Firing Frequency Research Articles

Wildfire ashes: evaluating threats on the Pantanal wetland reserve (Mato Grosso, Brazil) using ecotoxicological tests.

In 2020, the largest continuous wetland area on the planet, the Brazilian Pantanal, experienced an unprecedented fire that affected the entire ecosystem. Our goal was to elucidate the effects of ash presence following the fire events. We quantified the impact of ashes, collected in four Conservation Units, on soil, water, and atmosphere. On the edaphic system, we tested the impact through behavioral and acute toxicity tests using annelids exposed to contaminated soil at different ash concentrations. We assessed the effect of ash on the flux of soil greenhouse gases. In the water, we examined the impact through tests with the Daphnia similis Claus, 1876. On the edaphic system, Eisenia andrei (Bouché, 1972) exhibited reduced average mortality rates and negative sublethal responses, including behavioral and morphological changes. Annelids displayed rejection responses to the ash substrate, suggesting potential damage to soil function. D. similis showed high mortality rates. We noted an increase in carbon dioxide emissions after ash addition. Changes in soil characteristics were also observed, mainly an increase in minerals. Considering the escalating frequency and intensity of fires in tropical areas due to climate change and deforestation, our findings contribute to understanding the potential ecotoxicological impact of ash in wetlands.

Identification of the Operating Modes in Single-Phase DC Drives

In this study, operating modes of controlled single-phase rectifier-driven direct current (DC) drives were investigated. It was observed that the motor performance exhibited different behaviour depending on the combined interaction of the rectifier firing angle, motor parameters, motor load (or speed), supply voltage and frequency. It can be said that the voltage across the motor and the current through the motor take different waveforms in each of these different states, which are named drive operating modes in this study. Furthermore, analysis and simulations were conducted for two different types of drives: a) Single-phase fully controlled bridge rectifier drive (FCBRD) and b) Single-phase half-controlled bridge rectifier drive (HCBRD), including a freewheeling diode. As a result, the motor current waveform exhibits seven distinct operating modes, each performing different characteristics when driven by two types of rectifier circuits. On the other hand, the mathematical models of these seven modes were also presented in this study. The actual time variations of voltage across and current through the motor armature and the total harmonic distortion (THD) were presented through simulations for each mode using the obtained mathematical models in MATLAB.

Tip-to-base bark cross-sectional areas contribute to understanding the drivers of carbon allocation to bark and the functional roles of bark tissues.

Along their lengths, stems experience different functional demands. Because bark and wood traits are usually studied at single points on stems, it remains unclear how carbon allocation changes along tip-to-base trajectories across species. We examined bark vs wood allocation by measuring cross-sectional areas of outer and inner bark (OB and IB), IB regions (secondary phloem, cortex, and phelloderm), and wood from stem tips to bases of 35 woody angiosperm species of diverse phylogenetic lineages, climates, fire regimes, and bark morphologies. We examined how varied bark vs wood allocation was and how it was affected by precipitation, temperature, soil fertility, leaf habit, and fire regime. Allocation to phloem (relative to wood) varied little across species, whereas allocation to other tissues, strongly affected by the environment or shed in ontogeny, varied widely. Allocation to parenchyma-rich cortex and phloem was higher at drier sites, suggesting storage. Higher allocation to phloem and cortex also occurred on infertile soils, and to phloem in drought-deciduous vs cold-deciduous and evergreen species. Allocation to OB was highest at sites with frequent fires and decreased with fire frequency. Our approach contextualizes inferences from across-species studies, allows testing functional hypotheses, and contributes to disentangling the functional roles of poorly understood bark tissues.

An organic electrochemical neuron for a neuromorphic perception system

Human perception systems are highly refined, relying on an adaptive, plastic, and event-driven network of sensory neurons. Drawing inspiration from Nature, neuromorphic perception systems hold tremendous potential for efficient multisensory signal processing in the physical world; however, the development of an efficient artificial neuron with a widely calibratable spiking range and reduced footprint remains challenging. Here, we report an efficient organic electrochemical neuron (OECN) with reduced footprint (<37 mm2) based on high-performance vertical OECT (vOECT) complementary circuitry enabled by an advanced n-type polymer for balanced p-/n-type vOECT performance. The OECN exhibits outstanding neuronal characteristics, capable of producing spikes with a widely calibratable state-of-the art firing frequency range of 0.130 to 147.1 Hz. Leveraging this capability, we develop a neuromorphic perception system that integrates mechanical sensors with the OECN and integrates them with an artificial synapse for tactile perception. The system successfully encodes tactile stimulations into frequency-dependent spikes, which are further converted into postsynaptic responses. This bioinspired design demonstrates significant potential to advance cyborg and neuromorphic systems, providing them with perceptual capabilities.

Multi-criteria decision analysis for monitoring and evaluating soil erosion risk in forest fire-affected areas.

Wildfires lead to socio-economic and environmental impacts. These impacts include hydrological instability, which can cause severe damage, especially where infrastructures are present. Post-rehabilitation measures can be useful in reducing or preventing erosion or hydrogeological risks. Decision-makers are called on to prioritize post-fire intervention areas and allocate public funds for this purpose. This work focuses on the assessment of erosion and hydrological risk potential in forested slope areas affected by wildfire using a Multi-Criteria Decision Analysis (MCDA) approach integrated with a GIS environment on a regional scale. Expert perception was considered using the pairwise comparison method as part of the Analytical Hierarchy Process (AHP). This allows expert stakeholders to rank relevant criteria, providing a quantitative metric (weight) for qualitative data. Two MCDA methods are used and compared: Weighted Linear Combination (WLC) and Ordered Weighted Averaging (OWA). Fire frequency, slope (gradient and length), and proximity to infrastructures were found to be the most important factors by the stakeholders. The WLC method provides evidence classified into high and moderate suitability class areas characterized by high values for fire frequency or slope gradient. Conversely, the OWA method, ranging from low to high risks, makes it possible to adapt the method and obtain a range of suitability maps. Novelties of the MCDA-GIS combined methodology adopted in this work are its application on a regional scale and the combination of vulnerability and driving-force factors (namely presence of grey infrastructures, fire frequency). The MCDA-GIS methodology can be suitable for public administrations in that it allows for mapping a regional area more quickly and thus facilitates sector planning.

Simulating fuel management for protecting regional biodiversity under climate change.

Climate change is resulting in larger, more frequent, and more severe wildfires which have increasingly negative impacts on people and the environment. Under these circumstances, it is critical to determine whether fire management actions can mitigate biodiversity impacts under future fire regimes. However, it is currently unclear how changing climate and management interact to influence the spatial distribution of risks to biodiversity. We used fire simulations to quantify the influence of 13 fuel management strategies on animal biodiversity in the Otways, southeastern Australia, under four alternative climate scenarios. Our management strategies include combinations of prescribed burning, mulching, and strategic fuel breaks modelled in various spatial configurations and frequencies. We assessed the capacity of treatments to reduce risk of fire to animal biodiversity by quantifying changes to extent burnt, wildfire frequency and wildfire severity. All management strategies reduced the average annual area burnt across the landscape, however, there was considerable variability over time and under different climate models. Similarly, spatial shifts in fire frequency and severity in some cases resulted in the shifting of fires away from some areas of high value to animals. There is no one size fits all management strategy for reducing impacts to biodiversity under variable future climates. However, all the strategies tested here reduced median impacts relative to a do-nothing approach for at least some aspects of the fire regime or for animal biodiversity. We highlight the importance of evaluating fire management effectiveness against a range of metrics to ensure multiple objectives are met under the increasingly unknown climate conditions we can expect going forward.

Source-resolved black carbon and PM2.5 exposures during wildfires and prescribed burns.

Changes in climate and land-use have significantly increased both the frequency and intensity of wildland fires globally, exacerbating the potential for hazardous impacts on human health. A better understanding of particle exposure concentrations and scenarios is crucial for developing mitigation strategies to reduce the health risks. Here, PM2.5 and black carbon (BC) concentrations were monitored during wildland fires between 2022-2024, in fire-prone areas in Catalonia (NE Spain), by means of personal monitors (AirBeam2 and Micro-aethalometers AE51 and MA200). Results revealed that exposures to combustion aerosols (PM2.5 and BC) were significant and comparable during wildfires and prescribed burns (mean PM2.5 during wildfires = 152 μg/m3 vs. 110-145 μg/m3 for prescribed burns). Overall, BC/PM2.5 ratios showed a large variability as a function of the monitoring scenario, indicating varying contributions from mineral aerosols to the emissions mix originating from fire management and extinction tasks. Specifically, mop-up tasks (final extinction tasks involving stirring top soil using handheld tools) were identified as a significant contributor to PM2.5 exposures, with 1-minute PM2.5 peak concentrations reaching up to 1,190 μg/m3. These results may be especially valuable for emissions modelling. Source apportionment of multi-wavelength BC datasets provided deeper insights into emissions and their impact on exposure profiles: line operators (who control the fire perimeter) were predominantly exposed to biomass burning smoke (61%) when compared to BC from fossil-fuel combustion ( = 39%), while torchers (in charge of initiating technical fires using fossil-fuel drip-torches) were predominantly exposed to (77% vs. 23% ). These findings highlight the value of portable monitors in the assessment of wildfire emissions and impacts on human exposure and environment. The combination of these tools, reporting data in real-time and with high time-resolution, is key to the design and implementation of effective mitigation strategies for environmental and health concerns related to wildland fires.

Geobotanical indication of the drained state of disturbed peatlands for fire hazard assessment

The issue of fire hazard in abandoned peatlands is particularly relevant nowadays, as the negative consequences of peatland fires lead to deterioration in public health and the functioning of the entire infrastructure system. The problem of predicting and assessing peat burning is a global one, with numerous studies being conducted not only in Russia but also abroad, i. e., in CIS countries, Southeast Asia, Canada, and the United States. However, the relationship between vegetation communities and the frequency of fires receives insufficient attention. The study is devoted to assessing the condition of degraded peatlands using geobotanical indicators of peat soils on the example of peatlands in Leningrad and Pskov regions. Three key objects were selected, which represent abandoned peat deposits. The methodology for assessing the fire hazard of peatlands is based on a comprehensive approach, including the creation of large-scale vegetation maps using a series of satellite images and field geobotanical descriptions, and the analysis of fires on objects for the period from 2000 to 2023 using satellite images and thermal data. As a result of the study, maps of fire frequency and duration and maps of natural-territorial complexes for each plot were obtained. The analysis of the relationship between vegetation communities and the frequency of fires showed that the species composition of the communities correlates relatively well with the time elapsed since the date of the last fire, and to a lesser extent with the duration of the fires. Indicative relationships between fire frequency and vegetation cover are quite strong, so the type of vegetation cover can be used as an indicator of fire frequency on a peatland. On territories with peat bogs with a sparse birch forest, fire occurs at least once every 5 years. On territories with sphagnum associations and reed swamp associations, fire occurs no more than once every 20 years.

Suppression of MT5-MMP Reveals Early Modulation of Alzheimer's Pathogenic Events in Primary Neuronal Cultures of 5xFAD Mice.

We previously reported that membrane-type 5-matrix metalloproteinase (MT5-MMP) deficiency not only reduces pathological hallmarks of Alzheimer's disease (AD) in 5xFAD (Tg) mice in vivo but also impairs interleukin-1 beta (IL-1β)-mediated neuroinflammation and Aβ production in primary Tg immature neural cell cultures after 11 days in vitro. We now investigate the effect of MT5-MMP on incipient pathogenic pathways that are activated in cortical primary cultures at 21-24 days in vitro (DIV), during which time neurons are organized into a functional mature network. Using wild-type (WT), MT5-MMP-/- (MT5-/-), 5xFAD (Tg), and 5xFADxMT5-MMP-/- (TgMT5-/-) mice, we generated primary neuronal cultures that were exposed to IL-1β and/or different proteolytic system inhibitors. We assessed neuroinflammation, APP metabolism, synaptic integrity, and electrophysiological properties using biochemical, imaging and whole-cell patch-clamp approaches. The absence of MT5-MMP impaired the IL-1β-mediated induction of inflammatory genes in TgMT5-/- cells compared to Tg cells. Furthermore, the reduced density of dendritic spines in Tg neurons was also prevented in TgMT5-/- neurons. IL-1β caused a strong decrease in the dendritic spine density of WT neurons, which was prevented in MT5-/- neurons. However, the latter exhibited fewer spines than the WT under untreated conditions. The spontaneous rhythmic firing frequency of the network was increased in MT5-/- neurons, but not in TgMT5-/- neurons, and IL-1β increased this parameter only in Tg neurons. In terms of induced somatic excitability, Tg and TgMT5-/- neurons exhibited lower excitability than WT and MT5-/-, while IL-1β impaired excitability only in non-AD backgrounds. The synaptic strength of miniature global synaptic currents was equivalent in all genotypes but increased dramatically in WT and MT5-/- neurons after IL-1β. MT5-MMP deficiency decreased endogenous and overexpressed C83 and C99 levels but did not affect Aβ levels. C99 appears to be cleared by several pathways, including γ-secretase, the autophagolysosomal system, and also α-secretase, via its conversion to C83. In summary, this study confirms that MT5-MMP is a pivotal factor affecting not only neuroinflammation and APP metabolism but also synaptogenesis and synaptic activity at early stages of the pathology, and reinforces the relevance of targeting MT5-MMP to fight AD.

Gelatin-based spray for forest fire prevention and fertilization

Frequent forest fires, driven by hotter and drier climates, threaten biodiversity and human health, causing significant economic losses, air pollution, soil erosion, and degeneration. Current active and passive fire protection methods often suffer from environmental pollution, poor flexibility, and limited availability in remote areas. However, fast-acting surface flame retardants for passive forest fire protection, particularly for foliage, are rare. Herein, we report an easily obtainable gelatin-based fire spray, which resulted in 1.8 and 16.3-fold extension in ignition time, 34% and 39% reductions in total heat release, 78% and 92% reductions in fire growth index for dead and fresh leaves, respectively. After the fire warning is suppressed, for instance by rain, the sprayed substances can decompose and provide nitrogen and phosphorus as leaf and soil fertilizers without affecting soil microbial function, which increase plant net photosynthesis by 84% and effective nitrogen and phosphorus by 664% and 140%, respectively. Our green flame retardant and fertilizer material allows for simultaneous tree fire protection and growth.

Fire frequency shapes diversity in multi‐guild communities through direct and indirect pathways

Abstract Human‐induced changes in fire regimes worldwide are leading to changes in the diversity and composition of plant and insect communities through alterations in vegetation and habitat characteristics. As species interact in complex networks, environmental disturbances, such as an increase in fire frequency, can affect species directly and indirectly through cascading effects across trophic levels. This study examines the effects of fire frequency on multi‐guild communities in the Chaco region in Argentina, aiming to disentangle the direct and indirect pathways of influence between five different species groups: plants, phytophagous insects, ants, predators, and parasitoids. We assess cross‐taxon congruence by analysing α and β diversity indices and performing a structural equation model and Procrustes tests, respectively, trying to elucidate the pathways of influence between fire frequency and the different guilds. Multi‐guild communities responded to environmental changes produced by fire frequency via direct and indirect effects. Fire has both negative and positive, but weak indirect effects on predator richness through a bottom‐up cascading effect from plant richness across phytophagous insects and ants. However, when species relative abundances were considered, no effects have been observed on Shannon and Simpson diversity indices. A positive correlation between species composition of different guilds and fire frequency indicated congruence between connected guilds suggesting that changes in beta diversity propagate across all trophic chains. Given an increase in fire frequency, changes posed to vegetation translated in weak changes via species richness but through pronounced effects on species composition across different trophic levels. Our findings emphasise the importance of a multi‐guild approach to understanding biodiversity responses to environmental changes, highlighting the complexity and intricate dynamics of ecological communities in fire‐prone ecosystems.

Ecological dynamics in Banksia aemula woodlands following widespread, anthropogenic wildfires on a world heritage listed island (K'gari), Australia

AbstractThe increased severity and frequency of wildfires are a growing threat to biodiversity globally posing a complex challenge for the management of protected areas. K'gari, a World Heritage‐listed sand barrier island located off the coast of Australia, was extensively burnt in wildfires in 2019 and 2020. Banksia aemula low open woodland (BALOW) is a fire‐adapted ecosystem, and Banksia aemula is the dominant vegetation type on the island. This research explored interactions between vertebrate fauna and flora species richness and structure after fires in the BALOW habitat. We employed camera trapping and vegetation surveys to estimate species richness and habitat structure. We detected 28 fauna and 56 plant species, including two vulnerable species. Fauna species richness differed between sites; the site with the most intense, extensive, and recent fire had the lowest fauna species richness and mammal species richness. In contrast, the site with lower intensity and more frequent historical fires had the highest fauna diversity. The long unburnt site had higher overall tree diversity and reduced shrub diversity. This research further highlights the need for evidence‐based fire management in protected areas and the risk that large‐scale and/or high‐intensity fires may pose to biodiversity even within fire‐adapted ecosystems.

Long-term alpine summit vegetation cover change: Divergent trajectories driven by climate warming and fire

ABSTRACT Alpine summit vegetation, the highest point of species geographical distributions, is vulnerable to climate change (thermal niche contraction), and there is evidence of change in Northern Hemisphere summits. However, summits are experiencing multifaceted change due to warming and increasing fire frequency. Little is known about how these factors are affecting alpine summit vegetation. We used a revisitation approach to capture the long-term (eighteen years) dynamic changes in Australian alpine plant summit community patterns and to understand the mechanisms of change. We found that vegetation change was influenced by climate and moderated by site-specific factors. There was increased shrub cover over time; however, summit vegetation was largely stable unless disturbed. Fire-disturbed summits experienced higher instability in their vegetation cover over time. Linear mixed-effect models indicated that as time since fire increased and the growing degrees accumulated, there was a strong positive effect on forb and graminoid cover and a negative effect on shrub cover. Forb cover was higher at cooler, wetter, higher-elevation summits. These findings indicate the multifaceted nature of change that must be accounted for in alpine vegetation studies. We show that alpine summit vegetation will respond multidirectionally to a warming climate and changing fire regimes, with outcomes likely contingent on life history characteristics.

Wildfire Severity to Valued Resources Mitigated by Prescribed Fire in the Okefenokee National Wildlife Refuge

Prescribed fire is increasingly utilized for conservation and restoration goals, yet there is limited empirical evidence supporting its effectiveness in reducing wildfire-induced damages to highly valued resources and assets (HVRAs)—whether natural, cultural, or economic. This study evaluates the efficacy of prescribed fire in reducing wildfire severity to LANDFIRE-defined vegetation classes and HVRAs impacted by the 2017 West Mims event, which burned across both prescribed-fire treated and untreated areas within the Okefenokee National Wildlife Refuge. Wildfire severity was quantified using the differenced normalized burn ratio (dNBR) index, while treatment records were used to calculate the prescribed frequency and post-treatment duration, which is defined as the time elapsed between the last treatment and the West Mims event. A generalized additive model (GAM) was fit to model dNBR as a function of post-treatment duration, fire frequency, and vegetation type. Although dNBR exhibited considerable heterogeneity both within and between HVRAs and vegetation classes, areas treated with prescribed fire demonstrated substantial reductions in burn severity. The beneficial effects of prescribed fire were most pronounced within approximately two years post-treatment with up to an 88% reduction in mean wildfire severity. However, reductions remained evident for approximately five years post-treatment according to our model. The mitigating effect of prescribed fire was most pronounced in Introduced Upland Vegetation-Shrub, Eastern Floodplain Forests, and Longleaf Pine Woodland when the post-treatment duration was within 12 months. Similar trends were observed in areas surrounding red-cockaded woodpecker nesting sites, which is an HVRA of significant ecological importance. Our findings support the frequent application of prescribed fire (e.g., one- to two-year intervals) as an effective strategy for mitigating wildfire severity to HVRAs.

Insulin activates parasympathetic hepatic-related neurons of the paraventricular nucleus of the hypothalamus through mTOR signaling.

Integration of autonomic and metabolic regulation, including hepatic function, is a critical role played by the brain's hypothalamic region. Specifically, the paraventricular nucleus of the hypothalamus (PVN) regulates autonomic functions related to metabolism, such as hepatic glucose production. Although insulin can act directly on hepatic tissue to inhibit hepatic glucose production, recent evidence implicates central actions of insulin within PVN also regulates glucose metabolism. However, specific central circuits responsible for insulin signaling with relation to hepatic regulation are poorly understood. As a heterogenous nucleus essential to controlling parasympathetic motor output with notable expression of insulin receptors, PVN is an appealing target for insulin-dependent modulation of parasympathetic activity. Here, we tested the hypothesis that insulin activates hepatic-related PVN (PVNhepatic) neurons through a parasympathetic pathway. Using transsynaptic retrograde tracing, labeling within PVN was first identified 24 h after its expression in DMV and 72 h after hepatic injection. Critically, nearly all labeling in medial PVN was abolished after a left vagotomy, indicating that PVNhepatic neurons in this region are part of a central circuit innervating parasympathetic motor neurons. Insulin also significantly increased firing frequency of PVNhepatic neurons in this subregion. Mechanistically, rapamycin pretreatment inhibited insulin-dependent activation of PVNhepatic neurons. Therefore, central insulin signaling can activate a subset of PVNhepatic neurons which are part of a unique parasympathetic network in control of hepatic function. Taken together, PVNhepatic neurons related to parasympathetic output regulation could serve as a key central network in insulin's ability to control hepatic functions.

Actors, spatiotemporal changes, and (un)sustainable practices in community peatland management: A case study from West Kalimantan, Indonesia

This research explores the village community that manages large, degraded, abandoned, and ex‐logged peatlands in light of overlapping national development policy, global commodity market forces, and international conservation mandates. The transformation of peatland ownership from public to private owners has led to a predominant shift towards oil palm plantations, facilitated by village elites through partnerships, migration, and smallholder schemes. This conversion has resulted in extensive peatland degradation, drainage impacts, and frequent peat fires. In response, the local community has committed to reducing the use of fire for land clearance and water management. As an alternative, machinery is used to manage the peatland. However, employing excavators for land clearance and constructing peat water‐draining canals poses other threats, of peatland depletion, increased fire occurrences, degradation and compaction of peat. This study seeks to explore community‐level degraded peatland management dynamics by understanding (i) the actors’ conflicting intentions and continuous negotiation (between conservation, exploitation, and development), (ii) considering the impact of tenure insecurity and the power struggle surrounding further peatland exploitation, and (iii) the need for broader discussions about community peatland management beyond fires.

Biosphere reserves in the megadiverse Cape Floristic Region are effective in conserving arthropod diversity

AbstractBiosphere reserves (BRs) aim to protect global biodiversity alongside social and economic development. Each BR is composed of a core area where biodiversity conservation is maximal. Surrounding this zone is a buffer and then a transition zone where agroecological farming and other low‐intensity land‐uses are undertaken to an increasing degree. The Cape Floristic Region (CFR) is a biodiversity hotspot at the southern tip of Africa, extremely rich in endemic plants and arthropods. We review the instigation of four CFR BRs for effective conservation to protect this unique biodiversity, and where new species are regularly being discovered. Core areas protect many endemic and rare arthropod species with impacts from human activities in these critical areas being softened by the outer zones. Within the buffer and transition zones, agroecological approaches are advancing arthropod conservation, largely through maintenance of natural patches in the agricultural matrix. While larger patches are better, small patches also have high value for arthropods, especially when functionally connected. Other biodiversity‐friendly farming methods such as high vegetation cover between vine rows are also proving to be effective for indigenous arthropod conservation, as is an ecologically sensitive pest management strategy. Furthermore, a national programme aimed at removal of invasive alien trees is enabling arthropod recovery, especially endemic stream insects. Although fire is a natural CFR phenomenon, increased fire frequency is of concern. Nevertheless, natural fire refuges remain vitally important and are playing a critical role, especially for vulnerable species‐rich groups like pollinators. Overall, there is optimism that most arthropod species will remain at effective population levels in this megadiversity hotspot by putting in place effective precautionary measures. Here we show that the BR model contributes towards the protection of the CFR's endemic arthropod fauna, with potential to expand the BRs beyond the four official reserves.

The analysis of climate change and human activities in the Brazilian Amazon forest

In recent years, global warming has significantly altered weather patterns in many countries. Brazil, home to the biggest tropical rainforest on Earth the Amazon Forest, has experienced an uptick in extreme climate events, which has increasingly captured global attention. Human activities may contribute to phenomena such as the greenhouse effect, acid rain, and the depletion of the ozone layer. Additionally, the increasing frequency of extreme weather events has led to issues related to agricultural yield, infectious diseases, and other related problems. This article primarily explores the changes in climatic conditions of the Amazon Forest in Brazil and the measures the government ought to take. Through a review of the literature, this report examined the changes in temperature, precipitation, vegetation coverage, and fire in the Amazon Forest in Brazil in recent years, as well as the interconnections among these factors. Besides, this article also offers recommendations for addressing the more severe drought and frequent fires in the Brazilian Amazon Forest.

High fire severity and frequency threaten the persistence of a widespread obligate-seeder Banksia in south-eastern Australia

Context Obligate-seeding woody plants with long reproductive maturity periods and no soil seed banks are threatened with decline as climate change drives more frequent and severe fires, such as the extensive 2019–2020 wildfires in south-eastern Australia. Aims This study aimed to investigate the effects of fire intervals and severity on the persistence of one such species, Banksia cunninghamii (Hairpin Banksia), in temperate forests. Methods We measured post-fire seedling recruitment of B. cunninghamii at 25 sites in Victoria, burned at various severities in the 2019–2020 wildfires and with differing prior fire intervals. A Bayesian framework was used to model the relationship between seedling numbers, fire severity and fire interval. A spatial analysis compared a species distribution model for B. cunninghamii with fire severity and fire intervals. Key results There was a low chance of B. cunninghamii recruitment (&lt;25%) at sites that either had burned eucalypt canopies or a preceding fire interval of less than 12 years. Sixty-seven percent of its distribution in the south-east of the state of Victoria was mapped as burned at high severity (burned eucalypt canopies) between 1998 and 2020, or burned at shorter than 12 year intervals between 1960 and 2020, although some B. cunninghamii populations will have persisted due to the patchiness of past burns. Conclusions Banksia cunninghamii is vulnerable to local extinctions in the wildfire-affected areas if fires occur again before plants reach maturity, or if high fire severity destroys seeds. Implications More frequent and severe wildfires mean that burn planning needs to consider the reproductive cycles of serotinous obligate-seeding plants.

Neuronal activity inhibits mitochondrial transport only in synaptically connected segments of the axon.

Due to their large scale and uniquely branched architecture, neurons critically rely on active transport of mitochondria in order to match energy production and calcium buffering to local demand. Consequently, defective mitochondrial trafficking is implicated in various neurological and neurodegenerative diseases. A key signal regulating mitochondrial transport is intracellular calcium. Elevated Ca2+ levels have been demonstrated to inhibit mitochondrial transport in many cell types, including neurons. However, it is currently unclear to what extent calcium-signaling regulates axonal mitochondrial transport during realistic neuronal activity patterns. We created a robust pipeline to quantify with high spatial resolution, absolute Ca2+ concentrations. This allows us to monitor Ca2+ dynamics with pixel precision in the axon and other neuronal compartments. We found that axonal calcium levels scale with firing frequency in the range of 0.1-1 μM, whereas KCl-induced depolarization generated levels almost a magnitude higher. As expected, prolonged KCl-induced depolarization did inhibit axonal mitochondrial transport in primary hippocampal neurons. However, physiologically relevant neuronal activity patterns only inhibited mitochondrial transport in axonal segments which made connections to a target neuron. In "non-connecting" axonal segments, we were unable to trigger this inhibitory mechanism using realistic firing patterns. Thus, we confirm that neuronal activity can indeed regulate axonal mitochondrial transport, and reveal a spatial pattern to this regulation which went previously undetected. Together, these findings indicate a potent, but localized role for activity-related calcium fluctuations in the regulation of axonal mitochondrial transport.