Firing Frequency Research Articles

Decreased GABAergic Neurotransmission Promotes Breathing Upon Emergence From Hibernation

The respiratory network must produce reliable output for an animal to survive. Although respiratory motor plasticity is well appreciated, how plasticity mechanisms work to promote robustness following environmental perturbations that disrupt breathing is less clear. During underwater hibernation, respiratory neurons of bullfrogs remain inactive for months, triggering a suite of compensatory mechanisms that aim to maintain respiratory function. We hypothesized that GABAergic inhibition would decrease following hibernation. In control animals, respiratory frequency was under control of GABAAR signaling. Specifically, block of GABAARs dose-dependently decreased respiratory burst frequency in the in vitro brainstem preparation (n=5 preparations). After hibernation, GABAA receptor block had little to no impact on respiratory burst frequency, suggesting the network was no longer reliant on GABAergic inhibition to maintain normal frequency (n=5 preparations). The loss of inhibition was specific to the respiratory network because non-respiratory motor activity and large seizure-like bursts were similarly triggered by GABAA receptor blockade in intact brainstem preparations from controls and hibernators. We next used a semi-intact preparation that maintains functional respiratory-synaptic input onto rhythmic motor neurons to identify compensatory changes in GABAergic tone at the level of the motor neuron. In controls, the firing rate of respiratory motoneurons was constrained by a phasic GABAAR tone because focal application of bicuculline, a GABAAR antagonist, led to an increase in phasic firing frequency (n=12 cells). After hibernation, this bicuculline-mediated increase in phasic firing frequency was attenuated suggesting phasic inhibition onto the motor neuron had decreased (n=9 cells). Brain slice recordings of identified vagal motor neurons revealed that postsynaptic GABAA receptor strength was unchanged following hibernation (n=16 control cells; n=16 hibernation cells). Taken together, our results suggest that GABAergic activity is decreased in premotor networks following hibernation. Despite this dramatic loss of GABAergic function, respiratory output from control preparations was indistinguishable from hibernators. To elucidate the functional impacts of loss of GABAergic activity, we tested the network’s ability to produce output at colder temperatures. In controls, respiratory output slowed as temperature decreased, with most networks nearly silent at 8 degrees Celsius (n=5 preparations). Interestingly, in controls low dose block of GABAA receptors promoted respiratory activity at cold temperatures, with frequency not statistically different than baseline at any temperature tested (n=4 preparations). This suggests that the loss of premotor GABAergic activity we observed could work to promote motor output at colder temperatures, which works adaptively for the animal when emerging from hibernation. NIH R01NS114514 (JS). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

SIGNIFICANCE OF THE NAV 1.8. VOLTAGE-GATED, TETRODOTOXIN-RESISTANT SODIUM CHANNEL FOR THE RENAL SENSORY INNERVATION IN MICE AND RATS

Objective: Our previous work repeatedly showed that the sensory innervation of the kidney in rats has a peculiarity containing predominantly (more than 50%) highly active tonic neurons to electrical stimulation. In a previous publication demonstrated an increased mRNA expression of the TTX-resistant sodium channel Nav1.8 in renal sensory neurons. Hence, we tested the hypothesis that tonic firing pattern is related to the specific expression of Nav1.8 on the cell surface of neurons with renal sensoric axons in the dorsal root ganglia (DRG Th12-L2). Design and method: Harvested dorsal root ganglion neurons (DRG Th11-L2) from Sprague Dawley (SD) with renal afferents were investigated in neuronal cell culture using current clamp mode to assess action potential generation during current injection and to characterize neurons as tonic highly active and phasic less active neurons using a Nav1.8 blocker (A-803467) before and after stimulation. Further, renal DRG neurons from a Nav1.8 knock out mouse (C57BL6J-Scn10atm1Jwo) were investigated in a current clamp mode. C57BL6 mice were used as controls. Results: At a concentration of 0.3μM the maximum AP firing frequency of tonic neurons was blocked from 13+/- 1.1 APs/600ms to 7.6+/-1.4 APs/600ms under superfusion with a Nav1.8 blocker. No blocker effects were seen at a concentration of 0.1 μM and due to superfusion with the solvent methanol alone. The firing pattern of renal neurons in the C57BL6 mouse was similar to that in the SD rat with a dominance of the tonic highly active neurons. In a Nav1.8 knock out mouse (C57BL6J-Scn10atm1Jwo) in the population of neurons with dendrites from the kidney only a single cell out of 70 showed tonic firing behavior (control vs Nav1.8 KO mouse, z-test, p<0.05). Conclusions: Under physiological conditions, renal sensory neurons exhibit predominantly a firing pattern associated with higher excitability. Our findings in this study support the significance of the TTX-resistant sodium channel Nav1.8 for the specific tonic firing pattern of neurons with renal projections. That might be of importance for pharmacological interventions to influence renal nerve activity, which likely plays a crucial role in the regulation of blood pressure and control of cardiovascular function.

Mechanisms Underlying Long-Term Facilitation in the Carotid Body

Glutamate and γ-aminobutyric acid (GABA) are major modulators of excitatory and inhibitory transmission in the mammalian brain. Glutamate transmission is critical for neural plasticity, learning and memory, whereas GABA plays a fundamental role in regulating neuronal excitability and facilitating the generation of neural oscillations. Our data indicates that both glutamate and GABA are released in the carotid body (CB) to modulates its response to hypoxia. Objectives: We set out to investigate whether repeated stimulation with glutamate and GABA induces lasting effects on CB afferent discharge. Hypothesis: We hypothesised that glutamate/GABA mediates long-term facilitation (LTF) of CB afferent activity. Methods: We mined high-throughput RNA sequence data and used immunohistochemistry to map components underlying neuroplasticity in the CB in Wistar and Spontaneously-hypertensive rats (SHR). CSN discharge was measured as a functional readout of CB function from an ex vivo arterially perfused carotid artery-CB preparation. Data: We catalogue the expression of glutamate receptors (R) and transporters in the rat and mouse CB. We found N-methyl-D-aspartic acid receptor (NMDAR), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPAR) and transporters to be localised to the CB chemosensory cells. Targeted administration of 15 mM glutamate activated the carotid sinus nerve ( p=0.003). Repetitive [5 times, 2-minute duration, 5-minute intervals] application of 15 mM glutamate evoked LTF of CB afferent discharge as demonstrated by both a 12-fold increase in basal firing frequency (0.78 ± 0.37 vs 1232 ± 596 spikes 1s−1; p = 0.004) over 60 minutes ( p = 0.004) and amplification of the evoked response to chemical hypoxia (CN−; 1.23 μmol bolus) by 2-fold ( p = 0.009). The stimulation paradigm was specific as neither application of glutamate, 5 times for 1-minute at 5-minute intervals, nor a single glutamate exposure evoked LTF. In contrast, repeated application of 15mM GABA [3 times for 1-minute at 5-minute intervals] evoked long-term depression (LTD) of CB afferent activity as seen by a reduced basal discharge from 10.5 to 3.5 spikes 1s−1 ( p = 0.0004) and a 2-fold suppression of the response to chemical hypoxia ( p = 3.71 x 10−5). Summary of the data: Repetitive exposure to glutamate using a specific protocol increased basal discharge of CB afferent output akin to LTF and caused sensitisation of evoked responses to CN−. Repeated exposures of GABA depressed the CB basal discharge akin to LTD. A statement of the conclusions: It is conceivable that processes such as LTP and LTD operate in the CB to modulate the set point of peripheral chemoreceptor sensitivity and its state-dependent tonicity; the role of LTP in peripheral chemoreflex sensitisation in disease remains to be determined. Research was supported by the Health Research Council of New Zealand and the Sidney Taylor Trust. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Combustion Completeness and Sample Location Determine Wildfire Ash Leachate Chemistry

AbstractUnderstanding past fire regimes and how they vary with climate, human activity, and vegetation patterns is fundamental to the mitigation and management of changing fire regimes as anthropogenic climate change progresses. Ash‐derived trace elements and pyrogenic biomarkers from speleothems have recently been shown to record past fire activity in speleothems from both Australia and North America. This calls for an empirical study of ash geochemistry to aid the interpretation of speleothem palaeofire proxy records. Here we present analyses of leached ashes collected following fires in southwest and southeast Australia. We include a suite of inorganic elemental data from the water‐soluble fraction of ash as well as a selection of organic analytes (pyrogenic lipid biomarkers). We also present elemental data from leachates of soils collected from sites in southwest Australia. We demonstrate that the water‐soluble fraction of ash differs from the water‐soluble fraction of soils, with trace and minor element concentrations in ash leachates varying with combustion completeness (burn severity) and sample location. Changes in some lipid biomarker concentrations extracted from ashes may reflect burn severity. Our results contribute to building a process‐based understanding of how speleothem geochemistry may record fire frequency and severity, and suggest that more research is needed to understand the transport pathways for the inclusion of pyrogenic biomarkers in speleothems. Our results also demonstrate that potential contaminant loads from ashes are much higher than from soils, with implications for the management of karst catchments, which are a critical water resource.

Need for structured conservation inputs: a geospatial approach for habitat prioritization to restrict disturbance regime in the protected areas of the Western Himalayan region

AbstractThe population boom increases land-use requirements, and shrinking regions are available to preserve natural biodiversity. Unfortunately, scientific knowledge does not seem to have and might never get a correct solution to how much territory will be sufficient for satisfying the various biodiversity conservation goals. Prioritization of habitat, primarily for threatened species, is a critical management challenge. Habitat management efforts are gradually being performed over broader geographic regions, emphasizing the necessity of spatial and strategic prioritization. Habitat prioritization is a technique popular for identifying critical areas needing conservation initiatives. To develop a strategic conservation framework, key issues must be identified based on the ground knowledge and present land use status, which are difficult to gather for highly rough terrain areas. Incorporating spatial data sets thus helps to get the desired knowledge of the site on a large scale. This study used a grid-based multicriteria approach to create a spatial conservation management framework for the Rajaji-Corbett landscape (RCL) in Northern India. A grid-based prioritization assessment was conducted to identify priority areas for the RCL, keeping invasive species and fire as significant threats. The indicators or criteria were selected by looking at present vital concerns in the landscape. We took 20 indicators for our multicriteria assessment for landscape prioritization of RCL using 2 × 2 km grids for the evaluation and classified them according to low, medium, and high priority areas using Arc GIS Pro. The results identified 931 sq. km area of this landscape needs immediate management interventions where frequent fire incidents and presence of invasive species are high. RCL is well known for its biodiversity wealth and assemblage of various wildlife populations.

Forest fire susceptibility assessment under small sample scenario: A semi-supervised learning approach using transductive support vector machine

Forest fires threaten global ecosystems, socio-economic structures, and public safety. Accurately assessing forest fire susceptibility is critical for effective environmental management. Supervised learning methods dominate this assessment, relying on a substantial dataset of forest fire occurrences for model training. However, obtaining precise forest fire location data remains challenging. To address this issue, semi-supervised learning emerges as a viable solution, leveraging both a limited set of collected samples and unlabeled data containing environmental factors for training. Our study employed the transductive support vector machine (TSVM), a key semi-supervised learning method, to assess forest fire susceptibility in scenarios with limited samples. We conducted a comparative analysis, evaluating its performance against widely used supervised learning methods. The assessment area for forest fire susceptibility lies in Dayu County, Jiangxi Province, China, renowned for its vast forest cover and frequent fire incidents. We analyzed and generated maps depicting forest fire susceptibility, evaluating prediction accuracies for both supervised and semi-supervised learning methods across various small sample scenarios (e.g., 4, 8, 12, 16, 20, 24, 28, and 32 samples). Our findings indicate that TSVM exhibits superior prediction accuracy compared to supervised learning with limited samples, yielding more plausible forest fire susceptibility maps. For instance, at sample sizes of 4, 16, and 28, TSVM achieves prediction accuracies of approximately 0.8037, 0.9257, and 0.9583, respectively. In contrast, random forests, the top performers in supervised learning, demonstrate accuracies of approximately 0.7424, 0.8916, and 0.9431, respectively, for the same small sample sizes. Additionally, we discussed three key aspects: TSVM parameter configuration, the impact of unlabeled sample size, and performance within typical sample sizes. Our findings support semi-supervised learning as a promising approach compared to supervised learning for forest fire susceptibility assessment and mapping, particularly in scenarios with small sample sizes.

Spatiotemporal dynamics of forest fires in the context of climate change: a review.

Forest fires are sudden, destructive, hazardous, and challenging to manage and rescue, earning them a place on UNESCO's list of the world's eight major natural disasters. Currently, amid global warming, all countries worldwide have entered a period of high forest fire incidence. Due to global warming, the frequency of forest fires has accelerated, the likelihood of large fires has increased, and the spatial and temporal dynamics of forest fires have shown different trends. Therefore, the impact of climate change on the spatiotemporal dynamics of forest fires has become a hot issue in the field of forest fire research in recent years. Therefore, it is of great significance and necessity to conduct a review of the research in this area. This review delves into the interactions and impacts between climate change and the spatiotemporal dynamics of forest fires. To address this issue, scholars have mainly adopted the following research methods: first, statistical analysis methods, second, the establishment of spatiotemporal prediction models for meteorology and forest fires, and third, the coupling of climate models with forest fire risk forecasting models. The statistical analysis method relies on the analysis of historical meteorological and fire-related data to study the effects of climate change and meteorological factors on fire occurrence. Meanwhile, forest fire prediction models utilize technical tools such as remote sensing. These models synthesize historical meteorological and fire-related data, incorporating key meteorological factors such as temperature, rainfall, relative humidity, and wind. The models revealed the spatial and temporal distribution patterns of fires, identified key drivers, and explored the interactions between climate change and forest fire dynamics, culminating in the construction of predictive models. With the deepening of the study, the coupling of climate models and fire risk ranking systems became a trend in the prediction of forest fire risk trends. Moreover, as the climate warms, the increased frequency of extreme weather events like heatwaves, droughts, snow and ice storms, and El Niño-Southern Oscillation (ENSO) has accelerated forest fire occurrences and raised the risk of major fires. This review offers valuable technical insights by comprehensively analyzing the spatial and temporal characteristics of forest fires, elucidating key meteorological drivers, and exploring potential mechanisms. These insights serve as a scientific foundation for preventive measures and effective forest fire management. In the face of a changing climate, this synthesis contributes to the development of informed strategies to mitigate the escalating threat of forest fires.

PINEPEAT from Pinus roxburghii (Chir Pine) foliage

Pinus roxburghii commonly known as Chir Pine is a coniferous tree native to the Himalayas. Pine needles shed from pine trees decay very slowly, form a carpet on the forest floor and are a major cause of frequent forest fires. The abundantly available unutilized pine needles are rich source of lignocellulosic biomass, goes waste, and its management through sustainable utilization has been a challenge.In the present study, pine needles were fibrillated by using laboratory disc refiner without any chemical treatment under different refiner passes from 0.10 to 0.40 mm to prepare pinepeat. The biomasses under different refiner passes were characterized for pH (6.2–6.5), freeness (481–821 ml), water absorbency (350–580 %), drainage time (9.10–16.99 sec), carbon (45.08 %), nitrogen (0.93 %), hydrogen (6.49 %), sulfur (0.13 %) content and C/N ratio (50.86 %). Anatomical characteristics of pine needle and pinepeat were also examined. The study reported significant change in morphology of pine needles after refining treatment wherein tissues turned into flattened, fibrillated and separated in short groups, increasing the surface area of the fragmented biomass. Application of processed pinepeat as amendments in nursery substrates was further assessed. The significantly higher growth parameters in pinepeat in comparison to conventional growing media suggests pinepeat as an additional environmentally sustainable choice for nursery operations in near future. The utility of pinepeat in this way is imperative for environment waste management and would turn into an alternative, renewable, and reliable growing media as amendments in nursery substrates.

A novel isoquinoline alkaloid HJ-69 isolated from Zanthoxylum bungeanum attenuates inflammatory pain by inhibiting voltage-gated sodium and potassium channels

Ethnopharmacology relevanceZanthoxylum bungeanum Maxim. (Z. bungeanum), a member of the Rutaceae family, has a rich history of traditional use in Asia for treating arthritis and toothache conditions. As characteristic chemical components, numerous kinds of alkaloids have been extracted from plants and their diverse biological activities have been reported. However, research on the isoquinoline alkaloid, a specific type of alkaloids, in Z. bungeanum was scarce. Aim of the studyThe study aimed to isolate a novel isoquinoline alkaloid from Z. bungeanum and explore its pharmacological activity in vitro and analgesic activity in vivo. Materials and methodsIsoquinoline alkaloid isolation and identification from Z. bungeanum were conducted using chromatographic and spectroscopic methods. The whole-cell patch-clamp technique was applied to assess its impact on neuronal excitability, and endogenous voltage-gated potassium (Kv) and sodium (Nav) currents in acutely isolated mouse small-diameter dorsal root ganglion (DRG) neurons. Its inhibitory impacts on channels were further validated with HEK293 cells stably expressing Nav1.7 and Nav1.8, and Chinese hamster ovary (CHO) cells transiently expressing Kv2.1. The formalin inflammatory pain model was utilized to evaluate the potential analgesic activity in vivo. ResultsA novel isoquinoline alkaloid named HJ-69 (N-13-(3-methoxyprop-1-yl)rutaecarpine) was isolated and identified from Z. bungeanum for the first time. HJ-69 significantly suppressed the firing frequency and amplitudes of action potentials in DRG neurons. Consistently, it state-dependently inhibited endogenous Nav currents of DRG neurons, with half maximal inhibitory concentration (IC50) values of 13.06 ± 2.06 μM and 30.19 ± 2.07 μM for the inactivated and resting states, respectively. HJ-69 significantly suppressed potassium currents in DRG neurons, which notably inhibited the delayed rectifier potassium (IK) currents (IC50 = 6.95 ± 1.29 μM) and slightly affected the transient outward potassium (IA) currents (IC50 = 523.50 ± 39.16 μM). Furtherly, HJ-69 exhibited similar potencies on heterologously expressed Nav1.7, Nav1.8, and Kv2.1 channels, which correspondingly represent the main components in neurons. Notably, intraperitoneal administration of 30 mg/kg and 100 mg/kg HJ-69 significantly alleviated pain behaviors in the mouse inflammatory pain model induced by formalin. ConclusionThe study concluded that HJ-69 is a novel and active isoquinoline alkaloid, and the inhibition of Nav and Kv channels contributes to its analgesic activity. HJ-69 may be a promising prototype for future analgesic drug discovery based on the isoquinoline alkaloid.

Synchronization of two non-identical Chialvo neurons

We investigate the synchronization between two neurons using the stochastic version of the map-based Chialvo model. To simulate non-identical neurons, a mismatch is introduced in one of the main parameters of the model. Subsequently, the synchronization of the neurons is studied as a function of this mismatch, the noise introduced in the stochastic model, and the coupling strength between the neurons. We propose the simplest neural network for study, as its analysis is more straightforward and does not compromise generality. Within this network, two non-identical neurons are electrically coupled. In order to understand whether specific behaviors affect the global behavior of the system, we consider different cases related to the behavior of the neurons (chaotic or periodic). Furthermore, we study how variations in model parameters affect the firing frequency in each case. Additionally, we consider that the two neurons have both excitatory and inhibitory couplings. Consequently, we identify critical values of noise and mismatch for achieving satisfactory synchronization between the neurons in each case. Finally, we propose that the results have general applicability across various neuron models.

Experimental investigation on flame characteristics in a linear array of dual spill fire

In the process of petroleum production and transportation, a porous leakage accident can easily lead to combustion behaviors such as fire merging, resulting in more severe consequences. This study explores the combustion characteristics of merging spill fires through experimental investigations, incorporating dual leakage holes with varying spacing to examine their impact on the combustion process. The experimental results suggest that the flame height undergoes a pattern of initial decrease followed by an increase with the gradual expansion of leakage spacing, owing to the coupling effects of air entrainment and thermal radiation feedback within the additional entrainment zone. Based on the developmental pattern of flames with respect to leakage spacing, this study categorizes the dual spill fire into three states: which are: (1) full merging state, (2) intermittent merging state, and (3) separation state. The flame height prediction model is established for different merging states, considering parameters such as the fuel discharge rate and the leakage spacing of dual spill fire. The experiment reveals that the flame pulsation frequency (FPF) of the spill fire follows the pattern observed in pool fire FPF, and an FPF model for dual spill fire in all states is obtained through the fitting. Finally, the coupled heat transfer between dual fire sources is considered, and a burning rate model for dual spill fire in intermittent merging states is established.

Shifting fire regimes cause continent-wide transformation of threatened species habitat.

Human actions are causing widespread increases in fire size, frequency, and severity in diverse ecosystems globally. This alteration of fire regimes is considered a threat to numerous animal species, but empirical evidence of how fire regimes are shifting within both threatened species' ranges and protected areas is scarce, particularly at large spatial and temporal scales. We used a big data approach to quantify multidecadal changes in fire regimes in southern Australia from 1980 to 2021, spanning 415 reserves (21.5 million ha) and 129 threatened species' ranges including birds, mammals, reptiles, invertebrates, and frogs. Most reserves and threatened species' ranges within the region have experienced declines in unburnt vegetation (≥30 y without fire), increases in recently burnt vegetation (≤5 y since fire), and increases in fire frequency. The mean percentage of unburnt vegetation within reserves declined from 61 to 36% (1980 to 2021), whereas the mean percentage of recently burnt vegetation increased from 20 to 35%, and mean fire frequency increased by 32%, with the latter two trends primarily driven by the record-breaking 2019 to 2020 fire season. The strongest changes occurred for high-elevation threatened species, and reserves of high elevation, high productivity, and strong rainfall decline, particularly in the southeast of the continent. Our results provide evidence for the widely held but poorly tested assumption that threatened species are experiencing widespread declines in unburnt habitat and increases in fire frequency. This underscores the imperative for developing management strategies that conserve fire-threatened species in an increasingly fiery future.

Frequent burning and limited stand-replacing fire supports Mexican spotted owl pair occupancy

Changing fire regimes have the potential to threaten wildlife populations and communities. Understanding species’ responses to novel fire regimes is critical to formulating effective management and conservation strategies in an era of rapid change. Here, we examined the empirical effects of recent and historical wildfire activity on Mexican spotted owl (Strix occidentalis lucida) populations in the southwestern United States. Using region-wide, standardized detection/non-detection data of Mexican spotted owl breeding pairs collected from 2015 to 2022, we found (i) higher rates of pair occupancy at sites that experienced more frequent fires in the three decades prior to the initiation of our study, and (ii) lower rates of local persistence at sites that experienced more extensive high-severity fire during the study. Historical fire regimes throughout much of our study area were characterized by high fire frequencies and limited high-severity components, indicating that Mexican spotted owls responded to wildfire in a manner consistent with their evolutionary environment. Management activities such as prescribed burning and mechanical thinning that aim to reduce stand-replacing fire risk and re-introduce the potential for frequent-fire regimes will likely benefit Mexican spotted owl conservation objectives, as well as promote more resilient forest landscapes.

The effect of growth, deforestation, forest fires, and volcanoes on Indonesian regional air quality

As a rapidly developing country, Indonesia faces a challenge in improving air quality that is made more difficult by frequent forest fires linked to deforestation and volcanic eruptions. This paper analyses the link between development and air pollution in 30 Indonesian cities from 2002 to 2019. Air quality is measured using two novel regional air quality indicators (AQIs) for PM2.5 and PM10 estimated from weather observations and NASA satellite data on Aerosol Optical Depth (AOD). Results from an Environmental Kuznets Curve (EKC) analysis, based on a dynamic panel data model, show that forest fires and volcanic activity have significantly worsened regional air quality in Indonesia. The model also shows that the EKC hypothesis is rejected for Indonesia as cities have followed a monotonically increasing trend in air pollution with respect to economic growth. An additional 1% of economic growth increased long run pollution as measured by AQI PM2.5 and PM10 by 0.35% and 0.46%, and forest fire events by 0.11% and 0.06%. A partial Benefit-Cost Analysis (BCA) of forest fires shows that particulate matter pollution is excessive. Decreasing the frequency of forest fires by 1% would generate a net benefit of between US$17 million to 145 million. The lower estimate of the health benefits exceeds the agricultural benefits of forest fire without accounting for other non-market costs due to forest fires. Our results imply that, as Indonesia grows economically, air quality is likely to continue deteriorating. Further, regions affected by regular volcanic activity and wildfires should apply tighter emission standards to controllable point source emissions from industry and non-point source emissions such as agricultural forest fires.

Wildfire impacts on the carbon budget of a managed Nordic boreal forest

Wildfire is one of the most important disturbances affecting boreal forests. Most previous research on boreal forest fires has occurred in North American forests which have different fire regimes, tree species and are less intensively managed than their Eurasian counterparts. Recent extreme fire years have highlighted the vulnerability of the Nordic boreal forest to climatic shifts that are increasing forest fire frequency and severity. The Ljusdal fire (2018) was one of the largest wildfires in recorded history in Sweden. We established eddy covariance flux towers to track the impacts of this fire on the carbon balance of two Pinus sylvestris sites subject to different fire severities and forest management strategies 1–4 years post-fire. The ‘SLM’ site was a mature stand that experienced low-severity fire (trees survived) followed by salvage-logging and reseeding, whilst the ‘HY’ site was 10 years old when it experienced high-severity fire (all trees killed) then was replanted with seedlings. During the study period, both sites were net carbon sources at the annual scale. It took up to 4 years after the fire until the first day of net CO2 uptake was recorded at each site. We estimated that it will take 13 years (8, 21; mean ± 95 % confidence intervals) after the fire until the sites reach a neutral annual carbon balance. It will take up to 32 years (19, 53) at HY and 46 years (31, 70) at SLM to offset the carbon lost during and after the fire and salvage-logging. In addition, our measurements showed that more carbon was emitted in the first 4 years after the fire compared to the carbon lost from combustion during the fire. Quantifying carbon fluxes during the initial years after fire is therefore crucial for estimating the net impact of wildfire on the carbon budget of boreal forests.

Short-Interval, High-Severity Wildfire Depletes Diversity of Both Extant Vegetation and Soil Seed Banks in Fire-Tolerant Eucalypt Forests

Many plant species are well-adapted to historical fire regimes. An increase in the severity, frequency, and extent of wildfires could compromise the regenerative capacity of species, resulting in permanent shifts in plant diversity. We surveyed extant vegetation and soil seed banks across two forest types with contrasting historical fire regimes—Shrubby Dry Forest (fire return interval: 10–20 years) and Sub-Alpine Woodland (50–100 years). Over the past 20 years, both forests have been subject to repeated, high-severity wildfires at intervals significantly shorter than their historical return intervals. We examined the soil seed bank response to fire-cued germination, and whether the plant diversity in soil seed banks and extant vegetation demonstrated similar responses to short-interval, high-severity wildfires. The soil seed bank demonstrated a positive response to heat in combination with smoke, and for the Sub-Alpine Woodland, this was limited to sites more frequently burnt by fire. With an increase in fire frequency, there was a decline in species richness and Shannon’s Diversity and a shift in species composition in both extant vegetation and the soil seed bank. The fire frequency effects on the relative richness of trait associations were restricted to the Shrubby Dry Forest, and included an increase in short-lived obligate seeders, wind-dispersed species, and ant-dispersed shrubs in burnt relative to long unburnt sites in both extant vegetation and the soil seed bank. Graminoids were the most abundant component of the soil seed banks of Sub-Alpine Woodlands, and this increased with more frequent fire, with a similar trend (p = 0.06) in extant vegetation. Clear shifts in plant diversity in both soil seed banks and extant vegetation in forest types with contrasting historical fire regimes suggest that emerging fire regimes are pushing ecosystems beyond their historical range of variability, including potentially more flammable states and a decline in the buffering capacity of soil seed banks.

Dampak Perubahan Iklim Dapat Meningkatnya Kebakaran Hutan Dan Upaya Pelestarian Lingkungan

Climate change has become a major factor in increasing forest fires in various parts of the world. This phenomenon has had serious impacts on the environment, economy and human health. Environmental conservation efforts are becoming increasingly important to reduce the risk of forest fires and maintain ecosystem balance. With a better understanding of the relationship between climate change and forest fires, preventive and adaptation measures can be designed to protect forests and ecosystems that are vulnerable to this threat. The purpose of this article is to discuss the impact of climate change on the increase in forest fires and environmental conservation efforts that can be taken to overcome this problem. The method used in this research is using a literature study method to collect information about the impact of climate change on forest fires and environmental conservation efforts. Climate change is significantly increasing the risk of forest fires worldwide leading to rising global temperatures that are drying out forests and increasing the likelihood of fires occurring. Changing rainfall patterns also lengthen and strengthen the dry season, increasing the potential for forest fires. These factors, along with human activity and extreme weather, have led to an increase in the frequency and intensity of forest fires. The impacts are far-reaching, including destruction of wildlife habitat, carbon loss, ecosystem degradation, and negative impacts on air quality and human health.

Response of vulnerable karst forest ecosystems under different fire severities in the Northern Dinaric Karst mountains (Slovenia)

BackgroundThis study deals with wildfires in marginal areas of the Mediterranean climatic and biogeographical regions (Northern Mediterranean) where fires were not common. The aim of the research was to determine the differences in floristic composition and traits at different intensities of fire damage and to analyze the changes in forest ecosystems during the wildfires that took place in the summer of 2022. The study included both the zonal forests and non-native black pine (Pinus nigra) forests. Remote sensing techniques linked to the vegetation data sampled in the field during the 2023 vegetation season, the very first season after the fires, were also used in the fire assessment.ResultsThe study confirmed that satellite data analysis, orthophoto interpretation, and on-site vegetation sampling provide equivalent information on fire severity, opening up the possibility of transferring knowledge to similar post-fire sites without field sampling in the future. TWINSPAN classification analysis divided the sampled plots into clusters based on tree species prevalence and fire severity. The diagnostic species of the clusters were calculated using a fidelity measure. Ordination revealed that the first axis on the detrended correspondence analysis (DCA) correlated with wildfire severity. Ecological conditions and strategies, life forms, chorotypes, seed dispersal classes, and regeneration traits were analyzed along this gradient. We found that post-fire sites became warmer, drier, and lighter, which favored the growth of ruderal, theropytic, cosmopolitan, anemochorous and post-fire emergent species. After the fire, a “wave” of annual ruderal species was observed.ConclusionsThe results indicate that post-fire recovery can be left to natural processes without human intervention, except in the case of non-native pine stands where planting or seeding may be necessary. Otherwise, it is essential to control the possible occurrence of invasive species. Isolated adaptations of species to fire have also been observed, such as heat-stimulated germination. Such adaptations could develop in regions exposed to frequent fires and where fires act as an evolutionary factor.

Field-Programmable Analog Array Implementation of Neuromorphic Silicon Neurons with Fractional Dynamics

Silicon neurons are bioinspired circuits with the capability to reproduce the modulation through pulse-frequency observed in real neurons. They are of particular interest in closed-loop schemes to encode the control signal into pulses. This paper proposes the analog realization of neuromorphic silicon neurons with fractional dynamics. In particular, the fractional-order (FO) operator is introduced into classical neurons with the intention of reproducing the adaptation that has been observed experimentally in real neurons, which is the variation in the firing frequency even when considering a constant or periodic incoming stimulus. For validation purposes, simulations using a field-programmable analog array (FPAA) are performed to verify the behavior of the circuits.

Accelerated reduction in China's cropland fires against the background of policy enhancement

Cropland fires contribute significantly to the emission of air pollutants, with implications for the atmospheric environment, public health, and climate change. However, the development of cropland fires in response to straw burning policy interventions has not been fully explored. With the Moderate Resolution Imaging Spectroradiometer Collection 6 (MODIS C6) active fire products and China land-cover data (CLCD), counts and fire radiative power (FRP) of cropland fire spots were extracted in China from 2003 to 2022, followed by analyses of their spatiotemporal patterns and evolutionary characteristics at the provincial, regional, national, and grid (0.25° × 0.25°) levels and at monthly to annual scales via trend analysis, kernel density analysis, and geographic distribution analysis. The key findings include: (1) National policies banning straw burning reversed the changes in the quantity and intensity of China's cropland fires in 2013, with the frequency and FRP in 2022 declining by 58% and 62% compared with the 2014 peak. (2) Cropland fires were highly prevalent in Northeast and North China (NEC and NC), with significant regional differences, particularly in spring, summer and autumn. (3) A notable lag effect of burning ban policies was seen in Northeast China, where the increasing trends of the frequency and intensity of cropland fires were not reversed until 2017, followed by declines in frequency and FRP of 67% and 62%, respectively during 2017–2022. (4) Cropland fires showed an increasing concentration trend but with enormous regional differences, with an increasing trend of a “high-high” concentration pattern in NEC and a decreasing trend in NC. This study contributes to understanding the effectiveness of national policies that ban straw burning and support cropland fire management and policy-making.