Post-fire Survival Research Articles

Hydraulic segmentation explains differences in loss of branch conductance caused by fire.

The hydraulic death hypothesis suggests that fires kill trees by damaging the plant's hydraulic continuum in addition to stem cambium. A corollary to this hypothesis is that plants that survive fires possess 'pyrohydraulic' traits that prevent heat-induced embolism formation in the xylem and aid post-fire survival. We examine whether hydraulic segmentation within stem xylem may act as such a trait. To do so, we measured the percentage loss of conductance (PLC) and vulnerability to embolism axially along segments of branches exposed to heat plumes in two differing species, fire-tolerant Eucalyptus cladocalyx F. Muell and fire-sensitive Kiggelaria africana L., testing model predictions that fire-tolerant species would exhibit higher degrees of hydraulic segmentation (greater PLC in the distal parts of the branch than the basal) than fire-intolerant species (similar PLC between segments). Following exposure to a heat plume, K. africana suffered between 73 and 84% loss of conductance in all branch segments, whereas E. cladocalyx had 73% loss of conductance in whole branches, including the distal tips, falling to 29% in the most basal part of the branch. There was no evidence for differences in resistance segmentation between the species, and there was limited evidence for differences in distal vulnerability to embolism across the branches. Hydraulic segmentation in E. cladocalyx may enable it to resprout effectively post-fire with a functional hydraulic system. The lack of hydraulic segmentation in K. africana reveals the need to understand possible trade-offs associated with hydraulic segmentation in long-lived woody species with respect to drought and fire.

Post-fire survival of the threatened California red-legged frog in the Sierra Nevada following the Mosquito Fire

Post-fire survival of the threatened California red-legged frog in the Sierra Nevada following the Mosquito Fire

Using heat plumes to simulate post-fire effects on cambial viability and hydraulic performance in Sequoia sempervirens stems.

Injury to the xylem and vascular cambium is proposed to explain mortality following low severity fires. These tissues have been assessed independently, but the relative significance of the xylem and cambium is still uncertain. The goal of this study is to evaluate the xylem dysfunction hypothesis and cambium necrosis hypothesis simultaneously. The hot dry conditions of a low severity fire were simulated in a drying oven, exposing Sequoia sempervirens (Lamb. ex D. Don) shoots to 70 and 100 °C for 6-60min. Cambial viability was measured with Neutral Red stain and water transport capacity was assessed by calculating the loss of hydraulic conductivity. Vulnerability curves were also constructed to determine susceptibility to drought-induced embolism following heat exposure. The vascular cambium died completely at 100 °C after only 6min of heat exposure, while cells remained viable at 70 °C temperatures for up to 15min. Sixty minutes of exposure to 70 °C reduced stem hydraulic conductivity by 40%, while 45min at 100 °C caused complete loss of conductivity. The heat treatments dropped hydraulic conductivity irrecoverably but did not significantly impact post-fire vulnerability to embolism. Overall, the damaging effects of high temperature occurred more rapidly in the vascular cambium than xylem following heat exposure. Importantly, the xylem remained functional until the most extreme treatments, long after the vascular cambium had died. Our results suggest that the viability of the vascular cambium may be more critical to post-fire survival than xylem function in S. sempervirens. Given the complexity of fire, we recommend ground-truthing the cambial and xylem post-fire response on a diverse range of species.

Wildfire-dependent changes in soil microbiome diversity and function

Forest soil microbiomes have crucial roles in carbon storage, biogeochemical cycling and rhizosphere processes. Wildfire season length, and the frequency and size of severe fires have increased owing to climate change. Fires affect ecosystem recovery and modify soil microbiomes and microbially mediated biogeochemical processes. To study wildfire-dependent changes in soil microbiomes, we characterized functional shifts in the soil microbiota (bacteria, fungi and viruses) across burn severity gradients (low, moderate and high severity) 1 yr post fire in coniferous forests in Colorado and Wyoming, USA. We found severity-dependent increases of Actinobacteria encoding genes for heat resistance, fast growth, and pyrogenic carbon utilization that might enhance post-fire survival. We report that increased burn severity led to the loss of ectomycorrhizal fungi and less tolerant microbial taxa. Viruses remained active in post-fire soils and probably influenced carbon cycling and biogeochemistry via turnover of biomass and ecosystem-relevant auxiliary metabolic genes. Our genome-resolved analyses link post-fire soil microbial taxonomy to functions and reveal the complexity of post-fire soil microbiome activity.

Extent of recent fire-induced losses of ponderosa pine forests of Arizona and New Mexico, USA

Land management legacies coupled with climate change have led to shifts in western ponderosa pine (Pinus ponderosa) forest structure and fire regimes. A growing body of evidence suggests that under increasing area burned at high-severity, warming and drought, ponderosa pine forests are vulnerable to conversion to alternate forest types or non-forest vegetation. However, the extent and direction of recent fire-induced changes in southwestern US ponderosa pine forests have not been subject to region-wide evaluation. Here, we assess recent fire effects in ponderosa pine forests using long-term repeated samples of stand composition and structure from the US Forest Service’s Forest Inventory and Analysis (FIA) program, combined with metrics of satellite-derived burn severity (predicted Composite Burn Index, CBI; and differenced normalized burn ratio, dNBR). We compiled and analyzed FIA plots dominated by ponderosa pine and associated species within the southwestern states of Arizona and New Mexico to quantify regional trends for ponderosa pine (e.g., forest losses or gains), link changes to wildfire severity, and characterize vegetation shifts.Among 685 plots sampled three times between 1996 and 2017, 26% of plots burned at least once, with more than half of these burning at moderate to high severity. Plots that burned within the study period exhibited a net loss of 46% of ponderosa pine trees, but unburned plots also exhibited a net decline of 11%. While all tree size classes exhibited greater losses than gains, tree size was a positive predictor of post-fire survival. Satellite-derived burn severity (predicted CBI) was strongly related to tree mortality and shifts toward alternate post-fire vegetation types. Severely burned stands exhibited trajectories toward non-forest vegetation with high dominance by resprouting species, particularly Gambel oak (Quercus gambelii).These findings contribute to an emerging understanding of the potential ecological outcomes of growing forest vulnerability to changing climate and disturbance regimes. Methods employed herein offer scalable opportunities to quantify changes across forest biomes using long-term monitoring data. As importantly, our findings inform regional and local land management efforts to sustain these valued forest types in an era of change. We highlight two key themes for management to promote the long-term persistence of ponderosa pine forests in the southwestern US: restoration of low-severity fire regimes and retention of large, fire-resistant trees.

Resprouting in European beech confers resilience to high-frequency fire

AbstractEuropean beech (Fagus sylvatica L.) can regenerate successfully from seeds after mixed-severity fires with mid-to-long fire return intervals (>60 years). However, if fire return interval is lower than the age of sexual maturity, post-fire seeding will be limited, leaving vegetative resprouting as the only viable option for recovery. This means that the forecasted increase in fire frequency driven by climate change may erode beech forest resilience to fire. Here, we surveyed tree regeneration in a European beech forest affected by two consecutive fires, in 2003 and 2017, and applied experimental clipping of tree saplings to address the following questions: (1) What is the fire resistance and post-fire recovery via resprouting of tree saplings? (2) Which factors drive post-fire resprouting of beech saplings? (3) Does post-fire clipping of tree saplings increase the probability of survival and resprouting vigor? We monitored 2195 beech saplings and 953 saplings of other tree species during three consecutive years, from 2018 to 2020. Almost all beech saplings were top-killed by fire, and two-thirds of them died completely. However, 3 years after the second fire, 30 per cent of beech saplings survived by resprouting from the base. Post-fire resprouting was less likely in small-diameter saplings and in those more injured by fire. Overall, the second fire did not cause a major decline of beech regeneration and consequently did not alter the dominant species composition of post-fire recovery. Given the low specific resistance to fire, post-fire resprouting of saplings is therefore a key component of beech resilience to short-interval fires. The effects of clipping on post-fire survival and resprouting vigor were very limited, suggesting the unsuitability of actively clearing burned beech regeneration as a post-fire management prescription. In conclusion, basal resprouting from beech saplings after fire-induced top-kill led to a higher-than-expected resilience of beech to short-interval fires (i.e. circa 15 years).

Success of post-fire plant recovery strategies varies with shifting fire seasonality

Wildfires are increasing in size and severity and fire seasons are lengthening, largely driven by climate and land-use change. Many plant species from fire-prone ecosystems are adapted to specific fire regimes corresponding to historical conditions and shifts beyond these bounds may have severe impacts on vegetation recovery and long-term species persistence. Here, we conduct a meta-analysis of field-based studies across different vegetation types and climate regions to investigate how post-fire plant recruitment, reproduction and survival are affected by fires that occur outside of the historical fire season. We find that fires outside of the historical fire season may lead to decreased post-fire recruitment, particularly in obligate seeding species. Conversely, we find a general increase in post-fire survival in resprouting species. Our results highlight the trade-offs that exist when considering the effects of changes in the seasonal timing of fire, an already present aspect of climate-related fire regime change.

Impact of the 2019–20 drought, heatwaves and mega-fires on Greater Gliders (Petauroides volans) in the Greater Blue Mountains World Heritage Area, New South Wales

ABSTRACT We have investigated the impact of the unprecedented drought, heatwaves and fires of 2019–20 on a threatened arboreal marsupial, the Greater Glider (Petauroides volans), in the Greater Blue Mountains World Heritage Area, an area of over one million hectares. The study involved multiple post-fire surveys in 2020 and 2021 of 16 transects (eight burnt and eight unburnt) for which we had pre-2019 data on Greater Glider numbers. We were unable to find any gliders on two transects burnt at high to extreme severity (100% of eucalypt foliage killed in the canopy and understorey) but Greater Gliders were still present on all six transects burnt at low to moderate severity (44–77% of eucalypt foliage killed), although in significantly lower numbers (mean decline of 43% per transect). Greater Gliders feed on eucalypt leaves and their post-fire survival appears to be dependent on the presence of eucalypt trees with abundant unburnt foliage, which were absent from the more severely burnt transects. Even 17 months after the fires, Greater Gliders were still dependent on these trees, which constituted 36% of trees on low-moderate burnt transects but 77% of trees in which gliders were seen. Gliders were seen feeding on post-fire epicormic regrowth but generally avoided trees with mainly epicormic foliage, possibly because they provided insufficient protection from predators. Greater Gliders were also seriously impacted by the preceding drought and heatwaves, with patchy but significant declines on the eight unburnt transects (mean decline of 34% per transect). We measured the likely impact of the fires on Greater Glider habitat across the World Heritage Area by determining fire severity at a total of 773 precisely located points at which the species had been recorded. An extraordinary 84% of their known sites had been burnt, with 34% burnt at high-extreme severity, 50% burnt at low-moderate severity and only 16% unburnt. Combining these figures with the Greater Glider declines recorded on our transects, we estimate that the Greater Glider population of the World Heritage Area has been reduced by 61% by the extreme events of 2019–20. This is a broad extrapolation from a limited number of sites but it indicates the massive scale of the likely impacts.

Fire severity and tree size affect post-fire survival of Afrotemperate forest trees

BackgroundFire is recognized as an important factor in determining the distribution and composition of Southern Cape Afrotemperate Forest in South Africa, although comprehensive understanding of the resilience of these forests to fire is lacking. We investigated effects of fire severity and tree size on post-fire survival of Afrotemperate forest tree species.ResultsFire severity was estimated from observed damage to the main stem of trees, and trees were considered to have survived if they resprouted from the main stem or had green foliage in the canopy. A total of 88 plots, 40 species, and 1 378 trees were surveyed 19–24 months post-fire. We assessed the survival response of all trees collectively and for 10 species (with sample size > 40) individually, using logistic regression. Relative to other forests of the world, the post-fire survival rate (45%) of Afrotemperate forest trees collectively was comparable to that in coniferous and tropical forests but lower than that in other temperate forests and in neighboring dune thicket. Fire severity had a significant negative effect on survival and tree size had a significant positive effect. Total variance explained by the model (for species collectively) was 40.8%, of which fire severity and tree size combined explained 13.2%, and species as random factor, 27.6%. Respective tree species showed differential survival responses—four species showed high survival (> 60%), while five species showed low survival (< 40%). Further, some species exhibited strong resprouting from the base or main stem while others rarely resprouted. The survival response and resprouting abilities of species which occur in both Afrotemperate forest and neighboring, more fire-exposed dune thicket, were generally poorer in forest. Such discrepancies imply that historical fire regimes associated with vegetation types likely drive species adaptions.ConclusionsOur findings suggest that fire severity and fire frequency (in terms of how tree size relates to fire frequency) are important for maintaining species richness and diversity within and between forest types. Varying resilience to fire among species supports previous assertions that fire affects species composition and diversity in these forests and suggests that potential changes in fire regimes due to global change will have consequences for forest conservation.

Fire ecology for the 21st century: Conserving biodiversity in the age of megafire

Fire ecology for the 21st century: Conserving biodiversity in the age of megafire

Initial Floristic Response to High Severity Wildfire in an Old-Growth Coast Redwood (Sequoia sempervirens (D. Don) Endl.) Forest

Climate driven increases in fire frequency and severity are predicted for Mediterranean climatic zones, including the Pacific coast of California. A recent high severity wildfire that burned in the Santa Cruz Mountains affected a variety of vegetation types, including ancient coast redwood (Sequoia sempervirens (D. Don) Endl.) stands. The purpose of this study was to characterize the survival and initial recovery of vegetation approximately six months after the fire. We sampled thirty randomly selected points in an old-growth coast redwood forest to examine and compare survival, crown retention, and post fire regeneration of trees by species, and the recovery of associated understory plant species. Sequoia sempervirens exhibited the highest post-fire survival (95%), with lower survival rates for subcanopy hardwood associates including tanoak (Notholithocarpus densiflorus (Hook. &amp; Arn.) Manos) (88%), coast live oak (Quercus agrifolia Nee.) (93%), Pacific wax myrtle (Myrica californica (Cham. &amp; Schltdl.) Wilbur) (75%), Pacific madrone (Arbutus menziesii Pursh) (71%), and the lowest survival recorded for the canopy codominant Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) (15%). Canopy retention and post fire regeneration were also highest for S. sempervirens and lowest for P. menziesii, indicating that S. sempervirens had a competitive advantage over P. menziesii following high severity crown fire. Both canopy survival and regeneration were greater for larger height and diameter trees; and basal sprouting was positively associated with tree height and diameter for S. sempervirens and N. densiflorus. Observed recovery of understory species was modest but included the reemergence of coast redwood associated herbaceous species. The robust nature of survival and recovery of S. sempervirens following this extreme fire event suggest that the removal of scorched, and the seeding or planting of trees, following this type of fire is contraindicated. The decline of P. menziesii is of concern, however, and suggests that repeated high severity fires driven by climate change could eventually lead to vegetation type conversion.

Are fire temperatures and residence times good predictors of survival and regrowth for resprouters in Florida, USA, scrub?

BackgroundFire is a dominant ecological disturbance in many ecosystems. Post-fire resprouting is a widespread response to fire, but resprouting vigor varies with many components of the fire regime, including fire intensity. We measured responses in 46 species of resprouting plants of Florida, USA, scrub and related habitats, marking and measuring individual plants before fires. We then measured fire temperatures and residence times (time above 60 °C) during 13 fires, at the base of each plant. We measured post-fire plant sizes for up to six years. We hypothesized that high temperatures and long residence times would reduce survival and growth, and that these vital rates would vary by burn season, habitat type, and species group.ResultsFires had variable intensities with maximum temperatures ranging from 47 to 890 °C (mean temperature = 549 °C) and residence times ranging from 0 to 83 minutes (mean time = 10 minutes). Consumed plants experienced higher fire intensity than scorched plants, and residence times were higher during the wet season (July through October), than the dry season (November through April), and fire season (May to June) and with drier conditions. Across all species affected by fire, 86% of plants survived and resprouted post fire. First year survival was unrelated to fire variables, with high survival across all maximum temperatures and residence times. Burn season, habitat, and species group did not significantly affect survival. On average across all species, post-fire growth recovered to pre-fire heights within four years. Growth was not significantly affected by species group or burn season.ConclusionResprouting perennial plants that dominate Florida scrub and surrounding habitats appear resilient to a wide range of fire intensities, as measured by maximum temperatures and residence times. Post-fire growth was rapid, with recovery of pre-fire heights in four years. Species groups varied in post-fire recovery rates. In these habitats, fire is critical to maintain the habitat structure for many animals and plants, including many rare species. The slower recovery of biomass for resprouting shrubs results in the longer availability of gaps for rare herbaceous species. In addition, variability in post-fire survival and growth among species groups likely contributes to the persistence of species diversity and complexity across habitats. However, variation in fire intensity appears to have little effect on resprouting species or subsequent habitat structure. A range of fire regimes can be used in prescribed fire management without having major impacts on resprouting plants in Florida scrub and related vegetation.

Post-fire summer rainfall differentially affects reseeder and resprouter population recovery in fire-prone shrublands of South Africa

Summer rainfall can have strong effects on post-fire mediterranean-type shrubland recovery patterns, with potentially long-lasting implications on communities. Our three-year field rainfall manipulation experiment tested post-fire survival and physiological responses of reseeders and resprouters to contrasting summer rainfall patterns in Fynbos and Renosterveld shrublands in South Africa. Climate projections are uncertain for this region but indicate that increased convective summer rainfall events could occur. We irrigated treatment plots during the hottest summer months (i.e. Jan, Feb, March) to contrast the naturally dry summer conditions. This allowed for assessments of the potential limiting effects of summer drought on post-fire vegetation recovery and the responsiveness of vegetation to moisture inputs during this time.Natural summer droughts led to leaf dehydration, reduced photosynthesis and reduced photosynthetic capacity. This had a particularly severe effect on reseeders during the first summer after fire leading to high mortality rates. Summer irrigations strongly reduced levels of reseeder stress and mortality. Resprouters in both vegetation types were physiologically less sensitive to rainfall patterns and showed little drought-related mortality. Comparisons of final population sizes with emergence and survival patterns showed that summer rainfall during the first summer after fire had the potential to strongly alter reseeder population sizes. The physiological sensitivity of plants to summer rainfall patterns was higher in shrubland communities occurring on fine-textured, moderately fertile soils (e.g. Renosterveld). Shrublands occurring on sandy, nutrient-poor soils (e.g. Fynbos) were remarkably insensitive to summer drought after the first summer with lower irrigation responses. Our study demonstrated the potential for variation in post-fire summer rainfall to strongly affect reseeder and resprouter population recovery patterns.

Wiregrass (Aristida beyrichiana) survival and reproduction after fire in a long-unburned pine savanna.

Restoring fire regimes is a major goal of biodiversity conservation efforts in fire-prone ecosystems from which fire has been excluded. In the southeastern U.S.A., nearly a century of fire exclusion in pine savannas has led to significant biodiversity declines in one of the most species-rich ecosystems of North America. In these savannas, frequent fires that support biodiversity are driven by vegetation-fire feedbacks. Understory grasses are key components of these feedbacks, fueling the spread of fires that keep tree density low and maintain a high-light environment. When fire is reintroduced to long-unburned sites, however, remnant populations of bunchgrasses might experience high mortality from fuel accumulation during periods of fire exclusion. Our objective was to quantify fire effects on wiregrass (Aristida beyrichiana), a key component of vegetation-fire feedbacks, following 16 years without fire in a dry pine savanna typically considered to burn every 1–3 years. We examined how wiregrass size and fuel (duff depth and presence of pinecones) affected post-fire survival, inflorescence and seed production, and seed germination. Wiregrass exhibited high survival regardless of size or fuels. Probability of flowering and inflorescence number per plant were unaffected by fuel treatments but increased significantly with plant size (p = 0.016). Germination of filled seeds was consistent (29–43%) regardless of fuels, although plants in low duff produced the greatest proportion of filled seeds. The ability of bunchgrasses to persist and reproduce following fire exclusion could jumpstart efforts to reinstate frequent-fire regimes and facilitate biodiversity restoration where remnant bunchgrass populations remain.

Resprouting increases seedling persistence likelihood after fire in a semelparous bamboo species

Chusquea culeou is a semelparous bamboo species which dominates the understorey of temperate forests and shrublands of Patagonia, South America. After the massive flowering, seeding and subsequent die-off, it provides an extraordinary amount of fine and dry fuel that increases wildfire likelihood, which in turn threatens the survival of its own offspring. In this context, we tested if this species could have alternative survival mechanisms which allows the persistence of the single seedling cohort, specifically evaluating two stages: seed and seedling. After a massive flowering event that occurred in summer 2010–11 and reached a regional scale in north-western Patagonia, we experimentally tested: 1) the effect of heat (90 °C, 120 °C, 150 °C) and/or ash on germination capacity of C. culeou seeds; and 2) the effect of low to moderate intensity fires on resprouting response of seedlings (<2 yr). Heating treatments inhibited seed germination, whereas most of the seedlings survived after their above-ground biomass was burned. Resprouting ability increased with maximum temperature reached at shoot base. Post-fire survival was considerably high, since 68% of pots had surviving shoots at the end of the experiment. In a scenario of wildfire occurrence after a massive flowering and subsequent die-off event, our experimental results suggest that resprouting ability right from the seedling stage might ensure the persistence of C. culeou populations. Also, the differential vegetative response of the seedlings to distinct fire-intensities could trigger distinct recovery trajectories in the understorey, generating an opportunity for regeneration of other trees and/or shrub species.

Fire severity effects on resprouting of subtropical dune thicket of the Cape Floristic Region.

It has been hypothesised that high-intensity fires prevent fire-dependent fynbos from being replaced by fire-avoiding subtropical thicket on dune landscapes of the Cape Floristic Region (CFR). Recent extensive fires provided an opportunity to test this hypothesis. We posit that (1) fire-related thicket shrub mortality would be size dependent, with smaller individuals suffering higher mortality than larger ones; and (2) that survival and resprouting vigour of thicket shrubs would be negatively correlated with fire severity. We assessed survival and resprouting vigour post-fire in relation to fire severity and pre-fire shrub size at two dune landscapes in the CFR. Fire severity was scored at the base of the shrub and categorised into four levels. Pre-fire size was quantified as an index of lignotuber diameter and stem count of each shrub. Resprouting vigour consisted of two variables; resprouting shoot count and resprouting canopy volume. A total of 29 species were surveyed. Post-fire survival of thicket was high (83–85%). We found that smaller shrubs did have a lower probability of post-fire survival than larger individuals but could detect no consistent relationship between shrub mortality and fire severity. Fire severity had a positive effect on resprouting shoot count but a variable effect on resprouting volume. Pre-fire size was positively related to survival and both measures of resprouting vigour. We conclude that thicket is resilient to high-severity fires but may be vulnerable to frequent fires. Prescribed high-intensity fires in dune landscapes are unlikely to reduce the extent of thicket and promote fynbos expansion.

EFFECTS OF DROUGHT AND FIRE ON NATIVE STIPA PULCHRA (POACEAE) RECOVERY IN SOUTHERN CALIFORNIA GRASSLANDS

Mediterranean-type climate California experiences both frequent wildfires and periodic drought. Climate change models predict increased severity of drought, and wildfire size and frequency, leading to concern about the ability of some plant species to recover to pre-fire conditions when wildfires and drought coincide. During exceptional drought, drought-adapted native vegetation, such as perennial native grassland, can experience substantial die-off. Here we use three post-fire case studies in southern California to assess the combined effects of fire and drought on the resilience of a native perennial bunchgrass, Stipa pulchra Hitchc. (Poaceae). We hypothesized that resilience to fire, assessed as post-fire survival, resprouting and fecundity (i.e., number of flowering plants and inflorescences), would decrease if the fire occurred during a drought. Unburned (control) sites had about double the survival and resprouting, and about three times the fecundity compared to moderate-severity burn sites. Resprouting and fecundity in the low-severity burn sites was about twice that of moderate-severity burn sites, and survival was five times higher. Responses to two springtime fires that occurred during drought were similar (average mortality 37%), in contrast to a fall fire with no drought (6%). We cannot separate the relative contribution of drought effects from those of the time of year (spring vs. fall), burn severity, and other site factors. However, moderate-severity burns, in combination with drought, decreased survival, resprouting, and fecundity of S. pulchra.

Compound disease and wildfire disturbances alter opportunities for seedling regeneration in resprouter‐dominated forests

AbstractHuman‐altered disturbance regimes and changing climatic conditions can reduce seed availability and suitable microsites, limiting seedling regeneration in recovering forest systems. Thus, resprouting plants, which can persist in situ, are expected to expand in dominance in many disturbance‐prone forests. However, resprouters may also be challenged by changing regimes, and the mechanisms determining facultative seedling recruitment by resprouting species, which will determine both the future spread and current persistence of these populations, are poorly understood. In the resprouter‐dominated forests of coastal California, interactions between wildfire and an emerging disease, sudden oak death (SOD), alter disturbance severity and tree mortality, which may shift forest regeneration trajectories. We examine this set of compound disturbances to (1) assess the influence of seed limitation, biotic competition, and abiotic conditions on seedling regeneration in resprouting populations; (2) investigate whether disease‐fire interactions alter postfire seedling regeneration, which have implications for future disease dynamics and shifts in forest composition. Following a wildfire that impacted a preexisting plot network in SOD‐affected forests, we monitored seedling abundances and survival over eight years. With pre‐ and postfire data, we assessed relationships between regeneration dynamics and disturbance severity, biotic, and abiotic variables, using Bayesian generalized linear models and mixed models. Our results indicate that postfire seedling regeneration by resprouting species was shaped by contrasting mechanisms reflecting seed limitation and competitive release. Seedling abundances declined with decreasing postfire survival of mature, conspecific stems, while belowground survival of resprouting genets had no effect. However, where seed sources persisted, seedling abundances and survival generally increased with the prefire severity of disease impacts, suggesting that decreased competition with adults may enhance seedling recruitment in this resprouter‐dominated system. Species’ regeneration responses varied with their relative susceptibility to SOD and suggest compositional shifts, which will determine future disease management and forest restoration actions. These results additionally highlight that mechanisms related to biotic competition, seed limitation, and opportunities for seedling recruitment beneath mature canopies may determine possible shifts in the occurrence of resprouting traits. This result has broad applications to other systems impacted by human‐altered regimes where asexual persistence may be predicted to be a beneficial life history strategy.

Fire Survival of Longleaf Pine (Pinus palustris) Grass Stage Seedlings: The Role of Seedling Size, Root Collar Position, and Resprouting

Longleaf pine (Pinus palustris Mill.) forest is a well-known fire-dependent ecosystem. The historical dominance of longleaf pine in the southeast United States has been attributed to its adaptation known as the grass stage, which allows longleaf pine seedlings to survive under a frequent surface fire regime. However, factors affecting post-fire survival of grass stage seedlings are not well understood. In this study, we measured live and dead longleaf pine grass stage seedlings to quantify the role of seedling size, root collar position, and sprouting in seedling survival following a wildfire in the sandhills of South Carolina. We found that fire resulted in almost 50% mortality for longleaf pine grass stage seedlings. Fire survival rate increased with seedling size, but a size threshold for fire tolerance was not supported. Fire survival depended on the position of root collar relative to the mineral soil. Seedlings with protected root collars (i.e., buried in or at the level of mineral soil) experienced &lt;21%, while seedlings with exposed root collars (i.e., elevated above mineral soil) suffered &gt;90% post-fire mortality. Ability to resprout contributed to 45.6% of the total fire survival, with the small seedlings (root collar diameter (RCD) &lt; 7.6 mm) almost exclusively depending on resprouting. Our findings had significant implications for fire management in longleaf pine ecosystems, and the current frequency of prescribed fire in sandhills might need to be lengthened to facilitate longleaf pine natural regeneration.

Mortality and Flowering of Great Basin Perennial Forbs After Experimental Burning: Implications for Wild Bees

The fates of native bee communities in the Great Basin sagebrush steppe are linked with the susceptibilities of their floral hosts to increasingly frequent wildfires. Postfire survival and subsequent flowering of six prevalent perennial wildflowers representing five families were quantified across a range of realistic fire severities created using a calibrated propane burn barrel. Five burn prescriptions of varying intensity and duration were applied to cultivated rows of basalt milkvetch (Astragalus filipes Torr. ex A. Gray), Blue Mountain prairie clover (Dalea ornata Eaton & J. Wright), sulphur-flower buckwheat (Eriogonum umbellatum Torr.), fernleaf biscuitroot (Lomatium dissectum Nutt.), blue penstemon (Penstemon cyaneus Pennell), and gooseberryleaf globemallow (Sphaeralcea grossularifolia Hook. & Arn.). Overall differences in their fire sensitivities were maximal at peak fire severity, ranging from 80% survival (L. dissectum) to complete mortality (E. umbellatum and P. cyaneus). Although A. filipes survived well (85%), half of the 95 burn survivors then failed to flower the year after burning. The postfire fate of plant-pollinator interactions is a function of the bees’ nesting habits, their floral host’s sensitivity to a given burn intensity (both in terms of survival and flowering), and the reproductive interdependence of bee and floral host (taxonomic specialists vs. generalists).