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Shearman TM, Varner JM, Hood SM, van Mantgem PJ, Cansler CA, Wright M. Predictive accuracy of post-fire conifer death declines over time in models based on crown and bole injury. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2023; 33:e2760. [PMID: 36218008 DOI: 10.1002/eap.2760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 08/08/2022] [Accepted: 09/07/2022] [Indexed: 06/16/2023]
Abstract
A key uncertainty of empirical models of post-fire tree mortality is understanding the drivers of elevated post-fire mortality several years following fire, known as delayed mortality. Delayed mortality can represent a substantial fraction of mortality, particularly for large trees that are a conservation focus in western US coniferous forests. Current post-fire tree mortality models have undergone limited evaluation of how injury level and time since fire interact to influence model accuracy and predictor variable importance. Less severe injuries potentially serve as an indicator for vulnerability to additional stressors such as bark beetle attack or moisture stress. We used a collection of 164,293 individual tree records to examine post-fire tree mortality in eight western USA conifers: Abies concolor, Abies grandis, Calocedrus decurrens, Larix occidentalis, Pinus contorta, Pinus lambertiana, Pinus ponderosa, and Pseudotsuga menziesii. We evaluated the importance of fire injury predictors on discriminating between surviving trees versus immediate and delayed post-fire mortality. We fit balanced random forest models for each species using cumulative tree mortality from 1 to 5-years post-fire. We compared these results to multi-class random forest models using first-year mortality, 2-5-year mortality, and survival 5-years post-fire as a response variable. Crown volume scorched, diameter at breast height, and relative bark char height, were used as predictor variables. The cumulative mortality models all predicted trees that died within 1-year of fire with high accuracy but failed to predict 2-5-year mortality. The multi-class models were an improvement but had lower accuracy for predicting 2-5-year mortality. Multi-class model accuracies ranged from 85% to 95% across all species for predicting 1-year post-fire mortality, 42%-71% for predicting 2-5-year mortality, and 64%-85% for predicting trees that lived past 5-years. Our study highlights the differences in tree species tolerance to fire injury and suggests that including second-order predictors such as beetle attack or climatic water stress before and after fire will be critical to improve accuracy and better understand the mechanisms and patterns of fire-caused tree death. Random forest models have potential for management applications such as post-fire harvesting and simulating future stand dynamics.
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Affiliation(s)
| | | | - Sharon M Hood
- USDA Forest Service Rocky Mountain Research Station, Missoula, Montana, USA
| | | | - C Alina Cansler
- School of Environmental and Forest Sciences, University of Washington, Seattle, Washington, USA
| | - Micah Wright
- U.S. Geological Survey, Western Ecological Research Center, Arcata, California, USA
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Steel ZL, Goodwin MJ, Meyer MD, Fricker GA, Zald HSJ, Hurteau MD, North MP. Do forest fuel reduction treatments confer resistance to beetle infestation and drought mortality? Ecosphere 2021. [DOI: 10.1002/ecs2.3344] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Affiliation(s)
- Z. L. Steel
- John Muir Institute University of California Davis California95616USA
- Department of Environmental Science, Policy and Management University of California Berkeley California94720USA
| | - M. J. Goodwin
- Department of Biology University of New Mexico Albuquerque New Mexico87131USA
| | - M. D. Meyer
- Pacific Southwest Region USDA Forest Service Southern Sierra Province Bishop California93514USA
| | - G. A. Fricker
- Social Sciences Department California Polytechnic University San Luis Obispo California93407USA
| | - H. S. J. Zald
- Department of Forestry and Wildland Resources Humboldt State University Arcata California95521USA
| | - M. D. Hurteau
- Department of Biology University of New Mexico Albuquerque New Mexico87131USA
| | - M. P. North
- John Muir Institute University of California Davis California95616USA
- Pacific Southwest Research Station USDA Forest Service Mammoth Lakes California93546USA
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Foster DE, Battles JJ, Collins BM, York RA, Stephens SL. Potential wildfire and carbon stability in frequent‐fire forests in the Sierra Nevada: trade‐offs from a long‐term study. Ecosphere 2020. [DOI: 10.1002/ecs2.3198] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- Daniel E. Foster
- Ecosystem Sciences Division Department of Environmental Science, Policy, and Management University of California Berkeley California94720USA
| | - John J. Battles
- Ecosystem Sciences Division Department of Environmental Science, Policy, and Management University of California Berkeley California94720USA
| | - Brandon M. Collins
- Center for Fire Research and Outreach University of California Berkeley California94720USA
- USDA Forest Service Pacific Southwest Research Station Davis California95618USA
| | - Robert A. York
- Ecosystem Sciences Division Department of Environmental Science, Policy, and Management University of California Berkeley California94720USA
| | - Scott L. Stephens
- Ecosystem Sciences Division Department of Environmental Science, Policy, and Management University of California Berkeley California94720USA
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Crotteau JS, Keyes CR, Hood SM, Larson AJ. Vegetation dynamics following compound disturbance in a dry pine forest: fuel treatment then bark beetle outbreak. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2020; 30:e02023. [PMID: 31628705 DOI: 10.1002/eap.2023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 07/26/2019] [Accepted: 08/27/2019] [Indexed: 06/10/2023]
Abstract
In the western United States, restoration of forests with historically frequent, low-severity fire regimes often includes fuel reduction that reestablish open, early-seral conditions while reducing fuel continuity and loading. Between 2001 and 2016, fuel reduction (e.g., thinning, prescribed burning, etc.) was implemented on over 26 million hectares of federal lands alone in the United States, reflecting the urgency to mitigate risk from high-severity wildfire. However, between 2001 and 2012, nearly 20 million hectares in the United States were impacted by mountain pine beetle (MPB; Dendroctonus ponderosae), compounding restoration effects in wildfire-hazard-treated stands. Knowledge of the effects of treatments followed by natural disturbance on long-term forest structure and communities is needed, especially considering that fuel treatments are increasingly being implemented and warming climate is predicted to exacerbate disturbance frequency and severity. We tested the interacting effects of treatments designed to reduce high-severity wildfire hazard in stands subsequently challenged by MPB outbreak on vegetation dynamics using a factorial experimental design (control, thin only, burn only, thin + burn) in a ponderosa pine (Pinus ponderosa)-dominated forest. Stands were treated by 2002, then impacted by MPB outbreak from 2005 to 2012. We assessed change in overstory and understory forest community structure, composition, and diversity over time. There were distinct thinning, burning, and year effects. Thinning immediately reduced overstory density; pine density then declined 4.5 times more in unthinned than thinned treatments due to MPB. Burning immediately reduced graminoid, shrub, and total understory cover by as much as 52%, resulting in greater species evenness than unburned treatments, but differences disappeared by 2016 due to growth and MPB outbreak. Similarly, multivariate analyses indicated forest communities were starkly different after treatment but became more similar over time, though key understory and overstory attributes still distinguish control and thin + burn. This study shows the value of long-term silvicultural experiments to evaluate treatment longevity and the compounded effects of treatment and natural disturbance. We demonstrate the homogenizing effects of treatment-induced growth coupled with MPB-caused tree mortality on management strategies that just treat the overstory (thinning) or understory (burning), showing that only combined treatments can provide the unique structural and compositional outcomes expected of restoration.
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Affiliation(s)
- Justin S Crotteau
- Pacific Northwest Research Station, USDA Forest Service, 11175 Auke Lake Way, Juneau, Alaska, 99801, USA
| | - Christopher R Keyes
- WA Franke College of Forestry and Conservation, University of Montana, 32 Campus Drive, Missoula, Montana, 59812, USA
| | - Sharon M Hood
- Rocky Mountain Research Station, Fire, Fuel, and Smoke Science Program, USDA Forest Service, 5775 Highway 10 W., Missoula, Montana, 59808, USA
| | - Andrew J Larson
- WA Franke College of Forestry and Conservation, University of Montana, 32 Campus Drive, Missoula, Montana, 59812, USA
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Hessburg PF, Miller CL, Parks SA, Povak NA, Taylor AH, Higuera PE, Prichard SJ, North MP, Collins BM, Hurteau MD, Larson AJ, Allen CD, Stephens SL, Rivera-Huerta H, Stevens-Rumann CS, Daniels LD, Gedalof Z, Gray RW, Kane VR, Churchill DJ, Hagmann RK, Spies TA, Cansler CA, Belote RT, Veblen TT, Battaglia MA, Hoffman C, Skinner CN, Safford HD, Salter RB. Climate, Environment, and Disturbance History Govern Resilience of Western North American Forests. Front Ecol Evol 2019. [DOI: 10.3389/fevo.2019.00239] [Citation(s) in RCA: 113] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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We’re Not Doing Enough Prescribed Fire in the Western United States to Mitigate Wildfire Risk. FIRE-SWITZERLAND 2019. [DOI: 10.3390/fire2020030] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Prescribed fire is one of the most widely advocated management practices for reducing wildfire hazard and has a long and rich tradition rooted in indigenous and local ecological knowledge. The scientific literature has repeatedly reported that prescribed fire is often the most effective means of achieving such goals by reducing fuels and wildfire hazard and restoring ecological function to fire-adapted ecosystems in the United States (US) following a century of fire exclusion. This has translated into calls from scientists and policy experts for more prescribed fire, particularly in the Western US, where fire activity has escalated in recent decades. The annual extent of prescribed burning in the Western US remained stable or decreased from 1998 to 2018, while 70% of all prescribed fire was completed primarily by non-federal entities in the Southeastern US. The Bureau of Indian Affairs (BIA) was the only federal agency to substantially increase prescribed fire use, potentially associated with increased tribal self-governance. This suggests that the best available science is not being adopted into management practices, thereby further compounding the fire deficit in the Western US and the potential for more wildfire disasters.
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Stephens SL, Collins BM, Fettig CJ, Finney MA, Hoffman CM, Knapp EE, North MP, Safford H, Wayman RB. Drought, Tree Mortality, and Wildfire in Forests Adapted to Frequent Fire. Bioscience 2018. [DOI: 10.1093/biosci/bix146] [Citation(s) in RCA: 206] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Scott L Stephens
- Department of Environmental Science, Policy, and Management at the University of California, in Berkeley
| | - Brandon M Collins
- Center for Fire Research and Outreach at the University of California, in Berkeley
| | - Christopher J Fettig
- US Department of Agriculture (USDA) Forest Service, Pacific Southwest Research Station, in Davis, California
| | - Mark A Finney
- USDA Forest Service, Rocky Mountain Research Station, in Missoula, Montana
| | - Chad M Hoffman
- Department of Forest and Range Stewardship at Colorado State University, in Fort Collins
| | - Eric E Knapp
- USDA Forest Service, Pacific Southwest Research Station, in Redding, California
| | - Malcolm P North
- US Department of Agriculture (USDA) Forest Service, Pacific Southwest Research Station, in Davis, California
| | - Hugh Safford
- Department of Environmental Science and Policy at the University of California, in Davis
- HS is also with the USDA Forest Service, Pacific Southwest Region, in Vallejo, California
| | - Rebecca B Wayman
- Department of Environmental Science and Policy at the University of California, in Davis
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O'Connor CD, Falk DA, Lynch AM, Swetnam TW, Wilcox CP. Disturbance and productivity interactions mediate stability of forest composition and structure. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2017; 27:900-915. [PMID: 28029193 DOI: 10.1002/eap.1492] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 12/06/2016] [Accepted: 12/12/2016] [Indexed: 06/06/2023]
Abstract
Fire is returning to many conifer-dominated forests where species composition and structure have been altered by fire exclusion. Ecological effects of these fires are influenced strongly by the degree of forest change during the fire-free period. Response of fire-adapted species assemblages to extended fire-free intervals is highly variable, even in communities with similar historical fire regimes. This variability in plant community response to fire exclusion is not well understood; however, ecological mechanisms such as individual species' adaptations to disturbance or competition and underlying site characteristics that facilitate or impede establishment and growth have been proposed as potential drivers of assemblage response. We used spatially explicit dendrochronological reconstruction of tree population dynamics and fire regimes to examine the influence of historical disturbance frequency (a proxy for adaptation to disturbance or competition), and potential site productivity (a proxy for underlying site characteristics) on the stability of forest composition and structure along a continuous ecological gradient of pine, dry mixed-conifer, mesic mixed-conifer, and spruce-fir forests following fire exclusion. While average structural density increased in all forests, species composition was relatively stable in the lowest productivity pine-dominated and highest productivity spruce-fir-dominated sites immediately following fire exclusion and for the next 100 years, suggesting site productivity as a primary control on species composition and structure in forests with very different historical fire regimes. Species composition was least stable on intermediate productivity sites dominated by mixed-conifer forests, shifting from primarily fire-adapted species to competition-adapted, fire-sensitive species within 20 years of fire exclusion. Rapid changes to species composition and stand densities have been interpreted by some as evidence of high-severity fire. We demonstrate that the very different ecological process of fire exclusion can produce similar changes by shifting selective pressures from disturbance-mediated to productivity-mediated controls. Restoring disturbance-adapted species composition and structure to intermediate productivity forests may help to buffer them against projected increasing temperatures, lengthening fire seasons, and more frequent and prolonged moisture stress. Fewer management options are available to promote adaptation in forest assemblages historically constrained by underlying site productivity.
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Affiliation(s)
- Christopher D O'Connor
- School of Natural Resources and the Environment, University of Arizona, Tucson, Arizona, 85721, USA
- Laboratory of Tree-Ring Research, University of Arizona, Tucson, Arizona, 85721, USA
| | - Donald A Falk
- School of Natural Resources and the Environment, University of Arizona, Tucson, Arizona, 85721, USA
- Laboratory of Tree-Ring Research, University of Arizona, Tucson, Arizona, 85721, USA
| | - Ann M Lynch
- U.S. Forest Service, Rocky Mountain Research Station, Tucson, Arizona, 85721, USA
| | - Thomas W Swetnam
- Laboratory of Tree-Ring Research, University of Arizona, Tucson, Arizona, 85721, USA
| | - Craig P Wilcox
- U.S. Forest Service, Coronado National Forest, Safford, Arizona, 85546, USA
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Stephens SL, Collins BM, Biber E, Fulé PZ. U.S.
federal fire and forest policy: emphasizing resilience in dry forests. Ecosphere 2016. [DOI: 10.1002/ecs2.1584] [Citation(s) in RCA: 118] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Scott L. Stephens
- Division of Ecosystem ScienceDepartment of Environmental Science, Policy, and ManagementUniversity of California 130 Mulford Hall Berkeley California 94720 USA
| | - Brandon M. Collins
- Center for Fire Research and OutreachUniversity of California Berkeley California 94720 USA
| | - Eric Biber
- University of California, BerkeleySchool of Law 436 North Addition Berkeley California 94720 USA
| | - Peter Z. Fulé
- School of ForestryCollege of Engineering, Forestry, and Natural SciencesNorthern Arizona University Flagstaff Arizona 86011 USA
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Dow CB, Collins BM, Stephens SL. Incorporating Resource Protection Constraints in an Analysis of Landscape Fuel-Treatment Effectiveness in the Northern Sierra Nevada, CA, USA. ENVIRONMENTAL MANAGEMENT 2016; 57:516-530. [PMID: 26614351 DOI: 10.1007/s00267-015-0632-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 11/17/2015] [Indexed: 06/05/2023]
Abstract
Finding novel ways to plan and implement landscape-level forest treatments that protect sensitive wildlife and other key ecosystem components, while also reducing the risk of large-scale, high-severity fires, can prove to be difficult. We examined alternative approaches to landscape-scale fuel-treatment design for the same landscape. These approaches included two different treatment scenarios generated from an optimization algorithm that reduces modeled fire spread across the landscape, one with resource-protection constrains and one without the same. We also included a treatment scenario that was the actual fuel-treatment network implemented, as well as a no-treatment scenario. For all the four scenarios, we modeled hazardous fire potential based on conditional burn probabilities, and projected fire emissions. Results demonstrate that in all the three active treatment scenarios, hazardous fire potential, fire area, and emissions were reduced by approximately 50 % relative to the untreated condition. Results depict that incorporation of constraints is more effective at reducing modeled fire outputs, possibly due to the greater aggregation of treatments, creating greater continuity of fuel-treatment blocks across the landscape. The implementation of fuel-treatment networks using different planning techniques that incorporate real-world constraints can reduce the risk of large problematic fires, allow for landscape-level heterogeneity that can provide necessary ecosystem services, create mixed forest stand structures on a landscape, and promote resilience in the uncertain future of climate change.
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Affiliation(s)
- Christopher B Dow
- Ecosystem Sciences Division, Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA, 94720, USA.
| | - Brandon M Collins
- USDA Forest Service, Pacific Southwest Research Station, Davis, CA, 95618, USA
- Center for Fire Research and Outreach, University of California, Berkeley, CA, 94720-3114, USA
| | - Scott L Stephens
- Ecosystem Sciences Division, Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA, 94720, USA
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Management Impacts on Carbon Dynamics in a Sierra Nevada Mixed Conifer Forest. PLoS One 2016; 11:e0150256. [PMID: 26918460 PMCID: PMC4769083 DOI: 10.1371/journal.pone.0150256] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 02/11/2016] [Indexed: 11/24/2022] Open
Abstract
Forest ecosystems can act as sinks of carbon and thus mitigate anthropogenic carbon emissions. When forests are actively managed, treatments can alter forests carbon dynamics, reducing their sink strength and switching them from sinks to sources of carbon. These effects are generally characterized by fast temporal dynamics. Hence this study monitored for over a decade the impacts of management practices commonly used to reduce fire hazards on the carbon dynamics of mixed-conifer forests in the Sierra Nevada, California, USA. Soil CO2 efflux, carbon pools (i.e. soil carbon, litter, fine roots, tree biomass), and radial tree growth were compared among un-manipulated controls, prescribed fire, thinning, thinning followed by fire, and two clear-cut harvested sites. Soil CO2 efflux was reduced by both fire and harvesting (ca. 15%). Soil carbon content (upper 15 cm) was not significantly changed by harvest or fire treatments. Fine root biomass was reduced by clear-cut harvest (60–70%) but not by fire, and the litter layer was reduced 80% by clear-cut harvest and 40% by fire. Thinning effects on tree growth and biomass were concentrated in the first year after treatments, whereas fire effects persisted over the seven-year post-treatment period. Over this period, tree radial growth was increased (25%) by thinning and reduced (12%) by fire. After seven years, tree biomass returned to pre-treatment levels in both fire and thinning treatments; however, biomass and productivity decreased 30%-40% compared to controls when thinning was combined with fire. The clear-cut treatment had the strongest impact, reducing ecosystem carbon stocks and delaying the capacity for carbon uptake. We conclude that post-treatment carbon dynamics and ecosystem recovery time varied with intensity and type of treatments. Consequently, management practices can be selected to minimize ecosystem carbon losses while increasing future carbon uptake, resilience to high severity fire, and climate related stresses.
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