Wildfire and Prescribed Fire Effects on Biodiversity in US Forests: 2021

Symposium

Organizers: Angela White, USDA Forest Service; Brice Hanberry, USDA Forest Service; Cathryn Greenberg, USDA Forest Service, Southern Research Station

Supported by:
USDA Forest Service Research and Development

Due to great interest, we are continuing to explore fire effects on wildlife and biodiversity for 2021 to extend the symposium from 2020 with a new roster of presentations. Many vertebrate, invertebrate, and plant species in the United States 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 through removal of 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. Species responses to post-fire forest conditions vary. Some species require fire-maintained habitats, many are generalists that use a wide range of conditions, and others are adversely affected by fire. Differences in responses to fire and fire severity among diverse 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 species. This symposium will include presentations that describe wildfire and prescribed fire effects on various 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.

 
Pyrodiversity and biodiversity: state of the science and research needs
Gavin Jones, Morgan Tingley
Pyrodiversity is the spatial or temporal variability in fire effects across a landscape. Multiple ecological hypotheses, when applied to the context of post-fire systems, suggest that high pyrodiversity will lead to high biodiversity. This resultant “pyrodiversity–biodiversity” hypothesis has grown popular but has received mixed support by recent empirical research. We performed a systematic literature review of research related to pyrodiversity and the pyrodiversity–biodiversity hypothesis and also examined how two individual species with distinct relationships with fire (spotted owl Strix occidentalis and black-backed woodpecker Picoides arcticus) respond to pyrodiversity as case studies to illustrate underlying mechanisms. We identified 41 tests of the pyrodiversity–biodiversity hypothesis reported from 33 studies; 18 (44%) presented evidence in support of the pyrodiversity–biodiversity hypothesis, while 23 (56%) did not. Support for the pyrodiversity–biodiversity hypothesis varies considerably with no consistent patterns across taxonomic groups and ecosystem types. Studies examining the pyrodiversity–biodiversity hypothesis often define pyrodiversity in different ways, examine effects at different scales and are conducted in ecosystems with different natural fire regimes, baseline levels of biodiversity, and evolutionary histories. We suggest these factors independently and jointly have led to widely varying support for the pyrodiversity–biodiversity hypothesis. Clarifying the pyrodiversity–biodiversity hypothesis will be facilitated by stronger development of the different potential mechanisms underlying pyrodiversity–biodiversity relationships, which can be aided by examining how individual species respond to pyrodiversity. Future research would benefit from a closer examination of the role of scale (e.g. scale dependence) in pyrodiversity–biodiversity relationships, standardization of pyrodiversity metrics, broad-scale mapping of pyrodiversity, and macroecological study of pyrodiversity–biodiversity relationships.
 
Multi-species connectivity response to landscape management and climate scenarios in the Sierra Nevada Mountains
Katherine Zeller, Angela White, Pat Manley, Nicholas Povack
Restoring forest health and fire resilience are high priorities for forest managers. However, there are many uncertainties regarding the effectiveness of forest management strategies in the face of various stressors like disturbance and climate change. In an attempt to reduce this uncertainty, vegetative change in the Tahoe Central Sierra Mountains has been modeled using Landis II, a spatially-explicit disturbance-succession model over a 100-year time period. Different management strategy scenarios (area treated and frequency of treatment) and disturbances (fire and insect-caused tree mortality) were modeled under a climate pathway of RCP 8.5. We evaluated how a suite of terrestrial wildlife species respond to this landscape under different management strategies, both in terms of habitat suitability and connectivity. We estimated changes to the amount and distribution of habitat and connectivity for each focal species. We then combined results across species to, 1) determine changes in species richness and multispecies connectivity, and 2) identify areas of refugia for habitat and connectivity under different management scenarios and through time. These results will reduce some of the uncertainty around forest management decisions by informing how different management scenarios might affect biodiversity in the study area under a changing climate.
 
Contrasting bird diversity in burned versus beetle-killed forests: the role of disturbance agent in structuring communities
Rodney Siegel, Morgan Tingley, Flavia Montaño-Centellas, Andrew Stillman, Robert Wilkerson, Sarah Sawyer
In forests of western North America, both wildfire and insect outbreaks cause widespread disturbance that results in expansive patches of dead trees or snags. In some regions, such as the Sierra Nevada of California, outbreaks of bark beetles resulting in large-scale tree mortality are a relatively new phenomenon, leading managers to question the ecological and conservation value of large areas of beetle-killed forests vis-a-vis fire-killed forest. Using data from 2,157 bird surveys across recent post-fire and beetle-killed forest stands throughout the Sierra Nevada in 2016–2018, we compared bird community diversity, structure, and function in California forests disturbed by different agents. A multi-species community occupancy model demonstrated that birds responded positively to snag availability in both burned- and beetle-killed forests, but that the average bird species had significantly lower occurrence probabilities at points within beetle-killed forest than fire-killed forests. Beetle-killed forests were nevertheless estimated to have slightly but significantly higher species richness per survey point than burned forests. Complementary analyses of phylogenetic and functional diversity indicated that this disparity comes from burned forests hosting a subset of species that strongly respond to post-fire habitats, while beetle-killed forests benefit from a phylogenetically broader set of relatively rare yet generalist species. Overall, the results suggest that ‘snag forests’ are not monolithic, and that disturbance agent plays a potentially large role in post-disturbance biodiversity. The tighter community structure that clearly delineates a “post-fire” community may be the result of a long evolutionary history between birds and fire in western North America.
 
Incorporating pyrodiversity into wildlife habitat assessments for post-fire management: lessons from the black-backed woodpecker
Andrew Stillman, Robert Wilkerson, Danielle Kaschube, Rodney Siegel, Sarah Sawyer, Morgan Tingley
Pyrodiversity – variation in fire regime characteristics – plays an important role in structuring wildlife communities after fire, yet there is a need to better incorporate pyrodiversity into predictive models of animal distributions and abundance. For species that are heavily influenced by post-fire management, such as the black-backed woodpecker (Picoides arcticus) in the western U.S., these models often must be implemented rapidly to guide time-sensitive decisions about where and how to manage burned areas. Black-backed woodpeckers are highly associated with post-fire forests, and emerging evidence on the importance of pyrodiversity (e.g., spatial variation in burn severity) for this species highlights the need for updated management approaches. Here, we present a case study of how we are using this knowledge to reformulate an existing decision-support tool to aid post-fire management. Using a long-term dataset of yearly state-wide occupancy surveys, we show that black-backed woodpecker occupancy responds positively to increased pyrodiversity. In addition, we found that the relationship between occupancy and high burn severity changes over time, with strong positive effects shortly after fire diminishing to largely neutral effects by ten years after fire. We incorporated these relationships into an integrated space-use and occupancy model that can be used to predict black-backed woodpecker density and abundance rapidly after fire – without requiring lengthy on-the-ground surveys. To make this decision-support tool more available to managers, we built an online application to run this modified model using a point-and-click interface to produce results within minutes. Ongoing work will test and validate the decision-support tool using independent survey data.
 
Comparing disturbance effects in a disturbance-starved system: bird community responses to fire and forest management in the Sierra Nevada
L. Jay Roberts
In the Sierra Nevada, fire suppression and extensive logging over the past century have dramatically altered the structure and composition of forests. In this region, where plants and wildlife are highly adapted to a frequent-fire disturbance regime, fires set in motion important ecological processes that last for decades. The deficit of these natural disturbances has had profound effects on wildlife communities. While mechanical timber harvesting and fuels treatments can also impact habitat, it is unclear how important the differences in post-disturbance habitats are between fires and these other disturbances, and which bird species are dependent on, or averse to, each disturbance type. We sought to understand how the avian community (71 species) responded to low-severity fire ( 25% canopy cover loss), and mechanical forest treatments across a 20-year post-disturbance period. We found that moderate- to high-severity fire resulted in the highest bird diversity, and that this group of species was unique compared to the species assemblages that were typical of other habitats. In fact, the most unique species assemblage was found in moderate- to high-severity fire 13-19 years following disturbance, indicating that the importance of post-fire habitat lasts for two decades or more. Relatively small proportions (8-16%) of the bird species analyzed reached their highest abundances in undisturbed forest, low-severity fire, or mechanically treated forest, while 48% of species had their highest abundances following moderate-high-severity fires. Thus, moderate- to high-severity fire is an irreplaceable component of the disturbance regime in the fire-starved Sierra Nevada. Restoring forests that are resilient to future ecological stressors will depend on embracing a prescribed and managed wildfire program that incorporates a variety of fire severities to best maintain biodiversity in this region. 
 
Effects of fire on birds at Yosemite and Sequoia & Kings Canyon National Parks: a multi-decade perspective
Rodney Siegel, Robert Wilkerson, Chris Ray, Sylvia Haultain, Sarah Stock, Morgan Tingley
Fire management – including fuel reduction, prescribed fire, managed wildfire, and the decision not to actively manage some wildfire – represents the most powerful set of tools available to land managers for maintaining ecosystem function and biodiversity in fire-prone ecosystems like the Sierra Nevada mountains of California. Using these tools effectively for biodiversity conservation requires understanding how the changing fire regime affects wildlife species, and data from national parks can be particularly useful because of the absence of potentially confounding effects of timber harvest. We used Bayesian hierarchical N-mixture models to analyze avian point count data collected between 1998 and 2019 at >6,000 unique point count stations at Yosemite and Sequoia & Kings Canyon National Parks, in conjunction with fire regime data that summarize ~100 years of fire history in the parks. We modeled the response of dozens of bird species to fire, assessing fire regime variables including time since fire, number of fires during the period assessed, and severity of the most recent fire, while accounting for non-fire covariates including elevation, canopy cover, and canopy height. We also incorporated interval and distance sampling to estimate distinct components of detection probability. Our analysis assessed effects of fire on bird populations in the immediate post-fire period, and also over longer time frames commensurate with the duration of successional processes. We use our model outputs to identify bird species likely to benefit or suffer from fire exclusion, prescribed fire, and unmanaged wildfire across a variety of forest conditions and time scales.
 
Edge-effects on small mammal communities following high severity fire
Angela White, Kate Faber
Fire shapes habitat composition, structure, and distribution in the seasonally dry forests of the western US. Over the past century, a variety of environmental stressors, combined with the effects of past and current management activities, have led to an increase in the size and severity of wildfires. These fires raise concerns regarding large-scale change from forests to shrublands within increasing distances to seed sources limiting the potential for conifer regeneration. However, small mammals also mediate the structure of forest vegetation through seed predation and dispersal. Using capture-recapture data collected on the small mammal community in the central Sierra Nevada, we present data on the impact of fire severity and distance to live forest on the small mammal community over time. Our data is consistent with other studies on the impact of fire severity on small mammal communities and discuss how species-specific edge effects may influence the potential for natural regeneration.
 
Understanding the Impacts of Wildfire on Bats
Theodore Weller
The size and frequency of high intensity wildfires is increasing across western North America and other dry forests of the world.  Cumulative impacts of wildfire on the landscape are expected to precipitate changes in many species of wildlife. But how will these changes impact highly-mobile species, such as bats?  Most bat species in North America are associated with forests because they provide roosting, foraging, and drinking habitat in close proximity. Bat activity levels generally increase as tree densities decrease and openings form within forested habitats.  Accordingly, studies to date have used site occupancy metrics to demonstrate limited impacts of wildfire on bat communities. However, details of how bats use burned areas of various intensities remain unclear and we have little understanding of how use may change over time. Radio-telemetry studies have shown that bats in unburned forests select dead and deformed trees with large diameters in stands with open canopy and high snag density.  Fires can provide some of these same characteristics but the extent to which bats use burned areas to meet their roosting needs remains unclear.  High intensity fires also reset succession of vegetation and insect communities. Bats are known to exploit emergences of insects in other contexts, but the study of insect succession following fire is nascent and information on bat foraging and diet within burned areas, and how that may change over time, is lacking.  I advocate for a two-pronged approach to understanding relationships between wildfire and bats: a broad-scale site-occupancy approach to understand how cumulative impacts influence bat population status over large spatial scales, coupled with a nested set of intensive studies to determine how individual bats use burned forests of various intensities. The former will help evaluate conservation concerns while the latter can help guide post-fire restoration efforts.
 
Fishers, fire, and forests in western states: what we know and what we need to know
Rebecca Green, Eric McGregor, Kate Faber, Craig Thompson, Jody Tucker, Angela White
Recent wildfires in the western United States have highlighted the need to revisit the complicated relationship between forest dependent wildlife and fire in a landscape that has experienced significant change over the last century.  The fisher (Pekania pennanti) is a mesocarnivore of conservation concern in this region that is closely associated with characteristics of forests that take time to develop and thus time to replace – especially patches of forest with large decadent trees and dense canopy cover.  While fishers historically occurred within a landscape where “natural fire” was more common and played an important ecological role, the increasing size and intensity of recent wildfires are exceeding the natural range of variation in western forests and becoming more destructive in their influence on older forest and associated wildlife.  Risk of extreme habitat alteration or loss are especially concerning for the isolated population of fisher in the southern Sierra Nevada where drought and tree mortality have also dramatically altered the forested landscape.  We explore this complex topic in three steps: 1) review available information on the relationship between fisher ecology, fisher habitat, and fire, 2) identify key positive associations of fishers, forests, and fire, and 3) describe the extent of recent wildfires within areas known to be occupied by fishers (pre-fire) and predicted habitat in the southern Sierra Nevada.  We conclude with a summary of what we understand about the relationship between fishers, fire and forest habitat in western states and what we still need to learn to better inform forest management in this region.
 
Post-fire diversity of plant-pollinator communities of the Sierra Nevada
Gina Tarbill, Rahel Sollmann, Angela White
Understanding how deviations from natural disturbance regimes affect biodiversity is a key challenge in the Anthropocene. One such deviation is the shift of forests in Mediterranean climates from the historic frequent, low-moderate severity fire regime to the contemporary infrequent, high-severity regime attributed to climate change and fire suppression. Although low-moderate severity fire tends to create fine-grained habitat mosaics with higher biodiversity, high severity fire tends to be temporally and spatially homogenizing with lower biodiversity. We aimed to investigate how burn severity affects biodiversity of plant-pollinator communities in green, low-to-moderate, and high severity upland habitat and green and burned meadow habitat in and around the King Fire of the Sierra Nevada. We calculated Hill’s diversity profiles using species richness, relative abundance, sensitivity to rare species and taxonomic similarity to compare diversity of flowering plants and pollinators across burn-habitat treatments. We used a metacommunity approach to describe spatial patterns of alpha, beta, and gamma diversity of burn-habitat treatments. 
 
A primer on fire ecology for wildlife biology
Brice Hanberry
Surface fire was an integral part of many ecosystems in the United States, but fire has been excluded during the past century, resulting in new baselines in both ecosystems and ecology and an information deficit. Here, I provide a short introduction about fire ecology, including fire history specific to wildlife biology, with examples of the power of fire to structure ecosystems and support wildlife in North America. Surface fire is an understory disturbance that reduces small diameter tree densities and maintains grasslands, shrublands, and open forests of savannas and woodlands with an herbaceous or shrubland component. Historical forests predominantly were open forests, whereas early successional forests covered a small percentage 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. Fire exclusion results from a combination of management and land cover changes. Learning to coexist with fire is one of the challenges of our time.
 
A happy habitat-medium: The broad benefits of restoring fire-dependent forest structure for Eastern U.S. Biodiversity
David Buehler, Craig Harper, Emma Willcox, Andrew Vander Yacht, Patrick Keyser, Charles Kwit, Michael Stambaugh, Wayne Clatterbuck
Disturbance increases landscape-scale biodiversity by inserting components that may not otherwise regionally occur. In contrast, site-specific effects are often neutral as suites of species simply shift to a new suite following disturbance. Meeting landscape-level biodiversity goals then requires selecting site-specific “winners” and “losers” across present biodiversity. However, fire historically maintained intermediate woodland and savanna communities throughout the oak (Quercus spp.) and pine (Pinus spp.) dominated portions of the Southern Appalachian and Central Hardwood regions of the Eastern US (hereafter, Mid-South). Effectively restoring these transitional communities may present a rare “win-win” for regional and site-specific biodiversity. We explored this by monitoring herbaceous layer, woody plant, bird, and bat response to replicated fire-season (October or March) and thinning-level (none, 7, or 14 m2 ha-1) treatments at 3 sites throughout the Mid-South from 2008 to 2016. Thinning immediately restored woodland and savanna overstory properties; fire alone had little effect. Increased light and reduced leaf-litter facilitated 14-, 50-, 9-, and 10- fold increases in graminoid cover, forb cover, herbaceous richness, and herbaceous diversity, respectively, and only 6% (23/359) of species responded negatively to applied disturbances. Repeated fire facilitated, and persistent red maple (Acer rubrum) resprouting precluded, even greater herbaceous response. Thinning and burning also promoted formerly suppressed shade-intolerant and fire-tolerant woody species. These changes only negatively affected 3 of 41 monitored bird species; all others, including 13 in regional and 2 in national decline, increased as overstory density decreased and herbaceous cover increased. Thinning and fire also increased activity of large-bodied bats and had no effects on smaller-bodied species. Intermediate savanna and woodland conditions maximized bird and bat species diversity without strong negative effects on any one species. Similar trends occurred for plant species, suggesting woodland and savanna restoration via thinning and fire as an effective way to broadly increase site-specific biodiversity.
 
Breeding Bird Response to Burn Severity in the Southern Appalachians
Cathryn Greenberg, Christopher Moorman, Katherine Martin, Katherine Elliott, Mark Hopey
Populations of many disturbance-dependent breeding bird species are in decline, in part because availability of both open woodland and young forest conditions has decreased. Unprecedented wildfires throughout the southern Appalachians during fall, 2016 provided a unique opportunity to study breeding bird response across a range of fire severities in upland hardwood forest.  We measured forest structure and conducted point counts for breeding birds across a fire-severity gradient in 3 burned watersheds and in 3 unburned control watersheds, 2016-2021. Fire severity was ranked based on tree mortality, basal area loss, char height, leaf litter depth, and exposed soil. Preliminary data showed that bird species richness and abundance was greatest in areas burned with medium to high fire-severity, largely due to an influx  of disturbance-dependent species such as indigo bunting and eastern towhee and little response by several species typically associated with mature forest. This research has important, applied implications for breeding bird conservation and forest management, especially with predicted increases in high severity fire linked to climate change.
 
Interaction between wildfire and sea-level rise effects occupancy of bird communities in coastal forest systems
Paul Taillie
In recent decades, wildfire and prescribed fire have re-emerged as critical components of forest management in North America following a century of widespread fire suppression, largely motivated by the increasing evidence that fire is critical to maintaining biodiversity in fire-dependent systems. Less well understood, however, are the effects of fire in coastal wetlands, particularly as these systems are increasingly vulnerable to rising sea level. To begin to understand how fire and rising sea level interact to modify forest structure and the resulting implications for wildlife, we conducted multiple related observational studies in eastern North Carolina following a severe and persistent drought in 2011, which contributed to both widespread saltwater intrusion and one of the largest wildfires the region has experienced in recent decades. We used a combination of field measurements and remote sensing to quantify and map the changes in forest structure resulting from these disturbances. We also surveyed birds using point counts as part of 2 independent studies, one focused primarily on forest birds and the other focusing on marsh-associated birds. Our results suggested that salinization drove the transition from forest to marsh, and that this transition was catalyzed by fire. Bird communities in severely disturbed (by fire, salt, or both) were similarly diverse when compared to those occurring in intact forests. Furthermore, these disturbed areas supported a number of species of conservation concern, such as birds associated with early-seral conditions and coastal marshes. Given the likely trajectory of the global climate and sea level, our results suggest that facilitating the forest-to-marsh transition, potentially using prescribed fire, in areas vulnerable to rising sea level may effectively complement conserving forested wetlands in less-vulnerable areas toward to the broader goal of conserving biodiversity at regional scales.
 
Snag suitability for bat roosts varies with burn history, forest type, and slope position in the Southern Appalachian Mountains
Joy O’Keefe, Susan Loeb
Snags are significant resources, particularly for crevice-dwelling bats. Pine snags are particularly important roosts for endangered Indiana bats (Myotis sodalis) in the southern Appalachian Mountains. Prescribed fire is used for maintenance and restoration of pine-oak forests in this region, but we do not know how it affects snag abundance and condition and, therefore, availability of bat habitat. Our objective was to measure snag abundance and condition in relation to landscape position and prescribed fire history. We worked in the Cherokee and Nantahala National Forests and Great Smoky Mountains National Park. In each area, we established two 100 m X 40 m belt transects in stands with a mature pine component on upper, middle, or lower slopes that had been burned twice, once, or not at all in the past 10 years (54 transects). For each snag >18.4 cm-DBH encountered, we recorded taxon, height, DBH, and decay measures. We also tallied species and DBH class for live trees. Most snags encountered were yellow pines (43%) or white pines (17%); hardwoods (27%) and hemlocks (13%) were also present. Slope class affected overall snag abundance, with more snags on upper slopes (18.0 ± 3.0 snags) versus middle (14.5 ± 3.0 snags) and lower (12.9 ± 2.9 snags) slopes. However, yellow pine snags were more common on upper and middle slopes and hemlock snags more common on lower transects. White pine snags were more abundant in twice-burned transects, but fire frequency was not a strong predictor of abundance for other snag types. Most yellow pine snags were in late stages of decay and decay stage did not vary with fire frequency. Frequent prescribed fire may increase the abundance of white pine snags, but landscape position was a better predictor of yellow pine snag abundance. Future work should also consider fire timing and intensity.
 
Short-Term Responses of Terrestrial Salamanders to the Restoration of Fire to the Southern Appalachian Mountains
John Maerz, Lauren Head, Meghan Bierden, Cynthia Carter, Brian Crawford
Fire is an important natural disturbance that can shape plant and associated animal communities. After a long history of fire suppression in the U.S., there is increasing use of prescribed fire to manage southern Appalachian forests. Southern Appalachia is an area of global importance for salamanders, particularly within the family Plethodontidae, and there is interest in understanding whether and how fire may affect salamander populations. Using a paired watershed manipulation over four years, we monitored salamander microhabitat use and age-specific abundance before and after a sequence of two prescribed burns within the Coweeta Hydrologic Laboratory in Macon County, North Carolina. As expected, fire reduced shrub cover and increased the amount of bare ground compared to the reference watershed. We estimated a relatively small decline in abundance of all age classes following the first burn. We are currently estimating abundance changes following the second burn. Following burns, we observed a significant reduction in salamander surface activity and greater nighttime use of burrows compared to salamanders in the reference watershed. However, salamander surface activity appeared to return to pre-burn levels the year following a burn. Early results suggest prescribed fire has limited direct impacts on salamander abundance; however, effects on behavior may indirectly influence abundance through more chronic effects on fitness, depending on fire frequency. Evolutionary impacts on salamander phenotypes will also be discussed.
 
How woody vegetation structure affects landscape conservation value for a temperate butterfly community
Ralph Grundel
Temperate savannas and grasslands are globally threatened. Therefore, restoration of habitats of low and intermediate canopy cover is a landscape conservation priority that often emphasizes returning tree density to a savanna-like target value by cutting and burning. Understanding how animal species react to such changes in vegetation structure is important for assessing the value of that restoration trajectory. We examined how butterfly community attributes in northwest Indiana, including community composition, richness, and abundance responded to a grassland-to-forest canopy cover gradient. Butterfly community composition under intermediate canopy cover differed significantly from community composition in the most open or closed-canopy habitats. Composition of the plant community in flower was a significant predictor of three assessed attributes of the butterfly community—composition, richness, and abundance. Few butterfly species were habitat specialists as adults although canopy cover was a more important predictor of adult community composition than of richness or abundance of butterflies. Therefore, adult butterfly community differences along the canopy cover gradient were less about butterfly communities filled with habitat specialists for different canopy-defined habitats than about gradual changes in community composition along this gradient. Overall, butterfly community richness was predicted to peak at about 34% canopy cover, butterfly abundance at about 53% canopy cover, community conservation value at about 59% canopy cover, and a combination of desirable conservation attributes–high diversity, high abundance, and high conservation value–was predicted to reach a peak of co-occurrence at about 67% canopy cover suggesting that habitats of intermediate canopy cover might be particularly effective for butterfly conservation in this region.
 
Macroarthropod response to time-since-fire in the longleaf pine ecosystem.
Christopher Moorman, M. Colter Chitwood, Marcus Lashley, Clyde Sorenson, Christopher DePerno
Prescribed fire is used to restore and maintain fire-dependent ecosystems. However, fire could alter the abundance and persistence of some arthropods, in turn influencing vertebrate taxa that depend on those arthropods as a food source. We used replicated prescribed fire treatments to evaluate macroarthropod response to time-since-fire in the fire-maintained longleaf pine (Pinus palustris) ecosystem. We sampled macroarthropod assemblages using vinyl gutter pitfall traps for 5 consecutive days in each month of the study (May-August 2014) in each replicate burn block. We identified macroarthropods to Order and dried and weighed the samples to determine biomass (g) of all taxa detected. We focused our analyses on 4 macroarthropod taxa important as food for wild turkey (Meleagris gallopavo): Araneae, Coleoptera, Hymenoptera, and Orthoptera. We used standard least squares regression to evaluate the effect of time-since-fire on total biomass of the 4 Orders (and we also evaluated those Orders independently). The analysis indicated that time-since-fire had no effect (p = 0.2616) on combined biomass of these 4 taxa. Analyzing the 4 Orders separately, biomass of Araneae (p = 0.0057) and Orthoptera (p = 0.0004) showed significant effects of time-since-fire, whereas Coleoptera (p = 0.9465) and Hymenoptera (p = 0.1175) did not. Parameter estimates (Araneae = 0.0084; SE = 0.0029; Orthoptera = 0.0137; SE = 0.0036) indicated that greater time-since-fire resulted in greater biomass for those 2 Orders. Overall, time-since-fire did not appear to have substantial effects on macroarthropod biomass. However, responses by Araneae and Orthoptera provided evidence that longer time-since-fire may result in the greatest levels of biomass for some taxa. Our results indicate the use of frequent prescribed fire to restore and maintain longleaf forests is unlikely to pose risks to overall macroarthropod biomass, particularly if heterogeneity in fire frequency and spatial extent occurs on the landscape.
 
Fire-driven seed rain
Marcus Lashley, Kevin Robertson, David Mason
Fire produces a resource pulse for which many wildlife species resource track (i.e., magnet effect). More than 50% of plants rely at least in part on wildlife to disperse seeds and many of the wildlife species which are attracted to recently burned areas also participate in a diffuse mutualism as a disperser of those plants. Taken together, we hypothesized that fire may indirectly affect plant communities through the magnet effect on birds by elevating local seed rain of plants participating in the diffuse mutualism. In a paired crossover experimental design, we established three modified perches equipped with camera and seed traps in each of seven paired areas burned in the current or previous season. We continuously monitored bird use of the perches and seed rain for a full year. In the second year, treatments were crossed such that each perch received the opposite treatment from the year prior. Here we report the first year of data. Use of perches by frugivorous birds increased by 88% in areas burned during the same year relative to areas burned the year prior. Likewise, seed rain increased by 52% in burned areas including nearly 40 plant species dispersed by those birds. We are continuing to monitor bird use and seed rain to determine if patterns in each follow the treatment and additional experiments are underway to determine the degree to which elevated seed rain affects plant communities following fire. However, our initial results indicate that part of the effects of fire on plant communities may be related to the magnet effect being transmitted through birds to affect the dispersal of plants.   
 
Conserving a Threatened Species in Southwestern Forests Using Tribal Forestry
Serra Hoagland
Large, high-severity wildfire is the primary threat to nesting and roosting habitat of the Mexican spotted owl, a threatened species that occupies forests throughout the southwestern region of the US. Recent efforts focus on forest restoration practices to reduce the risk of stand-replacing fire yet the impacts of forest thinning and fuel reduction projects on the habitat needs of the owl is largely unknown. This presentation will focus on the long-term spotted owl research with the Mescalero Apache tribe in New Mexico. As a federally recognized sovereign nation, the Mescalero Apache sustainably manages nearly 500,000 acres of dry-mixed conifer forests and utilizes innovative forest management practices to protect the species while also balancing the risk of fire to their community.

Symposium
Location: Virtual Date: November 4, 2021 Time: 4:00 pm - 5:00 pm