Background and aims - Heatwaves and droughts are becoming more intense and frequent with climate warming, posing significant challenges for plant function. Leaf temperature regulation through transpiration is a key mechanism for coping with heat stress; however, current understanding of its small-scale spatial patterns remains limited due to conventional measurement and modelling approaches. Recent technological advances now allow the characterisation of sub-leaf-scale temperature heterogeneity, which is both feasible and essential, as it can reveal localized hotspots that exceed critical temperature thresholds and help explain variation in plant physiological performance and morphological responses across environmental conditions. Material and methods - To fill this gap, we applied a newly developed “double modelling” approach that simultaneously quantifies both the mean and variability of within-leaf temperature data derived from high-resolution thermal images. We exposed Xerochrysum bracteatum (Asteraceae, an Australian native forb) to twelve simulated heatwave-drought treatments that varied systematically in heat intensity, duration, and soil water availability under controlled, low-wind conditions. We quantified plant responses across thermal (within-leaf temperature), morphological and physiological dimensions. Key results - During heatwaves, leaves warmed relative to controls but remained substantially cooler than the surrounding air. However, this cooling was not spatially uniform: intense heatwaves increased intra-leaf temperature heterogeneity, particularly under higher soil moisture, suggesting increasingly uneven cooling within individual leaves. Across plant responses, heatwave characteristics had stronger effects than soil water availability, with intensity emerging as the dominant driver, followed by duration. Intense heatwaves reduced leaf production, with larger impacts than prolonged heatwaves or heatwave-drought combinations. Conclusion - Our findings suggest that leaf cooling dynamics under heatwave conditions are internally complex, with very different temperatures within the same leaf. Because of this spatial heterogeneity, single-point measurements of leaf temperature in heatwave conditions may not capture important aspects of heatwave effects.

BACKGROUND AND AIMS:Fire-related cues can influence germination and seedling establishment in fire-prone ecosystems by breaking physical dormancy (PY) or stimulating germination in species with water-permeable seeds. However, most studies rely on fresh seeds and overlook how soil seed bank storage may change germination responses to fire cues. We investigated whether in situ seed storage affects germination responses to heat shock and smoke in Cerrado species. METHODS:Seeds of 13 Cerrado species, dispersed at the beginning of either the dry or rainy season, were collected and exposed to heat shock (100°C and 200°C for 1 min) and smoke water treatments. Remaining seeds were buried in the field and exhumed after 1, 3, 6, 9, and 12 months. After each retrieval, seeds were exposed to the same fire-related cues and germinated under controlled conditions for 30 days. KEY RESULTS:In situ seed storage changed germination responses to fire-related cues in more than 60% of the studied species, but responses were highly species-specific. Smoke effects changed over time in two non-dormant species, with germination either increasing or ceasing after burial. Storage increased sensitivity to heat shock in seeds with PY, leading to higher germination after exposure to 200°C compared to fresh seeds. Species dispersing during the rainy season generally showed rapid loss of viability and weak responses to fire-related cues, whereas several species dispersing during the dry season maintained viability and exhibited stronger storage-related changes in germination. CONCLUSION:Our results demonstrate that germination responses to fire-related cues in Cerrado species depend not only on the fire cue itself, but also on seed storage time and dispersal season. These storage-mediated and species-specific responses suggest that recruitment dynamics in tropical savannas are more complex than inferred from experiments using only fresh seeds.

Climate change is accelerating species losses in ecosystems across the world. Seed germination is a critical, climate dependent phase of the plant life cycle; however, the ecological determinants of germination climate niches within diverse landscapes and across functional types (FTs) are still not well understood. In this study, we characterized seed germination temperature and water availability niches for 28 species that represent different FTs (tree, shrub, grass, forb) and vegetation types (grassy woodland, dry and wet forests) within a temperate bioregion (Sydney, Australia). We tested whether ecological determinants, specifically species climate of origin, seed traits, FT and vegetation type explain germination niches and predicted spatial and temporal patterns of germination potential across the landscape under high and low emission scenarios. We found wide variation in thermal and hydric germination niches among species. Optimal germination temperature (thermal niche) was predicted by FT, climate of origin and seed traits, such that shrubs, cool origin species, and species with large seeds had significantly cooler optimal temperatures for germination. We also quantified spatial and temporal changes in germination potential to identify vulnerable areas and FTs. We found strong species specific seasonal patterns in germination potential with future climate shifts affecting FTs differently; germination of woody species declined more than forbs. Future germination potential was predicted by historical climatic conditions, with warmer and drier localities being more vulnerable. Overall, our findings demonstrate that species germination responses to climate change depend on FT, seed traits, and species climate of origin, with woody species and warmer, drier parts of the landscape emerging as being particularly vulnerable to declines in recruitment. Our study provides a mechanistic understanding of germination responses to temperature and water availability, enabling predictions of vulnerable species and areas for conservation under climate change, and inform large scale ecosystem restoration approaches through improved species selection and sowing times.

BACKGROUND AND AIMS:The maintenance of seed banks and timing of germination are fundamental to ensuring population persistence. Physical dormancy (PY) in disturbance-prone environments contributes to these processes via an impermeable seed coat. Dormancy is broken often by heating, which in fire-prone regions is determined by species-specific threshold temperatures. However, the mechanisms by which seeds persist or control dormancy-breaking thresholds in such environments are unclear. We determined whether unsaturated and saturated fatty acids (FAs; within triacylglycerols), common lipids linked to heat-stress resilience, might contribute to seed coat dormancy and overall seed persistence, and whether fire selects for different FA compositions and drives PY function in fire-prone regions. METHODS:We characterized seed FA compositions of 26 Fabaceae species from fire-prone and fire-free ecosystems through gas chromatography-mass spectrometry. We compared FA saturation, total relative FA content and the highest melting point FA of each species across seed tissues (seed coat vs internal tissues) and habitat type (fire-prone vs fire-free) and, for fire-prone species, tested for a relationship with species-specific dormancy-breaking thresholds. KEY RESULTS:No relationship between FA composition and species-specific dormancy-breaking thresholds was found. Seeds of fire-free species had more saturated FAs than fire-prone species, particularly for internal tissues. FA saturation was higher in seed coats than in internal tissues across both habitat types. Relative FA content was similar in internal tissues across habitat type but differed for seed coats, with fire-prone species having marginally more FAs. CONCLUSIONS:While no correlation existed between FA composition and dormancy-breaking thresholds in fire-prone species, the consistent differences between seed tissue types we found highlight a similar role for FAs in seed coats across habitats, probably linked to maintaining impermeability. Some evidence supports fire selecting for greater total FA content in seed coats, but further work is needed to test its relationship with temperature thresholds.

Climate change has increased the likelihood of extreme events, increasing the number of days with dangerous fire weather conditions, resulting in fires with increased severity, frequency and extent. This can greatly impact vegetation communities by reducing diversity and slowing recovery. The role of in situ soil seed banks in mediating impacts of shifting fire regimes is often unclear and may vary between different vegetation types. In particular, the impact of high fire severity, an increasingly common fire regime shift, may increase the likelihood of temperatures lethal to seeds in the soil, while higher fire frequencies may reduce diversity via increased immaturity risk. Here we aim to assess how fire severity impacts the species' and functional group diversity of soil seed banks in a threatened mesic forest community. We collected 396 soil samples from 12 sites within wet sclerophyll forest in the Blue Mountains of New South Wales, Australia that had been burnt during the 2019/2020 Australian megafires at differing fire severities (moderate, high and extreme), as well as from unburnt (control) sites, 3 years post-fire. Soil samples were split into the leaf litter and soil, both treated with smoke and heat to break fire-related dormancy, and regularly watered in a greenhouse to observe germination for a year. This was compared to floristic surveys conducted at each site. Our data showed a hump-shaped relationship between species richness and fire severity in the extant vegetation. The lowest richness occurred at unburnt sites peaking at moderate severity burn sites and declining slightly at high and then extreme severity sites. This relationship was not significant in the soil seed bank, indicating it may buffer against losses in diversity long term. Obligate resprouters generally declined as severity increased. A distinct difference in composition between extant vegetation and in the soil seed bank emphasises that a significant portion of the species richness within these communities solely exists in the soil seed bank, fluctuating as environmental conditions change. Composition in both extant vegetation and the soil seed bank shifted with increasing fire severity, suggesting potential impacts on the future functioning of these ecosystems.Read the free for this article on the Journal blog.

AimTo compare field-based evidence of plant and animal responses to fire with remotely sensed signals of fire heterogeneity and post-fire biomass recovery.LocationSouth-eastern Australia; New South Wales.Time Period2019-2022.Major Taxa StudiedA total of 982 species of plants and animals, in eight taxonomic groups: amphibians, birds, fish, insects, mammals, molluscs, plants and reptiles.MethodsWe collated 545,223 plant and animal response records from 47 field surveys of 4613 sites that focussed on areas burnt in 2019-2020. For each site, we calculated remotely sensed signals of fire heterogeneity and post-fire biomass recovery, including the delayed recovery index. Meta-regression analyses were conducted separately for species that declined after fire (negative effect sizes) and species that increased after fire (positive effect sizes) for each buffer size (250 m, 500 m, 1 km, 1.5 km, 2 km and 2.5 km radius).ResultsWe found that species exposed to homogenous high-severity fire (i.e., low fire heterogeneity) were more likely to exhibit decreased abundance/occurrence or inhibited recovery. Areas with delayed recovery of biomass also had significant negative on-ground responses, with lower abundance or occurrence in areas where biomass recovery was slower.Main ConclusionsThe fire heterogeneity index and the delayed recovery index are suitable for inclusion in monitoring and reporting systems for tracking relative measures over time, particularly when field survey data is not available at the landscape scales required to support reporting and management decisions. Locations with remotely sensed signals of delayed recovery should be prioritised for protection against further disturbances that may interfere with the recovery process. Research attention must next focus on how cumulative fire heterogeneity patterns of successive fires affect the post-fire recovery dynamics to further inform the application of remote sensing indicators as management tools for biodiversity conservation.

Changing fire regimes, including increased fire severity, may impact plant community recovery, altering structure and composition, potentially causing a state change. For threatened wet sclerophyll forests, mesic forests which contain both dry sclerophyll and rainforest elements, this could mean a shift to a more fire-prone species composition. We investigate how species and functional group diversity responses differ across a gradient of fire severity and how recovery changes with time since fire in a mesic forest community. We hypothesize that increased fire severity can lead to reduced diversity and altered composition. We surveyed plant species cover and abundance three years post-fire at sites with different fire severities (moderate, high, or extreme) during the 2019/2020 Australian megafires, and sampled adjacent unburnt sites as controls. We calculated species and functional type beta diversity indices across a fire severity gradient. Our data showed a hump-shaped relationship between plant diversity and fire severity three years post-fire. Species richness was highest at moderately burnt sites and lower in unburnt and extremely burnt sites. Species composition also differed, with unburnt sites containing more rainforest-restricted species. Increased fire severity may reduce community-level diversity. The distinct compositional difference between recently burnt and long unburnt sites suggests how fire regimes may drive shifts in wet sclerophyll forest states. The differences identified three years post-fire indicate that recovery may be slow, with extremely burnt sites potentially taking the longest.

The European honeybee (Apis mellifera) is a highly abundant introduced pollinator with widely established feral populations across a large proportion of Australia. Both managed and feral populations contribute significantly to the pollination of many native plant species but have also disrupted native plant-pollinator dynamics. Varroa mite (Varroa destructor), a parasite associated with the collapse of feral or unmanaged European honeybee populations globally, has recently become established in Australia and will inevitably spread across the country. If feral honeybee populations decline significantly, there may be a range of effects on Australian native plant species, including pollination dynamics and seed set. This would have potential implications for the risks faced by native species, particularly those already threatened. However, the exact effects of a decline in feral honeybees on native plants are uncertain as the role of honeybees in Australian ecosystems is poorly understood. We identify potential consequences of the spread of varroa mite and highlight the large knowledge gaps that currently limit our understanding of the subsequent impacts on the Australian flora.

Variation in plant growth strategies facilitate species' coexistence in a community. Some functional traits are predicted to influence the growth rates of developing individuals by capturing trade-offs in resource allocation. However, despite being used broadly in community ecology, the assumed generality and predictability of trait-growth relationships lack widespread empirical testing. The megafires of 2019-2020 burned extensive areas throughout New South Wales and were followed by high rainfall, causing the large-scale synchronous regeneration of fire-adapted species. We took advantage of this mass disturbance event to test hypothesised relationships between functional traits and growth across six spatially distributed sclerophyllous systems throughout NSW, in which sampled vegetation was part of the same growth cohort. We investigated whether resprouting as a trait facilitated faster initial height growth compared to reseeding and, in reseeding species, tested whether the effects of four structural functional traits-stem specific density (SSD), leaf nitrogen per area, standardised stem diameter and specific leaf area (SLA)-on height growth rates followed directions predicted by theory. Resprouters grew an average of 25.92 cm year-1 more than reseeders at 14-15 months post-fire, indicating an advantage in light capture over reseeding species in the period soon after fire. Of the four structural functional traits tested, SSD and leaf nitrogen per area displayed evidence of relationships with height growth rate, while standardised stem diameter and SLA had no evidence of an effect. These relationships were consistent across sites. Our results indicate that (i) ontogenetic variation in growth rates should be integrated into the fast-slow growth economics spectrum and that (ii) while some functional traits predict height growth, this is not a guarantee for all traits.Read the free Plain Language Summary for this article on the Journal blog.

Summary Theory suggests that the dominance of resprouting and seeding, two key mechanisms through which plants persist with recurrent fire, both depend on other traits and vary with fire regime. However, these patterns remain largely untested over broad scales. We analysed the relationships between mean fire frequency, derived from MODIS satellite data, and resprouting and seeding strategies, respectively, for c . 10 000 woody and herbaceous species in Australia. We tested whether leaf economics traits differed among these strategies. Probability of resprouting exhibits a monotonic increase with fire frequency for woody plants; for herbaceous plants, a hump‐shaped relationship is observed. Probability of seeding exhibits a hump shape with fire frequency in woody plants. In herbaceous plants, probability of resprouting was associated with higher leaf mass per area (LMA), and probability of seeding with lower LMA. A broader range of leaf investment strategies occurred in woody plants. Our findings provide the largest empirical support to date for theory connecting fire response strategy to fire frequency. Woody seeders appear constrained by immaturity and senescence risk. Herbaceous and woody seeders showed different placements along the leaf economics spectrum, suggesting an important interaction between growth form and growth rate for seeders.

Background: One of the greatest challenges to biologists is to understand the adaptive mechanisms of how plants will respond to climate at all levels from individual physiology to whole populations. For example, variation (plasticity) in the composition and concentration of metabolites will determine productivity, reproduction, and ultimately survival and distribution of plants, especially those subjected to rapid climate change. Objectives: Our aim was to study how interspecific and intraspecific metabolic variation in plant species within a single community can be elucidated. Methods: We used a metabolomics approach to study metabolic acclimation (by measuring the metabolome between plants under “common garden” controlled environment conditions) and metabolic plasticity (using field based reciprocal transplant studies) in a set of Atlantic sand dune annual communities along a latitudinal gradient from Portugal to England. Results: In the common garden study, metabolically phenotyping (using a fingerprinting direct injection mass spectrometry approach) five species of annual plants showed that species living together in a community have distinct metabolic phenotypes (high inter-specific metabolic variation). There was low intra-specific metabolic variation between populations growing under standard environmental conditions. The metabolic variation in one species Veronica arvensis was measured in the reciprocal transplant study. Metabolic phenotypes obtained from all samples were similar across all sites regardless of where the plants originated from. Conclusions: This implies that the metabolome is highly plastic and the measurable metabolome in this study was influenced more by local environmental factors than inherent genetic factors. This work highlights that species are fulfilling different niches within this community. Furthermore, the measurable metabolome was highly plastic to environmental variation.

Seeds are a key pathway for plant population recovery following disturbance. To prevent germination during unsuitable conditions, most species produce dormant seeds. In fire-prone regions, physical dormancy (PY) enables seeds to germinate after fire. The pyro-thermal niche, incorporating temperature effects into seed dormancy and mortality, has not been characterised for PY seeds from fire-prone environments. We aimed to assess variation in thermal thresholds between species with PY seeds and whether the pyro-thermal niche is correlated with seed mass, ecosystem type or phylogenetic relatedness. We collected post heat-shock germination data for 58 Australian species that produce PY seeds. We applied species-specific thermal performance curves to define three critical thresholds (DRT50, dormancy release temperature; Topt, optimum temperature; and LT50, lethal temperature), defining the pyro-thermal niche. Each species was assigned a mean seed weight and ecosystem type. We constructed a phylogeny to account for species relatedness and calculated phylogenetic signal (h2) for DRT50, Topt and LT50. We found a consistent inverted u-shaped thermal response curve across all species examined. Seeds from species within Rhamnaceae exhibited higher temperature thresholds than those from Fabaceae. Seed mass was influential in explaining LT50 variation. The pyro-thermal niche analysis presented here provides a framework for direct comparisons between other fire-prone and nonfire-prone species, in which heat may play a role in postfire germination dynamics.

In Australia, species declared as 'extinct' are afforded no legal protection, even after rediscovery, despite rediscovery being the most common reason for changes to extinct species' listing. Here we use the rediscovery of Atriplex acutiloba R.H.Anderson, an Australian arid zone plant species listed as extinct, to examine how species listing policies may inhibit conservation once a species is, at least on paper, declared extinct. We also provide previously unpublished ecological notes to help reduce taxonomic confusion and improve the veracity of future records of Atriplex acutiloba. We provide recommendations for provisional relisting or emergency revisions where rediscovered species were presumed extinct to ensure that necessary protections are afforded until dedicated reassessment can occur.

An understanding of fire-response traits is essential for predicting how fire regimes structure plant communities and for informing fire management strategies for biodiversity conservation. Quantification of these traits is complex, encompassing several levels of data abstraction scaling up from field observations of individuals, to general categories of species responses. We developed the Fire Ecology Database to accommodate this complexity. Its conceptual framework is underpinned by a flexible data pipeline enabling links between fire-related trait data and event information at individual, population, and community levels. Key features include: (a) concise and documented trait and method vocabularies; (b) documented uncertainty in observations and aggregation; and (c) documented origin of data including field observations, laboratory experiments, and expert elicitation. We demonstrated application of our framework using data from new field surveys and existing data sets in New South Wales, Australia. The database includes 14 traits for 6,287 plant species derived from 8,936 field work records from 2007 to 2018, 7,054 field records from surveys after 2019, and 48,306 records from 301 existing sources.

The combined pressures of climate change and anthropogenic disturbance are increasingly pushing species toward extinction. However, many species remain unassessed for extinction risk, posing challenges to managers and decision makers when extreme events, such as megafires, impact large numbers of species. This has led to an increased need for rapid assessments, which can accelerate extinction risk assessments and help to ensure species receive timely conservation actions. In Australia, the 2019-2020 Black Summer fires had extensive impacts on native endemic flora, necessitating a prioritisation process to identify the species most in need of conservation interventions or extinction risk assessments. We used rapid assessments to identify priority species for full extinction risk assessments and compared how well the rapid assessments, with minimal information, predicted extinction risk in species that received a full assessment. Some 260 species received rapid assessments and 131 of these received full assessments. We found that 84 % of species identified as threatened by full assessments had been accurately identified as such during the rapid assessments. Rapid assessments also accurately predicted the specific threatened category in 53 % of cases compared to full assessments, however accuracy decreased with extinction risk (67 % for Critically Endangered, 54 % for Endangered, 11 % for Vulnerable). Our results show that rapid assessments can be a reliable and informative predictor of extinction risk and may be particularly useful in emergency circumstances. Recognising that effective conservation action relies on comprehensive and up-to-date threat listings, our results show the value of rapid assessments during biodiversity crises and highlight their utility to drive conservation actions.

PREMISE:Climate change is globally pushing fire regimes to new extremes, with unprecedented large-scale severe fires. Persistent soil seed banks are a key mechanism for plant species recovery after fires, but extreme fire severity may generate soil temperatures beyond thresholds seeds are adapted to. Seeds are protected from lethal temperatures through soil burial, with temperatures decreasing with increasing depth. However, smaller seeds, due to their lower mass and corresponding energy stores, are restricted to emerging from shallower depths compared to the depths for larger seeds. We examined recruitment patterns across a landscape-scale gradient of fire severity to determine whether seed mass and dormancy class mediate shifts in community assemblages. METHODS:We surveyed 25 sites in wet sclerophyll forests in southeastern Australia that had been burnt at either moderate, high, or extreme severity during the 2019-2020 Black Summer Fires. We measured abundance and calculated density of seedlings from 27 common native shrub species. RESULTS:Extreme severity fires caused significant declines in seedling recruitment. Recruitment patterns differed between dormancy class, with steeper declines in seedling emergence for species with physiologically dormant (PD) than for physically dormant (PY) seeds at extreme fire severity. Relative emergence proportions differed between fire severity and seed size groups for both PY and PD species. CONCLUSIONS:Large-scale extreme severity fires favor larger-seeded species, shifting community composition. Future recurrent extreme fire events could therefore place smaller-seeded species at risk. Seed mass, dormancy class, and other seed traits should be considered when exploring post-fire responses, to better predict impacts on plant species.

The extent of severe fires is projected to increase with climate change. Furthermore, changes to the fire regime, including the frequency, severity or seasonality of fire, can reduce resilience and promote persistent changes in ecosystem state. Wet sclerophyll forests are found in potentially dynamic mosaics of rainforest and dry sclerophyll forests and contain species from both these contrasting community types. As such, they create an opportunity to study alternative state theory in which states are mediated by fire regimes. To assess the resilience of wet sclerophyll forests to extreme fire events we specifically asked; do mortality rates and recruitment after fire differ between sclerophyllous and non-sclerophyllous components of wet sclerophyll forests, how do these impacts differ along gradients of fire severity and frequency, and is there evidence of positive fire feedback loops, and if so what levels of fire severity and frequency thresholds influence state shifts towards dry sclerophyll forest? We surveyed all canopy (upper and mid canopy) and grass species, to represent three key plant groups; Eucalyptus trees, non-sclerophyllous trees and grasses. We found strong evidence that fire frequency and severity determined the initial trajectory of wet sclerophyll forest recovery. Key findings showed that extreme fire severity can have significant impacts on non-sclerophyllous tree mortality, with an average of 72% of trees killed, much greater than in Eucalyptus species (mean mortality = 9%). However, our findings also highlighted the importance of analysing past fire regime variables, with sites experiencing 4-5 fires in 60 years also experiencing mortality rates of above 75% for non-sclerophyllous trees. Our results support the conclusion that a long multi-decadal fire-free interval is essential for these recovering wet sclerophyll forests, both to rebuild the resilience of their non-sclerophyllous biota and to reduce the risk of recurrent high severity fires in future.

Dormancy in seeds is a key persistence mechanism for many flowering plants. Physically dormant (PY) seeds have water impermeable seed coats, and in fire-prone systems a common mechanism for dormancy release is fire-induced soil heating. However, the thermal thresholds innate to seeds with PY may be influenced by vegetation, climate, and fire regimes, varying substantially between populations of the same species. To investigate intraspecific variation of thermal thresholds in PY seeds, we sampled obligate seeding Acacia pulchella (Fabaceae) which produces PY seeds. Sampling was undertaken from 13 populations across a climate gradient of rainfall and temperature, and between two vegetation communities in fire-prone Mediterranean-type ecosystems of south-west Western Australia. To test a range of weather and fire-induced soil heating dormancy-break scenarios, we conducted dry heat shock experiments between 40 and 140 °C for 10 min and scored germination for 16 weeks. We created population-specific thermal performance curves and extracted the dormancy release temperature at which 50 % of the seeds had germinated (DRT50), the optimum dormancy-breaking temperature to stimulate maximum germination (T0), and the lethal temperature at which 50 % of the seeds were killed (LT50). Generalised linear models were used to examine relationships between thermal thresholds and possible vegetation, climate, and fire regime drivers of intraspecific variation in seed traits. We found that thermal thresholds differed between vegetation communities, with thresholds consistently higher in forest-type ecosystems compared to open woodland, and the influence of climate varied significantly between the two communities. Seeds from Jarrah Forest populations had a DRT50 16.0 °C higher, a T0 9.7 °C higher, and LT50 7.8 °C higher than seeds from Banksia woodlands. A high rate of non-dormancy was identified in one population that had lost fire in its system and displayed significant germination after both summer and fire-related temperatures. The PY thermal thresholds modelled here provide insight into the strong influence of variable soil heating as a function of vegetation and fuel dynamics in fire-prone environments. Our findings highlight the significant intraspecific variation for this species and suggest that fire-induced soil heating generated by vegetation characteristics may be an overlooked element of fire regimes shaping seed traits.

PREMISE: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. METHODS: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. RESULTS: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. CONCLUSIONS: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.

Deadwood represents a significant carbon pool and unique biodiversity reservoir in forests and savannas but has been largely overlooked until recently. Storage and release of carbon from deadwood is controlled by interacting decomposition drivers including biotic consumers (animals and microbes) and abiotic factors (water, fire, sunlight, and freeze–thaw). Although previous research has focused mainly on forests, we synthesize deadwood studies across diverse ecosystems with woody vegetation. As changing climates and land-use practices alter the landscape, we expect accelerating but variable rates of inputs and outputs from deadwood pools. Currently, Earth system models implicitly represent only microbial consumers as drivers of wood decomposition; we show that many other factors influence deadwood pools. Forest management practices increasingly recognize deadwood as an important contributor to forest dynamics, biodiversity, and carbon budgets. Together, emerging knowledge from modeling and management suggests a growing need for additional research on deadwood contributions to carbon storage and greenhouse gas emissions.