Increase In Firing Frequency Research Articles

Forecasting the Frequency and Magnitude of Postfire Debris Flows Across Southern California

AbstractSouthern California has a long history of damaging debris flows after wildfire. Despite recurrent loss, forecasts of the frequency and magnitude of postfire debris flows are not available for the region like they are for earthquakes. Instead, debris flow hazards are typically assessed in a reactive manner after wildfires. Such assessments are crucial for evaluating debris flow risk by postfire emergency response teams; however, time between the fire and first rainstorm is often insufficient to fully develop and implement effective emergency response plans like those in place for earthquakes. Here, we use both historical distributions of fire and precipitation frequency and empirical models of postfire debris flow likelihood and volume to map the expected frequency and magnitude of postfire debris flows across southern California. We find that at least small debris flows can be expected almost every year, while major debris flows capable of damaging 40 or more structures have a recurrence interval between 10 and 13 years, a return interval that is comparable to a magnitude 6.7 earthquake. A sensitivity analysis to possible future changes in current fire and precipitation regimes indicates that debris flow activity in southern California is more sensitive to increases in precipitation intensity than increases in fire frequency and severity. Projected increases in rainfall intensity of 18% result in an overall 110% increase in the probability of major debris flows. Our results, in combination with an assessment of exposure, can be used to prioritize watersheds for further analysis and possible prefire mitigation.

Synergistic effects of a severe drought and fire on platypuses.

The strong inter-dependence between terrestrial and freshwater ecosystems, mediated by the character of vegetation and landscapes, can have significant impacts to freshwater species. A changing climate towards hotter and drier climates is already increasing fire frequencies and severity around the world. The platypus (Ornithorhynchus anatinus) is an iconic freshwater Australia species, facing increasing threats since European colonisation and with a distribution which coincides with fire prone areas. While some evidence suggest platypuses are resilience to fires, the combination of severe wildfires and reduced water availability may significantly impact platypus populations. In this short communication we investigated the effects of fire on platypus populations in two rivers, following an extreme drought, comparing burnt and unburnt in adjacent river catchments, with similar habitat and geomorphology. Findings suggests significantly low platypus numbers in burned sites compared to those on the unburnt river, as well as to known densities across the species' range. Whether the fires directly impacted platypuses remains undetermined but the timing of the fires as well as an extreme drought likely impacted recruitment as we did not record any juveniles on both rivers. Platypuses are increasingly under threat from direct and indirect human developments across much of their range and increased frequency and severity of fires and droughts will further strain the viability of platypus populations, particularly in small streams more likely to dry out. Improving the resilience of platypus populations and their freshwater environments to both droughts and fires needs to become a priority.

Erythromelalgia: A Child With V400M Mutation in the SCN9A Gene.

Erythromelalgia is a rare pain syndrome caused by gain-of-function mutations of the SCN9A gene. The gene encodes Nav1.7 channels, preferentially located in the sympathetic ganglia and nociceptive sensory neurons of the dorsal root ganglia (DRG),1 that play a key role in pain modulation.2 DRG hyperexcitability leads to decreased pain threshold and increased firing frequency of pain signaling neurons.3 Clinically, this presents as recurrent, severe burning pain, redness, warmth, and often swelling of the distal extremities. Exposure to cold may provide relief but can lead to skin ulcerations.4 There is anecdotal evidence of partial relief from NSAIDS, antihistamines, and sodium channel blockers.5,6 Carbamazepine and oxcarbazepine inactivate sodium channels but have been ineffective in most patients. Only 1 family with erythromelalgia and V400M mutation in the SCN9A gene that responded to carbamazepine was reported so far.3

Unmanned Aerial Vehicles for Wildland Fires: Sensing, Perception, Cooperation and Assistance

Wildfires represent a significant natural risk causing economic losses, human death and environmental damage. In recent years, the world has seen an increase in fire intensity and frequency. Research has been conducted towards the development of dedicated solutions for wildland fire assistance and fighting. Systems were proposed for the remote detection and tracking of fires. These systems have shown improvements in the area of efficient data collection and fire characterization within small-scale environments. However, wildland fires cover large areas making some of the proposed ground-based systems unsuitable for optimal coverage. To tackle this limitation, unmanned aerial vehicles (UAV) and unmanned aerial systems (UAS) were proposed. UAVs have proven to be useful due to their maneuverability, allowing for the implementation of remote sensing, allocation strategies and task planning. They can provide a low-cost alternative for the prevention, detection and real-time support of firefighting. In this paper, previous works related to the use of UAV in wildland fires are reviewed. Onboard sensor instruments, fire perception algorithms and coordination strategies are considered. In addition, some of the recent frameworks proposing the use of both aerial vehicles and unmanned ground vehicles (UGV) for a more efficient wildland firefighting strategy at a larger scale are presented.

Chronic intermittent hypoxia increases excitability and synaptic excitation of protrudor and retractor hypoglossal motoneurones.

Dysfunctions in the hypoglossal control of tongue extrinsic muscles are implicated in obstructive sleep apnoea (OSA) syndrome. Chronic intermittent hypoxia (CIH), an important feature of OSA syndrome, produces deleterious effects on the motor control of oropharyngeal resistance, but whether the hypoglossal motoneurones innervating the tongue extrinsic muscles are affected by CIH is unknown. We show that CIH enhanced the respiratory-related activity of rat hypoglossal nerve innervating the protrudor and retractor tongue extrinsic muscles. Intracellular recordings revealed increases in respiratory-related firing frequency and synaptic excitation of inspiratory protrudor and retractor hypoglossal motoneurones after CIH. CIH also increased their intrinsic excitability, depolarised resting membrane potential and reduced K+ -dominated leak conductance. CIH affected the breathing-related synaptic control and intrinsic electrophysiological properties of protrudor and retractor hypoglossal motoneurones to optimise the neural control of oropharyngeal function. Inspiratory-related tongue movements and oropharyngeal motor actions are controlled mainly by the protrudor and retractor extrinsic tongue muscles, which are innervated by the hypoglossal motoneurones. Chronic intermittent hypoxia (CIH), an important feature of obstructive sleep apnoea syndrome, produces detrimental effects on the contractile function of the tongue extrinsic muscles and the medullary inspiratory network of rodents. However, the impact of the CIH on the electrophysiological properties of protrudor and retractor hypoglossal motoneurones has not been described before. Using nerves and intracellular recordings in in situ preparation of rats (5weeks old), we tested the hypothesis that CIH (FiO2 of 0.06, SaO2 74%, during 30-40s, every 9min, 8h/day for 10days) increases the intrinsic excitability of protrudor and retractor motoneurones from the hypoglossal motor nucleus of rats. Recordings of hypoglossal nerve, before its bifurcation to innervate the tongue protrudor and retractor muscles, revealed that CIH enhances its pre-inspiratory, simultaneously with the presence of active expiration, and inspiratory activities. These changes were mediated by increases in the respiratory-related firing frequency and synaptic excitation of inspiratory protrudor and retractor hypoglossal motoneurones. Besides, CIH increases their intrinsic excitability and depolarises resting membrane potential by reducing a K+ -dominated leak conductance. In conclusion, CIH enhances the respiratory-related neural control of oropharyngeal function of rats by increasing the synaptic excitation, intrinsic excitability, and reducing leak conductance in both protrudor and retractor hypoglossal motoneurones. We propose that these network and cellular changes are important to optimise the oropharyngeal resistance in conditions related to intermittent hypoxia.

An Anticipatory Circuit Modification That Modifies Subsequent Task Switching.

Modulators are generally expected to establish a network configuration that is appropriate for the current circumstances. We characterize a situation where the opposite is apparently observed. A network effect of a peptide modulator is counterproductive in that it tends to impede rather than promote the creation of the configuration that is appropriate when the modulator is released. This raises a question: why does release occur? We present data that strongly suggest that it impacts task switching. Our experiments were conducted in an Aplysia feeding network that generates egestive and ingestive motor programs. Initial experiments focused on egestive activity and the neuron B8. As activity becomes egestive, there is an increase in synaptic drive to B8 and its firing frequency increases (Wang et al., 2019). We show that, as this occurs, there is also a persistent current that develops in B8 that is outward rather than inward. Dynamic clamp introduction of this current decreases excitability. When there is an egestive-ingestive task switch in Aplysia, negative biasing is observed (i.e., a bout of egestive activity has a negative impact on a subsequent attempt to initiate an ingestive response) (Proekt et al., 2004). Using an in vitro analog of negative biasing, we demonstrate that the outward current that develops during egestive priming plays an important role in establishing this phenomenon. Our data suggest that, although the outward current induced as activity becomes egestive is counterproductive at the time, it plays an anticipatory role in that it subsequently impacts task switching.SIGNIFICANCE STATEMENT In this study, we identify a peptide-induced circuit modification (induction of an outward current) that does not immediately promote the establishment of a behaviorally appropriate network configuration. We ask why this might occur, and present data that strongly suggest that it plays an important role during task switching. Specifically, our data suggest that the outward current we characterize plays a role in the negative biasing that is seen in the mollusc Aplysia when there is a transition from egestive to ingestive activity. It is possible that the mechanism that we describe operates in other species. A negative effect of egestion on subsequent ingestion is observed throughout the animal kingdom.

Investigating the role of striatal dopamine receptor 2 in motor coordination and balance: Insights into the pathogenesis of DYT1 dystonia

DYT1 or DYT-TOR1A dystonia is early-onset, generalized dystonia. Most DYT1 dystonia patients have a heterozygous trinucleotide GAG deletion in DYT1 or TOR1A gene, with a loss of a glutamic acid residue of the protein torsinA. DYT1 dystonia patients show reduced striatal dopamine D2 receptor (D2R) binding activity. We previously reported reduced striatal D2R proteins and impaired corticostriatal plasticity in Dyt1 ΔGAG heterozygous knock-in (Dyt1 KI) mice. It remains unclear how the D2R reduction contributes to the pathogenesis of DYT1 dystonia. Recent knockout studies indicate that D2R on cholinergic interneurons (Chls) has a significant role in corticostriatal plasticity, while D2R on medium spiny neurons (MSNs) plays a minor role. To determine how reduced D2Rs on ChIs and MSNs affect motor performance, we generated ChI- or MSN-specific D2R conditional knockout mice (Drd2 ChKO or Drd2 sKO). The striatal ChIs in the Drd2 ChKO mice showed an increased firing frequency and impaired quinpirole-induced inhibition, suggesting a reduced D2R function on the ChIs. Drd2 ChKO mice had an age-dependent deficient performance on the beam-walking test similar to the Dyt1 KI mice. The Drd2 sKO mice, conversely, had a deficit on the rotarod but not the beam-walking test. Our findings suggest that D2Rs on Chls and MSNs have critical roles in motor control and balance. The similarity of the beam-walking deficit between the Drd2 ChKO and Dyt1 KI mice supports our earlier notion that D2R reduction on striatal ChIs contributes to the pathophysiology and the motor symptoms of DYT1 dystonia.

Fire frequency effects on cleistogamy expression and progeny performance in Cologania broussonetii.

Increased fire frequency usually erodes microenvironmental conditions, causing a drastic limitation of edaphic resources. Thus, the production of permanently closed-small flowers (cleistogamous, CL) should increase in sites with high fire frequency as this implies a less expensive reproductive assurance strategy. However, because open, insect-pollinated flowers (chasmogamous, CH) have the potential capacity to outcross via pollinators, CH progeny produced at any site should outperform selfed CL progeny. We evaluate the effect of fire frequency on the relative production of CL/CH flowers and fruits, and their seed set, along with several progeny performance parameters in Cologania broussonetii (Fabaceae), a resprouting herb with dimorphic cleistogamy native to the Chaco Serrano. Fire frequency increased cleistogamy expression, reaching extreme levels in high fire frequency sites. Seed set was similarly high for both CH and CL flowers in the unburned condition, while in burned sites the few developed CH flowers set more seeds than CL flowers. However, progeny performance was similar between CH and CL progeny at each and across all fire frequency conditions. Cleistogamy expression in C. broussonetii is maximized in abiotically degraded frequently burned habitats, although the selfed CL progeny is as successful as potentially outcrossed CH progeny. Fire frequency may decreased floral size and abundance, selecting for autogamous reproduction, which restricts not only the genetic potential of plant populations but also the resources offered to pollinators. At the community level, increased cleistogamy expression may potentially have negative implications for non-cleistogamous, more outcrossing species surviving in frequently burned environments.

Does fire always accelerate shrub expansion in Arctic tundra? Examining a novel grass-dominated successional trajectory on the Seward Peninsula

ABSTRACT Over the last century in the circumpolar north, notable terrestrial ecosystem changes include shrub expansion and an intensifying wildfire regime. Shrub invasion into tundra may be further accelerated by wildfire disturbance, which creates opportunities for establishment where recruitment is otherwise rare. The Seward Peninsula currently experiences more frequent and larger fires than other tundra regions in Alaska. There are areas of overlapping burn scars dating back to the 1950s. Using a chronosequence approach, we examined vegetation and ecosystem dynamics in tussock tundra. Increasing burn severity and fire frequency corresponded with an increase in grass cover and a decrease in shrub basal area. We used multivariate ordination analysis to create a single integrator variable of fire effect that accounted for time after fire, burn severity, and number of times burned. This fire effect was significantly associated with decreases in soil organic layer thickness and overall plant biomass. Unlike previous studies in Arctic Alaska tundra, we found that increases in fire frequency and severity did not increase shrub cover and biomass. Instead, intensifying fire disturbance, and particularly repeat fires, led to grass dominance. Our findings support the hypothesis that intensifying tundra fire regimes initiate alternative post-fire trajectories that are not shrub dominated and that are structurally and functionally quite different from sedge or shrub-dominated tundra.

Comparison of vapour-exchange methods for predicting hourly twig fuel moisture contents of larch and birch stands in the Daxinganling Region, China

The Daxinganling Region, in Heilongjiang Province, China, has experienced considerable losses to forest resources owing to a recent increase in forest fire frequency. This necessitates the predictions of fire behaviour in this region, which requires assessment of fuel moisture content (FMC) at appropriate space and time intervals. Here, we compare and extrapolate results of vapour-exchange methods for predicting hourly moisture contents of downed wood. The FMC of larch and birch twig fuels was measured at 1-h intervals at different slope positions with respect to meteorological factors. The twigs were categorised based on diameter and degree of decay. The Nelson and Simard methods (which consider equilibrium moisture content and the associated time lag) and direct regression method (which allows direct attainment of the FMC) were used. Both Nelson and Simard methods predicted hourly twig moisture content more accurately than the direct regression method. The Simard method was the most accurate, with the lowest mean absolute error and mean relative error as well as relatively small variation coefficients based on results of the extrapolation analysis. Further, the resulting models applied to needle-leaved and lightly decomposed fuels performed better than for the broad-leaved and badly decomposed fuels on evaluation parameters.

Warming is here: using locomotor performance to infer thermal parameters and vulnerability for an endemic Argentinean tarantula Grammostola vachoni

1. Because of global climate change and its consequences, estimating the physiological responses of ectothermicorganisms to temperature is of high priority. The thermal increase and changes in fire frequency are some of the consequences of global warming, which could challenge the physiological performance and thermal tolerance of individuals.2. The present study estimates the thermal parameters from field individuals of the tarantula Grammostola vachoni. To achieve this, we determined the critical thermal limits for locomotor performance, the thermal optimum, and the preferred temperatures. We also calculate the thermal performance breadth and thermal tolerance zone.3. Temperature strongly affected the locomotor performance of spiders; the sprint speeds were significantly different between temperatures, and at 5 °C and 25 °C the parameter was significantly different between females and juveniles. The preferred temperature showed a mean value of 26.5 °C, and females preferred lower temperature than juveniles. Grammostola vachoni showed a wide thermal tolerance range (close to 43 °C) and thermal performance breadth (B80), an index defined as the range of temperatures at which performance is at least 80% of the maximum.4. For G. vachoni, these large breadths in the sprint speed represent a substantial buffer against future increases in habitat temperature and shows that the locomotor performance of this species is an adaptable parameter. Understanding the impact of warming in performances is important to make predictions about if this species can remain ecologically viable while facing global change, given the massive worldwide declines in arthropod populations.

The propagule doesn't fall far from the tree, especially after short-interval, high-severity fire.

Subalpine forests that historically burned every 100-300yr are expected to burn more frequently as climate warms, perhaps before trees reach reproductive maturity or produce a serotinous seedbank. Tree regeneration after short-interval (<30-yr) high-severity fire will increasingly rely on seed dispersal from unburned trees, but how dispersal varies with age and structure of surrounding forest is poorly understood. We studied wind dispersal of three conifers (Picea engelmannii, Abies lasiocarpa, and Pinus contorta var. latifolia, which can be serotinous and nonserotinous) after a stand-replacing fire that burned young (≤30yr) and older (>100yr) P. contorta forest in Grand Teton National Park (Wyoming, USA). We asked how propagule pressure varied with time since last fire, how seed delivery into burned forest varied with age and structure of live forest edges, what variables explained seed delivery into burned forest, and how spatial patterns of delivery across the burned area could vary with alternate patterns of surrounding live forest age. Seeds were collected in traps along 100-m transects (n=18) extending from live forest edges of varying age (18, 30, and >100yr) into areas of recent (2-yr) high-severity fire, and along transects in live forests to measure propagule pressure. Propagule pressure was low in 18-yr-old stands (~8seeds/m2 ) and similarly greater in 30- and 100-yr-old stands (~32seeds/m2 ). Mean dispersal distance was lowest from 18-yr-old edges and greatest from >100-yr-old edges. Seed delivery into burned forest declined with increasing distance and increased with height of trees at live forest edges, and was consistently higher for P. contorta than for other conifers. Empirical dispersal kernels revealed that seed delivery from 18-yr-old edges was very low (≤2.4seeds/m2 ) and concentrated within 10m of the live edge, whereas seed delivery from >100-yr-old edges was >4.9seeds/m2 out to 80m. When extrapolated throughout the burned landscape, estimated seed delivery was low (<49,400seeds/ha) in >70% of areas that burned in short-interval fire (<30yr). As fire frequency increases, immaturity risk will be compounded in short-interval fires because seed dispersal from surrounding young trees is limited.

Hydrological benefits of restoring wildfire regimes in the Sierra Nevada persist in a warming climate

Reducing the risk of wildfire and increasing the security of water supply from mountain catchments are both urgent priorities in the Western US. These goals may be synergistic, thanks to the reductions in transpiration and fire hazard associated with reducing forest cover. Data and modeling efforts based on the Illilouette Creek Basin (ICB) in Yosemite National Park, where fire use policies have been implemented to restore wildfire since 1972, suggest that these policies reduced fire hazards and increased annual streamflow production through large changes to landscape-scale forest cover and structure. Expanding fire use strategies through the Western US, however, would mean that any such changes in forest cover and structure would occur in the middle of the 21st century, under different fire frequency and climate conditions than experienced in the ICB to date. It is therefore important to understand if hydrological benefits of fire use are sensitive to anticipated changes in climate and fire frequency. Here, we force an ecohydrological model previously developed for the ICB with an ensemble of downscaled future climate predictions to assess the impacts of climate change and fire use strategies on the hydrology of the ICB. We find that the hydrological impacts of fire use are comparable under observed climate and projected future climates, and are largely insensitive to the significant uncertainties regarding post-fire successional trajectories for vegetation. While expected increases in fire frequency cause minor changes in the basin hydrology, the main impact of more frequent fires is to cause the basin to reach peak hydrological change more rapidly.

How Initial Forest Cover, Site Characteristics and Fire Severity Drive the Dynamics of the Southern Boreal Forest

Forest fires are a key driver of boreal landscape dynamics and are expected to increase with climate change in the coming decades. A profound understanding of the effects of fire upon boreal forest dynamics is thus critically needed for our ability to manage these ecosystems and conserve their services. In the present study, we investigate the long-term post-fire forest dynamics in the southern boreal forests of western Quebec using historical aerial photographs from the 1930s, alongside with modern aerial photographs from the 1990s. We quantify the changes in forest cover classes (i.e., conifers, mixed and broadleaved) for 16 study sites that were burned between 1940 and 1970. We then analyzed how interactions between pre-fire forest composition, site characteristics and a fire severity weather index (FSWI) affected the probability of changes in forest cover. In the 1930s, half of the cover of sampled sites were coniferous while the other half were broadleaved or mixed. Between the 1930s and the 1990s, 41% of the areas maintained their initial cover while 59% changed. The lowest probability of changes was found with initial coniferous cover and well drained till deposits. Moreover, an important proportion of 1930s broadleaved/mixed cover transitioned to conifers in the 1990s, which was mainly associated with high FSWI and well-drained deposits. Overall, our results highlight a relatively high resistance and resilience of southern boreal coniferous forests to fire, which suggest that future increase in fire frequency may not necessarily result in a drastic loss of conifers.

Methadone Suppresses Neuronal Function and Maturation in Human Cortical Organoids.

Accumulating evidence has suggested that prenatal exposure to methadone causes multiple adverse effects on human brain development. Methadone not only suppresses fetal neurobehavior and alters neural maturation, but also leads to long-term neurological impairment. Due to logistical and ethical issues of accessing human fetal tissue, the effect of methadone on brain development and its underlying mechanisms have not been investigated adequately and are therefore not fully understood. Here, we use human cortical organoids which resemble fetal brain development to examine the effect of methadone on neuronal function and maturation during early development. During development, cortical organoids that are exposed to clinically relevant concentrations of methadone exhibited suppressed maturation of neuronal function. For example, organoids developed from 12th week till 24th week have an about 7-fold increase in AP firing frequency, but only half and a third of this increase was found in organoids exposed to 1 and 10 μM methadone, respectively. We further demonstrated substantial increases in INa (4.5-fold) and IKD (10.8-fold), and continued shifts of Na+ channel activation and inactivation during normal organoid development. Methadone-induced suppression of neuronal function was attributed to the attenuated increase in the densities of INa and IKD and the reduced shift of Na+ channel gating properties. Since normal neuronal electrophysiology and ion channel function are critical for regulating brain development, we believe that the effect of prolonged methadone exposure contributes to the delayed maturation, development fetal brain and potentially for longer term neurologic deficits.

Enhancement of intrinsic neuronal excitability-mediated by a reduction in hyperpolarization-activated cation current (Ih ) in hippocampal CA1 neurons in a rat model of traumatic brain injury.

Traumatic brain injury (TBI) is associated with epileptiform activity in the hippocampus; however, the underlying mechanisms have not been fully determined. The goal was to understand what changes take place in intrinsic neuronal physiology in the hippocampus after blunt force trauma to the cortex. In this context, hyperpolarization-activated cation current (Ih ) currents may have a critical role in modulating the neuronal intrinsic membrane excitability; therefore, its contribution to the TBI-induced hyperexcitability was assessed. In a model of TBI caused by controlled cortical impact (CCI), the intrinsic electrophysiological properties of pyramidal neurons were examined 1 week after TBI induction in rats. Whole-cell patch-clamp recordings were performed under current- and voltage-clamp conditions following ionotropic receptors blockade. Induction of TBI caused changes in the intrinsic excitability of pyramidal neurons, as shown by a significant increase and decrease in firing frequency and in the rheobase current, respectively (p < .05). The evoked firing rate and the action potential time to peak were also significantly increased and decreased, respectively (p < .05). In the TBI group, the amplitude of instantaneous and steady-state Ih currents was both significantly smaller than those in the control group (p < .05). The Ih current density was also significantly decreased (p < .001). Findings indicated that TBI led to an increase in the intrinsic excitability in CA1 pyramidal neurons and changes in Ih current could be, in part, one of the underlying mechanisms involved in this hyperexcitability.

Modeling fire ignition probability and frequency using Hurdle models: a cross-regional study in Southern Europe

BackgroundWildfires play a key role in shaping Mediterranean landscapes and ecosystems and in impacting species dynamics. Numerous studies have investigated the wildfire occurrences and the influence of their drivers in many countries of the Mediterranean Basin. However, in this regard, no studies have attempted to compare different Mediterranean regions, which may appear similar under many aspects. In response to this gap, climatic, topographic, anthropic, and landscape drivers were analyzed and compared to assess the patterns of fire ignition points in terms of fire occurrence and frequency in Catalonia (Spain), Sardinia, and Apulia (Italy). Therefore, the objectives of the study were to (1) assess fire ignition occurrence in terms of probability and frequency, (2) compare the main drivers affecting fire occurrence, and (3) produce fire probability and frequency maps for each region.ResultsIn pursuit of the above, the probability of fire ignition occurrence and frequency was mapped using Negative Binomial Hurdle models, while the models’ performances were evaluated using several metrics (AUC, prediction accuracy, RMSE, and the Pearson correlation coefficient). The results showed an inverse correlation between distance from infrastructures (i.e., urban roads and areas) and the occurrence of fires in all three study regions. This relationship became more significant when the frequency of fire ignition points was assessed. Moreover, a positive correlation was found between fire occurrence and landscape drivers according to region. The land cover classes more significantly affected were forest, agriculture, and grassland for Catalonia, Sardinia, and Apulia, respectively.ConclusionsCompared to the climatic, topographic, and landscape drivers, anthropic activity significantly influences fire ignition and frequency in all three regions. When the distance from urban roads and areas decreases, the probability of fire ignition occurrence and frequency increases. Consequently, it is essential to implement long- to medium-term intervention plans to reduce the proximity between potential ignition points and fuels. In this perspective, the present study provides an applicable decision-making tool to improve wildfire prevention strategies at the European level in an area like the Mediterranean Basin where a profuse number of wildfires take place.

High‐severity and short‐interval wildfires limit forest recovery in the Central Cascade Range

AbstractIncreasing forest fuel aridity with climate change may be expanding mid‐to‐high‐elevation forests' vulnerability to large, severe, and frequent wildfire. Long‐lasting changes in forests' structure and composition may occur if dominant tree species are poorly adapted to shifting wildfire patterns. We hypothesized that altered fire activity may lower existing forest resilience and disrupt the recovery of upper‐montane and subalpine conifer forest types. We empirically tested this hypothesis by quantifying post‐fire forest structure and conifer tree regeneration after spatially large, severe, and rapidly repeated wildfires (&lt;12‐yr interval) in the Central Cascade Range in the U.S. Pacific Northwest. Post‐fire conifer regeneration was generally very poor among plots that experienced either a single high‐severity fire or rapid reburn, driven primarily by lack of proximate seed source. Pre‐fire dominant, shade‐tolerant species' abundance was highly negatively correlated with increasing seed source distances and dry, exposed post‐fire environmental conditions. In rapidly reburned plots, the order of burn severity was critical and promoted establishment of all conifer species, if low‐then‐high severity, or primarily fire‐adapted pines, if high‐then‐low severity. Our findings suggest that these forests, affected by expansive high‐severity and/or short‐interval wildfire, may transition into a patchy, low‐density, pine‐dominated forest state under future warming trends. These emerging, early seral ecosystems will incorporate more fire‐adapted tree species, lower tree densities, and more non‐forest patches than prior forests, likely expanding their resilience to anticipated increases in fire frequency. If future larger, more severe, and more frequent wildfire patterns manifest as expected in the Cascade Range, previously denser, moist mid‐to‐high‐elevation forests may begin resembling their drier, lower‐elevation mixed‐conifer counterparts in structure and composition.

Climate regime shift and forest loss amplify fire in Amazonian forests.

Frequent Amazonian fires over the last decade have raised the alarm about the fate of the Earth's most biodiverse forest. The increased fire frequency has been attributed to altered hydrological cycles. However, observations over the past few decades have demonstrated hydrological changes that may have opposing impacts on fire, including higher basin-wide precipitation and increased drought frequency and severity. Here, we use multiple satellite observations and climate reanalysis datasets to demonstrate compelling evidence of increased fire susceptibility in response to climate regime shifts across Amazonia. We show that accumulated forest loss since 2000 warmed and dried the lower atmosphere, which reduced moisture recycling and resulted in increased drought extent and severity, and subsequent fire. Extremely dry and wet events accompanied with hot days have been more frequent in Amazonia due to climate shift and forest loss. Simultaneously, intensified water vapor transport from the tropical Pacific and Atlantic increased high-altitude atmospheric humidity and heavy rainfall events, but those events did not alleviate severe and long-lasting droughts. Amazonia fire risk is most significant in the southeastern region where tropical savannas undergo long seasonally dry periods. We also find that fires have been expanding through the wet-dry transition season and northward to savanna-forest transition and tropical seasonal forest regions in response to increased forest loss at the "Arc of Deforestation." Tropical forests, which have adapted to historically moist conditions, are less resilient and easily tip into an alternative state. Our results imply forest conservation and fire protection options to reduce the stress from positive feedback between forest loss, climate change, and fire.

BK potassium currents contribute differently to action potential waveform and firing rate as rat hippocampal neurons mature in the first postnatal week.

The large-conductance calcium-activated potassium (BK) channel is a critical regulator of neuronal action potential firing and follows two distinct trends in early postnatal development: an increase in total expression and a shift from the faster activating STREX isoform to the slower ZERO isoform. We analyzed the functional consequences of developmental trends in BK channel expression in hippocampal neurons isolated from neonatal rats aged 1 to 7 days. Following overnight cultures, action potentials and currents were recorded using whole cell patch-clamp electrophysiology. These neurons undergo a steady increase in excitability during this time, and the effect of blockade of BK channel activity with 100 nM iberiotoxin changes as the neurons mature. BK currents contribute significantly more to total potassium current and single action potentials in neurons of 1-day old rats (with BK blockade extending action potential duration by 0.46 ± 0.12 ms) than in those of 7-day old rats (with BK blockade extending action potential duration by 0.17 ± 0.05 ms). BK currents contribute consistently to maintain firing rates in neurons of 1-day old rats throughout extended action potential firing; BK blockade evenly depresses firing frequency across action potential trains. In neurons from 7-day old rats, BK blockade initially increases firing frequency and then progressively decreases frequency as firing continues, ultimately depressing neuronal firing rates to a greater extent than in the neurons from 1-day-old animals. These results are consistent with a transition from low expression of a fast-activating BK isoform (STREX) to high expression of a slower activating isoform (ZERO).NEW & NOTEWORTHY This work describes the early developmental trends of large-conductance calcium-activated potassium (BK) channel activity. Early developmental trends in expression of BK channels, both total expression and relative isoform expression, have been previously reported, but little work describes the effect of these changes in expression patterns on excitability. Here, we show that early changes in BK channel expression patterns lead to changes in the role of BK channels in determining the action potential waveform and neuronal excitability.