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Fire-prone dry forests often face increasing fires from climate change with low resistance and resilience due to logging of large, old fire-resistant trees. Their restoration across large landscapes is constrained by limited mature trees, physical settings, and protection. Active restoration has been costly and shown limited effectiveness, but lower cost passive restoration is less studied. I used GIS and machine learning to see if passive restoration of old trees could overcome constraints in time, by 2060, across 667,000 ha of montane forests in the San Juan Mountains, Colorado, where temperatures are increasing faster than the global average. Random Forest models of physical locations of reconstructed historical old growth (OG) and relatively frequent fire (RFF) show historical OG with RFF was favored between 6.1-7.9°C annual mean temperatures. Random Forest models projected similar temperature-suitable locations were moved into the current middle montane ca 2015, and would be extended to just below the upper limit of the montane if the Paris 1.5°C goal is reached, but beyond if not. US Forest Service Common Stand Exam data, which covered ~15% of the study area and included 26,149 tree ages, show the highest potential for restoring resistance and resilience from old trees is a ≥120 year age class. This class could become a ≥160 year age class, which meets old-growth age criteria, over 81% of the area by ca 2060, nearly fully restoring historical old-growth levels. Half this age class is already protected, and much of the remainder could be retained using evidence-based diameter caps. Datasets thus are sufficient to show that passive restoration of old-tree resistance and resilience to fire is feasible by ca 2060 across a large montane landscape, although contingent on global success in achieving the Paris 1.5°C goal. Passive restoration may be viable elsewhere.
William L. Baker. Restoration of forest resilience to fire from old trees is possible across a large Colorado dry‐forest landscape by 2060, but only under the Paris 1.5℃ goal. Global Change Biology 2021, 27, 4074 -4095.
AMA StyleWilliam L. Baker. Restoration of forest resilience to fire from old trees is possible across a large Colorado dry‐forest landscape by 2060, but only under the Paris 1.5℃ goal. Global Change Biology. 2021; 27 (17):4074-4095.
Chicago/Turabian StyleWilliam L. Baker. 2021. "Restoration of forest resilience to fire from old trees is possible across a large Colorado dry‐forest landscape by 2060, but only under the Paris 1.5℃ goal." Global Change Biology 27, no. 17: 4074-4095.
Late-1800s land surveys were used to reconstruct historical forest structure and fire over more than 235,000 ha in ponderosa pine and mixed conifer landscapes of the San Juan Mountains, Colorado, to further understand differences among regional mountain ranges and help guide landscape-scale restoration and management. Historically, fire-resistant ponderosa pine forests with low tree density and relatively frequent fire, the most restorable forests, covered only the lower 15%–24% of the study area. The other 76%–85% had dominance by mixed- to high-severity fires. Both ponderosa pine and dry mixed conifer had generally pervasive, often dense understory shrubs, and ~20% of pine and ~50%–75% of mixed conifer forests also had high historical tree density. Intensive fuel reduction and mechanical restoration are infeasible and likely ineffective in the upper part of the pine zones and in mixed conifer, where restoring historical fire and creating fire-adapted communities and infrastructure may be the only viable option. Old-growth forests can be actively restored in the lower 15%–24% of the montane, likely increasing landscape resistance and resilience to fire, but mixed- to high-severity fires did also occur near these areas. This imperfect resistance suggests that fire-adapted human communities and infrastructure are needed throughout the study area.
William L. Baker. Variable Forest Structure and Fire Reconstructed Across Historical Ponderosa Pine and Mixed Conifer Landscapes of the San Juan Mountains, Colorado. Land 2019, 9, 3 .
AMA StyleWilliam L. Baker. Variable Forest Structure and Fire Reconstructed Across Historical Ponderosa Pine and Mixed Conifer Landscapes of the San Juan Mountains, Colorado. Land. 2019; 9 (1):3.
Chicago/Turabian StyleWilliam L. Baker. 2019. "Variable Forest Structure and Fire Reconstructed Across Historical Ponderosa Pine and Mixed Conifer Landscapes of the San Juan Mountains, Colorado." Land 9, no. 1: 3.
William L. Baker; Mark A. Williams. Estimating historical forest density from land‐survey data: Response. Ecological Applications 2019, 29, e02017 .
AMA StyleWilliam L. Baker, Mark A. Williams. Estimating historical forest density from land‐survey data: Response. Ecological Applications. 2019; 29 (8):e02017.
Chicago/Turabian StyleWilliam L. Baker; Mark A. Williams. 2019. "Estimating historical forest density from land‐survey data: Response." Ecological Applications 29, no. 8: e02017.
William L. Baker; Chad T. Hanson; Mark A. Williams. Improving the use of early timber inventories in reconstructing historical dry forests and fire in the western United States: Reply. Ecosphere 2018, 9, e02325 .
AMA StyleWilliam L. Baker, Chad T. Hanson, Mark A. Williams. Improving the use of early timber inventories in reconstructing historical dry forests and fire in the western United States: Reply. Ecosphere. 2018; 9 (7):e02325.
Chicago/Turabian StyleWilliam L. Baker; Chad T. Hanson; Mark A. Williams. 2018. "Improving the use of early timber inventories in reconstructing historical dry forests and fire in the western United States: Reply." Ecosphere 9, no. 7: e02325.
Reconstructing historical fire regimes is difficult at the landscape scale, but essential to determine whether modern fires are unnaturally severe. I synthesized evidence across 725,000 ha of montane forests in the San Juan Mountains, Colorado, from forest atlases, forest-reserve reports, fire-scar studies, early reports, and newspaper accounts. Atlases mapped moderate- to high-severity fires during 1850–1909 (~60 years), and 86% of atlas area was attributable to 24 fire years. Historical fire rotations from atlases were mostly 225–360 years for high-severity fires and 133–185 years for moderate- to high-severity fires. Historical low-severity fire from tree-ring data at 33 sites revealed a median fire rotation of 31 years in ponderosa pine, 78 years in dry mixed-conifer, and 113 years in moist mixed-conifer forests. Only 15% of montane sites had “frequent-fire” forests with fire rotations <25 years that kept understory fuels at low levels. Moderate- to high-severity fire rotations were long enough to enable old-growth forests, but short enough to foster heterogeneous landscapes with expanses of recovering forests and openings. About 38–39% is still recovering from the 1850–1909 fires. Large, infrequent severe fires historically enhanced resilience to subsequent beetle outbreaks, droughts, and fires, but have burned at lower rates in the last few decades.
William L. Baker. Historical Fire Regimes in Ponderosa Pine and Mixed-Conifer Landscapes of the San Juan Mountains, Colorado, USA, from Multiple Sources. Fire 2018, 1, 23 .
AMA StyleWilliam L. Baker. Historical Fire Regimes in Ponderosa Pine and Mixed-Conifer Landscapes of the San Juan Mountains, Colorado, USA, from Multiple Sources. Fire. 2018; 1 (2):23.
Chicago/Turabian StyleWilliam L. Baker. 2018. "Historical Fire Regimes in Ponderosa Pine and Mixed-Conifer Landscapes of the San Juan Mountains, Colorado, USA, from Multiple Sources." Fire 1, no. 2: 23.
Historical evidence suggests natural disturbances could allow more forest persistence, than expected from models, over 40 yr of transition to the net‐zero emissions needed to limit warming to <2.0°C (e.g., Paris Agreement). Forests must ultimately equilibrate with committed warming from accumulated emissions. Historical dry‐forest landscapes were heterogeneous from large, infrequent disturbances (LIDs) that reduced tree density and basal area, followed by slow, variable tree regeneration and recovery for 1–3 centuries. These together effectively provided bet‐hedging through stand‐ and landscape‐level heterogeneity that enhanced resistance and resilience to a diversity of unpredictable subsequent disturbances. Recent disturbances have not yet exceeded historical variability in rates and patterns, but could cause mortality of ∼26–51% of dry‐forest area in the transition. This also means 1/2 to 3/4 of dry‐forest area could escape most mortality and the mortality area could also have substantial forest persistence. Projections are unavailable for droughts or beetle outbreaks, but they recently caused about 3–4 times as much tree mortality as did moderate‐ to high‐severity fires. Mortality could reduce forest area if new trees do not regenerate, but 24 studies showed recent regeneration after high‐severity fires was slow, but indistinct from historical variability. Survival of smaller trees provided regeneration after beetle outbreaks and droughts. Regeneration in general was projected by 2060 to decline by ∼10% in one study and increase by 50% in another. If openings from disturbances increased, some grasslands and shrublands could be restored, increasing landscape heterogeneity and resistance to disturbance spread. Given these trends and our limited ability to prevent LIDs, I suggest (1) refocusing restoration to increase bet‐hedging resilience to droughts and beetle outbreaks by retaining small trees and diverse tree species, (2) expanding development of fire‐safe landscapes to protect people and infrastructure from unavoidable increased fire, (3) enabling more managed fire to restore and enhance stand‐ and landscape‐scale bet‐hedging, and (4) accepting that LIDs will revise resistance, resilience, and adaptation, which enhance forest persistence, particularly if post‐disturbance survivors are not logged and trees are not planted. Natural disturbance and slow recovery, if bet‐hedged to increase resistance and resilience, could enable substantial forest persistence.
William L. Baker. Transitioning western U.S. dry forests to limited committed warming with bet-hedging and natural disturbances. Ecosphere 2018, 9, e02288 .
AMA StyleWilliam L. Baker. Transitioning western U.S. dry forests to limited committed warming with bet-hedging and natural disturbances. Ecosphere. 2018; 9 (6):e02288.
Chicago/Turabian StyleWilliam L. Baker. 2018. "Transitioning western U.S. dry forests to limited committed warming with bet-hedging and natural disturbances." Ecosphere 9, no. 6: e02288.
An understanding of how historical fire and structure in dry forests (ponderosa pine, dry mixed conifer) varied across the western USA remains incomplete. Yet, fire strongly affects ecosystem services, and forest restoration programs are underway. We used General Land Office survey reconstructions from the late-1800s across 11 landscapes covering ∼1.9 million ha in four states to analyze spatial variation in fire regimes and forest structure. We first synthesized the state of validation of our methods using 20 modern validations, 53 historical cross-validations, and corroborating evidence. These show our method creates accurate reconstructions with low errors. One independent modern test reported high error, but did not replicate our method and made many calculation errors. Using reconstructed parameters of historical fire regimes and forest structure from our validated methods, forests were found to be non-uniform across the 11 landscapes, but grouped together in three geographical areas. Each had a mixture of fire severities, but dominated by low-severity fire and low median tree density in Arizona, mixed-severity fire and intermediate to high median tree density in Oregon-California, and high-severity fire and intermediate median tree density in Colorado. Programs to restore fire and forest structure could benefit from regional frameworks, rather than one-size-fits-all. This article is protected by copyright. All rights reserved.
William L. Baker; Mark A. Williams. Land surveys show regional variability of historical fire regimes and dry forest structure of the western United States. Ecological Applications 2018, 28, 284 -290.
AMA StyleWilliam L. Baker, Mark A. Williams. Land surveys show regional variability of historical fire regimes and dry forest structure of the western United States. Ecological Applications. 2018; 28 (2):284-290.
Chicago/Turabian StyleWilliam L. Baker; Mark A. Williams. 2018. "Land surveys show regional variability of historical fire regimes and dry forest structure of the western United States." Ecological Applications 28, no. 2: 284-290.
Early timber inventories in dry forests of the western United States offer detailed data sets that might provide historical information to guide restoration and preparation for future forests, but inventories have errors, biases, and limitations. We reviewed early documentation of errors and estimated errors by comparing inventory estimates to nearby tree-ring and plot estimates. In a case study in the Greenhorn Mountains, southern Sierra Nevada, California, we studied how selection and use of evidence affects findings and compared timber-inventory, land-survey, and other early evidence about historical forests and fire. Early documents showed inventories were unreliable, often with large underestimation errors from poor visual estimates, requiring correction multipliers of 2.0–2.5. Comparing inventory estimates to tree-ring estimates, we found commonly used two-chain-wide inventories required correction multipliers of about 1.4–3.2, consistent with, but wider than the 2.0–2.5 range. These needed corrections were not applied in any study. The case study showed (1) tree-density estimates from narrower one-chain-wide inventories could be more accurate, (2) data are often available, but unused, that provide quantitative evidence about historical high-severity fires consistent with nearby historical reports, and (3) differences in forest structure between inventories and land surveys may be explained by tree growth, stand development, and especially a significant fire. Our review also documented biased placement of inventories in merchantable timber, often excluding younger forests, chaparral, and other indicators of preceding mixed/high-severity fires. We found added significant bias introduced by omitting areas burned in mixed/high-severity fires, or by missing evidence of these fires on parts of forms or associated archival materials. Use of early timber inventories could be improved by (1) avoiding use of unreliable two-chain-wide inventories or applying correction multipliers to inventory estimates, (2) completing an accuracy test of one-chain-wide inventories, (3) locating and using notes, maps, and other data about small trees and high-severity fires often available in inventory archives, or omitting conclusions about these, (4) deriving an envelope model of inference space for inventories, and (5) specifying a large area, then including all available inventory data within it, or using unbiased selection criteria. These improvements could help bring timber-inventory data into congruence with other historical sources.
William L. Baker; Chad T. Hanson. Improving the use of early timber inventories in reconstructing historical dry forests and fire in the western United States. Ecosphere 2017, 8, e01935 .
AMA StyleWilliam L. Baker, Chad T. Hanson. Improving the use of early timber inventories in reconstructing historical dry forests and fire in the western United States. Ecosphere. 2017; 8 (9):e01935.
Chicago/Turabian StyleWilliam L. Baker; Chad T. Hanson. 2017. "Improving the use of early timber inventories in reconstructing historical dry forests and fire in the western United States." Ecosphere 8, no. 9: e01935.
Low-severity fires that killed few canopy trees played a significant historical role in dry forests of the western USA and warrant restoration and management, but historical rates of burning remain uncertain. Past reconstructions focused on on dating fire years, not measuring historical rates of burning. Past statistics, including mean composite fire interval (mean CFI) and individual-tree fire interval (mean ITFI) have biases and inaccuracies if used as estimators of rates. In this study, I used regression, with a calibration dataset of 96 cases, to test whether these statistics could accurately predict two equivalent historical rates, population mean fire interval (PMFI) and fire rotation (FR). The best model, using Weibull mean ITFI, had low prediction error and R2adj = 0.972. I used this model to predict historical PMFI/FR at 252 sites spanning dry forests. Historical PMFI/FR for a pool of 342 calibration and predicted sites had a mean of 39 years and median of 30 years. Short (< 25 years) mean PMFI/FRs were in Arizona and New Mexico and scattered in other states. Long (> 55 years) mean PMFI/FRs were mainly from northern New Mexico to South Dakota. Mountain sites often had a large range in PMFI/FR. Nearly all 342 estimates are for old forests with a history of primarily low-severity fire, found across only about 34% of historical dry-forest area. Frequent fire (PMFI/FR < 25 years) was found across only about 14% of historical dry-forest area, with 86% having multidecadal rates of low-severity fire. Historical fuels (e.g., understory shrubs and small trees) could fully recover between multidecadal fires, allowing some denser forests and some ecosystem processes and wildlife habitat to be less limited by fire. Lower historical rates mean less restoration treatment is needed before beginning managed fire for resource benefits, where feasible. Mimicking patterns of variability in historical low-severity fire regimes would likely benefit biological diversity and ecosystem functioning.
William L. Baker. Restoring and managing low-severity fire in dry-forest landscapes of the western USA. PLOS ONE 2017, 12, e0172288 .
AMA StyleWilliam L. Baker. Restoring and managing low-severity fire in dry-forest landscapes of the western USA. PLOS ONE. 2017; 12 (2):e0172288.
Chicago/Turabian StyleWilliam L. Baker. 2017. "Restoring and managing low-severity fire in dry-forest landscapes of the western USA." PLOS ONE 12, no. 2: e0172288.
Dry forests at low elevations in temperate-zone mountains are commonly hypothesized to be at risk of exceptional rates of severe fire from climatic change and land-use effects. Their setting is fire-prone, they have been altered by land-uses, and fire severity may be increasing. However, where fires were excluded, increased fire could also be hypothesized as restorative of historical fire. These competing hypotheses are not well tested, as reference data prior to widespread land-use expansion were insufficient. Moreover, fire-climate projections were lacking for these forests. Here, I used new reference data and records of high-severity fire from 1984–2012 across all dry forests (25.5 million ha) of the western USA to test these hypotheses. I also approximated projected effects of climatic change on high-severity fire in dry forests by applying existing projections. This analysis showed the rate of recent high-severity fire in dry forests is within the range of historical rates, or is too low, overall across dry forests and individually in 42 of 43 analysis regions. Significant upward trends were lacking overall from 1984–2012 for area burned and fraction burned at high severity. Upward trends in area burned at high severity were found in only 4 of 43 analysis regions. Projections for A.D. 2046–2065 showed high-severity fire would generally be still operating at, or have been restored to historical rates, although high projections suggest high-severity fire rotations that are too short could ensue in 6 of 43 regions. Programs to generally reduce fire severity in dry forests are not supported and have significant adverse ecological impacts, including reducing habitat for native species dependent on early-successional burned patches and decreasing landscape heterogeneity that confers resilience to climatic change. Some adverse ecological effects of high-severity fires are concerns. Managers and communities can improve our ability to live with high-severity fire in dry forests.
William L. Baker. Are High-Severity Fires Burning at Much Higher Rates Recently than Historically in Dry-Forest Landscapes of the Western USA? PLOS ONE 2015, 10, e0136147 .
AMA StyleWilliam L. Baker. Are High-Severity Fires Burning at Much Higher Rates Recently than Historically in Dry-Forest Landscapes of the Western USA? PLOS ONE. 2015; 10 (9):e0136147.
Chicago/Turabian StyleWilliam L. Baker. 2015. "Are High-Severity Fires Burning at Much Higher Rates Recently than Historically in Dry-Forest Landscapes of the Western USA?" PLOS ONE 10, no. 9: e0136147.
Ronald W. Abrams; André Arsenault; William L. Baker; Colden V. Baxter; Laurence E. Berry; Monica L. Bond; Dominick A. Dellasala; Jim Furnish; Richard W. Halsey; Chad T. Hanson; Petr Heneberg; Richard L. Hutto; Timothy Ingalsbee; Breeanne K. Jackson; Dominik Kulakowski; David B. Lindenmayer; Rachel L. Malison; Stephen Mitchell; Dennis C. Odion; Urooj Raja; Rosemary L. Sherriff; Holly Sitters; S. Mažeika P. Sullivan; Alexandra D. Syphard; Thomas T. Veblen; Cathy Whitlock; Shaye Wolf. List of Contributors. The Ecological Importance of Mixed-Severity Fires 2015, 1 .
AMA StyleRonald W. Abrams, André Arsenault, William L. Baker, Colden V. Baxter, Laurence E. Berry, Monica L. Bond, Dominick A. Dellasala, Jim Furnish, Richard W. Halsey, Chad T. Hanson, Petr Heneberg, Richard L. Hutto, Timothy Ingalsbee, Breeanne K. Jackson, Dominik Kulakowski, David B. Lindenmayer, Rachel L. Malison, Stephen Mitchell, Dennis C. Odion, Urooj Raja, Rosemary L. Sherriff, Holly Sitters, S. Mažeika P. Sullivan, Alexandra D. Syphard, Thomas T. Veblen, Cathy Whitlock, Shaye Wolf. List of Contributors. The Ecological Importance of Mixed-Severity Fires. 2015; ():1.
Chicago/Turabian StyleRonald W. Abrams; André Arsenault; William L. Baker; Colden V. Baxter; Laurence E. Berry; Monica L. Bond; Dominick A. Dellasala; Jim Furnish; Richard W. Halsey; Chad T. Hanson; Petr Heneberg; Richard L. Hutto; Timothy Ingalsbee; Breeanne K. Jackson; Dominik Kulakowski; David B. Lindenmayer; Rachel L. Malison; Stephen Mitchell; Dennis C. Odion; Urooj Raja; Rosemary L. Sherriff; Holly Sitters; S. Mažeika P. Sullivan; Alexandra D. Syphard; Thomas T. Veblen; Cathy Whitlock; Shaye Wolf. 2015. "List of Contributors." The Ecological Importance of Mixed-Severity Fires , no. : 1.
Questions Dry forests throughout the world were historically influenced by fires and climatic events, evidenced by tree recruitment pulses in forest age structures, but did these influences act randomly or were recruitment pulses contingent on the type, magnitude, order and timing of events? If recruitment was random or contingent, what are the implications for future forests? Location Unlogged, old‐growth ponderosa pine landscape in Grand Canyon National Park, Arizona, US. Methods We spatially reconstructed and compared tree recruitment pulses evident in forest age structures within plots with tree ring reconstructions of pluvials, droughts, fires and fire quiescence (longer fire‐free periods). We used chi‐square analysis to test for sequential contingency of combinations and permutations of pulse influences. Results Of 20 recruitment pulses, 17 were influenced to some extent by fire quiescence, 13 by fires and droughts each, and 11 by pluvials. Prevalence of pulses across the landscape did not correspond to the pronounced spatial variability in fire rotation. Analysis of combinations and permutations of these influences showed that potentially mortality‐inducing influences of fire and drought likely initiated pulses, whereas pluvials and quiescence, which enhance recruitment conditions, sustained 75% of pulses. Conclusions Successful tree recruitment pulses in dry forests historically were sequentially contingent on mortality‐inducing influences, followed by recruitment‐enhancing conditions. The impacts of climate change projections, including prolonged droughts and intense fires, on dry forests may depend on the order, timing and magnitude of influences.
Alexa J. Dugan; William L. Baker. Sequentially contingent fires, droughts and pluvials structured a historical dry forest landscape and suggest future contingencies. Journal of Vegetation Science 2015, 26, 697 -710.
AMA StyleAlexa J. Dugan, William L. Baker. Sequentially contingent fires, droughts and pluvials structured a historical dry forest landscape and suggest future contingencies. Journal of Vegetation Science. 2015; 26 (4):697-710.
Chicago/Turabian StyleAlexa J. Dugan; William L. Baker. 2015. "Sequentially contingent fires, droughts and pluvials structured a historical dry forest landscape and suggest future contingencies." Journal of Vegetation Science 26, no. 4: 697-710.
Dry forests are particularly subject to wildfires, insect outbreaks, and droughts that likely will increase with climate change. Efforts to increase resilience of dry forests often focus on removing most small trees to reduce wildfire risk. However, small trees often survive other disturbances and could provide broader forest resilience, but small trees are thought to have been historically rare. We used direct records by land surveyors in the late-1800s along 22,206 km of survey lines in 1.7 million ha of dry forests in the western USA to test this idea. These systematic surveys (45,171 trees) of historical forests reveal that small trees dominated (52-92% of total trees) dry forests. Historical forests also included diverse tree sizes and species, which together provided resilience to several types of disturbances. Current risk to dry forests from insect outbreaks is 5.6 times the risk of higher-severity wildfires, with small trees increasing forest resilience to insect outbreaks. Removal of most small trees to reduce wildfire risk may compromise the bet-hedging resilience, provided by small trees and diverse tree sizes and species, against a broad array of unpredictable future disturbances.
William L. Baker; Mark A. Williams. Bet-hedging dry-forest resilience to climate-change threats in the western USA based on historical forest structure. Frontiers in Ecology and Evolution 2015, 2, 1 .
AMA StyleWilliam L. Baker, Mark A. Williams. Bet-hedging dry-forest resilience to climate-change threats in the western USA based on historical forest structure. Frontiers in Ecology and Evolution. 2015; 2 ():1.
Chicago/Turabian StyleWilliam L. Baker; Mark A. Williams. 2015. "Bet-hedging dry-forest resilience to climate-change threats in the western USA based on historical forest structure." Frontiers in Ecology and Evolution 2, no. : 1.
Chad T. Hanson; Rosemary L. Sherriff; Richard L. Hutto; Dominick A. Dellasala; Thomas T. Veblen; William L. Baker. Setting the Stage for Mixed- and High-Severity Fire. The Ecological Importance of Mixed-Severity Fires 2015, 3 -22.
AMA StyleChad T. Hanson, Rosemary L. Sherriff, Richard L. Hutto, Dominick A. Dellasala, Thomas T. Veblen, William L. Baker. Setting the Stage for Mixed- and High-Severity Fire. The Ecological Importance of Mixed-Severity Fires. 2015; ():3-22.
Chicago/Turabian StyleChad T. Hanson; Rosemary L. Sherriff; Richard L. Hutto; Dominick A. Dellasala; Thomas T. Veblen; William L. Baker. 2015. "Setting the Stage for Mixed- and High-Severity Fire." The Ecological Importance of Mixed-Severity Fires , no. : 3-22.
Dominick A. Dellasala; Chad T. Hanson; William L. Baker; Richard L. Hutto; Richard W. Halsey; Dennis C. Odion; Laurence E. Berry; Ronald W. Abrams; Petr Heneberg; Holly Sitters. Flight of the Phoenix. The Ecological Importance of Mixed-Severity Fires 2015, 372 -396.
AMA StyleDominick A. Dellasala, Chad T. Hanson, William L. Baker, Richard L. Hutto, Richard W. Halsey, Dennis C. Odion, Laurence E. Berry, Ronald W. Abrams, Petr Heneberg, Holly Sitters. Flight of the Phoenix. The Ecological Importance of Mixed-Severity Fires. 2015; ():372-396.
Chicago/Turabian StyleDominick A. Dellasala; Chad T. Hanson; William L. Baker; Richard L. Hutto; Richard W. Halsey; Dennis C. Odion; Laurence E. Berry; Ronald W. Abrams; Petr Heneberg; Holly Sitters. 2015. "Flight of the Phoenix." The Ecological Importance of Mixed-Severity Fires , no. : 372-396.
Reconstructing historical habitat could help reverse declining animal populations, but detailed, spatially comprehensive data are rare. For example, habitat for the federally threatened Northern spotted owl (NSO; Strix occidentalis caurina) was thought historically rare because low-severity fires kept forests open and habitat restricted to fire refugia, but spatial historical data are lacking. Here I use public land-surveys to spatially reconstruct NSO habitat and old-growth forests in dry forests in Oregon’s Eastern Cascades in the late-1800s. I used reconstructions of forest structure across about 280,000 ha, including 9,605 tree records and 2,180 section-line descriptions. I was able to reconstruct likely NSO nest trees, nest stands, and foraging and roosting habitat, based on modern NSO habitat studies. Historical nest stands, including sufficient nest trees, were predicted across 22–39 % and foraging and roosting habitat across 11–68 % of the study area, thus neither were rare. More habitat than expected occurred in forests with preceding mixed-severity fires. Early post-fire succession produced foraging and roosting habitat. Mid- to late-succession produced nesting habitat. Late-succession after high-severity fires can also provide NSO habitat. Old-growth forests, covering 76 % of study-area forests, also likely link to preceding mixed-severity fires. Mixed- and high-severity fires strongly shaped historical dry forests and produced important components of historical NSO habitat. Focus on short-term loss of nest sites and territories to these fires is mis-directed. Fuel treatments to reduce these natural fires, if successful, would reduce future habitat of the NSO in dry forests.
William L. Baker. Historical Northern spotted owl habitat and old-growth dry forests maintained by mixed-severity wildfires. Landscape Ecology 2014, 30, 655 -666.
AMA StyleWilliam L. Baker. Historical Northern spotted owl habitat and old-growth dry forests maintained by mixed-severity wildfires. Landscape Ecology. 2014; 30 (4):655-666.
Chicago/Turabian StyleWilliam L. Baker. 2014. "Historical Northern spotted owl habitat and old-growth dry forests maintained by mixed-severity wildfires." Landscape Ecology 30, no. 4: 655-666.
Accurate assessment of changing fire regimes is important, since climatic change and people may be promoting more wildfires. Government wildland fire policies and restoration programmes in dry western US forests are based on the hypothesis that high‐severity fire was rare in historical fire regimes, modern fire severity is unnaturally high and restoration efforts should focus primarily on thinning forests to eliminate high‐severity fire. Using General Land Office (GLO) survey data over large dry‐forest landscapes, we showed that the proportion of historical forest affected by high‐severity fire was not insignificant, fire severity has not increased as a proportion of total fire area and large areas of dense forest were present historically (Williams & Baker, Global Ecology and Biogeography, 21, 1042–1052, 2012; W&B). In response, Fulé et al. (Global Ecology and Biogeography, 2013, doi: 10.1111/geb.12136; FE) suggest that our inferences are unsupported and land management based on our research could be damaging to native ecosystems. Here, we show that the concerns of FE are unfounded. Their criticism comes from misquoting W&B, mistaking W&B's methods, misusing evidence (e.g. from Aldo Leopold) and missing substantial available evidence. We also update corroboration for the extensive historical high‐severity fire shown by W&B. We suggest that restoration programmes are misdirected in seeking to reduce all high‐severity fire in dry forests, given findings from spatially extensive GLO data and other sources.
Mark A. Williams; William L. Baker. High-severity fire corroborated in historical dry forests of the western United States: response to Fuléet al. Global Ecology and Biogeography 2014, 23, 831 -835.
AMA StyleMark A. Williams, William L. Baker. High-severity fire corroborated in historical dry forests of the western United States: response to Fuléet al. Global Ecology and Biogeography. 2014; 23 (7):831-835.
Chicago/Turabian StyleMark A. Williams; William L. Baker. 2014. "High-severity fire corroborated in historical dry forests of the western United States: response to Fuléet al." Global Ecology and Biogeography 23, no. 7: 831-835.
Accuracy of small-area, fire-interval estimation methods has been inadequately assessed, thus we conducted modern calibration and historical testing of the traditional composite-fire-interval and a newer all-tree-fire-interval method for estimating population mean fire intervals. We tested in eight areas, at four scales, using 30 small plots across ponderosa pine forests on the South Rim of Grand Canyon National Park. In modern calibration, individual-plot all-tree-fire-intervals were equal to population mean fire intervals in all plots. Across the eight areas, a mean-plot version of the all-tree-fire-interval method never failed, whereas mean-plot versions of composite-fire-intervals failed in 37.5–100% of areas. Pooled composite-fire-intervals, the traditional method, failed in all subareas. In historical testing, pooled and mean-plot all-tree-fire-interval methods and two variations of a mean-plot composite-fire-interval method had the lowest mean relative errors. Again, pooled composite-fire-intervals performed poorly across the eight areas. Overall, in modern and historical tests, the mean-plot all-tree-fire-interval method outperformed all others, but highly filtered mean-plot composite-fire-intervals were fairly accurate in historical tests. Both could be reliable methods, if replicated in small plots averaged over 600–1000-ha landscapes, but for small areas, the all-tree-fire-interval method outperformed others. However, for general use, there may be more value in spatially explicit, landscape-scale methods, rather than any small-area method.
Alexa J. Dugan; William L. Baker. Modern calibration and historical testing of small-area, fire-interval reconstruction methods. International Journal of Wildland Fire 2014, 23, 58 -68.
AMA StyleAlexa J. Dugan, William L. Baker. Modern calibration and historical testing of small-area, fire-interval reconstruction methods. International Journal of Wildland Fire. 2014; 23 (1):58-68.
Chicago/Turabian StyleAlexa J. Dugan; William L. Baker. 2014. "Modern calibration and historical testing of small-area, fire-interval reconstruction methods." International Journal of Wildland Fire 23, no. 1: 58-68.
Fire scars are widely used to reconstruct fire history, yet patterns of scarring are poorly understood, hampering effective sampling and analysis. Factors that influence the probability a tree will receive a scar (SP) and the fraction of trees that scar (SF) are little studied. We analyzed scarring in 16 fires in ponderosa pine (Pinus ponderosa Douglas ex P. Lawson & C. Lawson) forests in northern Arizona. SP was significantly related to char height, presence of a preceding scar, tree diameter, and years since a preceding fire. Mean SF was 0.375, but varied from 0.121 to 0.728, with SF significantly higher with higher mean char height, larger scar dimensions, higher fire severity, larger tree diameter, and where no preceding fire had burned within 30 years. The expected healing times exceeded 55 years for 33% of scars and 100 years for 11% of scars. Scars with a preceding scar were 38% larger than new scars, with expected healing about 20–25 years longer. Scars were clustered, particularly at scales from >20 to >40 m. Scar directions generally aligned with fire-spread directions, which were complex. Variability in SF complicates fire-history methods that use fire counts rather then area burned. Methods that account for spatial and temporal variability in the abundance of evidence are needed.
William L. Baker; Alexa J. Dugan. Fire-history implications of fire scarring. Canadian Journal of Forest Research 2013, 43, 951 -962.
AMA StyleWilliam L. Baker, Alexa J. Dugan. Fire-history implications of fire scarring. Canadian Journal of Forest Research. 2013; 43 (10):951-962.
Chicago/Turabian StyleWilliam L. Baker; Alexa J. Dugan. 2013. "Fire-history implications of fire scarring." Canadian Journal of Forest Research 43, no. 10: 951-962.
We undertook reconstructions of historical ponderosa pine forest structure and fire regimes across an entire landscape to expand understanding of spatial variability in forest structure and dynamics. The study area includes the ponderosa pine forests of the Coconino Plateau, Arizona, USA. Using General Land Office survey data and newly developed methods, we examined surveyor descriptions of overstory and understory composition and structure across 60,998 ha. For 41,214 ha of forests, we reconstructed density, basal area, diameter-class distributions, and fire severity and used GIS to analyse their relationships with topography. Ponderosa pine forests were continuous in only 34 % of the 60,998 ha landscape. In 40 %, they were mixed with piñon–juniper, 24 % was pure piñon–juniper and 2 % were grass or shrubs. In ponderosa pine forests, the focus of this study, mean tree density was 144.2 trees ha−1; 18.8 % of the landscape had low tree density (200 trees ha−1). Small trees (50 % of all trees on 47 % of the landscape and large trees (>40 cm) composed >50 % of all trees on 21 % of the landscape. Low-severity fire likely structured the forest on 59 % of the landscape while 39 % was structured by mixed-severity fire, likely including small, patchy crown fires. Forest parameters displayed wide variability across environmental gradients. Broader-scale reconstructions revealed a much more spatially complex forest that was structured by wide range of fire severities. Variability in ponderosa pine forests was often under-reported in past studies, but is important in perpetuating biological diversity.
Mark A. Williams; William L. Baker. Variability of historical forest structure and fire across ponderosa pine landscapes of the Coconino Plateau and south rim of Grand Canyon National Park, Arizona, USA. Landscape Ecology 2012, 28, 297 -310.
AMA StyleMark A. Williams, William L. Baker. Variability of historical forest structure and fire across ponderosa pine landscapes of the Coconino Plateau and south rim of Grand Canyon National Park, Arizona, USA. Landscape Ecology. 2012; 28 (2):297-310.
Chicago/Turabian StyleMark A. Williams; William L. Baker. 2012. "Variability of historical forest structure and fire across ponderosa pine landscapes of the Coconino Plateau and south rim of Grand Canyon National Park, Arizona, USA." Landscape Ecology 28, no. 2: 297-310.