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Stephens SL, Foster DE, Battles JJ, Bernal AA, Collins BM, Hedges R, Moghaddas JJ, Roughton AT, York RA. Forest restoration and fuels reduction work: Different pathways for achieving success in the Sierra Nevada. Ecol Appl 2024; 34:e2932. [PMID: 37948058 DOI: 10.1002/eap.2932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 06/20/2023] [Accepted: 10/03/2023] [Indexed: 11/12/2023]
Abstract
Fire suppression and past selective logging of large trees have fundamentally changed frequent-fire-adapted forests in California. The culmination of these changes produced forests that are vulnerable to catastrophic change by wildfire, drought, and bark beetles, with climate change exacerbating this vulnerability. Management options available to address this problem include mechanical treatments (Mech), prescribed fire (Fire), or combinations of these treatments (Mech + Fire). We quantify changes in forest structure and composition, fuel accumulation, modeled fire behavior, intertree competition, and economics from a 20-year forest restoration study in the northern Sierra Nevada. All three active treatments (Fire, Mech, Mech + Fire) produced forest conditions that were much more resistant to wildfire than the untreated control. The treatments that included prescribed fire (Fire, Mech + Fire) produced the lowest surface and duff fuel loads and the lowest modeled wildfire hazards. Mech produced low fire hazards beginning 7 years after the initial treatment and Mech + Fire had lower tree growth than controls. The only treatment that produced intertree competition somewhat similar to historical California mixed-conifer forests was Mech + Fire, indicating that stands under this treatment would likely be more resilient to enhanced forest stressors. While Fire reduced modeled wildfire hazard and reintroduced a fundamental ecosystem process, it was done at a net cost to the landowner. Using Mech that included mastication and restoration thinning resulted in positive revenues and was also relatively strong as an investment in reducing modeled wildfire hazard. The Mech + Fire treatment represents a compromise between the desire to sustain financial feasibility and the desire to reintroduce fire. One key component to long-term forest conservation will be continued treatments to maintain or improve the conditions from forest restoration. Many Indigenous people speak of "active stewardship" as one of the key principles in land management and this aligns well with the need for increased restoration in western US forests. If we do not use the knowledge from 20+ years of forest research and the much longer tradition of Indigenous cultural practices and knowledge, frequent-fire forests will continue to be degraded and lost.
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Affiliation(s)
- Scott L Stephens
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, California, USA
| | - Daniel E Foster
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, California, USA
| | - John J Battles
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, California, USA
| | - Alexis A Bernal
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, California, USA
| | - Brandon M Collins
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, California, USA
- Center for Fire Research and Outreach, University of California, Berkeley, Berkeley, California, USA
- USDA Forest Service, Pacific Southwest Region, Vallejo, California, USA
| | - Rachelle Hedges
- Berkeley Forests, University of California, Berkeley, Berkeley, California, USA
| | | | - Ariel T Roughton
- Berkeley Forests, University of California, Berkeley, Berkeley, California, USA
| | - Robert A York
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, California, USA
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2
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Stephens SL, Steel ZL, Collins BM, Fry DL, Gill SJ, Rivera-Huerta H, Skinner CN. Climate and fire impacts on tree recruitment in mixed conifer forests in northwestern Mexico and California. Ecol Appl 2023; 33:e2844. [PMID: 36922398 DOI: 10.1002/eap.2844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 12/27/2022] [Accepted: 03/08/2023] [Indexed: 06/02/2023]
Abstract
Frequent-fire forests were once heterogeneous at multiple spatial scales, which contributed to their resilience to severe fire. While many studies have characterized historical spatial patterns in frequent-fire forests, fewer studies have investigated their temporal dynamics. We investigated the influences of fire and climate on the timing of conifer recruitment in old-growth Jeffrey pine-mixed conifer forests in the Sierra San Pedro Martir (SSPM) and the eastern slope of the Sierra Nevada. Additionally, we evaluated the impacts of fire exclusion and recent climate change on recruitment levels using statistical models with realized as well as fire suppression and climate change-free counterfactual scenarios. Excessive soil drying from anthropogenic climate change resulted in diminished recruitment in the SSPM but not in the Sierra Nevada. Longer fire-free intervals attributable to fire suppression and exclusion resulted in greater rates of recruitment across all sites but was particularly pronounced in the Sierra Nevada, where suppression began >100 years ago and recruitment was 28 times higher than the historical fire return interval scenario. This demonstrates the profound impact of fire's removal on tree recruitment in Sierra Nevada forests even in the context of recent climate change. Tree recruitment at the SSPM coincided with the early-20th-century North American pluvial, as well as a fire-quiescent period in the late 18th and early 19th centuries. Episodic recruitment occurred in the SSPM with no "average" recruitment over the last three centuries. We found that temporal heterogeneity, in conjunction with spatial heterogeneity, are critical components of frequent-fire-adapted forests. Episodic recruitment could be a desirable characteristic of frequent-fire-adapted forests, and this might be more amenable to climate change impacts that forecast more variable precipitation patterns in the future. One key to this outcome would be for frequent fire to continue to shape these forests versus continued emphasis on fire suppression in California.
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Affiliation(s)
- Scott L Stephens
- Department of Environmental Science, Policy and Management, University of California, Berkeley, Berkeley, California, USA
| | - Zachary L Steel
- Department of Environmental Science, Policy and Management, University of California, Berkeley, Berkeley, California, USA
- USDA Forest Service, Rocky Mountain Research Station, Fort Collins, Colorado, USA
| | - Brandon M Collins
- Department of Environmental Science, Policy and Management, University of California, Berkeley, Berkeley, California, USA
- Center for Fire Research and Outreach, University of California, Berkeley, Berkeley, California, USA
| | - Danny L Fry
- Department of Environmental Science, Policy and Management, University of California, Berkeley, Berkeley, California, USA
| | - Samantha J Gill
- Natural Resources Management and Bioresource and Agricultural Engineering Departments, California Polytechnic State University, San Luis Obispo, California, USA
| | - Hiram Rivera-Huerta
- Facultad de Ciencias Marinas, Universidad Autonoma de Baja California, Ensenada, Mexico
| | - Carl N Skinner
- USDA Forest Service, Pacific Southwest Research Station, Redding, California, USA
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3
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Steel ZL, Jones GM, Collins BM, Green R, Koltunov A, Purcell KL, Sawyer SC, Slaton MR, Stephens SL, Stine P, Thompson C. Mega-disturbances cause rapid decline of mature conifer forest habitat in California. Ecol Appl 2023; 33:e2763. [PMID: 36264047 DOI: 10.1002/eap.2763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 08/25/2022] [Accepted: 08/30/2022] [Indexed: 06/16/2023]
Abstract
Mature forests provide important wildlife habitat and support critical ecosystem functions globally. Within the dry conifer forests of the western United States, past management and fire exclusion have contributed to forest conditions that are susceptible to increasingly severe wildfire and drought. We evaluated declines in conifer forest cover in the southern Sierra Nevada of California during a decade of record disturbance by using spatially comprehensive forest structure estimates, wildfire perimeter data, and the eDaRT forest disturbance tracking algorithm. Primarily due to the combination of wildfires, drought, and drought-associated beetle epidemics, 30% of the region's conifer forest extent transitioned to nonforest vegetation during 2011-2020. In total, 50% of mature forest habitat and 85% of high density mature forests either transitioned to lower density forest or nonforest vegetation types. California spotted owl protected activity centers (PAC) experienced greater canopy cover decline (49% of 2011 cover) than non-PAC areas (42% decline). Areas with high initial canopy cover and without tall trees were most vulnerable to canopy cover declines, likely explaining the disproportionate declines of mature forest habitat and within PACs. Drought and beetle attack caused greater cumulative declines than areas where drought and wildfire mortality overlapped, and both types of natural disturbance far outpaced declines attributable to mechanical activities. Drought mortality that disproportionately affects large conifers is particularly problematic to mature forest specialist species reliant on large trees. However, patches of degraded forests within wildfire perimeters were larger with greater core area than those outside burned areas, and remnant forest habitats were more fragmented within burned perimeters than those affected by drought and beetle mortality alone. The percentage of mature forest that survived and potentially benefited from lower severity wildfire increased over time as the total extent of mature forest declined. These areas provide some opportunity for improved resilience to future disturbances, but strategic management interventions are likely also necessary to mitigate worsening mega-disturbances. Remaining dry mature forest habitat in California may be susceptible to complete loss in the coming decades without a rapid transition from a conservation paradigm that attempts to maintain static conditions to one that manages for sustainable disturbance dynamics.
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Affiliation(s)
| | - Gavin M Jones
- USFS Rocky Mountain Research Station, Albuquerque, New Mexico, USA
- University of New Mexico, Albuquerque, New Mexico, USA
| | - Brandon M Collins
- University of California, Berkeley, California, USA
- USFS Pacific Southwest Research Station, Davis, California, USA
| | - Rebecca Green
- Sequoia & Kings Canyon National Park, Three Rivers, California, USA
| | - Alexander Koltunov
- USFS Pacific Southwest Region, McClellan, California, USA
- University of California, Davis, California, USA
| | - Kathryn L Purcell
- USFS Pacific Southwest Research Station, Coarsegold, California, USA
| | | | | | | | - Peter Stine
- Stine Wildland Resources Science, Sacramento, California, USA
| | - Craig Thompson
- USFS Pacific Southwest Research Station, Fresno, California, USA
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Margolis EQ, Guiterman CH, Chavardès RD, Coop JD, Copes‐Gerbitz K, Dawe DA, Falk DA, Johnston JD, Larson E, Li H, Marschall JM, Naficy CE, Naito AT, Parisien M, Parks SA, Portier J, Poulos HM, Robertson KM, Speer JH, Stambaugh M, Swetnam TW, Tepley AJ, Thapa I, Allen CD, Bergeron Y, Daniels LD, Fulé PZ, Gervais D, Girardin MP, Harley GL, Harvey JE, Hoffman KM, Huffman JM, Hurteau MD, Johnson LB, Lafon CW, Lopez MK, Maxwell RS, Meunier J, North M, Rother MT, Schmidt MR, Sherriff RL, Stachowiak LA, Taylor A, Taylor EJ, Trouet V, Villarreal ML, Yocom LL, Arabas KB, Arizpe AH, Arseneault D, Tarancón AA, Baisan C, Bigio E, Biondi F, Cahalan GD, Caprio A, Cerano‐Paredes J, Collins BM, Dey DC, Drobyshev I, Farris C, Fenwick MA, Flatley W, Floyd ML, Gedalof Z, Holz A, Howard LF, Huffman DW, Iniguez J, Kipfmueller KF, Kitchen SG, Lombardo K, McKenzie D, Merschel AG, Metlen KL, Minor J, O'Connor CD, Platt L, Platt WJ, Saladyga T, Stan AB, Stephens S, Sutheimer C, Touchan R, Weisberg PJ. The North American tree‐ring fire‐scar network. Ecosphere 2022. [DOI: 10.1002/ecs2.4159] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Ellis Q. Margolis
- New Mexico Landscapes Field Station U.S. Geological Survey, Fort Collins Science Center Santa Fe New Mexico USA
| | | | - Raphaël D. Chavardès
- Institut de recherche sur les forêts Université du Québec en Abitibi‐Témiscamingue Rouyn‐Noranda Québec Canada
| | - Jonathan D. Coop
- School of Environment and Sustainability Western Colorado University Gunnison Colorado USA
| | - Kelsey Copes‐Gerbitz
- Department of Forest and Conservation Sciences, Faculty of Forestry University of British Columbia Vancouver British Columbia Canada
| | - Denyse A. Dawe
- Northern Forestry Centre Canadian Forest Service Edmonton Alberta Canada
| | - Donald A. Falk
- Laboratory of Tree‐Ring Research University of Arizona Tucson Arizona USA
- School of Natural Resources and the Environment, ENR2 Building University of Arizona Tucson Arizona USA
| | | | - Evan Larson
- Department of Environmental Sciences and Society University of Wisconsin‐Platteville Platteville Wisconsin USA
| | - Hang Li
- Department of Earth and Environmental Systems Indiana State University Terre Haute Indiana USA
| | | | | | - Adam T. Naito
- Department of Earth, Environmental, and Geographical Sciences Northern Michigan University Marquette Michigan USA
| | - Marc‐André Parisien
- Northern Forestry Centre, Canadian Forest Service Natural Resources Canada Edmonton Alberta Canada
| | - Sean A. Parks
- Aldo Leopold Wilderness Research Institute Rocky Mountain Research Station, US Forest Service Missoula Montana USA
| | - Jeanne Portier
- Forest Resources and Management Swiss Federal Institute for Forest, Snow and Landscape Research WSL Birmensdorf Switzerland
| | - Helen M. Poulos
- College of the Environment Wesleyan University Middletown Connecticut USA
| | | | - James H. Speer
- Department of Earth and Environmental Systems Indiana State University Terre Haute Indiana USA
| | - Michael Stambaugh
- School of Natural Resources University of Missouri Columbia Missouri USA
| | - Thomas W. Swetnam
- Laboratory of Tree‐Ring Research University of Arizona Tucson Arizona USA
| | - Alan J. Tepley
- Canadian Forest Service Northern Forestry Centre Edmonton Alberta Canada
- Smithsonian Conservation Biology Institute Front Royal Virginia USA
| | - Ichchha Thapa
- Department of Earth and Environmental Systems Indiana State University Terre Haute Indiana USA
| | - Craig D. Allen
- Department of Geography and Environmental Studies University of New Mexico Albuquerque New Mexico USA
| | - Yves Bergeron
- Institut de recherche sur les forêts Université du Québec en Abitibi‐Témiscamingue Rouyn‐Noranda Québec Canada
- Département des Sciences Biologiques Université du Québec à Montréal Montreal Quebec Canada
| | - Lori D. Daniels
- Department of Forest and Conservation Sciences, Faculty of Forestry University of British Columbia Vancouver British Columbia Canada
| | - Peter Z. Fulé
- School of Forestry Northern Arizona University Flagstaff Arizona USA
| | - David Gervais
- Canadian Forest Service Natural Resources Canada Québec Québec Canada
| | | | - Grant L. Harley
- Department of Earth and Spatial Sciences University of Idaho Moscow Idaho USA
| | - Jill E. Harvey
- Department of Natural Resource Science Thompson Rivers University Kamloops British Columbia Canada
| | - Kira M. Hoffman
- Department of Forest and Conservation Sciences, Faculty of Forestry University of British Columbia Vancouver British Columbia Canada
- Bulkley Valley Research Centre Smithers British Columbia Canada
| | - Jean M. Huffman
- Tall Timbers Research Station Tallahassee Florida USA
- Department of Biological Sciences Louisiana State University Baton Rouge Louisiana USA
| | - Matthew D. Hurteau
- Department of Biology University of New Mexico Albuquerque New Mexico USA
| | - Lane B. Johnson
- Cloquet Forestry Center University of Minnesota Cloquet Minnesota USA
| | - Charles W. Lafon
- Department of Geography Texas A&M University College Station Texas USA
| | - Manuel K. Lopez
- New Mexico Landscapes Field Station U.S. Geological Survey, Fort Collins Science Center Santa Fe New Mexico USA
| | | | - Jed Meunier
- Division of Forestry Wisconsin Department of Natural Resources Madison Wisconsin USA
| | - Malcolm North
- USFS PSW Research Station Mammoth Lakes California USA
| | - Monica T. Rother
- Department of Environmental Sciences University of North Carolina‐Wilmington Wilmington North Carolina USA
| | - Micah R. Schmidt
- College of Forestry Oregon State University Corvallis Oregon USA
| | - Rosemary L. Sherriff
- Department of Geography, Environment and Spatial Analysis Humboldt State University Arcata California USA
| | | | - Alan Taylor
- Department of Geography and Earth and Environmental Systems Institute The Pennsylvania State University University Park Pennsylvania USA
| | - Erana J. Taylor
- Laboratory of Tree‐Ring Research University of Arizona Tucson Arizona USA
| | - Valerie Trouet
- Laboratory of Tree‐Ring Research University of Arizona Tucson Arizona USA
| | - Miguel L. Villarreal
- U.S. Geological Survey, Western Geographic Science Center Moffett Field California USA
| | - Larissa L. Yocom
- Department of Wildland Resources and the Ecology Center Utah State University Logan Utah USA
| | - Karen B. Arabas
- Department of Environmental Science Willamette University Salem Oregon USA
| | - Alexis H. Arizpe
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna BioCenter Vienna Austria
| | - Dominique Arseneault
- Département de Biologie, Chimie et Géographie Université du Québec à Rimouski Rimouski Quebec Canada
| | | | - Christopher Baisan
- Laboratory of Tree‐Ring Research University of Arizona Tucson Arizona USA
| | - Erica Bigio
- Department of Natural Resources and Environmental Science University of Nevada, Reno Reno Nevada USA
| | - Franco Biondi
- Department of Natural Resources and Environmental Science University of Nevada, Reno Reno Nevada USA
| | | | - Anthony Caprio
- Sequoia & Kings Canyon National Parks Three Rivers California USA
| | | | - Brandon M. Collins
- Center for Fire Research and Outreach University of California Berkeley California USA
| | - Daniel C. Dey
- US Forest Service, Northern Research Station Columbia Missouri USA
| | - Igor Drobyshev
- Swedish Agricultural University, Southern Swedish Research Centre Uppsala Sweden
- Université du Québec en Abitibi‐Témiscamingue Rouyn‐Noranda Quebec Canada
| | | | | | - William Flatley
- Department of Geography University of Central Arkansas Conway Arkansas USA
| | | | - Ze'ev Gedalof
- Department of Geography, Environment and Geomatics University of Guelph Guelph Ontario Canada
| | - Andres Holz
- Department of Geography Portland State University Portland Oregon USA
| | - Lauren F. Howard
- Department of Biology Arcadia University Glenside Pennsylvania USA
| | - David W. Huffman
- Ecological Restoration Institute Northern Arizona University Flagstaff Arizona USA
| | - Jose Iniguez
- USDA Forest Service, Rocky Mountain Research Station Flagstaff Arizona USA
| | - Kurt F. Kipfmueller
- Department of Geography, Environment, and Society University of Minnesota Minneapolis Minnesota USA
| | | | - Keith Lombardo
- Southern California Research Learning Center San Diego California USA
| | - Donald McKenzie
- School of Environmental and Forest Sciences University of Washington Seattle Washington USA
| | | | | | - Jesse Minor
- University of Maine System Farmington Maine USA
| | - Christopher D. O'Connor
- Forestry Sciences Laboratory Rocky Mountain Research Station, USDA Forest Service Missoula Montana USA
| | - Laura Platt
- Department of Geography Portland State University Portland Oregon USA
| | - William J. Platt
- Department of Biological Sciences Louisiana State University Baton Rouge Louisiana USA
| | - Thomas Saladyga
- Department of Physical and Environmental Sciences Concord University Athens West Virginia USA
| | - Amanda B. Stan
- Department of Geography, Planning and Recreation Northern Arizona University Flagstaff Arizona USA
| | - Scott Stephens
- Department of Environmental Science, Policy, and Management University of California, Berkeley Berkeley California USA
| | - Colleen Sutheimer
- Department of Forest and Wildlife Ecology University of Wisconsin‐Madison Madison Wisconsin USA
| | - Ramzi Touchan
- Laboratory of Tree‐Ring Research University of Arizona Tucson Arizona USA
| | - Peter J. Weisberg
- Department of Natural Resources and Environmental Science University of Nevada, Reno Reno Nevada USA
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Collins BM, Bernal A, York RA, Stevens JT, Juska A, Stephens SL. Mixed-conifer forest reference conditions for privately owned timberland in the southern Cascade Range. Ecol Appl 2021; 31:e02400. [PMID: 34214228 DOI: 10.1002/eap.2400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 01/22/2021] [Accepted: 03/03/2021] [Indexed: 06/13/2023]
Abstract
The overwhelming majority of information on historical forest conditions in western North America comes from public lands, which may provide an incomplete description of historical landscapes. In this study we made use of an archive containing extensive timber survey data collected in the early 1920s from privately owned forestland. These data covered over 50,000 ha and effectively represent a 19% sample of the entire area. The historical forest conditions reconstructed from these data fit the classic model of frequent-fire forests: large trees, low density, and pine-dominated. However, unlike other large-scale forest reconstructions, our study area exhibited relatively low overall variability in forest structure and composition across the historical landscape. Despite having low variability, our analyses revealed evidence of biophysical controls on tree density and pine fraction. Annual climatic variables most strongly explained the range in historical tree densities, whereas historical pine fraction was explained by a combination of topographic and climatic variables. Contemporary forest inventory data collected from both public and private lands within the same general area, albeit not a direct remeasurement, revealed substantial increases in tree density and greatly reduced pine fractions relative to historical conditions. Contemporary forests exhibited a far greater range in these conditions than what existed historically. These findings suggest that private forestland managed with multiaged silviculture may be similar to public forestland with respect to departure in forest structure and compositions from that of historical forests. However, there may be differences between management objectives that favor timber production, more typical on private lands, vs. those that favor restoration, increasingly supported on public lands.
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Affiliation(s)
- Brandon M Collins
- U.S. Department of Agriculture Forest Service, Pacific Southwest Research Station, Davis, California, 95618, USA
- Center for Fire Research and Outreach, University of California, Berkeley, Berkeley, California, 94720-3114, USA
| | - Alexis Bernal
- Department of Environmental Science, Policy, and Management, Ecosystem Sciences Division, University of California, Berkeley, Berkeley, California, 94720, USA
| | - Robert A York
- Department of Environmental Science, Policy, and Management, Ecosystem Sciences Division, University of California, Berkeley, Berkeley, California, 94720, USA
| | - Jens T Stevens
- U.S. Geological Survey, Fort Collins Science Center, New Mexico Landscapes Field Station, Santa Fe, New Mexico, 87508, USA
| | - Andrew Juska
- Collins Pine Company, P.O. Box 796, Chester, California, 96020, USA
| | - Scott L Stephens
- Department of Environmental Science, Policy, and Management, Ecosystem Sciences Division, University of California, Berkeley, Berkeley, California, 94720, USA
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Abstract
Pyrodiversity or variation in spatio-temporal fire patterns is increasingly recognized as an important determinant of ecological pattern and process, yet no consensus surrounds how best to quantify the phenomenon and its drivers remain largely untested. We present a generalizable functional diversity approach for measuring pyrodiversity, which incorporates multiple fire regime traits and can be applied across scales. Further, we tested the socioecological drivers of pyrodiversity among forests of the western United States. Largely mediated by burn activity, pyrodiversity was positively associated with actual evapotranspiration, climate water deficit, wilderness designation, elevation and topographic roughness but negatively with human population density. These results indicate pyrodiversity is highest in productive areas with pronounced annual dry periods and minimal fire suppression. This work can facilitate future pyrodiversity studies including whether and how it begets biodiversity among taxa, regions and fire regimes.
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Affiliation(s)
- Zachary L Steel
- Department of Environmental Science, Policy and Management, University of California-Berkeley, Berkeley, CA 94720, USA
| | - Brandon M Collins
- Center for Fire Research and Outreach, University of California, Berkeley, CA 94720, USA.,USDA Forest Service, Pacific Southwest Research Station, Davis, CA 95618, USA
| | - David B Sapsis
- California Department of Forestry and Fire Protection, Sacramento, CA 95814, USA
| | - Scott L Stephens
- Department of Environmental Science, Policy and Management, University of California-Berkeley, Berkeley, CA 94720, USA
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7
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Ziegler JP, Hoffman CM, Collins BM, Knapp EE, Mell W(R. Pyric tree spatial patterning interactions in historical and contemporary mixed conifer forests, California, USA. Ecol Evol 2021; 11:820-834. [PMID: 33520169 PMCID: PMC7820164 DOI: 10.1002/ece3.7084] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 10/23/2020] [Accepted: 11/12/2020] [Indexed: 11/30/2022] Open
Abstract
Tree spatial patterns in dry coniferous forests of the western United States, and analogous ecosystems globally, were historically aggregated, comprising a mixture of single trees and groups of trees. Modern forests, in contrast, are generally more homogeneous and overstocked than their historical counterparts. As these modern forests lack regular fire, pattern formation and maintenance is generally attributed to fire. Accordingly, fires in modern forests may not yield historically analogous patterns. However, direct observations on how selective tree mortality among pre-existing forest structure shapes tree spatial patterns is limited. In this study, we (a) simulated fires in historical and contemporary counterpart plots in a Sierra Nevadan mixed-conifer forest, (b) estimated tree mortality, and (c) examined tree spatial patterns of live trees before and after fire, and of fire-killed trees. Tree mortality in the historical period was clustered and density-dependent, because trees were aggregated and segregated by tree size before fire. Thus, fires maintained an aggregated distribution of tree groups. Tree mortality in the contemporary period was widespread, except for dispersed large trees, because most trees were a part of large, interconnected tree groups. Thus, postfire tree patterns were more uniform and devoid of moderately sized tree groups. Postfire tree patterns in the historical period, unlike the contemporary period, were within the historical range of variability identified for the western United States. This divergence suggests that decades of forest dynamics without significant disturbances have altered the historical means of pyric pattern formation. Our results suggest that ecological silvicultural treatments, such as forest restoration thinnings, which emulate qualities of historical forests may facilitate the reintroduction of fire as a means to reinforce forest structural heterogeneity.
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Affiliation(s)
- Justin P. Ziegler
- Department of Forest & Rangeland StewardshipColorado State UniversityFort CollinsCOUSA
| | - Chad M. Hoffman
- Department of Forest & Rangeland StewardshipColorado State UniversityFort CollinsCOUSA
| | - Brandon M. Collins
- Center for Fire Research & OutreachUniversity of CaliforniaBerkeleyCAUSA
- Pacific Southwest Research StationUS Forest ServiceDavisCAUSA
| | - Eric E. Knapp
- Pacific Southwest Research StationUS Forest ServiceReddingCAUSA
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Stephens SL, Battaglia MA, Churchill DJ, Collins BM, Coppoletta M, Hoffman CM, Lydersen JM, North MP, Parsons RA, Ritter SM, Stevens JT. Forest Restoration and Fuels Reduction: Convergent or Divergent? Bioscience 2020. [DOI: 10.1093/biosci/biaa134] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
For over 20 years, forest fuel reduction has been the dominant management action in western US forests. These same actions have also been associated with the restoration of highly altered frequent-fire forests. Perhaps the vital element in the compatibility of these treatments is that both need to incorporate the salient characteristics that frequent fire produced—variability in vegetation structure and composition across landscapes and the inability to support large patches of high-severity fire. These characteristics can be achieved with both fire and mechanical treatments. The possible key to convergence of fuel reduction and forest restoration strategies is integrated planning that permits treatment design flexibility and a longer-term focus on fire reintroduction for maintenance. With changing climate conditions, long-term forest conservation will probably need to be focused on keeping tree density low enough (i.e., in the lower range of historic variation) for forest conditions to adapt to emerging disturbance patterns and novel ecological processes.
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Affiliation(s)
- Scott L Stephens
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, in Berkeley, California
| | - Mike A Battaglia
- US Department of Agriculture (USDA), Forest Service, Rocky Mountain Research Station, Fort Collins, Colorado
| | - Derek J Churchill
- Forest Health and Resiliency Division of the Washington Department of Natural Resources, Olympia, Washington
| | - Brandon M Collins
- Fire Research and Outreach at the University of California, Berkeley, Berkeley, California, and with the USDA Forest Service, Pacific Southwest Research Station, Davis, California
| | - Michelle Coppoletta
- USDA Forest Service, Sierra Cascade Province Ecology Program, Quincy, California
| | - Chad M Hoffman
- Department of Forest and Rangeland Stewardship, Colorado State University, Fort Collins, Colorado
| | - Jamie M Lydersen
- California Department of Forestry and Fire Protection, Fire and Resource Assessment Program, Sacramento, California
| | - Malcolm P North
- USDA Forest Service, PSW Research Station, Mammoth Lakes, California, and with the Department of Plant Sciences, University of California, Davis, Davis, California
| | | | - Scott M Ritter
- Department of Forest and Rangeland Stewardship, Colorado State University, Fort Collins, Colorado
| | - Jens T Stevens
- US Geological Survey, New Mexico Landscapes Field Station, Santa Fe, New Mexico
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Affiliation(s)
- Mark W Schwartz
- Department of Environmental Science & Policy, University of California, Davis, Davis, CA 95616, USA.
| | - James H Thorne
- Department of Environmental Science & Policy, University of California, Davis, Davis, CA 95616, USA
| | - Brandon M Collins
- Center for Fire Research and Outreach, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Peter A Stine
- Retired, Pacific Southwest Research Station, U.S. Department of Agriculture Forest Service, Richmond, CA 94804, USA
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10
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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11
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Coop JD, Parks SA, Stevens-Rumann CS, Crausbay SD, Higuera PE, Hurteau MD, Tepley A, Whitman E, Assal T, Collins BM, Davis KT, Dobrowski S, Falk DA, Fornwalt PJ, Fulé PZ, Harvey BJ, Kane VR, Littlefield CE, Margolis EQ, North M, Parisien MA, Prichard S, Rodman KC. Wildfire-Driven Forest Conversion in Western North American Landscapes. Bioscience 2020; 70:659-673. [PMID: 32821066 PMCID: PMC7429175 DOI: 10.1093/biosci/biaa061] [Citation(s) in RCA: 103] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Changing disturbance regimes and climate can overcome forest ecosystem resilience. Following high-severity fire, forest recovery may be compromised by lack of tree seed sources, warmer and drier postfire climate, or short-interval reburning. A potential outcome of the loss of resilience is the conversion of the prefire forest to a different forest type or nonforest vegetation. Conversion implies major, extensive, and enduring changes in dominant species, life forms, or functions, with impacts on ecosystem services. In the present article, we synthesize a growing body of evidence of fire-driven conversion and our understanding of its causes across western North America. We assess our capacity to predict conversion and highlight important uncertainties. Increasing forest vulnerability to changing fire activity and climate compels shifts in management approaches, and we propose key themes for applied research coproduced by scientists and managers to support decision-making in an era when the prefire forest may not return.
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Affiliation(s)
- Jonathan D Coop
- School of Environment and Sustainability, Western Colorado University, Gunnison
| | - Sean A Parks
- Research ecologist with the Aldo Leopold Wilderness Research Institute, Rocky Mountain Research Station, US Forest Service, Missoula, Montana
| | | | - Shelley D Crausbay
- Senior scientist with Conservation Science Partners, Fort Collins, Colorado
| | - Philip E Higuera
- Department of Ecosystem and Conservation Sciences, University of Montana, Missoula, Montana
| | | | - Alan Tepley
- Natural Resources Canada, Canadian Forest Service, Northern Forestry Centre, Edmonton, Alberta, Canada
| | - Ellen Whitman
- Natural Resources Canada, Canadian Forest Service, Northern Forestry Centre, Edmonton, Alberta, Canada
| | - Timothy Assal
- Department of Geography, Kent State University, Kent, Ohio
| | - Brandon M Collins
- Fire Research and Outreach, University of California, Berkeley, Berkeley, California, and with the Pacific Southwest Research Station, US Forest Service, in Davis, California
| | - Kimberley T Davis
- Department of Ecosystem and Conservation Sciences, University of Montana, Missoula
| | | | - Donald A Falk
- Natural Resources and the Environment, University of Arizona, Tucson
| | - Paula J Fornwalt
- Rocky Mountain Research Station, US Forest Service, Fort Collins, Colorado
| | - Peter Z Fulé
- School of Forestry, Northern Arizona University, Flagstaff
| | - Brian J Harvey
- School of Environmental and Forest Sciences, University of Washington, Seattle
| | - Van R Kane
- School of Environmental and Forest Sciences, University of Washington, Seattle
| | - Caitlin E Littlefield
- Caitlin Littlefield is a postdoctoral research associate, Rubenstein School of Environment and Natural Resources, University of Vermont, Burlington
| | - Ellis Q Margolis
- US Geological Survey, New Mexico Landscapes Field Station, Santa Fe
| | - Malcolm North
- US Forest Service, Pacific Southwest Research Station, Mammoth Lakes, California
| | - Marc-André Parisien
- Natural Resources Canada, Canadian Forest Service, Northern Forestry Centre, Edmonton, Alberta, Canada
| | - Susan Prichard
- School of Environmental and Forest Sciences, University of Washington, Seattle
| | - Kyle C Rodman
- Department of Forest and Wildlife Ecology, University of Wisconsin, Madison
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12
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Levine CR, Cogbill CV, Collins BM, Larson AJ, Lutz JA, North MP, Restaino CM, Safford HD, Stephens SL, Battles JJ. Estimating historical forest density from land-survey data: a response to Baker and Williams (2018). Ecol Appl 2019; 29:e01968. [PMID: 31257657 DOI: 10.1002/eap.1968] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 05/20/2019] [Accepted: 06/14/2019] [Indexed: 06/09/2023]
Affiliation(s)
- Carrie R Levine
- Department of Environmental Science and Policy, University of California, Davis, One Shields Avenue, Davis, California, 95616, USA
| | - Charles V Cogbill
- Harvard Forest, Harvard University, 324 North Main Street, Petersham, Massachusetts, 01366, USA
| | - Brandon M Collins
- USDA Forest Service, Pacific Southwest Research Station, 1731 Research Park Drive, Davis, California, 95618, USA
- Center for Fire Research and Outreach, College of Natural Resources, University of California, Berkeley, California, 94720-3114, USA
| | - Andrew J Larson
- Department of Forest Management, University of Montana, 32 Campus Drive, Missoula, Montana, 59812, USA
| | - James A Lutz
- S. J. & Jessie E. Quinney College of Natural Resources, Utah State University, 5230 Old Main Hill, Logan, Utah, 84322-5230, USA
| | - Malcolm P North
- USDA Forest Service, Pacific Southwest Research Station, 1731 Research Park Drive, Davis, California, 95618, USA
- Department of Plant Sciences, University of California, Davis, One Shields Avenue, Davis, California, 95616, USA
| | | | - Hugh D Safford
- Department of Environmental Science and Policy, University of California, Davis, One Shields Avenue, Davis, California, 95616, USA
- USDA Forest Service, Pacific Southwest Region, 1323 Club Drive, Vallejo, California, 94592, USA
| | - Scott L Stephens
- Department of Environmental Science, Policy, and Management, University of California, 130 Mulford Hall, Berkeley, California, 94720-3114, USA
| | - John J Battles
- Department of Environmental Science, Policy, and Management, University of California, 130 Mulford Hall, Berkeley, California, 94720-3114, USA
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13
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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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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14
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Hagmann RK, Stevens JT, Lydersen JM, Collins BM, Battles JJ, Hessburg PF, Levine CR, Merschel AG, Stephens SL, Taylor AH, Franklin JF, Johnson DL, Johnson KN. Improving the use of early timber inventories in reconstructing historical dry forests and fire in the western United States: Comment. Ecosphere 2018. [DOI: 10.1002/ecs2.2232] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- R. Keala Hagmann
- Applegate Forestry LLC; 28831 Tampico Road Corvallis Oregon 97330 USA
- School of Environmental and Forest Sciences; University of Washington; Seattle Washington 98195 USA
| | - Jens T. Stevens
- Ecosystem Sciences Division; Department of Environmental Science, Policy, and Management; University of California; Berkeley California 94720 USA
| | - Jamie M. Lydersen
- Ecosystem Sciences Division; Department of Environmental Science, Policy, and Management; University of California; Berkeley California 94720 USA
| | - Brandon M. Collins
- Center for Fire Research and Outreach; University of California; Berkeley California 94720 USA
| | - John J. Battles
- Ecosystem Sciences Division; Department of Environmental Science, Policy, and Management; University of California; Berkeley California 94720 USA
| | - Paul F. Hessburg
- School of Environmental and Forest Sciences; University of Washington; Seattle Washington 98195 USA
- USDA-FS, Pacific Northwest Research Station; Wenatchee Washington 98801 USA
| | - Carrie R. Levine
- Department of Environmental Science and Policy; University of California; Davis California 95616 USA
| | - Andrew G. Merschel
- Department of Forest Engineering Resources and Management; College of Forestry; Oregon State University; Corvallis Oregon 97333 USA
| | - Scott L. Stephens
- Ecosystem Sciences Division; Department of Environmental Science, Policy, and Management; University of California; Berkeley California 94720 USA
| | - Alan H. Taylor
- Department of Geography, Earth and Environmental Institute; The Pennsylvania State University; University Park Pennsylvania 16802 USA
| | - Jerry F. Franklin
- School of Environmental and Forest Sciences; University of Washington; Seattle Washington 98195 USA
| | - Debora L. Johnson
- Applegate Forestry LLC; 28831 Tampico Road Corvallis Oregon 97330 USA
| | - K. Norman Johnson
- Department of Forest Ecosystems and Society; Oregon State University; Corvallis Oregon 97331 USA
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15
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Lydersen JM, Collins BM. Change in Vegetation Patterns Over a Large Forested Landscape Based on Historical and Contemporary Aerial Photography. Ecosystems 2018. [DOI: 10.1007/s10021-018-0225-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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16
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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17
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Collins BM, Fry DL, Lydersen JM, Everett R, Stephens SL. Impacts of different land management histories on forest change. Ecol Appl 2017; 27:2475-2486. [PMID: 28873261 DOI: 10.1002/eap.1622] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 06/07/2017] [Accepted: 07/18/2017] [Indexed: 06/07/2023]
Abstract
Many western North American forest types have experienced considerable changes in ecosystem structure, composition, and function as a result of both fire exclusion and timber harvesting. These two influences co-occurred over a large portion of dry forests, making it difficult to know the strength of either one on its own or the potential for an interaction between the two. In this study, we used contemporary remeasurements of a systematic historical forest inventory to investigate forest change in the Sierra Nevada. The historical data opportunistically spanned a significant land management agency boundary, which protected part of the inventory area from timber harvesting. This allowed for a robust comparison of forest change between logged and unlogged areas. In addition, we assessed the effects of recent management activities aimed at forest restoration relative to the same areas historically, and to other areas without recent management. Based on analyses of 22,007 trees (historical, 9,573; contemporary, 12,434), live basal area and tree density significantly increased from 1911 to the early 2000s in both logged and unlogged areas. Both shrub cover and the proportion of live basal area occupied by pine species declined from 1911 to the early 2000s in both areas, but statistical significance was inconsistent. The most notable difference between logged and unlogged areas was in the density of large trees, which declined significantly in logged areas, but was unchanged in unlogged areas. Recent management activities had a varied impact on the forest structure and composition variables analyzed. In general, areas with no recent management activities experienced the greatest change from 1911 to the early 2000s. If approximating historical forest conditions is a land management goal the documented changes in forest structure and composition from 1911 to the early 2000s indicate that active restoration, including fire use and mechanical thinning, is needed in many areas.
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Affiliation(s)
- Brandon M Collins
- Center for Fire Research and Outreach, University of California, Berkeley, California, 94720-3114, USA
| | - Danny L Fry
- Ecosystem Sciences Division, Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, 94720, USA
| | - Jamie M Lydersen
- Pacific Southwest Research Station, USDA Forest Service, Davis, California, 95618, USA
| | - Richard Everett
- Ecosystem Sciences Division, Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, 94720, USA
- Department of Natural Resources, Salish Kootenai College, 58138 Highway 93, P.O. Box 70, Pablo, Montana, 59855, USA
| | - Scott L Stephens
- Ecosystem Sciences Division, Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, 94720, USA
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18
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Levine CR, Cogbill CV, Collins BM, Larson AJ, Lutz JA, North MP, Restaino CM, Safford HD, Stephens SL, Battles JJ. Evaluating a new method for reconstructing forest conditions from General Land Office survey records. Ecol Appl 2017; 27:1498-1513. [PMID: 28370925 DOI: 10.1002/eap.1543] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 01/10/2017] [Accepted: 02/22/2017] [Indexed: 06/07/2023]
Abstract
Historical forest conditions are often used to inform contemporary management goals because historical forests are considered to be resilient to ecological disturbances. The General Land Office (GLO) surveys of the late 19th and early 20th centuries provide regionally quasi-contiguous data sets of historical forests across much of the Western United States. Multiple methods exist for estimating tree density from point-based sampling such as the GLO surveys, including distance-based and area-based approaches. Area-based approaches have been applied in California mixed-conifer forests but their estimates have not been validated. To assess the accuracy and precision of plotless density estimators with potential for application to GLO data in this region, we imposed a GLO sampling scheme on six mapped forest stands of known densities (159-784 trees/ha) in the Sierra Nevada in California, USA, and Baja California Norte, Mexico. We compared three distance-based plotless density estimators (Cottam, Pollard, and Morisita) as well as two Voronoi area (VA) estimators, the Delincé and mean harmonic Voronoi density (MHVD), to the true densities. We simulated sampling schemes of increasing intensity to assess sampling error. The relative error (RE) of density estimates for the GLO sampling scheme ranged from 0.36 to 4.78. The least biased estimate of tree density in every stand was obtained with the Morisita estimator and the most biased was obtained with the MHVD estimator. The MHVD estimates of tree density were 1.2-3.8 times larger than the true densities and performed best in stands subject to fire exclusion for 100 yr. The Delincé approach obtained accurate estimates of density, implying that the Voronoi approach is theoretically sound but that its application in the MHVD was flawed. The misapplication was attributed to two causes: (1) the use of a crown scaling factor that does not correct for the number of trees sampled and (2) the persistent underestimate of the true VA due to a weak relationship between tree size and VA. The magnitude of differences between true densities and MHVD estimates suggest caution in using results based on the MHVD to inform management and restoration practices in the conifer forests of the American West.
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Affiliation(s)
- Carrie R Levine
- Department of Environmental Science, Policy, and Management, University of California, 130 Mulford Hall, Berkeley, California, 94720, USA
| | - Charles V Cogbill
- Harvard Forest, Harvard University, 324 North Main Street, Petersham, Massachusetts, 01366, USA
| | - Brandon M Collins
- University of California Center for Fire Research and Outreach, College of Natural Resources, University of California, Berkeley, California, 94720, USA
| | - Andrew J Larson
- Department of Forest Management, University of Montana, 32 Campus Drive, Missoula, Montana, 59812, USA
| | - James A Lutz
- S. J. & Jessie E. Quinney College of Natural Resources, Utah State University, 5230 Old Main Hill, Logan, Utah, 84322, USA
| | - Malcolm P North
- USDA Forest Service, Pacific Southwest Research Station, 1731 Research Park Drive, Davis, California, 95618, USA
| | - Christina M Restaino
- Department of Environmental Science and Policy, University of California, Davis, One Shields Avenue, Davis, California, 95616, USA
| | - Hugh D Safford
- Department of Environmental Science and Policy, University of California, Davis, One Shields Avenue, Davis, California, 95616, USA
- USDA Forest Service, Pacific Southwest Region, 1323 Club Drive, Vallejo, California, 94592, USA
| | - Scott L Stephens
- Department of Environmental Science, Policy, and Management, University of California, 130 Mulford Hall, Berkeley, California, 94720, USA
| | - John J Battles
- Department of Environmental Science, Policy, and Management, University of California, 130 Mulford Hall, Berkeley, California, 94720, USA
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19
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Chiono LA, Fry DL, Collins BM, Chatfield AH, Stephens SL. Landscape-scale fuel treatment and wildfire impacts on carbon stocks and fire hazard in California spotted owl habitat. Ecosphere 2017. [DOI: 10.1002/ecs2.1648] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Affiliation(s)
- Lindsay A. Chiono
- Ecosystem Sciences Division; Department of Environmental Science, Policy, and Management; University of California, Berkeley; 130 Mulford Hall Berkeley California 94720 USA
| | - Danny L. Fry
- Ecosystem Sciences Division; Department of Environmental Science, Policy, and Management; University of California, Berkeley; 130 Mulford Hall Berkeley California 94720 USA
| | - Brandon M. Collins
- USDA Forest Service; Pacific Southwest Research Station; Davis California 95618 USA
- Center for Fire Research and Outreach; University of California, Berkeley; Berkeley California 94720 USA
| | - Andrea H. Chatfield
- Western EcoSystems Technology, Inc.; 456 SW Monroe Ave Suite 106 Corvallis Oregon 97333 USA
| | - Scott L. Stephens
- Ecosystem Sciences Division; Department of Environmental Science, Policy, and Management; University of California, Berkeley; 130 Mulford Hall Berkeley California 94720 USA
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20
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Kramer HA, Collins BM, Gallagher CV, J. Keane J, Stephens SL, Kelly M. Accessible light detection and ranging: estimating large tree density for habitat identification. Ecosphere 2016. [DOI: 10.1002/ecs2.1593] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Heather A. Kramer
- Ecosystem Sciences Division Department of Environmental Science, Policy, and Management University of California 130 Mulford Hall Berkeley California 94720 USA
| | - Brandon M. Collins
- Center for Fire Research and Outreach University of California Berkeley California 94720 USA
- USDA Forest Service Pacific Southwest Research Station 1731 Research Park Drive Davis California 95618 USA
| | - Claire V. Gallagher
- USDA Forest Service Pacific Southwest Research Station 1731 Research Park Drive Davis California 95618 USA
| | - John J. Keane
- USDA Forest Service Pacific Southwest Research Station 1731 Research Park Drive Davis California 95618 USA
| | - Scott L. Stephens
- Ecosystem Sciences Division Department of Environmental Science, Policy, and Management University of California 130 Mulford Hall Berkeley California 94720 USA
| | - Maggi Kelly
- Ecosystem Sciences Division Department of Environmental Science, Policy, and Management University of California 130 Mulford Hall Berkeley California 94720 USA
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21
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Stephens SL, Miller JD, Collins BM, North MP, Keane JJ, Roberts SL. Wildfire impacts on California spotted owl nesting habitat in the Sierra Nevada. Ecosphere 2016. [DOI: 10.1002/ecs2.1478] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- Scott L. Stephens
- Division of Ecosystem Science Department of Environmental Science, Policy, and Management University of California 130 Mulford Hall Berkeley California 94720 USA
| | - Jay D. Miller
- USDA Forest Service Pacific Southwest Region, Fire and Aviation Management McClellan California 95652 USA
| | - Brandon M. Collins
- Pacific Southwest Research Station USDA Forest Service Davis California 95618 USA
- Center for Fire Research and Outreach University of California Berkeley California 94720 USA
| | - Malcolm P. North
- Pacific Southwest Research Station USDA Forest Service Davis California 95618 USA
| | - John J. Keane
- Pacific Southwest Research Station USDA Forest Service Davis California 95618 USA
| | - Susan L. Roberts
- University of California, Merced, Sierra Nevada Research Station 7799 Chilnualna Falls Road Wawona California 95389 USA
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22
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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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23
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Stevens JT, Collins BM, Long JW, North MP, Prichard SJ, Tarnay LW, White AM. Evaluating potential trade‐offs among fuel treatment strategies in mixed‐conifer forests of the Sierra Nevada. Ecosphere 2016. [DOI: 10.1002/ecs2.1445] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Jens T. Stevens
- John Muir Institute of the Environment University of California Davis California 95616 USA
| | - Brandon M. Collins
- Center for Fire Research and Outreach University of California Berkeley California 94720 USA
- USDA Forest Service Pacific Southwest Research Station Davis California 95618 USA
| | - Jonathan W. Long
- USDA Forest Service Pacific Southwest Research Station Davis California 95618 USA
| | - Malcolm P. North
- John Muir Institute of the Environment University of California Davis California 95616 USA
- USDA Forest Service Pacific Southwest Research Station Davis California 95618 USA
| | - Susan J. Prichard
- College of Forest Resources University of Washington Seattle Washington 98195 USA
| | - Leland W. Tarnay
- USDA Forest Service Pacific Southwest Research Station Davis California 95618 USA
| | - Angela M. White
- USDA Forest Service Pacific Southwest Research Station Davis California 95618 USA
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24
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Coppoletta M, Merriam KE, Collins BM. Post-fire vegetation and fuel development influences fire severity patterns in reburns. Ecol Appl 2016; 26:686-699. [PMID: 27411243 DOI: 10.1890/15-0225] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In areas where fire regimes and forest structure have been dramatically altered, there is increasing concern that contemporary fires have the potential to set forests on a positive feedback trajectory with successive reburns, one in which extensive stand-replacing fire could promote more stand-replacing fire. Our study utilized an extensive set of field plots established following four fires that occurred between 2000 and 2010 in the northern Sierra Nevada, California, USA that were subsequently reburned in 2012. The information obtained from these field plots allowed for a unique set of analyses investigating the effect of vegetation, fuels, topography, fire weather, and forest management on reburn severity. We also examined the influence of initial fire severity and time since initial fire on influential predictors of reburn severity. Our results suggest that high- to moderate-severity fire in the initial fires led to an increase in standing snags and shrub vegetation, which in combination with severe fire weather promoted high-severity fire effects in the subsequent reburn. Although fire behavior is largely driven by weather, our study demonstrates that post-fire vegetation composition and structure are also important drivers of reburn severity. In the face of changing climatic regimes and increases in extreme fire weather, these results may provide managers with options to create more fire-resilient ecosystems. In areas where frequent high-severity fire is undesirable, management activities such as thinning, prescribed fire, or managed wildland fire can be used to moderate fire behavior not only prior to initial fires, but also before subsequent reburns.
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25
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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. Environ Manage 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] [What about the content of this article? (0)] [Affiliation(s)] [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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Tempel DJ, Gutiérrez RJ, Battles JJ, Fry DL, Su Y, Guo Q, Reetz MJ, Whitmore SA, Jones GM, Collins BM, Stephens SL, Kelly M, Berigan WJ, Peery MZ. Evaluating short- and long-term impacts of fuels treatments and simulated wildfire on an old-forest species. Ecosphere 2015. [DOI: 10.1890/es15-00234.1] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Collins BM, Lydersen JM, Everett RG, Fry DL, Stephens SL. Novel characterization of landscape-level variability in historical vegetation structure. Ecol Appl 2015; 25:1167-1174. [PMID: 26485946 DOI: 10.1890/14-1797.1] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We analyzed historical timber inventory data collected systematically across a large mixed-conifer-dominated landscape to gain insight into the interaction between disturbances and vegetation structure and composition prior to 20th century land management practices. Using records from over 20 000 trees, we quantified historical vegetation structure and composition for nine distinct vegetation groups. Our findings highlight some key aspects of forest structure under an intact disturbance regime: (1) forests were low density, with mean live basal area and tree density ranging from 8-30 m2 /ha and 25-79 trees/ha, respectively; (2) understory and overstory structure and composition varied considerably across the landscape; and (3) elevational gradients largely explained variability in forest structure over the landscape. Furthermore, the presence of large trees across most of the surveyed area suggests that extensive stand-replacing disturbances were rare in these forests. The vegetation structure and composition characteristics we quantified, along with evidence of largely elevational control on these characteristics, can provide guidance for restoration efforts in similar forests.
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Stephens SL, Lydersen JM, Collins BM, Fry DL, Meyer MD. Historical and current landscape-scale ponderosa pine and mixed conifer forest structure in the Southern Sierra Nevada. Ecosphere 2015. [DOI: 10.1890/es14-00379.1] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Stephens SL, Bigelow SW, Burnett RD, Collins BM, Gallagher CV, Keane J, Kelt DA, North MP, Roberts LJ, Stine PA, Van Vuren DH. California Spotted Owl, Songbird, and Small Mammal Responses to Landscape Fuel Treatments. Bioscience 2014. [DOI: 10.1093/biosci/biu137] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Fry DL, Stephens SL, Collins BM, North MP, Franco-Vizcaíno E, Gill SJ. Contrasting spatial patterns in active-fire and fire-suppressed Mediterranean climate old-growth mixed conifer forests. PLoS One 2014; 9:e88985. [PMID: 24586472 PMCID: PMC3930671 DOI: 10.1371/journal.pone.0088985] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Accepted: 01/13/2014] [Indexed: 11/19/2022] Open
Abstract
In Mediterranean environments in western North America, historic fire regimes in frequent-fire conifer forests are highly variable both temporally and spatially. This complexity influenced forest structure and spatial patterns, but some of this diversity has been lost due to anthropogenic disruption of ecosystem processes, including fire. Information from reference forest sites can help management efforts to restore forests conditions that may be more resilient to future changes in disturbance regimes and climate. In this study, we characterize tree spatial patterns using four-ha stem maps from four old-growth, Jeffrey pine-mixed conifer forests, two with active-fire regimes in northwestern Mexico and two that experienced fire exclusion in the southern Sierra Nevada. Most of the trees were in patches, averaging six to 11 trees per patch at 0.007 to 0.014 ha−1, and occupied 27–46% of the study areas. Average canopy gap sizes (0.04 ha) covering 11–20% of the area were not significantly different among sites. The putative main effects of fire exclusion were higher densities of single trees in smaller size classes, larger proportion of trees (≥56%) in large patches (≥10 trees), and decreases in spatial complexity. While a homogenization of forest structure has been a typical result from fire exclusion, some similarities in patch, single tree, and gap attributes were maintained at these sites. These within-stand descriptions provide spatially relevant benchmarks from which to manage for structural heterogeneity in frequent-fire forest types.
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Affiliation(s)
- Danny L. Fry
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, United States of America
- * E-mail:
| | - Scott L. Stephens
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, United States of America
| | - Brandon M. Collins
- USDA Forest Service, Pacific Southwest Research Station, Davis, California, United States of America
- University of California Center for Fire Research and Outreach, College of Natural Resources, Berkeley, California, United States of America
| | - Malcolm P. North
- USDA Forest Service, Pacific Southwest Research Station, Davis, California, United States of America
| | - Ernesto Franco-Vizcaíno
- Departamento de Biología de la Conservación, Centro de Investigación Científica y de Educación Superior de Ensenada, Ensenada, Baja California, México
| | - Samantha J. Gill
- Natural Resources Management and Bioresource and Agricultural Engineering Departments, California Polytechnic State University, San Luis Obispo, California, United States of America
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Collins BM, Das AJ, Battles JJ, Fry DL, Krasnow KD, Stephens SL. Beyond reducing fire hazard: fuel treatment impacts on overstory tree survival. Ecol Appl 2014; 24:1879-1886. [PMID: 29185659 DOI: 10.1890/14-0971.1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Fuel treatment implementation in dry forest types throughout the western United States is likely to increase in pace and scale in response to increasing incidence of large wildfires. While it is clear that properly implemented fuel treatments are effective at reducing hazardous fire potential, there are ancillary ecological effects that can impact forest resilience either positively or negatively depending on the specific elements examined, as well as treatment type, timing, and intensity. In this study, we use overstory tree growth responses, measured seven years after the most common fuel treatments, to estimate forest health. Across the five species analyzed, observed mortality and future vulnerability were consistently low in the mechanical- only treatment. Fire-only was similar to the control for all species except Douglas-fir, while mechanical-plus-fire had high observed mortality and future vulnerability for white fir and sugar pine. Given that overstory trees largely dictate the function of forests and services they provide (e.g., wildlife habitat, carbon sequestration, soil stability) these results have implications for understanding longer-term impacts of common fuel treatments on forest resilience.
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Miller JD, Collins BM, Lutz JA, Stephens SL, van Wagtendonk JW, Yasuda DA. Differences in wildfires among ecoregions and land management agencies in the Sierra Nevada region, California, USA. Ecosphere 2012. [DOI: 10.1890/es12-00158.1] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Stephens SL, Boerner REJ, Moghaddas JJ, Moghaddas EEY, Collins BM, Dow CB, Edminster C, Fiedler CE, Fry DL, Hartsough BR, Keeley JE, Knapp EE, McIver JD, Skinner CN, Youngblood A. Fuel treatment impacts on estimated wildfire carbon loss from forests in Montana, Oregon, California, and Arizona. Ecosphere 2012. [DOI: 10.1890/es11-00289.1] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Collins BM, Everett RG, Stephens SL. Impacts of fire exclusion and recent managed fire on forest structure in old growth Sierra Nevada mixed-conifer forests. Ecosphere 2011. [DOI: 10.1890/es11-00026.1] [Citation(s) in RCA: 153] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Collins BM, Harrop SJ, Kornfeld GD, Dawes IW, Curmi PM, Mabbutt BC. Crystal structure of a heptameric Sm-like protein complex from archaea: implications for the structure and evolution of snRNPs. J Mol Biol 2001; 309:915-23. [PMID: 11399068 DOI: 10.1006/jmbi.2001.4693] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The Sm/Lsm proteins associate with small nuclear RNA to form the core of small nuclear ribonucleoproteins, required for processes as diverse as pre-mRNA splicing, mRNA degradation and telomere formation. The Lsm proteins from archaea are likely to represent the ancestral Sm/Lsm domain. Here, we present the crystal structure of the Lsm alpha protein from the thermophilic archaeon Methanobacterium thermoautotrophicum at 2.0 A resolution. The Lsm alpha protein crystallizes as a heptameric ring comprised of seven identical subunits interacting via beta-strand pairing and hydrophobic interactions. The heptamer can be viewed as a propeller-like structure in which each blade consists of a seven-stranded antiparallel beta-sheet formed from neighbouring subunits. There are seven slots on the inner surface of the heptamer ring, each of which is lined by Asp, Asn and Arg residues that are highly conserved in the Sm/Lsm sequences. These conserved slots are likely to form the RNA-binding site. In archaea, the gene encoding Lsm alpha is located next to the L37e ribosomal protein gene in a putative operon, suggesting a role for the Lsm alpha complex in ribosome function or biogenesis.
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Affiliation(s)
- B M Collins
- Department of Chemistry, Macquarie University, NSW 2109, Australia
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Corthals GL, Collins BM, Mabbutt BC, Williams KL, Gooley AA. Purification by reflux electrophoresis of whey proteins and of a recombinant protein expressed in Dictyostelium discoideum. J Chromatogr A 1997; 773:299-309. [PMID: 9228801 DOI: 10.1016/s0021-9673(97)00237-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Protein purification that combines the use of molecular mass exclusion membranes with electrophoresis is particularly powerful as it uses properties inherent to both techniques. The use of membranes allows efficient processing and is easily scaled up, while electrophoresis permits high resolution separation under mild conditions. The Gradiflow apparatus combines these two technologies as it uses polyacrylamide membranes to influence electrokinetic separations. The reflux electrophoresis process consists of a series of cycles incorporating a forward phase and a reverse phase. The forward phase involves collection of a target protein that passes through a separation membrane before trailing proteins in the same solution. The forward phase is repeated following clearance of the membrane in the reverse phase by reversing the current. We have devised a strategy to establish optimal reflux separation parameters, where membranes are chosen for a particular operating range and protein transfer is monitored at different pH values. In addition, forward and reverse phase times are determined during this process. Two examples of the reflux method are described. In the first case, we described the purification strategy for proteins from a complex mixture which contains proteins of higher electrophoretic mobility than the target protein. This is a two-step procedure, where first proteins of higher mobility than the target protein are removed from the solution by a series of reflux cycles, so that the target protein remains as the leading fraction. In the second step the target protein is collected, as it has become the leading fraction of the remaining proteins. In the second example we report the development of a reflux strategy which allowed a rapid one-step preparative purification of a recombinant protein, expressed in Dictyostelium discoideum. These strategies demonstrate that the Gradiflow is amenable to a wide range of applications, as the protein of interest is not necessarily required to be the leading fraction in solution.
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Affiliation(s)
- G L Corthals
- Macquarie University Centre for Analytical Biotechnology (MUCAB), School of Biological Sciences, Macquarie University, Sydney, NSW, Australia
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Arnold SF, Bergeron JM, Tran DQ, Collins BM, Vonier PM, Crews D, Toscano WA, McLachlan JA. Synergistic responses of steroidal estrogens in vitro (yeast) and in vivo (turtles). Biochem Biophys Res Commun 1997; 235:336-42. [PMID: 9199193 DOI: 10.1006/bbrc.1997.6779] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Many environmental agents exert estrogenic activity. Previous studies from our laboratories demonstrated that certain combinations of environmental estrogens (i) reverse the sex of male turtle embryos in a synergistic manner (Bergeron et al., (1994) Environ. Hlth Perspect. 102, 780-782), and (ii) synergistically transactivate the human estrogen receptor (hER) in yeast and mammalian cells (Arnold et al., (1996) Science 272, 1489-1492). Because our findings with synthetic estrogens suggested that combinations of naturally-occurring steroidal estrogens might also produce synergistic activity of the ER, we used the same model systems to measure the activity of combinations of steroidal estrogens. The activity of combinations of estrone, estradiol-17beta or estradiol-17alpha in yeast strains expressing hER was synergistic at submaximal concentrations of both estrogenic compounds. However, synergy was not observed with mixtures of estrogens when the concentration of one of the estrogens alone was maximally active in yeast. Ligand-binding assays in yeast performed with various radiolabeled estrogens suggested that multiple estrogens may interact with the receptor. The estrogen-dependent process of sex-reversal of turtle embryos incubated at a male-producing temperature was used to determine whether steroidal estrogens also had synergistic activity in vivo. In this instance, a combination of estriol and estradiol-17beta was effective in reversing the gonadal sex of turtle embryos from males to females in a synergistic manner. Our results suggest that the synergy of some combinations of estrogens, synthetic or steroidal, may play a role in the estrogen-dependent process of sexual development in certain species.
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Affiliation(s)
- S F Arnold
- Department of Environmental Health Sciences, Tulane School of Public Health, New Orleans, Louisiana 70112, USA.
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Abstract
We have used the expression of the human estrogen receptor (hER) and two estrogen response elements linked to the lacZ gene in yeast (YES) to study the estrogenic and antiestrogenic activities of various phytochemicals. Coumestrol, alpha-zearalenol, or genistein could produce beta-galactosidase activity comparable to estradiol, but these required concentrations 100 to 1000-fold greater than estradiol. These compounds did not possess antiestrogenic activity. Narigenin, kaempferide, phloretin, biochanin A, flavone, or chrysin only partially induced beta-galactosidase activity in the YES at any concentration tested. When narigenin, kaempferide, or phloretin was given concurrently with estradiol, the estradiol-dependent beta-galactosidase activity was not inhibited by more than 50%. However, biochanin A, flavone, or chrysin could inhibit the activity of estradiol in a dose-response manner with IC50 values of 500 nM, 2 microM, and 10 microM, respectively. Combinations of biochanin A, chrysin, and flavone decreased estradiol-dependent beta-galactosidase activity in an additive fashion. Similar to the antiestrogens tamoxifen or ICI 182, 780, the antiestrogenic activity of these compounds with the exception of chrystin involved the disruption of hER dimerization, as demonstrated in the yeast two-hybrid system. Biochanin A, chrysin, or flavone were less effective in inhibiting the activity of an estrogenic polychlorinated biphenyl than they were inhibiting the activity of estradiol. Interestingly, this latter group of antiestrogenic phytocompounds did not inhibit the estrogenic activity of such phytochemicals as coumestrol or genistein. These results suggest that the antiestrogenic activity of biochanin A and flavone occurs by a mechanism similar to tamoxifen or ICI 182,780. Moreover, it seems that phytochemicals functioning as antiestrogens do not inhibit the activity of all estrogenic chemicals to the same extent. This suggests that conformational changes induced by different estrogens bound to the hER may regulate the antiestrogenic activity of a compound.
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Affiliation(s)
- B M Collins
- Tulane-Xavier Center for Bioenvironmental Research, Tulane University Medical Center, New Orleans, LA 70112, USA
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Arnold SF, Vonier PM, Collins BM, Klotz DM, Guillette LJ, McLachlan JA. In vitro synergistic interaction of alligator and human estrogen receptors with combinations of environmental chemicals. Environ Health Perspect 1997; 105 Suppl 3:615-8. [PMID: 9168004 PMCID: PMC1469900 DOI: 10.1289/ehp.97105s3615] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The effect of mixtures of environmental chemicals with hormonal activity has not been well studied. To investigate this phenomenon, the estrogen receptor (ER) from the American alligator (aER) or human (hER) was incubated with [3H]17beta-estradiol in the presence of selected environmental chemicals individually or in combination. The environmental chemicals included the insecticide chlordane, which has no estrogenic activity, and the pesticides dieldrin and toxaphene, which have very weak estrogenic activity. Chlordane, dieldrin, and toxaphene individually demonstrated no appreciable displacement of [3H]17beta-estradiol from aER and hER at the concentration tested. A combination of these chemicals inhibited the binding of [3H]17beta-estradiol by 20 to 40%. Alachlor, a chemical recently discovered to have weak estrogenic activity, also displaced [3H]17beta-estradiol more effectively in combination with dieldrin than alone. These results indicate that combinations of some environmental chemicals inhibit [3H]17beta-estradiol binding in a synergistic manner. This suggests that the ER may contain more than one site for binding environmental chemicals. The possibility that the ER binds multiple environmental chemicals adds another level of complexity to the interaction between the environment and the endocrine system.
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Affiliation(s)
- S F Arnold
- Tulane-Xavier Center for Bioenvironmental Research, Department of Environmental Health Sciences, Tulane University School of Public Health and Tropical Medicine, New Orleans, Louisiana 70112, USA.
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Arnold SF, Collins BM, Robinson MK, Guillette LJ, McLachlan JA. Differential interaction of natural and synthetic estrogens with extracellular binding proteins in a yeast estrogen screen. Steroids 1996; 61:642-6. [PMID: 8916358 DOI: 10.1016/s0039-128x(96)00183-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We have used the yeast estrogen (YES) consisting of the human estrogen receptor and a reporter containing two estrogen response elements linked to the lacZ gene to evaluate the interaction between ovarian, phyto-, and synthetic estrogens with extracellular binding proteins. YES was incubated with charcoal-stripped human serum, human sex hormone-binding globulin, or human alpha-fetoprotein in the presence of concentrations of various estrogens that induced a 100% estrogenic response, as measured by beta-galactosidase activity. The activity of estradiol and coumestrol, a phytoestrogen, was reduced 75% with physiological levels of serum, sex hormone-binding globulin, or alpha-fetoprotein. The beta-galactosidase activity of genistein, another phytoestrogen, also decreased with extracellular proteins but to a lower extent than estradiol. In contrast, the activity of the synthetic estrogens diethylstilbestrol, kepone, and p,'p-DDD was only minimally reduced with extracellular proteins. These results indicate a potential fundamental difference in the interaction of estrogens from diverse sources with extracellular binding proteins. This suggests that the capacity for various estrogens to induce estrogen-associated responses is in part regulated by their affinity for extracellular bindings proteins.
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Affiliation(s)
- S F Arnold
- Department of Environment Health Sciences, Tulane University, School of Public Health and Tropical Medicine, New Orleans, LA, USA
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Affiliation(s)
- S F Arnold
- Tulane-Xavier Center for Bioenvironmental Research, New Orleans, LA 70112, USA
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Arnold SF, Klotz DM, Collins BM, Vonier PM, Guillette LJ, McLachlan JA. Synergistic activation of estrogen receptor with combinations of environmental chemicals. Science 1996; 272:1489-92. [PMID: 8633243 DOI: 10.1126/science.272.5267.1489] [Citation(s) in RCA: 353] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Certain chemicals in the environment are estrogenic. The low potencies of these compounds, when studied singly, suggest that they may have little effect on biological systems. The estrogenic potencies of combinations of such chemicals were screened in a simple yeast estrogen system (YES) containing human estrogen receptor (hER). Combinations of two weak environmental estrogens, such as dieldrin, endosulfan, or toxaphene, were 1000 times as potent in hER-mediated transactivation as any chemical alone. Hydroxylated polychlorinated biphenyls shown previously to synergistically alter sexual development in turtles also synergized in the YES. The synergistic interaction of chemical mixtures with the estrogen receptor may have profound environmental implications. These results may represent a previously uncharacterized level of regulation of estrogen-associated responses.
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Affiliation(s)
- S F Arnold
- Department of Environmental Health Sciences, Tulane University of Public Health and Tropical Medicine, New Orleans, LA 70112, USA
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Affiliation(s)
- B M Collins
- Department of Oral Diagnostic Sciences, University of Florida College of Dentistry, Gainesville, USA
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Affiliation(s)
- B M Collins
- Department of Oral Diagnostic Sciences, University of Florida College of Dentistry, Gainesville 32610-0414
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