Historical, observed, and modeled wildfire severity in montane forests of the Colorado Front Range

PLoS One. 2014 Sep 24;9(9):e106971. doi: 10.1371/journal.pone.0106971. eCollection 2014.

Abstract

Large recent fires in the western U.S. have contributed to a perception that fire exclusion has caused an unprecedented occurrence of uncharacteristically severe fires, particularly in lower elevation dry pine forests. In the absence of long-term fire severity records, it is unknown how short-term trends compare to fire severity prior to 20th century fire exclusion. This study compares historical (i.e. pre-1920) fire severity with observed modern fire severity and modeled potential fire behavior across 564,413 ha of montane forests of the Colorado Front Range. We used forest structure and tree-ring fire history to characterize fire severity at 232 sites and then modeled historical fire-severity across the entire study area using biophysical variables. Eighteen (7.8%) sites were characterized by low-severity fires and 214 (92.2%) by mixed-severity fires (i.e. including moderate- or high-severity fires). Difference in area of historical versus observed low-severity fire within nine recent (post-1999) large fire perimeters was greatest in lower montane forests. Only 16% of the study area recorded a shift from historical low severity to a higher potential for crown fire today. An historical fire regime of more frequent and low-severity fires at low elevations (<2260 m) supports a convergence of management goals of ecological restoration and fire hazard mitigation in those habitats. In contrast, at higher elevations mixed-severity fires were predominant historically and continue to be so today. Thinning treatments at higher elevations of the montane zone will not return the fire regime to an historic low-severity regime, and are of questionable effectiveness in preventing severe wildfires. Based on present-day fuels, predicted fire behavior under extreme fire weather continues to indicate a mixed-severity fire regime throughout most of the montane forest zone. Recent large wildfires in the Front Range are not fundamentally different from similar events that occurred historically under extreme weather conditions.

Publication types

  • Historical Article
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Altitude
  • Colorado
  • Conservation of Natural Resources / methods
  • Conservation of Natural Resources / trends
  • Disasters / classification
  • Ecosystem*
  • Fires / history*
  • Forests*
  • Geography
  • History, 20th Century
  • History, 21st Century
  • Models, Theoretical
  • Trees / physiology*

Grants and funding

Data collection and analysis were funded by the National Science Foundation (awards BCS-0540928, 0541480, 0802667, 0541594 to TTV, RLS and RVP) and Humboldt State University Sponsored Programs Foundation and College of Arts, Humanities, and Social Sciences (awards to RLS). The funders had no role in the study design, decision to publish, or preparation of the manuscript.