Past Fire Research Articles

Biodiversity impacts of the 2019–2020 Australian megafires

With large wildfires becoming more frequent1,2, we must rapidly learn how megafires impact biodiversity to prioritize mitigation and improve policy. A key challenge is to discover how interactions among fire-regime components, drought and land tenure shape wildfire impacts. The globally unprecedented3,4 2019–2020 Australian megafires burnt more than 10 million hectares5, prompting major investment in biodiversity monitoring. Collated data include responses of more than 2,000 taxa, providing an unparalleled opportunity to quantify how megafires affect biodiversity. We reveal that the largest effects on plants and animals were in areas with frequent or recent past fires and within extensively burnt areas. Areas burnt at high severity, outside protected areas or under extreme drought also had larger effects. The effects included declines and increases after fire, with the largest responses in rainforests and by mammals. Our results implicate species interactions, dispersal and extent of in situ survival as mechanisms underlying fire responses. Building wildfire resilience into these ecosystems depends on reducing fire recurrence, including with rapid wildfire suppression in areas frequently burnt. Defending wet ecosystems, expanding protected areas and considering localized drought could also contribute. While these countermeasures can help mitigate the impacts of more frequent megafires, reversing anthropogenic climate change remains the urgent broad-scale solution.

The landscape genetics of a mass-flowering fire-ephemeral plant.

Obligate fire ephemerals are annual plants that have germination and reproduction cued by fire occurrence, persisting between fire events in a long-lived soil seed bank. Within these species, gene flow is restricted not only geographically but also temporally because individuals are limited to reproducing with others affected by the same fire event. The patchwork-like distribution of fires may therefore promote population isolation. In contrast to past fires, the Australian fires of 2019-2020 were of unprecedented extent, providing an opportunity to investigate the landscape genetics of a fire ephemeral, Actinotus forsythii, across multiple populations and to compare it to a common congener, Actinotus helianthi. For both species, we used single nucleotide polymorphisms to infer patterns of population structure and calculate measures of genetic diversity. We also estimated a phylogeny of Actinotus forsythii to understand the differentiation of a geographically isolated population. For A. forsythii, the within-population diversity (allelic richness = 1.56) was greater, and the among-population differentiation (FST = 0.30) was lower than that observed for A. helianthi (allelic richness = 1.33, FST = 0.57). Actinotus forsythii had distinct geographic groupings, and a geographically isolated population of this species was genetically highly differentiated. Despite the fire-dependent, asynchronous gene flow, predicted between site disconnect, and possible within-site homogeneity, our results suggest that burn mosaic could be influencing gene flow patterns and fire-triggered mass flowering may promote genetic diversity within Actinotus forsythii.

Severity of a megafire reduced by interactions of wildland fire suppression operations and previous burns

Abstract Burned area and proportion of high severity fire have been increasing in the western USA, and reducing wildfire severity with fuel treatments or other means is key for maintaining fire-prone dry forests and avoiding fire-catalyzed forest loss. Despite the unprecedented scope of firefighting operations in recent years, their contribution to patterns of wildfire severity is rarely quantified. Here we investigate how wildland fire suppression operations and past fire severity interacted to affect severity patterns of the northern third of the 374 000 ha Dixie Fire, the largest single fire in California history. We developed a map of the intensity and type of suppression operations and a statistical model of the Composite Burn Index (CBI) including weather, fuels, and terrain variables during the fire to quantify the importance of operations and prior fires on wildfire severity. Wildfire severity was estimated without operations and previous fires and then compared with modeled severity under observed conditions. Previous low and moderate-severity fire without operations decreased CBI by 38% and 19% respectively. Heavy operations and offensive firing in the footprint of past fires lowered fire severity even more compared to prior fire alone. Medium operations and defensive firing reduced but did not eliminate the moderating effects of past fires. This analysis demonstrates important interactions between suppression operations and previous burns that drive patterns of fire severity and vegetation dynamics in post-fire landscapes. Given the need to reduce wildfire severity to maintain forest resilience, particularly with a warming climate, increased attention to using operations and severity patterns of previous fires known to reduce wildfire severity in megafires are likely to increase forest resilience and improve ecological outcomes.

How Are Weather and Climate Products and Decision Support Systems Used in Wildland Fire Decision-Making in the U.S. Southwest?

Abstract Wildland fire management is a challenging environment in which to utilize scientific information. Despite the robust information system that supports U.S. wildland fire management, recent studies demonstrate that some data/information products and decision support tools available to that community are not being used to their full potential. In the U.S. Southwest, the convergence of climate change, past wildland fire policy, and an expanding wildland–urban interface have increased pressure on wildland fire managers to use science-based information to improve management outcomes. This tension between the perceived need for more science in fire management and the practical challenges of using science to inform decisions led us to ask two basic questions: 1) How is information about weather and climate used in wildland fire management decision-making in the Southwest? 2) How are decision support tools used in Southwest wildland fire management? We found that relatively few sources of weather and climate information are consulted by Southwest wildland fire managers; a small percentage of those sources are used to inform the specific decisions and tasks we asked about; and decision support tools are commonly used to justify rather than inform decisions. We further found evidence that suggests that products and tools that are thoughtfully designed to fit within the specific information use environment of wildland fire management—rather than being produced in isolation from that environment—are more likely to be used and therefore have more impact than those that are produced in isolation from that environment. Significance Statement This study set out to understand how weather and climate information and decision support systems (DSSs) are perceived and used by the Southwest wildland fire management community. We found that the wildland fire community consults relatively few weather and climate products, even fewer are used to inform decisions, and that DSSs are frequently used to justify rather than inform decisions. We argue that the climate services community and other scientists who develop science-based tools and products for fire management will benefit from better understanding the information use environment in which their science may be used if they want to increase the utility of their work.

Past fire shaping future fuel: influence of recent fire history on forest foliage chemistry

Past fire shaping future fuel: influence of recent fire history on forest foliage chemistry

Sustainable insulation panel for buildings made of rice husks and posidonia

The design of the building envelope is crucial to achieve adequate thermal comfort by means of insulating materials that prevent heat flow without excessive energy costs. Generally, materials based on fossil fuel content a large carbon footprint, so when environmental criteria are becoming increasingly important, it is necessary to search for more sustainable insulation materials with a low environmental impact, lower energy use or few CO2 emissions. The aim of this work is focussed on using the agricultural residue or plant debris that sea expels, specifically rice husk and posidonia oceanic leaves. The properties of both materials are studied by experimental tests at different densities to define appropriate thermal conductivity. In addition, acoustic performance, sensitivity to water, durability (mould fungus), mechanical properties and fire reaction are tested to evaluate their behaviour in comparison to other commercial insulation materials. The results highlight the proper performance of rice husks and posidonia as material for insulation panels with 0.055 and 0.045 W/mK of thermal conductivity, respectively. Furthermore, rice husks and posidonia offer a promising reaction to fire with low heat release and smoke production for an element that has been critical in buildings in past catastrophic fires.

Wildfire influences species assemblage and habitat utilisation of boreal wildlife after more than a decade in northern Sweden

Fires can strongly change the vegetation structure and the availability of resources for wildlife, but fire suppression has long affected the natural role of fire in shaping boreal ecosystems in northern Europe. Recently, wildfires have increased in frequency, possibly due to global warming. In contrast to the boreal systems in North America, there have been few studies on responses of wildlife to wildfires in northern Europe. Based on the findings from North America, we predict that responses of wildlife to wildfire vary among wildlife species: where mammalian herbivores, such as moose Alces alces and mountain hare Lepus timidus, will be attracted to burnt areas following an increase in food availability, other species, such as reindeer Rangifer tarandus, are negatively impacted due to fire reducing their preferred food. We then tested our predictions by contrasting wildlife utilization of sites that burnt by wildfire in 2006 with nearby unburnt control sites in three areas in northern Sweden. To measure wildlife utilization, we used 72 camera traps, equally divided between the burnt and control sites, with two placement strategies: random and on wildlife trails. The cameras recorded 27 mammal and bird species during summer 2018. Species assemblage differed between burnt and control sites. Fieldfare Turdus pilaris used burnt sites more than control sites, while pine marten Martes martes and western capercaillie Tetrao urogallus used control sites more than burnt sites. We however did not find support for a positive effect of past forest fires on any of the observed wild mammals. We discuss how, due to the impact of forestry, forage‐rich habitat may not be as limiting in Scandinavia as in the North‐American context, potentially leading to recently burnt sites being less attractive to herbivores such as moose.

Safely Managed Barbeque Use of Charcoal as Traditional Renewable Energy

While coal is a fossil fuel, traditional charcoal is an inherently renewable energy source. In addition to fuel, charcoal can also be used as a functional material such as adsorbents and catalysts. Charcoal is still used for heating in safe cooking situations, such as barbecues. However, in recent years in Japan, there have been many cases of barbecue fire accidents. This study is a case study in which the author experimented with charcoal (made from Malaysian mangroves) barbecue using a safe method within an established facility. Based on past fire incidents, the main causes are the ignition of liquid or fluid combustion aids, the spread of sparks bythe wind, and insufficient trailing fire. In this case study, under calm wind conditions (artificially fanning at an appropriate level of strength), using a solid firelighter, and collecting used and extinguished charcoal ash in a metal container, these three points was found to be important for safety fire management in barbeque.

Past fire dynamics in sub-Saharan Africa during the last 25,000 years: Climate change and increasing human impacts

The aim of this study is to provide the drivers of long-term fire dynamics in various regions of Sub-Saharan Africa using a synthesis of updated sedimentary charcoal records, from 25,000 years ago to the present. We used the charcoal data currently available in the Global Paleofire Database, updated with the most recent published charcoal data, to reconstruct past biomass burning across the continent. We analyzed standardized charcoal data grouped by region (central Africa, eastern Africa, southern Africa, and Indian Ocean) and by vegetation type (forest, savanna, and shrubland). Within this framework, we found that quality data were lacking to reconstruct a robust trend in biomass burning before 5000 years at the continental scale. This large spatial scale was indeed masking regional peculiarities. Our results suggest that past changes in biomass burning were nuanced and cannot be simply attributed to either climate- or humans, and that they varied from each sub-regions and vegetation type history. In central Africa, biomass burning increased after the end of the African Humid Period and the first wave of Bantu-speaking people migration, whereas in East Africa and the Indian Ocean islands, it seems that human population growth was the main driver of fire activity. In South Africa, reduced rainfall seemed to offset fire activity due to population growth by reducing potentially flammable biomass. While the diversity of methodological techniques used to produce charcoal quantification made comparisons difficult, regional patterns still emerged from these data. This synthesis thus highlights the need to increase the number of sites with charcoal data and to harmonize charcoal extraction and quantification methods across Africa to improve regional to continental assessments of fire histories.

Past Fire and Vegetation Change in the Hyperdiverse Forests of the Ecuadorian Amazon.

The Ecuadorian Amazon holds more biodiversity than most other places on Earth. Palms are a particularly dominant component of the vegetation; however, it remains unknown to what degree the pattern has persisted through time. Here, we investigate the persistence of palm dominance through time and the degree to which past human activities (e.g., fire, cultivation, and forest opening) have affected changes in palm abundances across five regions of the Ecuadorian Amazon. We analyzed soil cores (40-80 cm depth) from each region for charcoal (evidence of past fire) and phytoliths (evidence of past vegetation change). The timings of fires (based on 14C radiocarbon dates), the occurrence, recurrence, and number of fires (based on charcoal presence and abundance in samples), and the amount of change in palm abundances (based on phytoliths) varied within and between the studied regions. The charcoal and phytolith results indicate the presence of low levels of past human activity at all sites. Our results show that patterns of modern palm hyperdominance found in Amazonian forests have not been persistent through time, and that even low levels of past human activities can affect palm abundance.

Differences in the intensity of past forest fire events inferred from stable oxygen isotope analysis of charred bark

Understanding past fire regimes requires reliable proxy data that record fire conditions and preserve them over time. The objective of this study was to determine if the oxygen isotope composition of charred bark samples (pyrogenic organic matter) could be used as proxy data to differentiate wildfires based on burn intensity. We collected charred and uncharred bark samples from three fire sites in northern Ontario, Canada that represented a gradient of fire intensity as depicted by Fire Weather Index (FWI) data. We hypothesized that the mean Δ18Obark-char (the difference between δ18O of uncharred bark and a charred sample) would be greater for fires with higher intensities. Analysis of variance of Δ18Obark-char indicated a significant effect of fire event ( F = 73.6, p < 0.001), which explained 57.0% of the variance. A prescribed surface fire treatment (mean FWI = 9.5) had significantly lower Δ18Obark-char than two natural crown fires (FWI = 21 and 27). These results demonstrate that Δ18Obark-char differentiated moderate from high intensity fires in a similar manner to the FWI data.

Data driven forest fire susceptibility mapping in Bangladesh

Forests are essential natural resources that serve to facilitate economic activity while also providing an essential impact on climate regulation and the carbon cycle. In the Chittagong hill tracts, forest fires significantly contribute to the eradication of forests and the depletion of biodiversity. As a result, addressing the forest fire hazard is crucial for mitigating its potential negative effects. By implementing machine learning (ML) and deep learning (DL) algorithms, the primary aim of this research is to determine which areas within the CHT are most prone to forest fires. Artificial Neural Network (ANN), Classification and Regression Trees (CART), Categorical Boosting (Catboost), Convolutional Neural Network (CNN), Deep Neural Network (DNN), Gradient Boosting Decision Tree (GBDT), Random Forest (RF), Support Vector Machine (SVM), eXtreme Gradient Boosting (XGboost) are among these algorithms. This research investigates 267 past forest fire incidents while incorporating fifteen predictive parameters for forest fires. The utmost accuracy is demonstrated by the Catboost model, which has an AUC value of 0.83. Applied models the Bandarbon and Rangamati regions of the Chittagong hill tracts have been thoroughly analyzed and discovered to be extremely and moderately vulnerable to forest fires due to their intricate physical and social characteristics. The Catboost model indicates that 67.38% of the total regions and 0.59% of the regions in Chittagoong hill tracts are classified as moderate and high susceptible zones, respectively. The results of this study present the models utilized in the present analysis exhibit a high level of effectiveness. Furthermore, the findings indicated that the NDVI and annual temperature had the most influence. The application of both ML and DL approaches in the Chittagong hill tracts for the first time resulted in models that exhibited excellent accuracy and precision, combining perfectly with the actual conditions on the ground. This study will undeniably assist the local government in implementing efficient governance and preservation strategies for the sustainable maintenance of forest resources, while enhancing the well-being of individuals living in and around the forest. Forest fire susceptibility assessment can be utilized in various locations worldwide that include significant natural and human-induced characteristics.

Koala density, habitat, conservation, and response to logging in eucalyptus forest; a review and critical evaluation of call monitoring

ABSTRACT This study is the second in a series that examines the habitat requirements and response to logging of koalas (Phascolarctos cinereus) inhabiting tall eucalypt forests of north-east NSW. It presents the findings of koala population and habitat monitoring surveys in Pine Creek State Forest and Bongil Bongil National Park using a combination of call-counting and direct observation (spotlighting). The 6400 ha study area was mapped into 6 zones of increasing koala habitat quality by ground survey of forest structure and floristics on a 200 m grid. The accuracy of habitat definition and mapping was tested by stratified transect counts of koala calls and sightings over two consecutive years (1997–98). Average koala density increased steeply and significantly, from 0.02 – 0.20 koalas/hectare, with increasing mapped habitat quality based on increasing forest age, structural complexity, local food tree species diversity, history of prior koala occurrence and decreased past logging intensity. This relationship was driven primarily by breeding females, with the number of male koala calls weakly or uncorrelated with koala sightings and mapped habitat quality. Male koalas were more widely and uniformly distributed than females, including areas of low quality, plantation, and intensively logged forest. This finding explains the discrepancy between our results and those of other recent studies which concluded that koalas are tolerant of intensive logging based on modelling of calling male koalas and reliance on an untested assumption that male calling is indicative of female breeding success. Koala density in a subset of the highest quality habitat was relatively stable at 0.28 koalas/ha (3 hectares/koala) over the long term (1997–98 and 2012–2023). Key characteristics of the forest koala population, including low stable density, large home ranges, preference for high food tree diversity and locally unique food trees (including Allocasuarina torulosa and Syncarpia glomulifera), are not adequately explained by existing koala habitat models. We present a new paradigm to explain regional variation in koala distribution, habitat and foraging preferences based on variations in foliage chemistry (toxicity and nutritional value) determined by the duration and stability of local plant-koala interactions in response to past fire, hunting, predation and logging disturbance history. We hypothesize that koala density in stable forest populations is regulated at low levels by a combination of selected and induced increases in leaf toxicity and decreases in leaf nutrition that limit koala browsing to benign levels of about 1-2% of annual leaf production. Large home ranges, complex mature forest structure, high food tree diversity and a specialized or diverse gut microbiome may be essential to allow females to rotate and change food trees frequently to minimize induced toxicity and select individual leaves with sufficient nutrients to support breeding and lactation with minimal risk of predation. High density koala populations (> 0.6/ha) occur primarily in areas where koalas have been introduced or re-introduced to planted habitats and natural areas where aboriginal hunters and dingoes were historically present but are now absent, and where food trees have not been selected for resistance to koala browsing pressure.

Victoria’s Secret: the falling angels

Research methodology Secondary research Case overview/synopsis Victoria’s Secret, a lingerie retailer founded by Roy Raymond in 1977, is the largest retailer in women’s intimate apparel in North America. Nevertheless, the business has been under fire in the recent past for failing to be inclusive and diverse, declining revenues and engaging in high-profile controversies. Victoria's Secret has experienced competition from emerging lingerie brands including Savage X Fenty, which Rihanna established in 2018, ThirdLove and Aerie by American Eagle & Knix. Victoria's Secret tried to reinvent itself in reaction to these difficulties by altering its marketing approach, switching out its “angels” for more diversified models, and launching a new range of cozy, informal loungewear. However, there were conflicting reactions to these initiatives, and the company's sales have been declining. Complexity academic level Executive training programs, upper level undergraduate and graduate MBA students in strategic, marketing and general management. Students should understand the basics of strategic management and marketing before undertaking to analyse this case.

Fire in the rainforest: A 3200‐year history of fire in a West Kalimantan, Indonesia, tropical rainforest

AbstractDespite its perceived historical rarity, fire is an important disturbance in tropical rainforests. Very large rainforest fires have been observed multiple times in recent decades, often during years of strong El Niño‐Southern Oscillation droughts. Fire in rainforest has major short‐term consequences for humans and wildlife by converting forest to fire‐prone fern, shrub, and grass, but the long‐term effects remain to be seen. Borneo's indigenous groups have been using fire to clear land for centuries, yet the prevalence and spatial patterns of premodern fire across forest types in Borneo are not well understood. This research set out to reconstruct fire in a 1500‐ha primary rainforest spanning 800 m of elevation in Indonesian Borneo with the goal of elucidating the role humans have played in rainforest fire. We found that humans played an important role in the occurrence of fire in recent centuries. Evidence of fire—charcoal >2 mm—is more abundant in forest types where humans would be more likely to live and/or practice swidden agriculture. However, pyrogenic material is ubiquitous across the study area, showing that all forest types have experienced fire. A set of 50 radiocarbon dates showed that in lowland areas—where human‐caused fire is most likely—fire occurred throughout the last 3200 years, peaking 1300–1600 ce. The upland areas lacked evidence of fire before 1250 ce but otherwise had a similar pattern to the lowlands. The period of high fire coincides with regional demographic changes as well as regional droughts documented elsewhere in Southeast Asia. In upland areas, fires likely burned only under regional drought when fires could more easily spread upslope. Although forest plot studies at this site show little structural evidence of past fires, tree diversity is lower than expected in the most burned areas (alluvial benches). Thus, our results suggest that land clearance was a major source of fire, but the current intact state of these rainforests indicates that they were largely resilient to fires and land use hundreds of years ago. Recent fires mirror patterns of fire spread that occurred hundreds of years ago, though their severity and extent are likely much greater.

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.

Post-fire reference densities for giant sequoia seedlings in a new era of high-severity wildfires

Many forests globally are experiencing increases in large, high-severity wildfires, often with increasingly inadequate post-fire tree regeneration. To identify areas that might need post-fire planting, forest managers have a growing need for seedling reference densities – the natural seedling densities expected to be adequate to regenerate a forest – to compare with observed post-fire seedling densities. The most useful reference densities will meet five criteria: they will (1) be specific to natural post-fire reproduction rather than planted seedlings (because planted seedlings can have substantially greater survival than natural seedlings, thus underestimating adequate natural reproduction), (2) apply to the first few years following fire (when management decisions and actions are most likely), (3) be specific to each of those post-fire years (because post-fire seedling densities can change rapidly with time since fire), (4) be associated with estimates of uncertainty, and (5) include consideration of novel environmental conditions during management applications (because most reference densities will be based on data collected under more environmentally benign conditions). The world’s most massive tree species, the giant sequoia (Sequoiadendron giganteum) of California’s Sierra Nevada, recently experienced historically unprecedented wildfires that killed an estimated 13–19% of mature sequoias across their native range. Seedlings germinating after these fires then experienced exceptional summer heat and the two most severe summer droughts of the 121-year historical record. To help inform management responses to these events, we used seedling censuses from past fires (mostly prescribed fires) to calculate sequoia seedling reference densities meeting the five criteria. The reference densities had three striking features, which are partly attributable to giant sequoia’s status as a pioneer species. First, despite being inherently conservative, the reference densities were quite high. For example, mean first-year reference density was 172,599 seedlings ha−1. Second, reference densities declined precipitously with time since fire: the mean fifth-year reference density was only 5% of the mean first-year density. Third, the reference densities were associated with relatively substantial uncertainty, a consequence of density variations among seedling plots; for example, the 95% credible interval for first-year reference density was 64,377 to 313,438 seedlings ha−1. Despite this uncertainty, a case-study sequoia grove that recently burned in a high-severity wildfire had second-year post-fire seedling densities that were significantly (and dramatically) lower than the corresponding second-year reference density, suggesting inadequate post-fire reproduction. Our results highlight the value of the five criteria for reference densities – criteria that, in current practice, are rarely all met.

Assessing Potential Distributions of Bird Endemic Species: Case Studies of Macrocephalon maleo and Rhyticeros cassidix and Their Threats

Maleo and knobbed hornbill are bird species that are endemic on the island of Sulawesi, which is highly threatened by forest fires. Fires tend to destroy any affected species; however, it is not possible to survey the entire range of the original distribution of the two endemic bird species that are affected by forest fires due to practical constraints. Species distribution modeling using maximum entropy is considered to be an alternative to understanding the potential distribution area of species against the threat of forest fires. The prediction model from MaxEnt all have AUC values of greater than 0.70, which means that the model is good enough to classify the records of the presence of M. maleo and R. cassidix along with the past forest fires. The environmental variables that affect the distribution of M. maleo are its distance from hot water, rivers, and roads, while the distribution of R. cassidix is strongly influenced by its distance from roads, settlements, and rivers. Forest fire distribution is mostly influenced by soil type, land-use land cover, and rainfall. It is predicted that around 238,690 and 677,070 ha of the potential distribution of M. maleo and R. cassidix, respectively, are potentially disturbed and affected by forest fires. However, this number much greater outside conservation areas. The results of this study can be used by the government of the Republic of Indonesia (especially the Ministry of Environment and Forestry) for determining conservation actions for both species in the future.

Demographic change and loss of big trees in resprouting eucalypt forests exposed to megadisturbance

AbstractAimIncreased tree mortality linked to droughts and fires is occurring across temperate regions globally. Vegetation recovery has been widely reported; however, less is known about how disturbance may alter forests structurally and functionally across environmental gradients. We examined whether dry forests growing on low‐fertility soils were more resilient to coupled extreme drought and severe fire owing to lower tree mortality rates, higher resprouting success and persistence of juveniles relative to wetter forests on more fertile soils.LocationFire‐tolerant eucalypt forests of temperate southeastern Australia.Time period2020–2023.Major taxa studiedEucalyptus, Corymbia, Angophora.MethodsDemographic surveys of tree mortality and regeneration in all combinations of dry/wet forest, fertile/less fertile substrates exposed to extreme drought and fire were conducted. We used Bayesian regression modelling to compare tree mortality, diameter, response traits, population structure and occurrence of fire scars between substrates/forest types.ResultsOverall mortality (20%–33%) and topkill (34%–41%) were within historically reported ranges for various forests and soil types. However, we observed an atypical trend of increased mortality and topkill in the largest trees, particularly when they had structural damage from past fires. Trees in wet forests on more fertile soils had the highest levels of mortality. Numbers of persistent resprouting juveniles were highest in dry forests on low‐fertility soils. Dry forests growing on low‐fertility soils appear more resilient to compound disturbances due to lower rates of mortality and higher rates of juvenile persistence. Wet forests on more fertile soils may experience greater demographic change due to higher mortality of small and large trees.Main conclusionsMesic forests on relatively fertile soils were found to be at relatively high risk of demographic change from compound disturbances. Combined, fire and drought are likely to reduce the number of large trees in affected areas, with consequences for forest carbon cycling and storage.

Monitoring Intra-Annual Wood Formation of Pinus nigra J.F. Arnold (Black Pine) to Understand the Fire Seasonality in Western Anatolia

Recent climate and societal changes have increased wildfire activity and prolonged the fire season in many regions of the world. The precision of fire seasonality analysis from tree-ring records can be improved by complementing the subjectively determined intra-ring position of fire scars with more precise studies of wood formation. With this aim, we monitored the wood formation dynamics of Pinus nigra J.F. Arnold (black pine) trees along a climatic gradient in western Anatolia to better understand the wood formation for the interpretation of fire seasonality. Wood microcores were collected from April to November 2021 from trees at four sites across (from north; the Black Sea climate in Bolu to the south; and the Mediterranean climate in Isparta) the areas where previous fire history reconstructions were conducted. These previous studies showed that most fires occurred during the latewood formation period. We found that matured latewood tracheids were observed between September (August) and November, thus suggesting that these fires occurred during late summer and fall. Our results show the importance of temperature and water availability for the timing of earlywood and latewood formations. These findings can be used to better inform planning activities for fire management and as a proxy to reconstruct past fire seasonality.