, we demonstrate that the Kere is a phenomenon compounded by multiple interacting, debilitating factors including deforestation, drought, pests and diseases, food insecurity, extreme poverty, lawlessness, and political malaise; thus, solutions require a comprehensive, sustained, holistic response.
Summary
The Australian Government has sanctioned development of greenhouse gas emissions (GHG) abatement methodologies to meet international emissions reduction obligations. Savanna burning emissions ...abatement methodologies have been available since 2012, and there are currently 72 registered projects covering approximately 32 million ha. Abatement to date has exceeded 4 million tonnes of carbon dioxide equivalent (CO2‐e) principally through the application of low intensity early dry season fire management to reduce the amount of biomass combusted in higher intensity late dry season (LDS) fires. Savanna burning projects can only be conducted on areas with eligible fire‐prone vegetation fuel types where implementing the improved fire management regime is considered ecologically appropriate. This study assesses the suitability of including tall Acacia shrublands (‘Pindan’) as a new eligible fuel type. These shrublands make up 12% (~2 million ha) of the Kimberley region, Western Australia, where, on average, 32% is fire affected annually, mostly in the LDS. A standard assessment protocol was applied to describe vegetation fuel type structural and pyrolysis characteristics. We show that Pindan (i) can be identified and mapped as a unique tall Acacia shrubland vegetation fuel type, (ii) characterised by a significantly greater shrubby fuel load biomass, and (iii) the conservation status of which would benefit from imposition of strategic prescribed burning programme. Savanna burning projects in the Pindan fuel type could potentially abate up to 24.43 t.CO2‐e/km2 per year, generating significant income and employment opportunities for predominantly Indigenous land managers in the region.
Aim: Building on a substantial literature addressing the fire responses of woody plants, particularly under mediterranean climates, we assess the extent to which fire persistence traits can be used ...to predict vegetation responses to fire regime changes in fire-prone arid and savanna landscape settings. Location: Australia, applying data from arid central to monsoonal northern regions (11–26° S, 129–138° E). Methods: With reference to a substantial sub-continental floristics dataset, we first assigned the fire response (obligate seeder, resprouter) and seedbank persistence (transient, dormant) of rapid and longer-maturing (> 3 years) woody taxa. Using logistic regression, we then modelled the proportions of taxa possessing these traits as a function of mean annual rainfall (highly correlated with fire frequency) and terrain roughness (a measure of topographic variability) in 0.25° x 0.25° and 1° x 1° grid cells. Separate assessments were undertaken with datasets for 1264 sclerophyll and 236 rain forest taxa. Results: This woody flora is characterized by taxa exhibiting mostly resprouting and dormant seedbank traits that promote site persistence. While numbers of obligate seeder and resprouter taxa were related positively to both rainfall and roughness, the relative abundance of both sclerophyll and rain forest obligate seeders decreased significantly with rainfall. The relative abundance of sclerophyll (especially long-lived) obligate seeders alone increased with topographic roughness. The proportion of taxa with transient seedbanks increased with rainfall in resprouters generally, and in rain forest obligate seeders alone. Main conclusions: We find that resprouters are favoured on more productive, fire-prone sites, and obligate seeders are favoured in less productive, more fireprotected settings. Seedbank persistence responses are more variable. These findings concur generally with theoretical constructs, and support comparable assessments in Australian and other fire-prone systems ranging from mediterranean to boreal environments. Our observations illustrate that resprouting and obligate seeding syndromes, but not necessarily seedbank persistence, are useful predictors of vegetation responses to changing fire regime conditions at large landscape scales.
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