Fire Intervals Research Articles

Conceptual model for assessing a science–policy–management framework for threat mitigation

AbstractFire regimes are changing globally, leading to an increased need for management interventions to protect human lives and interests, potentially conflicting with biodiversity conservation. We conceptualized 5 major aspects of the process required to address threats to flora and used this conceptual model to examine and identify areas for improvement. We focused on threat identification, policy design, and action implementation. We illustrated the application of the conceptual model through a case study in southeastern Australia, where policies have been designed to prevent hazard reduction burns from exposing threatened flora to high‐frequency fire (HFF). We examined whether threatened species have been accurately identified as threatened by HFF, species were accounted for in key policies, and implementation of the policy reduced the incidence of HFF for target species. Species were mostly identified accurately as being threatened by HFF, and, broadly, the policy effectively minimized the threat from HFF. However, 96 species did not have HFF identified as a threat, and another 36 were missing from the policy entirely. Outcomes regarding the reduction of threat from HFF since policy introduction were species specific, despite an average increase in fire interval of 2 years. Despite the policy, over half (55%) the species studied have been affected by HFF since the policy was introduced. Although relatively minor improvements could optimize threat identification and policy design, the mixed success of action implementation highlights limitations that warrant further investigation. Our conceptual model enabled us to make clear and targeted recommendations for how different aspects of the policy could be improved and where further work is needed. We propose the conceptual model can be useful in a variety of contexts.

Alcohol exposure induces cortical activity change during quiescent state

Alcohol Use Disorder (AUD) is a significant global mental health issue that impacts both the central and peripheral systems, leading to widespread cognitive and motor dysfunctions. The primary motor cortex (M1) plays a critical role in motor planning, control, and execution, yet the effects of chronic alcohol exposure on M1 remain underexplored, particularly during quiescent states. This study investigates the functional changes in M1 due to chronic alcohol exposure using high-resolution Neuropixels electrode recordings in a mouse model. Our findings reveal alterations in neuronal firing mode, particularly in layer V, highlighting disruptions in the excitatory/inhibitory (E/I) balance. Despite similar overall firing rates, changes in firing interval distributions suggest altered temporal dynamics of neuronal activity due to alcohol exposure. These results align with existing literature on cortical disruptions caused by alcohol and provide new insights into the specific neuronal dynamics within M1, especially in quiescent states.

The impact of plant-derived fire management prescriptions on fire-responsive bird species.

In fire-prone regions, the occurrence of some faunal species is contingent on the presence of resources that arise through post-fire plant succession. Through planned burning, managers can alter resource availability and aim to provide the conditions required to promote biodiversity. Understanding how species occurrence changes at different spatial and temporal scales after fire is essential to achieve this goal. However, many fire prescriptions are guided primarily by the responses of fire-sensitive plants when setting tolerable fire intervals. This approach assumes that maintaining floristic diversity will satisfy the requirements of fauna. We surveyed bird species in two semi-arid vegetation types across an environmental gradient in south-eastern Australia. We conducted four surveys at each of 253 sites across a 75-year chronosequence of time since fire and used generalized additive mixed models to examine changes in the occurrence of birds in response to time since fire. Model predictions were compared to plant-derived fire prescriptions currently guiding fire management in the region. Time since fire was a significant predictor for 18 of 28 species modeled, in at least one vegetation type, over a gradient of 1.3° of latitude. We detected considerable variation in the responses of some species, both between vegetation types and geographically within a vegetation type. Our evaluation of plant-derived fire prescriptions suggests that the intervals considered acceptable for maintaining floristic diversity may not be sustainable for populations of birds requiring longer unburnt vegetation, with 6 of the 12 species assessed attaining a mean occurrence probability of 20.3% by the minimum tolerable fire interval, and 57.3% by the maximum tolerable fire interval, in their respective vegetation types. Our findings highlight the potential vulnerability of fire-responsive bird species if fire prescriptions are applied in a manner that fails to account for the slow development of habitat resources needed by some species, and the variation detected within the responses of species. This highlights the need for species-specific data collected at an appropriate spatial scale to inform management plans.

Historical pyrodiversity in Douglas-fir forests of the southern Cascades of Oregon, USA

Our understanding of forest dynamics and successional pathways in coastal Douglas-fir (Pseudotsuga menziesii var menziesii) forests with relatively frequent mixed-severity fires is limited by a lack of annually precise dendroecological reconstructions that combine records of historical fires and tree establishment. The processes by which old-forest heterogeneity developed under historical fire regimes with recurrent low- and moderate-severity fires has not been well studied at fine temporal scales and across spatial scales. We developed crossdated multi-century records of fire and tree establishment histories in old forests (170 – 550 years) at 34 plots distributed across six sites. Study sites include warm-dry to cool-moist Douglas-fir forest types found in the southern west Cascades of Oregon, USA. Spatial variability in historical fire frequency and fire effects resulted in tremendous diversity in forest developmental histories, age structure, and forest conditions. Most historical fire intervals were very frequent (<10 years) to frequent (<25 years) in dry Douglas-fir forests. Exceptionally high fire frequency and an abrupt decrease in fire frequency after European colonization in dry Douglas-fir forests adds to growing evidence and recognition of Indigenous fire stewardship in montane Douglas-fir forests. In moist forests where Douglas-fir is seral to western hemlock, fire intervals were frequent to moderately frequent (<50 years), but intervals varied substantially over time. Relatively young moist forests burned frequently while mature moist forests had long fire intervals (50–160 years). Nearly all tree establishment cohorts were preceded by either stand-replacing (28 %) or non-stand-replacing fires (64 %). However, tree cohorts only provided evidence of 16 % of historical fire events that we reconstructed from cambial fire scars. This study demonstrates that frequent fire can be an important driver of forest development and in some contexts shapes the structure of coastal old-growth Douglas-fir forests, which are often characterized as developing from endogenous disturbances during long fire-free periods. The high level of pyrodiversity we observed was associated with variation in and interactions of micro-climate, topography, fuels, and Indigenous fire stewardship. We recommend rigorous dendroecological reconstructions across the coastal Douglas-fir region to refine our understanding of the geography of fire-mediated forest developmental dynamics in this important forest type, to inform forest management, conservation, and ecocultural restoration.

Short-term soil fungal community dynamics following fire in mediterranean climate-type banksia woodlands

Fire is a dominant ecosystem process in many Mediterranean climate type ecosystems, and is predicted to increase in severity and frequency, shifting away from previous regimes in many regions. Responses of flora and fauna to fire are relatively well studied, but less is known about the responses of belowground microbiota. We quantified soil fungal dynamics over the first 12–15 months after fire, focusing on attributes of the fire regime (season, interval, severity). Soil samples were collected from three sites in a threatened woodland ecosystem in southwestern Australia, a Mediterranean-type climate region. Fungal taxa were identified via high throughput sequencing of the ITS subregion and taxonomy assigned using reference databases. Richness, diversity, abundance, community composition, and functional groups were quantified. Over the post-fire sampling period, richness and diversity declined and soil fungal community composition changed significantly throughout the sampling period, with family level taxa and functional groupings experiencing the most change. Through the sampling period, an increase in saprotrophic and endophytic fungi was observed, along with a decrease in all pathogenic fungi. We found that the post-fire fungal community is quite dynamic in the first 12–15 months after fire. We found little effect of fire interval or fire season, though our inference was limited. Our work contributes to putting belowground biota into the same conceptual frameworks as aboveground taxa and serves to inform fire managers in fire-prone Mediterranean climate type regions.

How do intervals between fires influence canopy seed production and viability?

Abstract Canopy storage of seed (serotiny) is an important persistence strategy in fire‐prone environments. Serotinous populations can be threatened when fire intervals are shorter than the time needed to accumulate seed, or when longer than plant lifespans. Understanding how fire regimes influence canopy seedbanks requires study of the timing of plant maturity, seed output and germination traits. Research that spans plant functional types, such as resprouters or obligate seeders, helps to understand the mechanisms through which fire has influence. Using field data collected at 57 sites in a Mediterranean shrubland of southeastern Australia, we modelled how time since fire and mean fire interval influenced infructescence (hereby cone) production. Additionally, seed output, viability and germination speed were assessed in the laboratory. Reproductively mature resprouters were first observed 2 to 4 years post‐fire in the field, and reproductively mature obligate seeders 6 years post‐fire, depending on the species. Reproductively mature plants were not observed at short mean fire intervals: until 3 and 9 years for resprouters and nine and 18 years for obligate seeders, again, varying by species. When resprouter species reached maturity, we observed a decline in cone production as time since fire increased. This decline was not observed for obligate seeder species. Fire influenced the number of viable seeds produced within cones for one resprouter species, Allocasuarina paludosa, but we did not detect a relationship for other species. Germination speed was faster for species that produce few seeds per cone, and slower for species that produce many seeds, indicating a trade‐off between fire‐related seed traits. For example, Hakea rostrata, which holds two seeds per cone, germinated mostly within the first few weeks, while Callitris rhomboidea, which holds many seeds per cone, germinated asynchronously over 9 months. Short intervals between fires reduce canopy seed production for the serotinous species studied. Obligate seeders were more sensitive to frequent fire than resprouters. In the context of expected increases in wildfire frequency and droughts in Mediterranean ecosystems, our findings suggest that serotinous species' reproduction and recruitment will be differentially impacted depending on a suite of functional traits. Read the free Plain Language Summary for this article on the Journal blog.

Plant life-history data as evidence of an historical mixed-severity fire regime in Banksia Woodlands

Context The concept of the fire regime is central to understanding and managing fire-prone ecosystems globally, and information on past regimes can provide useful insights into species disturbance adaptations. Although observations from satellite imagery or palaeoecological proxy data can provide direct evidence of past, pre-colonial fire regimes, they may be limited in temporal or spatial resolution and are not available for all ecosystems. However, fire-related plant-trait and demographic data offer an alternative approach to understand species–fire regime associations at the ecosystem scale. Aims We aimed to quantify the life-history strategies and associated fire regimes for six co-occurring shrub and tree species from fire-prone, Mediterranean-climate Banksia Woodlands in south-western Australia. Methods We collected static demographic data on size structure, seedling recruitment, and plant mortality across sites of varying time since last fire. We combined demographic data with key fire-related species traits to define plant life-history strategies. We then compared observed life histories with a priori expectations for surface, stand-replacing, and mixed-severity fire-regime types to infer historical fire-regime associations. Key results Fire-killed shrubs and weakly serotinous trees had abundant post-fire seedling recruitment, but also developed multi-cohort populations during fire-free periods via inter-fire seedling recruitment. Resprouting shrubs had little seedling recruitment at any time, even following fire, and showed no signs of decline in the long absence of fire, likely owing to their very long lifespans. Conclusions The variation in life-history strategies for these six co-occurring species is consistent with known ecological strategies to cope with high variation in fire intervals in a mixed-severity fire regime. Whereas resprouting and strong post-fire seedling recruitment indicate a tolerance of shorter fire intervals, inter-fire recruitment and weak serotiny are interpreted as a bet-hedging strategy to cope with occasional long fire-free periods that may otherwise exceed adult and seed-bank lifespans. Implications Our findings suggested that Banksia Woodlands have evolved with highly variable fire intervals in a mixed-severity fire regime. Further investigations of species adaptations to varying fire size and patchiness can help extend our understanding of fire-regime tolerances.

Multi-century times-since-fire and prior fire interval determine biomass carbon stocks in obligate-seeder eucalypt woodlands

Multi-century times-since-fire and prior fire interval determine biomass carbon stocks in obligate-seeder eucalypt woodlands

Assessment of Oklahoma Phlox (Phlox oklahomensis: Polemoniaceae) in the Gypsum Hills of Northwestern Oklahoma and Southern Kansas

Phlox oklahomensis Wherry, Oklahoma phlox, occurs within the tall grass prairie of the southern Flint Hills of Kansas, and other populations occur within the southern mixed grass prairie of the Gypsum Hills of northwestern Oklahoma and southern Kansas. The first census of Oklahoma phlox in northwestern Oklahoma and southern Kansas was conducted over a three-year period (1980-1982). The second and third censuses occurred approximately 20 years after the first census, in 2002 and 2003. Since the 1980s two major wildfires and several droughts have occurred throughout its distribution range. The goals of this research were to compare the 1980-1982 census and the 2002 and 2003 censuses of Oklahoma phlox to censuses conducted in 2020 and 2021 and assess the current status of the species. In addition, we used a geographic information system (GIS) to identify factors that influence the likelihood of finding Oklahoma phlox in the region. The final census found that the occurrence of Oklahoma phlox has not changed significantly over the last 40 years. Populations thrive in areas where the fire interval is &gt;5 years, and it commonly occurs on the upper elevations of the landscape on hilltops and/or ridges where the slope is &gt; 7%. Although plants were observed on all landscape exposures, populations occur more frequently on west and northwest facing slopes. The authors recommend an S3 ranking for Oklahoma phlox.

Severe and Short Interval Fires Rearrange Dry Forest Fuel Arrays in South-Eastern Australia

Fire regimes have shaped extant vegetation communities, and subsequently fuel arrays, in fire-prone landscapes. Understanding how resilient fuel arrays are to fire regime attributes will be key for future fire management actions, given global fire regime shifts. We use a network of 63-field sites across the Sydney Basin Bioregion (Australia) to quantify how fire interval (short: last three fires &lt;10 years apart, long: last two fires &gt;10 years apart) and severity (low: understorey canopy scorched, high: understorey and overstorey canopy scorched), impacted fuel attribute values 2.5 years after Australia’s 2019–2020 Black Summer fires. Tree bark fuel hazard, herbaceous (near-surface fuels; grasses, sedges &lt;50 cm height) fuel hazard, and ground litter (surface fuels) fuel cover and load were higher in areas burned by low- rather than high-severity fire. Conversely, midstorey (elevated fuels: shrubs, trees 50 cm–200 m in height) fuel cover and hazard were higher in areas burned by high- rather than low-severity fire. Elevated fuel cover, vertical connectivity, height and fuel hazard were also higher at long rather than short fire intervals. Our results provide strong evidence that fire regimes rearrange fuel arrays in the years following fire, which suggests that future fire regime shifts may alter fuel states, with important implications for fuel and fire management.

Fire has contrasting effects on the survival, growth, and reproduction of Cerrado grasses with differing regenerative strategies

AbstractBackgroundCerrado grasses are closely linked to fire, but the mechanisms underlying their responses are poorly understood. Fire affects populations by altering vital rates, and different regenerative strategies likely influence responses as resprouting ability trades off with seeding investment. Specialist grasses mostly occupy old‐growth habitats and rely almost entirely on vegetative regeneration, suggesting potentially higher fire tolerance than habitat generalists that can colonize anthropized and degraded habitats due to high seeding investment. Thus, we explored the effect of fire on one specialist (Trachypogon spicatus) and two generalist (Aristida riparia and Schizachyrium microstachyum) tussock grasses.LocationFrequently burned grassland in Central Brazil.MethodsWe monitored the vital rates of 150 individuals/species in burned (prescribed late‐dry‐season fire) and unburned plots. Survival, resprouting, and reproduction were assessed monthly for six months post‐fire and then again 16 months after fire. Tussocks were measured for size (area of the base) and vegetative height for changes in structure. We collected seed mass, seed fill, and germination rates from the literature.ResultsFire negatively affected the generalist grasses, increasing mortality (+12%), decreasing size (50%), and inhibiting flowering and inflorescence production. The specialist benefited from burns, showing high survival (97%), recovery of pre‐fire structure, and stimulated reproduction. Generalist species had a high investment in seeds (seed fill &gt; 60%; germination &gt; 50%), while the specialist produced empty seeds (88%) with low germination (3%). Size was not related to the probability of survival but significantly increased the reproductive output.ConclusionsResults suggest that the specialist Trachypogon spicatus could persist under very frequent fires (e.g., annual), given its robust fire tolerance and post‐fire recovery. Where this species is a restoration priority, it would likely benefit from techniques that promote vegetative regeneration rather than direct seeding. Contrarily, generalist grasses are less resilient to fires and require longer fire intervals to allow population persistence.

Top-down control of climate on long-term interactions between fires, tree-cover and soil erosion in a Mediterranean mountain, Corsica

Fire is a potential significant driver of soil erosion in the Mediterranean area, as it results in the partial removal of vegetation and the alteration of organic matter, affecting soil structure and stability. The erosion of particle sizes is influenced by the intensity and duration of rainfall, regulated by disturbance regimes and vegetation cover. We hypothesize that, during the Holocene, high fire frequency and intensity under precipitation control may have contributed to soil erosion, while plant cover and composition could have mitigated it. This plant cover, in turn, might have been influenced by biomass burning. To test this hypothesis, we conducted a detailed analysis of sediments spanning the last 11,500 years from a small mountain lake, Corsica, situated in the black pine forest belt. The high temporal resolution analysis (∼10 years per sample), used granulometry and loss-on-ignition as proxies for erosion and ecosystem productivity in both the lake and watershed, and fire and plant macroremains as fire and tree cover proxies, respectively. The correlation between particle size and the contents of organic or mineral matter with mean fire return intervals (FRI) revealed significant patterns. Long fire intervals were associated with more fine and coarse sands, whereas short mean FRI positively correlated with clay and, fine and coarse silt, along with higher total mineral and organic matter contents. These findings suggest that fires were more frequent when rain duration was sustained but runoff intensity was lower. Conversely, wildfires were less frequent during intense runoff periods (wetter climate). Unlike fire frequency, fire severity did not correlate with erosion, and tree cover and plant richness had minimal to no effect. The 8.2 kyr event was characterized by runoff transporting primarily coarse sands, i.e. a dry period with very intense rains. This suggests that the system is primarily top-down controlled by climate. Multimillennial erosion trends are influenced by fire frequency and precipitation regimes, whereas vegetation does not seem to have a mitigating effect on this process.

Utilizing GO/PEDOT:PSS/PtNPs-enhanced high-stability microelectrode arrays for investigating epilepsy-induced striatal electrophysiology alterations.

The striatum plays a crucial role in studying epilepsy, as it is involved in seizure generation and modulation of brain activity. To explore the complex interplay between the striatum and epilepsy, we engineered advanced microelectrode arrays (MEAs) specifically designed for precise monitoring of striatal electrophysiological activities in rats. These observations were made during and following seizure induction, particularly three and 7days post-initial modeling. The modification of graphene oxide (GO)/poly (3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)/platinu-m nanoparticles (PtNPs) demonstrated a marked reduction in impedance (10.5 ± 1.1kΩ), and maintained exceptional stability, with impedance levels remaining consistently low (23kΩ) even 14days post-implantation. As seizure intensity escalated, we observed a corresponding increase in neuronal firing rates and local field potential power, with a notable shift towards higher frequency peaks and augmented inter-channel correlation. Significantly, during the grand mal seizures, theta and alpha bands became the dominant frequencies in the local field potential. Compared to the normal group, the spike firing rates on day 3 and 7 post-modeling were significantly higher, accompanied by a decreased firing interval. Power in both delta and theta bands exhibited an increasing trend, correlating with the duration of epilepsy. These findings offer valuable insights into the dynamic processes of striatal neural activity during the initial and latent phases of temporal lobe epilepsy and contribute to our understanding of the neural mechanisms underpinning epilepsy.

Temporal and spatial patterns of fire regime disruption in conifer forests of western North America

ABSTRACT Temporal and spatial patterns of fire regime disruption were reconstructed in conifer forests of western North America from information on pre-disruption and disrupted mean fire intervals (MFIs) of 498 dendrochronology-based fire chronologies. We identified the conifer forest types most affected by MFI shift and the influence of land category designation on MFI change. We also mapped the years of the MFI shift, the last fire recorded, and disrupted/pre-disruption MFI ratios. Fire cessation and longer MFIs predominated in most fire chronologies and conifer forest types. MFI was significantly higher in most conifer forest types, with most differences in dry conifer forests. MFI shift occurred mainly before the designation of protected, federal, social-property, and private areas. MFI shift began in 1829 in the United States of America Southwest, a region subjected to prolonged fire exclusion and with the highest disrupted/pre-disruption MFI ratios. Fire regime disruption moved gradually into the Pacific Northwest and the Sierra Nevada until reaching the northern conifer forests of Canada and Alaska. In contrast, one-third of fire chronologies in Mexican conifer forests retained pre-disruption MFIs. Our findings allowed us to identify areas with MFIs outside of their natural variability, with prolonged fire exclusion, or with intact fire regimes.

Historical fire regimes from red pines (Pinus resinosa Ait.) across the Tension Zone in the Lower Peninsula, Michigan USA

Currently, no multiple century fire scar records have been constructed in the Lower Peninsula of Michigan, USA, a region where historical vegetation ranged from prairies and oak-dominated woodlands in the south to conifer-northern hardwood forests and swamps to the north. The western portion of the Huron-Manistee National Forests is located within this strong vegetation transition (i.e., “Tension Zone”) and, based on this study, has well-preserved remnant red pine trees dating back to at least the late 1400s with fire scars dating back to 1523. From fire scar records constructed at four study sites, we documented historical fires as having a wide range of fire intervals and seasonalities. A general timeline of fire activity changes in this region can be described as relatively frequent fire in the pre- and early-European contact eras, variable and generally less fire from this point forward until the period of major logging activities after which fire frequency was significantly increased. Historical fires were associated with drought in the year of fire. Some broad synchronies of fire occurrence existed among sites such as 3 of 4 sites recording fires in years 1717, 1774, and 1829. Interestingly, these years were not exceptionally dry nor among the driest fire years. Future development of fire scar records will likely improve spatio-temporal characterization of regional fire regimes including understanding of human-climate-fire dynamics.

Fire regimes of the Southern Appalachians may radically shift under climate change

BackgroundIncreased drought due to climate change will alter fire regimes in mesic forested landscapes where fuel moisture typically limits fire spread and where fuel loads are consistently high. These landscapes are often extensively modified by human land use change and management. We forecast the influence of varying climate scenarios on potential shifts in the wildfire regime across the mesic forests of the Southern Appalachians. This area has a long history of fire exclusion, land use change, and an expanding wildland urban interface. We considered interactions among climate, vegetation, and anthropogenic influences to forecast future fire regimes and changes to the forest structure. We used climate scenarios representing divergent drought patterns (overall drought trend and interannual variability) within a process-based fire model that captures the influence of climate, fuels, and fire ignition on wildfire patterns and suppression.ResultsCompared to simulations using historical climate (1972–2018), future total burned area (2020–2100: 782,302.7 (716,655.0–847,950.3) ha) increased by 42.3% under high drought variability (1,134,888.4 (1,067,437.2–1,202,339.6) ha), 104.8% under a substantial increase in drought trend (1,602,085.7 (1,511,837.5–1,692,334.0) ha), and 484.7% when combined (4,573,925.0 (4,434,910.5–4,712,939.5) ha). Landscape patterns of fire exclusion and suppression drove the spatial variability of fire return intervals (FRI). Our projections indicate wide spatial variability in future fire regimes with some areas experiencing multiple fires per decade while others experience no fire. More frequent fires corresponded with increased oak prevalence and a reduction in the biomass of mesic hardwoods and maple; however, mesic hardwoods remained prevalent under all fire intervals because of their contemporary dominance.ConclusionsOur study illustrates how future drought–fire–management interactions and a history of fire exclusion could alter future fire regimes and tree species composition. We find that increasing trends in drought magnitude and variability may increase wildfire activity, particularly in areas with minimal fire suppression. In ecosystems where fuel moisture (and not load) is the standard limitation to fire spread, increased pulses of drought may provide the conditions for more fire activity, regardless of effects on fuel loading. We conclude the effects of climate and human management will determine the novel conditions for both fire regime and ecosystem structure.

Squalamine reverses age-associated changes of firing patterns of myenteric sensory neurons and vagal fibres

Vagus nerve signaling is a key component of the gut-brain axis and regulates diverse physiological processes that decline with age. Gut to brain vagus firing patterns are regulated by myenteric intrinsic primary afferent neuron (IPAN) to vagus neurotransmission. It remains unclear how IPANs or the afferent vagus age functionally. Here we identified a distinct ageing code in gut to brain neurotransmission defined by consistent differences in firing rates, burst durations, interburst and intraburst firing intervals of IPANs and the vagus, when comparing young and aged neurons. The aminosterol squalamine changed aged neurons firing patterns to a young phenotype. In contrast to young neurons, sertraline failed to increase firing rates in the aged vagus whereas squalamine was effective. These results may have implications for improved treatments involving pharmacological and electrical stimulation of the vagus for age-related mood and other disorders. For example, oral squalamine might be substituted for or added to sertraline for the aged.

202 years of changes in Mediterranean fire regime in Pinus nigra forest, Corsica

Wildfires are critical socio-ecological features in the Mediterranean basin. In a context of global changes (climate, land use), we questioned whether the wildfire regime was altered in the mountains of Corsica, France. Using tree-ring analysis of fire-scarred trees, we tested for changes in frequency, seasonality, and area. We hypothesized that the fire regime changed during the middle-20th century due to human activities, as observed elsewhere in the Mediterranean. We sampled fire-scarred trees, geolocated for mapping fire areas, in a forest of black pine (Pinus nigra laricio). The oldest fire was in 1684 but the fire chronology with adequate sample depth for analysis covered 202 years [1820–1921]. Between 1820–2012, 15 fires were recorded, 8 of which scarred at least 25% of the sampled trees. The mean fire interval was 14 years, corresponding to a high fire frequency with 4 major fires per century. Most fires occurred between 1931–1970. On average, about 50% of trees were scarred by fires before 1931, but this percentage decreased thereafter. The exception was the 2000 fire that impacted 100% of living trees. Mapping showed spatially heterogenous fire areas. These results match other Mediterranean studies showing longer fire intervals since the late-20th century, and wildfires generally occurred during the period of late-earlywood or latewood formation, i.e., summer or early autumn, which is the season of contemporary fires. Although fires were recurrent for more than 200 years with no change in the fire season, the regime changed twice in frequency. These changes likely result from a combination of land use and warmer summer conditions. While pines survived most past fires of low intensity through the last large fire in the 1970’s, the severe fire of 2000, following ca 30 years of fire suppression, killed large patches of mature trees. Such chronology provides rational arguments for black pine ecosystem management, notably to consider seeking to recover the sustainable fire regime of the 19th century, for instance by using prescribed fires to manage surface fuel.

Photographic documentation of melanism in bobcats (Lynx rufus) in the Greater Everglades.

We document the presence of bobcats (Lynx rufus) that demonstrate melanism in the Greater Everglades. The South Florida landscape is driven by a myriad of disturbance regimes particularly that of short fire intervals. We monitored 180 camera traps for 3 years and obtained 9503 photographs of bobcats 25 (<0.5%) of these detections included melanistic individuals. Our observations and historical accounts suggest melanism is a phenotype that persists, albeit it at an exceedingly low frequency, in bobcats in the region. While we do not know if the expression of melanism conferred a fitness benefit in our system, the vegetation structure that was characterized by frequently burned uplands and low-light and densely vegetated swamps produced conditions that may render a benefit from melanism through enhanced crypsis. The investigation of rare phenomenon in ecology is important yet difficult within a given field study, but reporting novel observations, like melanism in bobcats, allows for science to gain insight across studies that would not be otherwise possible.

Carbon dynamics of prescribed fire in pine- and oak-dominated forests on the mid-Atlantic coastal plain, USA

The use of prescribed fire to reduce the risk of wildfires and maintain or enhance desired ecological conditions is increasing in forests of the Mid-Atlantic region. Accurate estimates of forest carbon (C) dynamics associated with prescribed burning, including net ecosystem productivity (NEP) and time to accumulate the C lost during burns, termed neutral net ecosystem C balance (NECB), as a function of fire intensity and burn intervals would assist fire managers optimize treatment timing while balancing other ecosystem services provided by forests. We quantified forest C dynamics and evapotranspiration in two pine- and oak-dominated forests in the Pinelands National Reserve of southern New Jersey that have been managed using prescribed fire over two decades. Using long-term C flux data, we found that NEP, ecosystem respiration (RE) and gross ecosystem production (GEP) were similar among stands during undisturbed years. Estimated C loss during three prescribed burns at the pine-dominated stand averaged 4.3 ± 0.9 Mg C ha-1, which is equivalent to 2–3 years of NEP during undisturbed years, and consistent with fuel consumption during prescribed burns throughout the Pinelands. Only annual NEP was lower during years when burns were conducted compared to unburned years, while annual RE, GEP, evapotranspiration and ecosystem water use efficiency were similar. Over a two-decade period, NEP totaled 28.3 Mg C ha-1 and NECB was 15.5 Mg C ha-1, indicating that stands managed using repeated prescribed burns still sequester moderate amounts of C. At an oak-dominated stand, a prescribed burn released lower amounts of C (1.7 Mg C ha-1), and annual NEP was greater over the following 3-year period compared to a decade of low annual NEP following severe spongy moth defoliation and associated tree mortality, suggesting that prescribed fires could play a role in the restoration of ecosystem functioning in insect-damaged stands. Patterns of forest C dynamics during and following prescribed burns in these mid-Atlantic forests are similar to intermediate age pine-dominated stands throughout the southeastern USA, which also sequester moderate amounts of C through repeated prescribed burning regimes.