Fuel and restoration treatments seeking to mitigate the likelihood of uncharacteristic high‐severity wildfires in forests with historically frequent, low‐severity fire regimes are increasingly common, but long‐term treatment effects on fuels, aboveground carbon, plant community structure, ecosystem resilience, and other ecosystem attributes are understudied. We present 20‐year responses to thinning and prescribed burning treatments commonly used in dry, low‐elevation forests of the western United States from a long‐term study site in the Northern Rockies that is part of the National Fire and Fire Surrogate Study. We provide a comprehensive synthesis of short‐term (<4 years) and mid‐term (<14 years) results from previous findings. We then place these results in the context of a mountain pine beetle (MPB;
- NSF-PAR ID:
- 10298946
- Date Published:
- Journal Name:
- Ecological Applications
- ISSN:
- 1051-0761
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Dendroctonus ponderosae ) outbreak that impacted the site 5–10 years post‐treatment and describe 20‐year responses to assess the longevity of restoration and fuel reduction treatments in light of the MPB outbreak. Thinning treatments had persistently lower forest density and higher tree growth, but effects were more pronounced when thinning was combined with prescribed fire. The thinning+prescribed fire treatment had the additional benefit of maintaining the highest proportion of ponderosa pine (Pinus ponderosa ) for overstory and regeneration. No differences in understory native plant cover and richness or exotic species cover remained after 20 years, but exotic species richness, while low relative to native species, was still higher in the thinning+prescribed fire treatment than the control. Aboveground live carbon stocks in thinning treatments recovered to near control and prescribed fire treatment levels by 20 years. The prescribed fire treatment and control had higher fuel loads than thinning treatments due to interactions with the MPB outbreak. The MPB‐induced changes to forest structure and fuels increased the fire hazard 20 years post‐treatment in the control and prescribed fire treatment. Should a wildfire occur now, the thinning+prescribed fire treatment would likely have the lowest intensity fire and highest tree survival and stable carbon stocks. Our findings show broad support that thinning and prescribed fire increase ponderosa pine forest resilience to both wildfire and bark beetles for up to 20 years, but efficacy is waning and additional fuel treatments are needed to maintain resilience. -
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Abstract Interactions at multiple scales can shape how forest ecosystems respond to both climate change and disturbance. At landscape scales, feedbacks cause vegetation and wildfire regimes to alter one another, while forest patterns at local scales can result from feedbacks between plants and their abiotic environment. Consequently, disturbances and abiotic changes may give rise to forest patterns that further affect processes like wildfire.
Examples may exist in the history of subalpine ribbon forests, which are alternating areas of forest and meadow where snow drifting and linear bands of trees depend upon each other. Just as ongoing climate changes may change snow levels and the dynamics in these forests, past climate changes and wildfires may have generated the conditions suitable for ribbon forests.
To examine feedbacks in subalpine forests and the potential that climate changes and fires gave rise to ribbon forests, we obtained six fossil pollen records from a subalpine landscape in Colorado. Forests there may have responded to climate change and widespread wildfires ˜1,000 years ago when >80% of sites on the landscape burned within a century. The fires coincided with regional warming, but the extent of burning declined before the climate cooled, possibly driven by changes in fuel structure and composition.
The pollen records indicate that large vegetation changes coincided with the widespread wildfires at five of the six sites. Pollen assemblages consistent with ribbon forests first became important at this time as sagebrush (
Artemisia ) and other meadow taxa increased and conifers, especially spruce (Picea ) declined. The ribbon forests emerged as novel fuel breaks at the time when temperatures rose ˜0.5°C but the number of sites burned per century declined. Cooling during the Little Ice Age then expanded the openings and extent of ribbon forests, probably helping to reduce the frequency of fires across our sites to its minimum.Synthesis . The rise of ribbon forests in northern Colorado illustrates how climate and fire can interact to rapidly transform landscapes and disturbance regimes. The interactions can produce forest patterns with unexpected consequences such as reduced wildfire despite regional warming. -
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Abstract Background Wilderness areas are important natural laboratories for scientists and managers working to understand fire. In the last half-century, shifts in the culture and policy of land management agencies have facilitated the management practice of letting some naturally ignited fires burn, allowing fire to fulfill its ecological role and increasing the extent of fire-related research opportunities. With the goal of identifying the global scientific advances enabled by this paradigm shift in wilderness fire management, we conducted a systematic review of publications that either (1) selected protected areas for investigation because of an active fire regime enabled by wilderness fire management, (2) studied modern fires or fire regimes deliberately located in a wilderness area, or (3) conducted applied research to support wilderness fire management.
Results Our systematic review returned a sample of 222 publications that met these criteria, with an increase in wilderness fire science over time. Studies largely occurred in the USA and were concentrated in a relatively small number of protected areas, particularly in the Northern Rocky Mountains. As a result, this sample of wilderness fire science is highly skewed toward areas of temperate mixed-conifer forests and historical mixed-severity fire regimes. Common principal subjects of publications included fire effects (44%), wilderness fire management (18%), or fire regimes (17%), and studies tended to focus on vegetation, disturbance, or wilderness management as response variables.
Conclusions This work identifies major scientific contributions facilitated by fire in wilderness, including self-limitation of fire, the effects of active fire regimes on forest and aquatic systems, barriers and potential solutions to wilderness fire management, and the effect of fire on wilderness recreation and visitor experiences. Our work reveals geographic and bioclimatic areas where more research attention is needed and highlights under-represented wilderness areas that could serve to fill these gaps. Finally, we identify priorities for future wilderness fire research, including the past and potential role of Indigenous and prescribed burning, the effects of changing climate and fire regimes on ecosystem processes, and how to overcome barriers to wilderness fire management.
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Abstract Climate change is altering disturbance regimes and recovery rates of forests globally. The future of these forests will depend on how climate change interacts with management activities. Forest managers are in critical need of strategies to manage the effects of climate change.
We co‐designed forest management scenarios with forest managers and stakeholders in the Klamath ecoregion of Oregon and California, a seasonally dry forest in the Western US subject to fire disturbances. The resultant scenarios span a broad range of forest and fire management strategies. Using a mechanistic forest landscape model, we simulated the scenarios as they interacted with forest growth, succession, wildfire disturbances and climate change. We analysed the simulations to (a) understand how scenarios affected the fire regime and (b) estimate how each scenario altered potential forest composition.
Within the simulation timeframe (85 years), the scenarios had a large influence on fire regimes, with fire rotation periods ranging from 60 years in a minimal management scenario to 180 years with an industrial forestry style management scenario. Regardless of management strategy, mega‐fires (>100,000 ha) are expected to increase in frequency, driven by stronger climate forcing and extreme fire weather.
High elevation conifers declined across all climate and management scenarios, reflecting an imbalance between forest types, climate and disturbance. At lower elevations (<1,800 m), most scenarios maintained forest cover levels; however, the minimal intervention scenario triggered 5 × 105 ha of mixed conifer loss by the end of the century in favour of shrublands, whereas the maximal intervention scenario added an equivalent amount of mixed conifer.
Policy implications . Forest management scenarios that expand beyond current policies—including privatization and aggressive climate adaptation—can strongly influence forest trajectories despite a climate‐enhanced fire regime. Forest management can alter forest trajectories by increasing the pace and scale of actions taken, such as fuel reduction treatments, or by limiting other actions, such as fire suppression. -
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Abstract Prescribed fire has been increasingly promoted to reduce wildfire risk and restore fire‐adapted ecosystems. Yet, the complexities of forest ecosystem dynamics in response to disturbances, climate change, and drought stress, combined with myriad social and policy barriers, have inhibited widespread implementation. Using the forest succession model LANDIS‐II, we investigated the likely impacts of increasing prescribed fire frequency and extent on wildfire severity and forest carbon storage at local and landscape scales. Specifically, we ask how much prescribed fire is required to maintain carbon storage and reduce the severity and extent of wildfires under divergent climate change scenarios? We simulated four prescribed fire scenarios (no prescribed fire, business‐as‐usual, moderate increase, and large increase) in the Siskiyou Mountains of northwest California and southwest Oregon. At the local site scale, prescribed fires lowered the severity of projected wildfires and maintained approximately the same level of ecosystem carbon storage when reapplied at a ~15‐year return interval for 50‐year simulations. Increased frequency and extent of prescribed fire decreased the likelihood of aboveground carbon combustion during wildfire events. However, at the landscape scale, prescribed fire did not decrease the projected severity and extent of wildfire, even when large increases (up to 10× the current levels) of prescribed fire were simulated. Prescribed fire was most effective at reducing wildfire severity under a climate change scenario with increased temperature and precipitation and on sites with north‐facing aspects and slopes greater than 30°. Our findings suggest that placement matters more than frequency and extent to estimate the effects of prescribed fire, and that prescribed fire alone would not be sufficient to reduce the risk of wildfire and promote carbon sequestration at regional scales in the Siskiyou Mountains. To improve feasibility, we propose targeting areas of high concern or value to decrease the risk of high‐severity fire and contribute to meeting climate mitigation and adaptation goals. Our results support strategic and targeted landscape prioritization of fire treatments to reduce wildfire severity and increase the pace and scale of forest restoration in areas of social and ecological importance, highlighting the challenges of using prescribed fire to lower wildfire risk.
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1002/eap.2433
