Wildfire and Prescribed Fire Effects on Wildlife in US Forests

Symposium

 

Symposia will be available on-demand on their scheduled date, then again at the conclusion of the conference.

 
Many wildlife species in the US require forest conditions created by large-scale disturbances, including fire. For thousands of years, fire was a driving process in shaping composition and structure of many ecosystems by killing encroaching woody vegetation. Fire regimes (frequency, size, severity, season) differed geographically, ranging from frequent low- or mixed-severity fires that maintained grasslands, barrens, and open oak and pine savannas or woodlands across much of the US, to infrequent stand-replacing fires in some western and boreal forest types. However, fire exclusion and fuel build-up due to fire suppression, increased ignition sources, and climate change have altered fire regimes across much of the US. Animal responses to post-fire forest conditions vary; some require fire-maintained habitats; many are generalists that use a wide range of conditions, and others are adversely affected. Differences in responses to fire and fire severity among the diverse wildlife species across US forests highlight the need to appropriately target prescribed fire frequency and severity to specific ecosystems, and balance the use of fire with the forest structures they require. Prescribed fire is commonly used for restoring and maintaining the composition and structure of fire-adapted ecosystems. Other silvicultural practices such as tree thinning and shelterwood harvests are potential alternatives for achieving the same open canopy conditions required by disturbance-dependent wildlife species. This symposium will include presentations that describe wildfire and prescribed fire effects on various wildlife taxa in the eastern and western US, and a panel discussion of fire as a management tool to achieve target forest conditions and wildlife habitats.

 

An Overview of Historical and Current Fire Regimes across US Forests
Cathryn H. Greenberg; Beverly Collins
For thousands of years, fire was a driving process that shaped composition, structure, and wildlife communities of many ecosystems by killing encroaching woody vegetation, and driving regeneration. Fire regimes (frequency, size, severity, season) differed geographically, ranging from frequent low- or mixed-severity fires that maintained grasslands, barrens, and open oak and pine savannas or woodlands across much of the US, to infrequent stand-replacing fires in some western and boreal forest types. However, fire exclusion and fuel build-up due to fire suppression, increased ignition sources, and climate change have altered fire regimes across much of the US. Today, prescribed fire is commonly used to restore and maintain the composition and structure of fire-adapted ecosystems such as southern pine forests. Differences in responses to fire and fire severity among the diverse wildlife species across US forests highlight the need to appropriately target prescribed fire frequency and severity to specific ecosystems, and balance the use of fire with the forest structures the wildlife require. Other silvicultural practices such as tree thinning and shelterwood harvests are potential alternatives for achieving the same open canopy conditions required by disturbance-dependent wildlife species. In this talk we present an overview of patterns of variation in frequencies, severities, scales, and spatial patterns of fire across ecoregions and among forested ecosystems across the US in relation to climate, fuels, topography and soils, ignition sources (lightning or anthropogenic), and vegetation. Our presentation “sets the stage” for this symposium on fire effects on wildlife and forest management alternatives for achieving canopy cover conditions required by disturbance-dependent wildlife species.
Fire Ecology, Open Forests, and Wildlife in the Eastern United States
Brice Hanberry; Frank Thompson
Fire ecology was integral to historical ecosystems, by reducing understory tree densities and maintaining open forests of savannas and woodlands with an herbaceous component. Historical forests predominantly were open forests, whereas early successional forests covered 1-13% of forestlands in the eastern United States prior to Euro-American settlement. Early successional bird species are declining in the eastern United States, regardless of the amount of early successional forests available by region. One reason for continued decline may be that these species relied on relatively stable oak and pine forests, which were kept open by fire, rather than ephemeral successional vegetation. Early successional songbirds reach great densities in open forests and potentially greater numbers in landscapes with historical amounts of open forest than in present day landscapes and those under intensive even-aged forest management. Restoration and management of open forests have not been prioritized or well-articulated for management of early successional birds and other species, but open forests provide an alternative option to consider for supporting early successional bird species. Additionally, open forests may be well-accepted by landowners.
The Role of Prescribed Fire in Restoring Pine Woodlands, Songbirds, and Nightjars in the Ozark and Ouachita Highlands
Frank R. Thompson III; Melissa C. Roach; Thomas W. Bonnot; Sarah W. Kendrick
Woodland and savanna occur at a small fraction of historic levels but are now being restored through the use of prescribed fire and tree thinning in the Ozark and Ouachita Highlands of Missouri, Arkansas, and Oklahoma. Over the past decade, we investigated the effects of prescribed fire and thinning on songbird abundance and nesting success, abundance of nightjars, and determined if shortleaf- pine woodland restoration efforts have been successful enough to reintroduce brown-headed nuthatches to Missouri. Abundance or reproductive success of brown-headed nuthatch, Eastern towhee, Eastern wood-pewee, pine warbler, prairie warbler, red-headed woodpecker, white-eyed vireo, yellow-breasted chat, blue-winged warbler, Kentucky warbler, whip-poor-will, chuck-will’s-widow were positively associated with fire or thinning or the resultant vegetation structure. We then compared predicted large-scale abundances between landscapes composed of historic amounts of open forest to contemporary landscapes with closed forest managed by timber harvest and determined abundances for most species were much greater in the historic landscape. We fit an abundance model for Brown-headed Nuthatch from surveys conducted in Arkansas and applied it to restored woodlands in Missouri. We determined sufficient habitat once again exists in Missouri to support a small population of this extirpated species and their reintroduction is underway. The use of fire is an important tool in restoring oak and pine woodland ecosystems in Missouri with clear benefits to a suite of declining species that require open or young forests.
Passerine Responses to Frequent Understory Fire in Cross Timbers Oak Woodland
Timothy O’Connell; Caitlin Laughlin
In recent decades, secondary succession in temperate hardwood forests of the eastern US has occurred in the absence of prescribed fire. Combined with browsing pressure from deer, loss of leaf litter from invasive earthworms, and other factors, forest succession has created a proliferation of relatively young, even-aged forest stands with high canopy closure and little understory vegetation. These pressures are exacerbated along the western edge of the Eastern Forest biome, especially within the cross timbers/oaks and prairies ecoregion, where encroaching eastern redcedar within otherwise hardwood-dominated stands has created a novel, dense, evergreen midstory. Native wildlife did not evolve under such conditions, and prescribed fire has been employed for ecological restoration in many areas. One such location is the Okmulgee Wildlife Management Area near Muskogee, Oklahoma. We examined breeding songbird communities in oak-hickory forest in response to a gradient of condition resulting from a 28-year history of prescribed fire management implemented at this site. Our objective was to describe bird community response to understory structure associated with prescribed fire treatments. We studied vegetation, flying insect biomass, and breeding landbirds using detection-corrected estimates of bird density at 158 plots sampled 2015-2016. There were some winners and losers associated with treatments: Eastern Wood-Pewee, Summer Tanager, and Indigo Bunting reached higher densities in areas burned most frequently (approximately every other year); in contrast Black-and-white Warbler density was highest on unburned plots. Overall, however, the vegetation structural changes associated with frequent prescribed fire were not mirrored by changes in flying insect biomass or significant changes in bird community composition. We conclude that prescribed fire at this site was compatible with the native biodiversity of the region.
Breeding Bird Response to Fire and Other Disturbances in Eastern Hardwood Forests
Cathryn H. Greenberg
Historically, natural and anthropogenic disturbances in eastern hardwood forests maintained a heterogeneous landscape, with variable levels of canopy cover. Today, prescribed fire is used to restore disturbance-adapted plant communities, and presumably the associated wildlife. However, little is known about wildlife response to prescribed fire or wildfire variability in eastern hardwood forest, especially over a relatively long time period (i.e., >10 years). In this talk I present overviews of multiple, multi-partner short- and long-term studies that together address breeding bird responses to single or repeated low- and high-severity prescribed fire, mixed-severity wildfires, season of burning, wind disturbance, shelterwood harvests, and other silvicultural treatments in the southern Appalachians. Together, study results indicate that bird abundance and species richness increases in response to forest canopy reduction, whether by high-severity burns, wind disturbance, or shelterwood harvests. Increases are due to an influx of disturbance-adapted species, with little change in the abundance of most species associated with mature forests. In general, breeding bird communities show little change in response to low-severity prescribed burns or wildfire, or silvicultural midstory reductions if canopy cover is left intact. In the short-term, substantial forest overstory reduction by timber harvests or high-severity burns may be required to create forest conditions suitable for disturbance-dependent species.
Cooking for Critters: Fire Effects on Wildlife Foods and Foraging in the Piney Woods
Marcus Lashley
Many wildlife species in Southern pines (Pinus spp.) have strong associations with an open-canopy forest community and a well-developed herbaceous understory. Contemporary management practices effectively can be applied to create this structure with a combination of canopy reducing treatments and relatively frequent fire. Here I will summarize several experiments from across the piney woods that characterized nuances associated with the effects of fire frequency and phenology on the production of wildlife foods, wildlife behavior, and the role of wildlife in indirectly linking fire to plant community assembly. Fire causes a resource pulse in high quality vegetative forage for a short time period which attracts herbivores. Granivores, insectivores, and generalist mammalian carnivores all exhibit a similar behavioral response. The timing of the resource pulse is dictated by the phenology of fire and so to is the ensuing resource tracking by the wildlife community. Shifting fire phenology from the typical prescribed fire season (March ignition) to the typical peak in lightning season fire (June ignition), delays the resource pulse into the late summer and so to the peak in wildlife use. Interestingly, top-killing perennial plants transforms the selectivity of herbivores for particular plant species and changing fire phenology rearranges which plants are selected. As a result, June fires indirectly suppresses fire-intolerant tree invasions. Fire frequency has a strong effect on production of fleshy fruits which peak in availability 2-5 years post fire and can be nearly eliminated when fire is ignited in <2 year return intervals, especially in poor productivity areas. Fire phenology also affects the phenology of fruiting and frugivores may play an important role in community assembly by directing seeds to newly burned areas. Overall, variability in fire frequency and phenology best provides resources for the wildlife community.
Reptile and Amphibian Response to Prescribed Fire and Silvicultural Disturbances in Upland Hardwood Forests
Christopher E. Moorman; Cathryn H. Greenberg
Historically, natural and anthropogenic disturbance in eastern hardwood forest maintained a heterogeneous landscape, with variable levels of canopy cover. Today, prescribed fire is used to restore disturbance-adapted vegetation communities, and presumably the associated wildlife. However, little is known about wildlife response to prescribed fire variability in eastern hardwood forest, especially over a relatively long time period (i.e., >10 years). We monitored the long-term response of reptiles and amphibians to prescribed burning at 2 study areas in southern Appalachian upland hardwood forest. Prescribed fire treatments varied in intensity and included repeated burns over the length of the studies. Single, low-intensity burns had little effect on herpetofauna, though delayed overstory mortality following repeated applications of low-intensity fire led to subtle increases in lizard abundance over time. High-intensity burns led to greater lizard abundance. Amphibians generally were not affected by the range of burn conditions present in the 2 studies, though salamander abundance declined temporarily after high intensity burns that reduced leaf litter and canopy cover. Different responses among taxonomic groups, and even among species within a guild, indicate that reptile and amphibian diversity can be maximized through landscape-level pyro-diversity. Together, these studies indicate that single, low-intensity burns do not substantially change herpetofaunal communities. In the short-term, substantial forest overstory reduction by timber harvests or high-intensity burns likely will be required to improve forest conditions for lizards and other disturbance-dependent species.
Differential Responses of Insectivorous Bats to Wildfire and Prescribedfire
Susan Loeb
Many bat species in the eastern U.S. are experiencing significant population declines due to habitat loss and fragmentation, disease, and wind energy development. Previous studies in the eastern U.S. have suggested that prescribed fire may be a beneficial tool for improving foraging and roosting habitat for bats. However, no research has been conducted on the effects of wildfire on bats in the eastern U.S. I conducted a systematic review of published studies on responses of temperate-zone bats to prescribed fire and wildfire to determine whether inferences based on studies of prescribed fire can be used to predict responses of bats to wildfire. For each study I characterized the response of closed-, edge-, and open-space foragers as negative, neutral, or positive based on foraging habitat selection, activity, or occupancy, or roost site selection in burned versus unburned areas. Thirty-four studies met criteria for inclusion in the review, 24 prescribed fire studies and 10 wildfire studies. Only open-spaced foragers showed similar responses (primarily positive) to prescribed fire and wildfire. In contrast, closed-space foragers exhibited primarily neutral or positive responses to prescribed fire but primarily negative responses to wildfire. Edge-space foragers exhibited primarily positive responses to prescribed fire but primarily negative and neutral responses to wildfire. Differences in responses to prescribed fire and wildfire are likely due to differences in severity and extent of the two types of fires. These results suggest that we cannot rely on studies of prescribed fire to predict the responses of eastern bats to wildfire, especially for closed- and edge-space foragers which are the species that are most imperiled.
Prescribed Fire Effects on Bats and Bat Habitat in the Eastern United States
Roger Perry
Fire is increasingly used by land managers to promote regeneration, improve wildlife habitat, and reduce hazardous fuel loads. Prescribed fire on the landscape affects bats directly through heat and smoke during the burning process or indirectly through modifications in habitat. Herein, I present an overview of the direct and indirect effects of prescribed fire on forest bats. Many bat species benefit from the alterations in habitat resulting from prescribed fires. Studies suggest fire can improve roosting habitat by creating snags. Fire can also improve foraging habitat for some species by reducing midstory clutter, creating more open forests, and increasing abundance of flying insects. Direct effects of fire on bats during burning are less understood, but likely vary based on bat species, roosting guild, fire season, and fire intensity. In general, low-intensity burns during the growing season likely have few negative effects on bats, whereas high-intensity burns may be more problematic. During the dormant season, ambient temperature likely affects the ability of litter-roosting bats to flee during burns. Potential negative effects of burning on bats may be mitigated by modifying burn season, times, intensities, and temperatures during ignition.
Restoring Inland Pitch Pine-Scruboak Barrens Through Fire, Mechanical and Chemical Processes in Amosaic, Semi-Urban Landscape
Tyler Briggs
The Albany Pine Bush Preserve is an inland PPSOB ecosystem that was protected by New York State law in 1988. The 3,300 acre preserve contains one of the best remaining examples of an inland PPSOB and provides habitat for 78 of New York’s 366 wildlife Species of Greatest Conservation Need (SGCN). This includes the federally endangered Karner blue (Plebejus samuelis). The protected lands are not contiguous, and the preserve exists as a mosaic of protected land parcels between the cities of Schenectady and Albany. Geographically, the preserve is divided by highways, developments and businesses, making restoration and maintenance on this fire-adapted ecosystem a challenge. Working with state, private and federal partners the Albany Pine Bush Preserve Commission has employed a variety of strategies to restore fire’s fundamental role in this landscape. Since our wildland fire program began in 1991, more than 2,988 acres of fire-suppressed PPSOB have been treated with prescribed fire. These treatments have improved ecosystem viability and facilitated an increased distribution and abundance of fire-dependent SGCN wildlife, including the recovery of the local Karner blue metapopulation and the return of eastern whip-poor-will. This presentation will examine solutions to the many logistical challenges associated with successfully using fire in a fragmented urban landscape.
What Do We Know About the Effects of Fire and Forest Management on Terrestrial Species in Western Us Forests and Where Do We Go from Here?
Angela White
Dry coniferous forests of the western United States are now experiencing increasing wildfire activity and severity due to both an accumulation of forest fuels and changing climatic conditions. While fire has been the dominant force shaping forest structure and wildlife communities in this region, the size and intensity of recent fires is generally described as outside the historic range of variation, and may have impacts on species that evolved under a different disturbance regime. Previous research has suggested that while species that are flexible in their use of forest structures will likely remain fairly constant, we expect species that are strongly associated with particular habitat features to occur intermittently as forest succession results in different habitat over time. However, research designed to understand the effects of disturbance have focused on a limited number of high-profile species and on particular taxa, primarily birds. With management focused on increasing the pace and scale of restoration efforts, more research is need to “up-scale” our understanding of treatment and wildfire effects on wildlife beyond the limited temporal and spatial scales typically considered. Process-based management designed to re-establish appropriate disturbance regimes may be more sustainable than more conventional management practices.
Multiple Mechanisms Underly the Pyrodiversity-Biodiversity Relationship in California Birds
Morgan W. Tingley; Andrew N. Stillman; Robert L. Wilkerson; Rodney B. Siegel
There is growing evidence supporting the hypothesis that landscapes with greater pyrodiversity support more species diversity. Deriving from the intermediate disturbance hypothesis, the pyrodiversity-biodiversity hypothesis is largely premised on greater fire heterogeneity producing landscapes with mixtures of different successional stages, yielding habitat for a greater number of species in a given area. Working in the montane forests of California and drawing from thousands of avian surveys in areas burned by over 100 distinct fires, we show that bird diversity following fire supports this mechanism of biodiversity generation; pyrodiversity relates positively to bird diversity, and the relationship strengthens over the 10 years following fire. Consequently, landscapes with greater habitat diversity provide the conditions needed by a greater number of bird species. However, pyrodiversity may also benefit individual species in complex ways. Using the case study of a single bird species closely associated with burned forests, we demonstrate how different life stages of this species differentially select low-severity versus high-severity burned patches. Greater aggregations of individuals occur in areas with greater pyrodiversity, where the contrasting needs of multiple life stages can be met in a relatively circumscribed area. Individual species can thus show strong affinities for pyrodiversity, further strengthening the overall pyrodiversity-biodiversity relationship.
California Spotted Owl Responses to Fire in Fire-Restored and Fire-Suppressed Landscapes
Gavin M. Jones; H. A. Kramer; R. J. Gutiérrez; M. Z. Peery
Fire suppression, logging, and climate change have led to changing fire regimes in many ecological systems. In California’s Sierra Nevada, a history of large tree logging and fire suppression on National Forests has contributed to recent large stand-replacing fires on those landscapes. On adjacent National Parks, lack of historical logging and a longer history of fire use as a management tool has contributed to recent fires that are smaller and less severe by comparison; these fires are more characteristic of the broader region’s historical fire regime. We studied California spotted owl (Strix occidentalis occidentalis) habitat selection using mini-GPS tags in burned landscapes across both fire-suppressed National Forests and fire-restored National Parks. Our goals were to (1) understand potential thresholds in owl responses to stand-replacing fire, and (2) infer whether increased prescribed and managed fire use on National Forests could represent a viable management option for increasing forest resilience while maintaining owl populations. We found that owls selected smaller patches and avoided larger patches of severely-burned forest on both ownerships, even though patch sizes were much smaller on National Parks. On National Forests, owls avoided severely-burned areas if their home range experienced >5% severe fire, and also avoided traveling more than 100m into severely-burned forest patches. On National Parks, owls more strongly selected areas that had recently experienced low-severity fire when those areas were more abundant in their home range; the more low-severity fire, the better. Our results suggest that across both fire-suppressed and fire-restored landscapes, spotted owls demonstrate selections patterns that reflect their adaptation to historical frequent-fire regimes. Increased use of prescribed and managed fire, characterized by mosaic fire effects, may benefit spotted owls in fire-suppressed landscapes.
Modeling Wildfire Risk to Northern Goshawk Habitat in Ponderosa Pine and Mixed Conifer Forests In the American Southwest.
Richard T. Reynolds; Douglas A. Boyce; Alan A. Ager; Ken Bunzel
Natural disturbances including wildfire, insects and disease are a growing threat to the remaining old ponderosa pine (Pinus ponderosa) and mixed-conifer forests in the American southwest, USA. These forests provide essential habitat to several uncommon terrestrial and aquatic species including the northern goshawk (Accipiter gentilis atricapillus). Wildfires have reduced the amount of old forests over the past two decades, prompting land managers to expand investments in forest management to slow losses and mitigate wildfire risk. Much of the effort is focused specifically on old forest conditions where important prey species of the northern goshawk reside. In this paper, we demonstrate a probabilstic risk analysis system for quantifying wildfire threats to goshawk habitat and comparing the efficacy of fuel treatment scenarios. We used wildfire simulation methods to calculate spatially explicit probabilities of habitat loss for fuel treatment scenarios on a 1,728 km2 study area in northern Arizona, USA. We simulated 1000 wildfires with randomly located ignitions and weather conditions that replicated a recent large high-severity fire in the study area. A flame length threshold for each goshawk territory (2,800 ac) was determined using the forest vegetation simulator to predict the proportion of fires that resulted in habitat loss. We modeled both low intensity and high intensity wildfire. We report on 1) probability of habitat loss in the study area given 2020 fuel loads, 2) probability of habitat loss for each territory, 3) ranking territories on the risk of habitat loss to fire, and 4) the probability of large-scale habitat loss based on restoration of frequent fire forests that includes the habitats of the goshawk and its prey. The modeling system advances the application of quantitative and probabilistic risk assessment for habitat and species conservation planning.
Bat Community Responses to Fire in Western United States Forests
Rachel Blakey
Wildfires are increasing in incidence and severity across coniferous forests of the western US, leading to changes in forest structure and wildlife habitats. Highly mobile animals like bats respond to extent, configuration and diversity of resources in the landscape at a variety of scales, yet we know little about their landscape-scale relationships with fire, or the traits that underpin these relationships. We investigated drivers of occupancy of a diverse bat community in a fire-altered landscape at multiple spatial scales, while identifying functional traits that underpinned these relationships. Bat richness was positively associated with pyrodiversity, as well as burned and forested edge density, but decreased with vegetation structural diversity. Focal patch types influenced bat richness at different scales; richness was most strongly associated with forested areas at larger scales (6-8 km) and burned areas at finer scales (1-3 km). Relationships between bat traits and fire regime were underpinned by adaptations to diverse forest structure. Bats with traits adapting them to foraging in open habitats, including emitting longer duration and narrow bandwidth calls, were associated with higher severity and more frequent fires, whereas bats with traits consistent with clutter tolerance were negatively associated with fire frequency and burn severity. Predicted increases in fire frequency and severity in western US coniferous forests are likely to shift dominance in the bat community to open-adapted species and those able to exploit post-fire resource pulses (aquatic insects, beetles, snags). Managing for patchy, pyrodiverse landscapes with high edge density is likely to support the greatest number of bat species in a fire-maintained coniferous forest.
Effects of Wildfire and Restoration Activities on Bird and Small Mammal Communities in Western Vegetation Types
Jamie Sanderlin
This synthesis will broadly focus on the effects of wildfire and restoration activities on bird and small mammal communities within western United States vegetation types. At the community scale, there is an assumption that landscape heterogeneity (pyrodiversity) will lead to increased biodiversity. This relationship is nuanced depending on several factors, including historical fire regimes and management activities. To explore these pyrodiversity spatial and temporal themes further, I will build upon existing literature and discuss several collaborative studies across the West, including studies that: 1) evaluate long-term wildfire effects on bird communities; 2) evaluate treatment effects on songbird communities; and 3) evaluate prescribed fire effects on small mammal communities. Metrics of species richness, individual species’ occupancy probabilities, and local extinction and colonization probabilities will be discussed as a function of different metrics leading to landscape heterogeneity (i.e., time since fire, fire severity, scale, vegetation type, management activity). These studies vary geographically, from southeastern Arizona Sky Islands (with vegetation types from pinon-juniper, Madrean oak, pine oak, ponderosa pine, mixed conifer) and northern Arizona (primarily ponderosa pine) to grassland systems in New Mexico. A range of restoration and management activities will be highlighted within these systems, including thinning, prescribed fire, and managed wildfire. Finally, next steps in evaluating these ecological assumptions of landscape heterogeneity to support management activities will be discussed.
Fire and Forest Carnivores in the Western United States – Reconciling the Tradeoff between Optimal and Resilient Habitat
Craig Thompson
The multi-scale relationships between disturbance regimes, landscape pattern, and critical habitat for sensitive wildlife species is often poorly understood. While we may have extensive data on the specific elements species rely on, such as den sites or prey species, we are generally less able to connect the dots between these elements and the ecological processes that create and maintain them over time. Understanding and managing these interactions gets exponentially harder, yet all the more important, as changes in climate alter historic disturbance patterns and transform baseline habitat conditions. The problem is particularly acute when considering our management of forest carnivore habitat in the western United States; the conflict between habitat conservation and fire/fuel management is often viewed as a struggle between ideals rather than an opportunity to integrate multiple goals. I present two examples based on high-profile endangered species, the fisher and Canada lynx, and discuss how considering spatial pattern may offer a path to reconciling this perceived conflict.
Plant-Pollinator Interactions in Changing Landscapes of the Western United States
Lauren Ponisio
Theory predicts that network characteristics may help anticipate how populations and communities respond to extreme climatic events, but local environmental context may also influence responses to extreme events. For example, altered fire regimes in many ecosystems may significantly affect the context for how species and communities respond to changing climate. In this study, I tested whether the responses of a pollinator community to extreme drought were influenced by the surrounding diversity of fire histories (pyrodiversity) which can influence their interaction networks via changing partner availability. I found that at the community-level, pyrodiverse landscapes promote functional complementarity and generalization, but did not consistently enhance functional redundancy or resistance to simulated co-extinction cascades. Pyrodiversity instead supported flexible behaviors that enable populations to resist perturbations. Specifically, pollinators that can shift partners and network niches are better able to take advantage of the heterogeneity generated by pyrodiversity, thereby buffering pollinator populations against changes in plant abundances. These findings suggest that pyrodiversity is unlikely to improve community-level resistance to droughts, but instead promotes population resistance and community functionality. This study provides unique evidence that resistance to extreme climatic events depends on both network properties and historical environmental context.
The Effectof Megafires on Wildlife Communities
Rahel Sollmann; Angela White
Large wildfires have increased in western forests; yet, little is known about how they affect wildlife. We aim to disentangle direct fire effects of from indirect effects, mediated by changes in vegetation, on vertebrate populations. Field work took place in 2017 in the King Fire (CA), which burned 40,000 ha in 2014. We established 27 sampling plots in unburned, mixed severity, and high severity burn areas and sampled vegetation, medium/large mammals, small mammals, birds, and bats. We developed a model jointly describing the effect of fire on the percentage of dead trees, shrub density and percent herbaceous cover, as well as the effect of vegetation variables on each other. We combined the vegetation model with a community Royle-Nichols occupancy model for each vertebrate group, to investigate the effects of fire and vegetation on local abundance of vertebrates. Fire significantly affected all vegetation variables. Fire also directly and significantly affected several vertebrate species; most effects were negative and caused by high-severity fire. Vegetation effects were consistently weak, suggesting that direct effects of high-severity fire outweighed vegetation-mediated effects. Most species appeared largely insensitive to fire effects, likely due to high mobility, community recovery post-fire, and the study excluding some fire-sensitive sparse-data species.
THURSDAY 3:00PM – 4:00PM Panel Discussion

 
Organizers: Brice Hanberry, USDA Forest Service, Rocky Mountain Research Station, Rapid City, SD; Cathryn (Katie) H. Greenberg, USDA Forest Service, Southern Research Station, Asheville, NC; Angela White, USDA Forest Service, Pacific Southwest Research Station, Davis California
 
Supported by: USDA Forest Service Research and Development

Symposium
Location: Virtual Date: September 30, 2020 Time: -