Severity of an uncharacteristically large wildfire, the Rim Fire, in forests with relatively restored frequent fire regimes

The 2013 Rim Fire, originating on Forest Service land, burned into old-growth forests within Yosemite National Park with relatively restored frequent-fire regimes (P2 predominantly low and moderate severity burns within the last 35 years). Forest structure and fuels data were collected in the field 3–4 years before the fire, providing a rare chance to use pre-existing plot data to analyze fire effects. We used regression tree and random forests analysis to examine the influence of forest structure, fuel, fire history, topographic and weather conditions on observed fire severity in the Rim Fire, as estimated from an initial fire severity assessment based on the relative differenced normalized burn ratio (RdNBR). Plots that burned on days with strong plume activity experienced moderate- to high-severity fire effects regardless of forest conditions, fire history or topography. Fire severity was also highly negatively associated with elevation, with lower severity observed in plots over 1700 m. Burning index (a composite index of fire weather), time since the last fire, and shrub cover had strong positive associations with fire severity. Plots that had experienced fire within the last 14 years burned mainly at low severity in the Rim Fire, while plots that exceeded that time since last fire tended to burn at moderate or high severity. This effect of time since last fire was even more pronounced on days when the burning index was high. Our results suggest that wildfire burning under extreme weather conditions, as is often the case with fires that escape initial attack, can produce large areas of high-severity fire even in fuels-reduced forests with restored fire regimes. Published by Elsevier B.V.

[1]  S. Stephens,et al.  Wildfire and Spatial Patterns in Forests in Northwestern Mexico: The United States Wishes It Had Similar Fire Problems , 2008 .

[2]  James K. Brown.  Handbook for inventorying downed woody material , 1974 .

[3]  Maggi Kelly,et al.  Interactions Among Wildland Fires in a Long-Established Sierra Nevada Natural Fire Area , 2009, Ecosystems.

[4]  E. Knapp,et al.  Trends and causes of severity, size, and number of fires in northwestern California, USA. , 2012, Ecological applications : a publication of the Ecological Society of America.

[5]  S. Stephens,et al.  Harnessing fire for wildlife , 2010 .

[6]  Andrew T. Hudak,et al.  Burn Severity of Areas Reburned by Wildfires in the Gila National Forest, New Mexico, USA , 2010 .

[7]  Russell T. Graham,et al.  Hayman Fire Case Study , 2003 .

[8]  G. Tutz,et al.  An introduction to recursive partitioning: rationale, application, and characteristics of classification and regression trees, bagging, and random forests. , 2009, Psychological methods.

[9]  Alex Hall,et al.  Observed Climate–Snowpack Relationships in California and their Implications for the Future , 2008 .

[10]  Brandon M. Collins,et al.  Fire weather and large fire potential in the northern Sierra Nevada , 2014 .

[11]  Joshua H. Viers,et al.  Modern departures in fire severity and area vary by forest type, Sierra Nevada and southern Cascades, California, USA , 2013 .

[12]  S. Stephens,et al.  Spatial patterns of large natural fires in Sierra Nevada wilderness areas , 2007, Landscape Ecology.

[13]  T. Swetnam,et al.  Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity , 2006, Science.

[14]  Joseph W. Sherlock,et al.  Calibration and validation of the relative differenced Normalized Burn Ratio (RdNBR) to three measures of fire severity in the Sierra Nevada and Klamath Mountains, California, USA , 2009 .

[15]  K. Hornik,et al.  Unbiased Recursive Partitioning: A Conditional Inference Framework , 2006 .

[16]  Sierra Nevada Ecosystem,et al.  Assessments and scientific basis for management options , 1996 .

[17]  Scott L. Stephens,et al.  Temperate and boreal forest mega‐fires: characteristics and challenges , 2014 .

[18]  P. Bartlein,et al.  Long-term perspective on wildfires in the western USA , 2012, Proceedings of the National Academy of Sciences.

[19]  Sierra Nevada Ecosystem,et al.  Sierra Nevada Ecosystem Project final report to Congress , 1997 .

[20]  P. J. Mantgem,et al.  Negligible Influence of Spatial Autocorrelation in the Assessment of Fire Effects in a Mixed Conifer Forest , 2009 .

[21]  Carolin Strobl,et al.  An AUC-based permutation variable importance measure for random forests , 2013, BMC Bioinformatics.

[22]  B. Collins,et al.  Early forest dynamics in stand-replacing fire patches in the northern Sierra Nevada, California, USA , 2013, Landscape Ecology.

[23]  C. Halpern,et al.  Long‐term vegetation responses to reintroduction and repeated use of fire in mixed‐conifer forests of the Sierra Nevada , 2010 .

[24]  C. Skinner,et al.  Fire regimes, past and present , 1996 .

[25]  Jay D. Miller,et al.  Climate, lightning ignitions, and fire severity in Yosemite National Park, California, USA. , 2009 .

[26]  Anne van der Veen,et al.  Research, part of a Special Feature on New Methods for Adaptive Water Management Dealing with Uncertainty in Flood Management Through Diversification , 2008 .

[27]  Charles W. McHugh,et al.  Fire behavior, fuel treatments, and fire suppression on the Hayman Fire - Part 5: Fire suppression activities , 2003 .

[28]  S. Hurlbert.  Pseudoreplication and the Design of Ecological Field Experiments , 1984 .

[29]  A. Larson,et al.  Tree spatial patterns in fire-frequent forests of western North America, including mechanisms of pattern formation and implications for designing fuel reduction and restoration treatments , 2012 .

[30]  David J. Parsons,et al.  Impact of fire suppression on a mixed-conifer forest , 1979 .

[31]  Neil G. Sugihara,et al.  Fire in California's ecosystems , 2006 .

[32]  R. Weiss,et al.  Trace gas and particulate emissions from the 2003 southern California wildfires , 2007 .

[33]  Carl H. Key,et al.  Landscape Assessment (LA) , 2006 .

[34]  M. Moritz,et al.  Large wildfire trends in the western United States, 1984–2011 , 2014 .

[35]  Achim Zeileis,et al.  BMC Bioinformatics BioMed Central Methodology article Conditional variable importance for random forests , 2008 .

[36]  Achim Zeileis,et al.  Bias in random forest variable importance measures: Illustrations, sources and a solution , 2007, BMC Bioinformatics.

[37]  A. Taylor.  Fire disturbance and forest structure in an old-growth Pinus ponderosa forest, southern Cascades, USA , 2010 .

[38]  Frederick W. Smith,et al.  Influence of topography and forest structure on patterns of mixed severity fire in ponderosa pine forests of the South Dakota Black Hills, USA , 2006 .

[39]  S. Stephens,et al.  FEDERAL FOREST‐FIRE POLICY IN THE UNITED STATES , 2005 .

[40]  S. Stephens,et al.  Western pine forests with continuing frequent fire regimes: Possible reference sites for management , 2005 .

[41]  S. Roberts.  Managing Sierra Nevada Forests , 2012 .

[42]  Jay D. Miller,et al.  Quantifying burn severity in a heterogeneous landscape with a relative version of the delta Normalized Burn Ratio (dNBR) , 2007 .

[43]  A. Taylor,et al.  Fire regimes, forest change, and self-organization in an old-growth mixed-conifer forest, Yosemite National Park, USA. , 2010, Ecological applications : a publication of the Ecological Society of America.

[44]  E. Knapp,et al.  Quantifying spatial patterns of tree groups and gaps in mixed-conifer forests: Reference conditions and long-term changes following fire suppression and logging , 2013 .

[45]  S. Stephens,et al.  Managing natural wildfires in Sierra Nevada wilderness areas , 2007 .

[46]  Topographic Variation in Structure of Mixed-Conifer Forests Under an Active-Fire Regime , 2012, Ecosystems.

[47]  R. T. Belote,et al.  Latent resilience in ponderosa pine forest: effects of resumed frequent fire. , 2013, Ecological applications : a publication of the Ecological Society of America.

[48]  Carol Miller,et al.  Previous Fires Moderate Burn Severity of Subsequent Wildland Fires in Two Large Western US Wilderness Areas , 2013, Ecosystems.

[49]  Jan W. van Wagtendonk,et al.  The History and Evolution of Wildland Fire Use , 2007 .

[50]  T. Spies,et al.  Factors associated with crown damage following recurring mixed-severity wildfires and post-fire management in southwestern Oregon , 2010, Landscape Ecology.

[51]  John F. Caratti,et al.  FIREMON: Fire Effects Monitoring and Inventory System , 2012 .

[52]  A. J. Parker,et al.  THE TOPOGRAPHIC RELATIVE MOISTURE INDEX: AN APPROACH TO SOIL-MOISTURE ASSESSMENT IN MOUNTAIN TERRAIN , 1982 .

[53]  Jan W. van Wagtendonk,et al.  Factors Associated with the Severity of Intersecting Fires in Yosemite National Park, California, USA , 2012 .

[54]  A. Taylor,et al.  Southern cascades bioregion , 2006 .

[55]  M. Parisien,et al.  Multi-scale evaluation of the environmental controls on burn probability in a southern Sierra Nevada landscape , 2011 .

[56]  Cynthia Fowler,et al.  Human Health Impacts of Forest Fires in the Southern United States: A Literature Review , 2003 .

[57]  Scott L. Goodrick,et al.  Wildland fire emissions, carbon, and climate: Wildfire-climate interactions , 2014 .

[58]  S. Stephens,et al.  Impacts of fire exclusion and recent managed fire on forest structure in old growth Sierra Nevada mixed-conifer forests , 2011 .