Scott L. Stephens’s research while affiliated with University of California, Berkeley and other places

The national Fire and Fire Surrogate (FFS) study was initiated more than two decades ago with the goal of evaluating the ecological impacts of mechanical treatments and prescribed fire in different ecosystems across the United States. Since then, 4 of the original 12 sites remain active in managing and monitoring the original FFS study which provides a unique opportunity to look at the long‐term effects of these treatments in different regions. These sites include California (Blodgett Forest Research Station), Montana (Lubrecht Experimental Forest), North Carolina (Green River Game Land), and Ohio (Ohio Hills). Although regions differed in ecosystem type (e.g., conifer‐ vs. hardwood‐dominated), the overall goals of the FFS study were to promote desirable, fire‐adapted species, reduce fire hazard, and improve understory diversity. Our study uses multivariate techniques to compare how these desired outcomes were maintained over the last 20 years and discusses whether we would modify the original treatments given what we know now. Our findings indicate that mechanical treatments and prescribed fire can promote desired tree species, mitigate potential fire behavior by reducing fuels and retaining larger‐sized trees, decrease tree mortality, and stimulate regeneration—effects that are still apparent even after 20 years. However, we also found that maintaining desired outcomes was regionally specific with western sites (California and Montana) showing more desirable characteristics under mechanical treatments, while the eastern sites (North Carolina and Ohio) showed more desirable characteristics after prescribed burning. The beneficial effects of treatment were also more apparent in the long term when sites followed up with repeated treatments, which can be adapted to meet new objectives and conditions. These findings highlight the FFS study as an invaluable resource for research and provide evidence for meeting long‐term restoration goals if treatments can be adapted to ecosystem type, be maintained by repeated treatments, and accommodate new goals by adapting treatments to changing conditions.

Fire exclusion over the last two centuries has driven a significant fire deficit in the forests of western North America, leading to widespread changes in the composition and structure of these historically fire‐adapted ecosystems. Fuel treatments have been increasingly applied over the last few decades to mitigate fire hazard, yet it is unclear whether these fuel‐focused treatments restore the fire‐adapted conditions and species that will allow forests to persist into the future. A vital prerequisite of restoring fire‐adaptedness is ongoing establishment of fire‐tolerant tree species, and both the type and reoccurrence of fuel treatments are likely to strongly influence stand trajectories. Here, we leveraged a long‐term study of repeated fuel treatments in a Sierra Nevada mixed‐conifer forest to examine the regeneration response of six native tree species to the repeated application of common fuel treatments: prescribed fire, mechanical, mechanical plus fire, and untreated controls. Our objectives were to (1) quantify differences in forest structure and composition following the repeated application of alternative fuel treatments that may influence the establishment environment and then (2) identify the stand structure and climate conditions influencing seedling dynamics. We found that both treatment type and intensity are highly influential in shifting forests toward more fire‐adapted conditions and determining species‐specific regeneration dynamics. Specifically, the conifer species tracked here increased in either colonization or persistence potential following repeated applications of fire, indicating fire may be most effective for restoring regeneration conditions broadly across species. Fire alone, however, was not enough to promote fire‐adapted composition, with concurrent mechanical treatments creating more favorable conditions for promoting colonization and increasing abundances of fire‐tolerant ponderosa pine. Yet, even with repeated fuel treatment application, establishment of fire‐intolerant species far exceeded that of fire‐tolerant species over this 20‐year study period. Moreover, increasing growing season water stress negatively impacted seedling dynamics across all species regardless of treatment type and intensity, an important consideration for ongoing management under heightened climatic stress. While repeated treatments are waypoints in restoring fire‐adapted conditions, more intense treatments via gap‐creation or hotter prescribed fires targeting removal of fire‐intolerant species will be necessary to sustain recruitment of fire‐tolerant species.

Background Fire suppression, timber harvesting, and the forced removal of Indigenous burning have fundamentally changed conditions in coast redwood forests. The contemporary approach of forest preservation and fire exclusion has produced high densities of small trees, elevated fuel loads, and increased vulnerability to wildfire and climate change. Prescribed broadcast burning presents a viable treatment option to meet forest management goals, especially where mechanical treatments are not feasible. Forest and fire managers utilizing fire modeling software such as the Fire and Fuels Extension of Forest Vegetation Simulator (FFE) to predict prescribed fire effects in redwoods are limited by model accuracy due to a lack of empirical research and model verification across a breadth of site conditions. Results We compared the difference between pre- and post-treatment conditions for two fall-season prescribed burns in Sonoma and Santa Cruz counties in California to quantify changes to forest structure, fuel loads, and modeled wildfire hazard. Observed data was used to analyze the accuracy of FFE modeled prescribed fire treatment outputs for post-treatment forest and fuel conditions. Observed burn treatments were low intensity and resulted in no significant change to forest structure and composition, but there was a reduction in seedling and sapling densities and an increase in resprout density. There was a reduction in duff and litter fuels, and litter and fine woody debris reduction was driven by pre-treatment total fuel loads. The modeled probability of torching was very low pre- and post-treatment. FFE underpredicted scorch height, duff fuel reduction, and redwood regeneration, but slightly overpredicted tree mortality and significantly overpredicted reduction of litter and fine woody debris. Conclusion Our results highlight a need for model refinement in regard to species-specific mortality, tree regeneration dynamics, fuel recruitment and deposition, and moisture-dependent fuel consumption. In order to achieve desired forest management goals, fire practitioners may need to burn at moderate to high intensities, and potentially pair burning with mechanical thinning. Long-term health of coast redwood forests also relies on the restoration of cultural fire and stewardship partnerships that equally share decision making power between western science and Indigenous knowledge bearers.

Background Understanding the role of fire in forested landscapes is fundamental to fire reintroduction efforts, yet few studies have examined how fire dynamics vary in response to interactions between local conditions, such as soil productivity, and more broadscale changes in climate. In this study, we examined historical fire frequency, seasonality, and spatial patterning in mixed conifer forests across a distinct gradient of soil productivity in the northern Sierra Nevada. We cross-dated 46 different wood samples containing 377 fire scars from 6 paired sites, located on and off of ultramafic serpentine soils. Forests on serpentine-derived soils have slower growth rates, lower biomass accumulation, and patchier vegetation than adjacent, non-serpentine sites. Due to these differences, we hypothesized that historical fire frequency and spatial extent would be reduced in mixed conifer forests growing on serpentine soils. Results Fire scars revealed a history of frequent fire at all of our sites (median composite interval: 6–22.5 years) despite clear differences in soil productivity. Fire frequency was slightly shorter in more productive non-serpentine sites, but this difference was not consistently significant within our sample pairs. While fires were frequent, both on and off of serpentine, they were also highly asynchronous, and this was largely driven by differing climate–fire relationships. Fires in more productive sites were strongly associated with drought conditions in the year of the fire, while fires in less productive serpentine sites appeared to be more dependent on a cycle of wet and dry conditions in the years preceding the fire. Widespread fires that crossed the boundary between serpentine and non-serpentine were associated with drier than normal years. Conclusions In our study, fine-scale variation in historical fire regime attributes was linked to both bottom-up and top-down controls. Understanding how these factors interact to create variation in fire frequency, timing, and spatial extent can help managers more effectively define desired conditions, develop management objectives, and identify management strategies for fire reintroduction and forest restoration projects.

Background Enactment of the Clean Air Act (CAA), Endangered Species Act (ESA), and National Environmental Policy Act (NEPA), three of the primary federal environmental laws, all coincided with the height of fire suppression and exclusion in the United States. These laws fail to acknowledge or account for the importance of fire in many fire-adapted and fire-dependent ecosystems, particularly in the American west, or the imperative for fire restoration to improve resiliency and reduce wildfire risk as identified by western science and Indigenous knowledge. We review the statutory and regulatory provisions of these federal laws to identify how the existing policy framework misaligns with the unique role of fire in ecosystems and with Tribal sovereignty, identify specific barriers and disincentives to beneficial fire use, and propose specific policy reforms. Results The CAA, the ESA, and NEPA inhibit the use of beneficial fire as they are founded in a policy framework that treats fire restoration and maintenance as a federal action or human activity, rather than as a natural, baseline, or keystone process. The emergency exceptions in these policies reduce accountability and incentivize the wrong kind of fire, and compliance creates a perverse outcome by disincentivizing fire restoration. Further, these federal policies impede Tribal sovereignty. Conclusions Modifications to these laws would better enable fire restoration in fire-dependent and fire-adapted ecosystems, reduce wildfire risk, and ultimately meet the statutes’ core purposes. Federal agencies and Congress should reform regulatory frameworks to explicitly recognize fire as a baseline, natural, or keystone process, such that restoring fire in fire-dependent and fire-adapted ecosystems at levels not significantly exceeding pre-1800 fire return intervals is not treated as a federal or agency action. Further, non-Tribal governments should not attempt to regulate cultural burning, as it is a retained right of Indigenous peoples.

Background: Fire suppression, timber harvesting, and the forced removal of Indigenous burning have fundamentally changed conditions in coast redwood forests. The contemporary approach of forest preservation and fire exclusion has produced high densities of small trees, elevated fuel loads, sparse understories with limited herbaceous plant diversity and cover, and increased vulnerability to wildfire and climate change. Prescribed broadcast burning presents a viable treatment option to meet forest restoration goals, especially where mechanical treatments are not feasible. Forest and fire managers utilizing fire modeling software such as the Fire and Fuels Extension of Forest Vegetation Simulator (FFE) to predict prescribed fire effects in coast redwoods are limited by model accuracy due to a lack of empirical research and model verification across a breadth of site and weather conditions. Results: We compared the difference between pre- and post-treatment conditions for two fall-season prescribed burns in Sonoma and Santa Cruz counties in California to quantify changes to forest structure, fuel loads, and treatment effectiveness in mitigating future wildfire behavior. This observed data was used to analyze the accuracy of FFE modeled prescribed fire treatment outputs for post-treatment forest and fuels conditions. Observed burn treatments were low intensity and resulted in no significant change to forest structure and composition, but there was a reduction in seedling and sapling densities and an increase in resprout density. There was a reduction in duff and litter fuels, and we found litter and fine woody debris reduction was driven by pre-treatment total fuel loads. The modeled probability of torching was very low pre- and post-treatment. FFE underpredicted scorch height, duff fuel reduction, and redwood regeneration, but slightly overpredicted tree mortality and significantly overpredicted reduction of litter and fine woody debris. Conclusion: Our results highlight a need for model refinement in regards to species-specific mortality, tree regeneration dynamics, and moisture-dependent fuel consumption. In order to achieve desired forest restoration goals, fire practitioners may need to burn at moderate to higher intensities than those typically implemented in these forests, and potentially pair burning with mechanical thinning. Long-term health of coast redwood forests also relies on the restoration of cultural fire and stewardship partnerships that equally share decision making power between western science and Indigenous knowledge bearers.

Background Over the last four decades, wildfires in forests of the continental western United States have significantly increased in both size and severity after more than a century of fire suppression and exclusion. Many of these forests historically experienced frequent fire and were fuel limited. To date, fuel reduction treatments have been small and too widely dispersed to have impacted this trend. Currently new land management plans are being developed on most of the 154 National Forests that will guide and support on the ground management practices for the next 15–20 years. Results During plan development, we recommend that Strategic Fire Zones (SFZs) be identified in large blocks (≥ 2,000 ha) of Federal forest lands, buffered (≥ 1–2.4 km) from the wildland-urban interface for the reintroduction of beneficial fire. In SFZs, lightning ignitions, as well as prescribed and cultural burns, would be used to reduce fuels and restore ecosystem services. Although such Zones have been successfully established in a limited number of western National Parks and Wilderness Areas, we identify extensive remote areas in the western US (8.3–12.7 million ha), most outside of wilderness (85–88%), where they could be established. Potential wildland fire Operational Delineations or PODs would be used to identify SFZ boundaries. We outline steps to identify, implement, monitor, and communicate the use and benefits of SFZs. Conclusions Enhancing collaboration and knowledge-sharing with Indigenous communities can play a vital role in gaining agency and public support for SFZs, and in building a narrative for how to rebuild climate-adapted fire regimes and live within them. Meaningful increases in wildland fire use could multiply the amount of beneficial fire on the landscape while reducing the risk of large wildfires and their impacts on structures and ecosystem services.

Background Understanding the role of fire in forested landscapes is fundamental to fire reintroduction efforts, yet few studies have examined how fire dynamics vary in response to interactions between local conditions, such as soil productivity, and more broadscale changes in climate. In this study we examined historical fire frequency, seasonality, and spatial patterning in mixed conifer forests across a distinct gradient of soil productivity in the northern Sierra Nevada. We cross-dated 46 different wood samples containing 377 fire scars from six paired sites, located on and off of ultramafic serpentine soils. Forests on serpentine-derived soils have slower growth rates, lower biomass accumulation, and patchier vegetation than adjacent, non-serpentine sites. Due to these differences, we hypothesized that historical fire frequency and spatial extent would be reduced in mixed conifer forests growing on serpentine soils. Results Fire scars revealed a history of frequent fire at all of our sites (median composite interval: 6-22.5 years) despite clear differences in soil productivity. Fire frequency was slightly shorter in more productive non-serpentine sites, but this difference was not significant within any of our sample pairs. While fires were frequent, both on and off of serpentine, they were also highly asynchronous, and this was largely driven by differing climate-fire relationships. Fires in more productive sites were strongly associated with drought conditions in the year of the fire, while fires in less productive serpentine sites appeared to be more dependent on a cycle of wet and dry conditions in the years preceding the fire. Widespread fires that crossed the boundary between serpentine and non-serpentine were associated with drier than normal years. Conclusions In our study, fine-scale variation in historical fire regime attributes was linked to both bottom-up and top-down controls. Understanding how these factors interact to create variation in fire frequency, timing, and spatial extent can help managers more effectively define desired conditions, develop management objectives, and identify management strategies for fire reintroduction and forest restoration projects.