Fire Resilience: Can Fish, Wildlife, and Humans Adapt to Shifts in Wildfire Disturbance? Part II

This symposium will provide a forum for research and management at the nexus of climate, fire disturbance, and biodiversity. The science surrounding wildfire is controversial. Have wildfire regimes changed? Prolonged and widespread high-intensity wildfires have disrupted at least one large geographic region, but is it a worldwide trend? If they have changed, why? Did climate trends play a role, or are changes in land management responsible, or both? If regimes did change, were the effects on fish and wildlife positive or negative? In the short term, wildfires change water and air quality, threaten fish and wildlife, and destroy human lives and infrastructure. Yet long-term consequences may be positive in part because many ecosystems are adapted to historical fire regimes. Occasional fires generate open patches that can be colonized to enhance biodiversity. Similarly, occasional influxes of large woody debris from landslides in burned areas eventually create good habitat for fish in rivers. If future changes are ominous, can humans adapt? Scientists are beginning to investigate how fish, wildlife and human societies adapted to fire in the past and how resilience to fire disturbances might be improved in the future. This symposium’s objective is to explore controversies at the nexus of wildfire, fish and wildlife science and land management. The value of this symposium to attendees is that it will provide the state-of-the-science view of wildfire effects and management.

8:00AM Aquatic Food Web and Community Response to Wildfire in Interior Alaska Boreal Streams.
  Elizabeth Hinkle, Jeffrey Falke
Wildfires are the primary natural disturbance in boreal forest stream ecosystems and fire regimes are expected to continue to change owing to climate warming. Wildfire may stimulate primary production through nutrient input and increased solar exposure and lead to increased community complexity owing to higher food resource availability. As a result, fire may play a key role in determining macroinvertebrate and fish assemblage structure in boreal streams. During summer 2019 we investigated macroinvertebrate and fish community responses to wildfire at a set of fifty spatially-balanced sites in interior Alaska with different times since fire disturbance (recent: 0-10 years, historic: 10-30 years, control: 40+ years). At each site, we measured physical habitat and water chemistry, and quantified macroinvertebrate and fish community structure, food web structure via stable isotope analyses, and fish body size-abundance relationships. We used multivariate statistical analyses to determine the effects of fire on stream physical habitats, community assemblages, and food web complexity. Understanding how mass-abundance relationships and food web structure relate to variables associated with fire disturbance may promote a better understanding of how climate warming and fire interact to impact boreal stream ecosystem food webs and provide insight into community-wide responses to wildfire.
8:20AM Resilience of Linked Stream-Riparian Organisms to High-Severity Wildfire in Idaho’s Salmon River Basin
  Rachel L. Malison, Hannah Harris, Matthew Schenk, Breeanne Jackson, G.W. Minshall, Mazeika SP Sullivan, Colden V. Baxter
Increasing frequency and severity of wildfires is causing concerns about whether or not stream organisms are resilient to wildfire. However, in many cases short-term effects of fire on stream organisms are minimal or recovery occurs rapidly. In fact, numerous indirect, positive effects may benefit linked stream-riparian communities in the mid-term following high-severity wildfire. A combination of long-term and intensive studies in the Frank Church Wilderness of Idaho have revealed that while linked stream-riparian habitats are often dramatically changed, there are positive pulses of productivity that reverberate between water and land. Organisms in some streams rapidly return to pre-fire conditions, invertebrate diversity appears stable or may even increase, prolonged pulses in invertebrate productivity can benefit predatory invertebrates and endangered fish populations as well as downstream resource availability, and fish have exhibited preference for confluences with burned tributaries. This “fire pulse” extends to riparian organisms through increased insect emergence that can fuel greater abundances of birds, spiders, and bats. Responses vary with the degree of fire severity and other coupled disturbances (e.g. debris flows). In such context, allowing high-severity wildfires to burn may contribute to heterogeneity (in space and time) that helps maintain native biodiversity and the function of stream-riparian ecosystems.
8:40AM Population and Individual Responses of Rainbow Trout to Wildfire: An Integrated Analysis of Observation and Models
  Amanda Rosenberger, Jason Dunham, Jason Neuswanger, Steven F. Railsback
Management of aquatic resources in fire-prone areas requires understanding of factors that contribute to fish species’ response to the effects of disturbances. We paired empirical observation with a mechanistic simulation to examine population and individual characteristics of rainbow trout in headwater streams a decade after a major wildfire: three unburned, three burned, and three burned with subsequent, massive channel-reorganizing events. We tested proposed drivers for observed differences among streams in an individual-based model to provide insight into rainbow trout demographic patterns under the thermal regimes characteristic of each disturbance type. Trout were present throughout disturbed streams at densities comparable to unburned streams; however, age structure of populations differed. Rainbow trout in burned streams were faster growing, lower in lipid content, and matured early; these patterns were most dramatic for the warmest streams. Modeling suggested that moderate warming associated with wildfire and channel reorganizing leads to faster individual growth, exacerbating competition for limited food, decreasing overall population densities. Results provide an intuitive mechanistic explanation for the trends we observed in fish growth and density among streams with contrasting disturbance histories, and the inferred mechanisms suggest the transferability of ecological patterns to a variety of temperature disturbance scenarios.
9:00AM Canceled Talk
9:20AM Post-Wildfire Sediment Dynamics and Fish Population Response to Habitat Disturbance
  Brendan Murphy, Patrick Belmont, Phaedra Budy, Jonathan Czuba, Timothy Walsworth
Understanding the response of fish populations after wildfire requires understanding the locations, magnitude, and timing of wildfire impacts to the physical river system. Thus, our ability to predict ecological response after wildfire depends on not only our knowledge of both physical and ecological systems, but also our ability to create and link appropriate models. Ultimately, achieving this goal requires targeted, interdisciplinary approaches in studying post-wildfire effects. Here we present two complimentary models, one physical and the other ecological, that we are integrating into a comprehensive post-wildfire modeling framework. First, we present a new geomorphic model capable of predicting watershed-scale sediment dynamics after wildfire, from the sources of debris flow erosion to the downstream propagation of sedimentation and grain-size changes that may occur for many years after fire. Second, we present a new PVA-style metapopulation model that accommodates migration in potentially fragmented river networks, incorporates the effects of local habitat condition on population demographics, and allows for modeling of spatially-variable and temporally-dynamic landscape disturbances such as wildfire. Finally, we discuss the goals, challenges, and management implications of linking these models to improve predictions of the location, magnitude, and timing of impacts to fish populations after wildfire.
09:40AM Break
1:10PM Winner and Losers: Wildfire Effects and the Ecology of Native Fishes
  Rebecca Flitcroft
Fishes native to the Pacific Northwest are adapted to natural disturbance regimes that create dynamic habitat patterns over space and time. This includes naturally occurring wildfire under historic wildfire return intervals and intensities. A variety of adaptive strategies from movement, shifts in life stage development timelines, and use of alternative habitats allowed many native fishes to thrive under dynamic landscape conditions. Human land use, particularly long-term fire suppression, has altered the intensity and frequency of wildfire in forested upland and riparian areas. Land management has often included the installation of barriers to fish movement and migration, thereby compromising one of the strongest adaptive behaviors of highly migratory fishes. It is possible that for some species, and in some situations, wildfires that are allowed to burn may be a useful habitat restoration tool. However, the effectiveness of wildfire in species-specific habitat restoration outcomes may be complicated by narrow habitat requirements, or the lack of movement options in river networks that have been fragmented due to dams or culverts. Wildfire as a management tool, therefore, must be considered with respect to current species population size, fire intensity predictions throughout river networks, and the broader impact of wildfire on other species.
1:30PM Simulated Effects of Forest Treatments on Salmonids in the Pacific Northwest
  Henriette Jager, Mark Wigmosta, Zhuoran Duan, Rebecca Flitcroft
Fish and wildlife are experiencing shifts in wildfire disturbance regimes across the western landscape. Our research seeks to understand spatial opportunities for applying forest thinning and prescribed burn treatments in ways that will improve ecosystem services derived from forests and the rivers that drain them. We compared forest thinning treatments by evaluating the downstream effects of seasonal changes in timing of snowmelt flows and water temperature (simulated by DHSVM), and the spatial variation in geomorphology (NetMap) across the Wenatchee basin, WA. Because ESA-listed salmonids are highly valued in the Pacific Northwest, we produced a spatially distributed version of the QUANTUS model to simulate incubation and rearing success for juvenile bull trout and spring Chinook salmon in each reach as a function of watershed treatments. For spring Chinook salmon, modest increases in water temperatures associated with thinning improved habitat for incubating and rearing fish. In future, we will evaluate results for resident Bull trout and partition the interacting effects of shifted timing of snowmelt and elevated temperatures. This research will help to understand how forest treatments for wildfire management might help to offset fossil energy sources and reduce GHG emissions under current and future climate conditions.
1:50PM Sensitivity and Resilience of Arid-Land Stream Communities Following Consecutive Years of Mega-Wildfires
  Keith B. Gido, David L. Propst, Skyler Hedden, Tyler J. Pilger, James E. Whitney, Thomas Turner
Arid regions of the American southwest have experienced increasing severity of drought associated with decreased stream discharge and increased frequency and intensity of wildfires. Combined, these factors, particularly ash flows following wildfires, can have devastating effects on warm-water stream fish communities. Long-term data indicated fish species richness and density declined with drought and wildfire, and that native species were more responsive to inter-annual variation in climate than nonnative fishes. The resistance and resilience of fishes to and extreme drought and ash flows following wildfire was highly variable across nine sites and different species. Five years after the disturbance, all but two species had recovered across the intensively sampled sites. The severity of wildfire impacts were generally greater in smaller tributaries at higher elevation, but some of these tributaries remained un-impacted and served as refugia from disturbance. The ability of species to persist in the face of increasing wildfire severity hinges on their ability to establish multiple populations on the landscape and immigrate to disturbed habitats from nearby refuge populations.
2:10PM Fish and Fire: Time for a New Perspective?
  Gordon Reeves
Fire has been assumed to have negative effects on fish and their aquatic ecosystems. One primary reason for this is the perspective that aquatic ecosystems are stable through time, returning to an equilibrium condition shortly after disturbance. However, a dynamic perspective of aquatic ecosystems and has emerged in recent year which view disturbances, such as fire as an integral component of aquatic. Also, several recent studies on the effect of fire on fish and aquatic ecosystems have found that native fish are well adapted to changes resulting from fire, and not necessarily affected negatively. These presents the opportunity to consider adjustments to existing institutional management policies and practices to the extent feasible. It will also require convincing the public and interested parties about the validity of the new perspective and provide them an understanding of the implications to policy and practices. This presentation examines the new perspective and the challenges of incorporating it, or some part of it, into policies, practices, and public perceptions and the consequences of not being able to make these changes.
2:30PM The Influence of Burn Severity and Pyrodiversity on Bat Communities in Sierra Nevada Forests
  Zachary Steel
Wildfire is an important ecological process that influences species occurrence and biodiversity. How fire-induced shifts in habitat influence bat species is understudied, creating challenges for habitat management and bat conservation. To fill this knowledge gap, we conducted acoustic surveys in and around three wildfire areas during 2014-2017 in conifer forests of California’s Sierra Nevada. We tested effects of mean burn severity and its variation or pyrodiversity on bat occupancy and diversity using a hierarchical models that account for imperfect detection. Of the 17 species that occur in the region, occupancy rates increased with severity for at least 7 and with pyrodiversity for 2. Individual species models predicted maximum occupancy rates across the range of burn severity with the exception of unburned areas. Species richness increased with burn severity and pyrodiversity from 8 species in unburned areas to 11 species in pyrodiversity areas with moderate- to high-severity. Positive responses to wildfire may be attributable to increased accessibility of foraging habitats for many species, as well as increased habitat heterogeneity where burn severity is mixed. Bat species appear well adapted to an active fire regime and past densification of forests from fire exclusion likely reduced habitat quality for the community generally.
2:50PM Refreshment Break
3:20PM The Effect of 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.
3:40PM Out of the Sage and into the Fire: Thermal Niches Explain Greater Sage-Grouse Nest Success
  Christopher Anthony, Christian Hagen, Dwayne Elmore, Katie Dugger
Sagebrush (Artemisia spp.) communities have high thermal heterogeneity at fine spatial scales, thereby providing thermal options for Greater Sage-Grouse (Centrocercus urophasianus, hereafter sage-grouse). Thermal refuge might be important for nest site selection and survival as specific microclimates can protect embryos from extreme temperatures and reduce thermal stress of incubating females. At fine spatial scales, thermal environments are influenced by vegetation structure and abiotic factors. Therefore, changes to vegetation structure due to wildfire could influence thermal environments for individuals that nest within the post-fire landscape. Our objective was to describe the thermal environments at unburned (n = 77) and burned nest sites (n = 18) and quantify thermal differences among three spatial scales: nest-bowl, nest microsites (6-m around nest), and the surrounding landscape (n = 34) in the Trout Creek Mountains, Oregon, USA. This region experienced the Holloway wildfire in 2012 that burned ~200,000 ha of sage-grouse habitat. We modeled the thermal environments at each spatial scale based on the relationship between operative and ambient temperature. Thermal variability was lower at nests-bowls compared to nest microsites and the landscape. Nest-bowls moderated temperature more than microsites and the landscape by remaining 5° C warmer when ambient temperature was 0° C and 10° C cooler when ambient temperature was 25° C. Unburned nest-bowls and microsites were less variable than both burned nest-bowls and burned microsites. Yet, even the burned nest-bowls buffered ambient temperature more than burned microsites. Successful nests better moderated thermal conditions during the mid-day hours when ambient temperature was the warmest as compared to unsuccessful nests. Thus, sagebrush communities affected by fire provided thermal options regarding individual nest site selection during the breeding season and sage-grouse appear to be selecting for sites that better moderate the thermal environment. Further, differences in thermal environments are associated with nest success.
4:00PM Responses of American Black Bears to the Chimney Tops Fire in Great Smoky Mountains National Park
  Joseph Clark, Jessica Braunstein, Coy Blair, Lisa Muller
Little is known about how wildfire may affect American black bear (Ursus americanus) movements in the eastern U.S. On November 23, 2016, wildfire was reported in the Chimney Tops region of Great Smoky Mountains National Park near Gatlinburg, Tennessee. On 28 November, strong winds, with gusts up to 87 mph (140 kph) caused the fire to spread rapidly. Multiple wildfires developed and spread to large the city of Gatlinburg with about 72-km2 being burned, including a large area in Great Smoky Mountains National Park. Eight bears within the vicinity of the wildfire were equipped with Global Positioning System (GPS) wildlife tracking collars as part of 2 separate studies prior to the fire event. We evaluated space use, movement rates, and mean direction of travel in a before-after-control-impact design to determine how bears reacted to the fire. We found no differences in spatial use between bears that were exposed to fire (treatment, n=8) and not exposed (control, n=12) and no mortalities of collared bears were documented. Several bears were in the path of the fire but survived. Possible reasons for these results will be discussed.
4:20PM Health Outcomes of Wildfire Smoke Exposure in an Outdoor Colony of Nonhuman Primates
  Lisa Miller
Climate change has contributed to increased incidence of wildfire events due to dry weather in conjunction with overgrowth of vegetation in affected regions. Prescribed burns and wildfires are now recognized as significant sources of air pollution in the United States. Currently there is little known about the long-term respiratory outcomes of wildfire smoke exposure in both human and wildlife populations. To address this gap in knowledge, we have monitored the health status of an outdoor colonyof California National Primate Research Center rhesus monkeys progressively over a 10-year span following exposure to ambient smoke from the Trinity/Humboldt County wildfires in 2008. In adolescence, monkeys that were acutely exposed to wildfire smoke as infants showed innate immune dysregulation in peripheral blood, reduced lung volumes, and lung function deficits. With maturation into adulthood, exposed animals showed similarly altered immune parameters with evidence of lung remodeling. Ongoing studies following the recent Butte County wildfires in 2018 will monitor the health impacts of ambient smoke exposure on a cohort of pregnant and infant rhesus monkeys at the center. Collectively, our findings in an outdoor colony of nonhuman primates suggest that young populations are particularly vulnerable to long-term health outcomes from wildfire smoke.
4:40PM When Wildfires Warrant Interventions for Ecosystem Conservation and Restoration in Western U.S. Montane Ecosystems
  Jonathan Long
I will present a brief overview of some of the more problematic long-term effects of wildfires on both terrestrial and aquatic montane ecosystems in the Western U.S., based upon several research syntheses and targeted field studies. Large high-severity fires have become increasingly common in dry forests of the Pacific West, and they have been accompanied by sharp debates about whether interventions are warranted. Stand-replacing wildfire and post-fire erosion has been found to be particularly important for rejuvenating and reforming habitats, particularly in the northern Rocky Mountains. However, exceptionally large fires in some montane ecosystems in the Southwest have extirpated isolated fish populations and degraded culturally and ecologically important wetland ecosystems, particularly in headwater areas. In some Western terrestrial forests, research has demonstrated the potential for state shifts following wildfires, particularly as lower-elevation forest vegetation, such as ponderosa pine, is supplanted by persistent shrubfields. Key ecosystem services afforded by mature trees may also diminish, for example, when fires consume mature black oaks that produce acorns and provide cavities for wildlife. In these contexts, active interventions following wildfires, in addition to proactive restoration measures, are important to conserve ecosystems.
5:00PM Understanding the Effects of High Severity Fire on Meadow Restoration Efforts
  Angela White, Gina Tarbill, Rahel Sollmann
Whereas large, high-severity fire has been identified as one of the biggest threats to forest health and persistence due to large scale tree mortality, these fires may help to reset meadows in areas on the landscape where meadow systems have succeeded to conifer forest. Mountain meadows cover only 2% of the Sierra Nevada and Cascade ranges, yet their unique ecological functions make them critical to overall watershed health. Functional meadows filter, store, and release water downstream well after snowmelt, attenuate floods, store vast amounts of carbon in their soils, and provide critical habitat for plant and wildlife communities. Climatic warming and changes to the fire regime from fire suppression and grazing have degraded meadows and facilitated conifer encroachment. Once invaded, positive feedbacks between conifers and soil can reinforce the process of encroachment, ultimately impacting soil biogeochemistry, water and carbon storage, and biodiversity. Approximately half of the meadow systems in the Sierra Nevada are degraded and experiencing widespread conifer encroachment, thus meadow restoration has become a critical management issue. Using a combination of datasets we describe the variability in meadow systems and quantify how fires alter their community composition and function.

Organizers: Mark D. Bowen, Ph.D., Henriette Jager, Luiz Silva, Serra Hoagland, Ph.D., Tracy Melvin, Jeff Thomas

Location: Reno-Sparks CC Date: October 1, 2019 Time: 8:00 am - 5:20 pm