You are here

Tree-ring-based reconstructions of historical fire regimes for quaking aspen, Great Basin bristlecone pine and mountain sagebrush communities

Status: 
Action
Dates: 
October, 2007 to October, 2020

Crew sampling a ponderosa pine stump with evidence of multiple fires in an aspen co-dominant, mixed-conifer stand in the Tushar Mountains, Fishlake National Forest.
Crew sampling a ponderosa pine stump with evidence of multiple fires in an aspen co-dominant, mixed-conifer stand in the Tushar Mountains, Fishlake National Forest.

Wildland fire plays a key role in shaping natural plant communities. Managers benefit from a thorough understanding of the relationship between fire and vegetation. Multi-century fire histories provide a means to quantify past variation in fire regimes and to assess fire regime effects on ecosystem composition, structure, function and resilience. Fire histories developed from tree-ring evidence are well suited for such assessments and can be developed wherever recording trees are present. Although abundant work has been completed documenting fire regime and forest variability for many coniferous forest types, knowledge of historical fire regime variability is lacking for some widespread or high-value forest and non-forest vegetation types in the Intermountain West (USA), including persistent and seral aspen (aspen dominant or co-dominant), mountain sagebrush and Great Basin bristlecone pine.

Fig. 1: Repeat photos taken of Bee Lake on Boulder Mountain, Dixie National Forest show vegetation change over time. The original photo (a) was taken in 1872 by John Hillers and retaken in 1996 (b) by Charles Kay.
Fig. 1: Repeat photos taken of Bee Lake on Boulder Mountain, Dixie National Forest show vegetation change over time. The original photo (a) was taken in 1872 by John Hillers and retaken in 1996 (b) by Charles Kay.

In Fig. 1, Six fire-scarred Douglas fir trees sampled in 2006 recorded multiple fires with a mean fire free interval of 36 years from 1708-1869 – three years before the original picture was taken and the last recorded fire. Today, dense stands of spruce and fir are becoming dominant in the area in the absence of fire.

 

Approach

3.	A partial cross-section was taken from this fire-scarred Great Basin bristlecone pine located on the Markagunt Plateau, Dixie National Forest. The position of the injuries in the annual growth rings allows dating of each fire with annual accuracy.
A partial cross-section was taken from this fire-scarred Great Basin bristlecone pine located on the Markagunt Plateau, Dixie National Forest. The position of the injuries in the annual growth rings allows dating of each fire with annual accuracy.
Intensive field searches are conducted to locate fire-scarred trees (living and dead) both within and in close proximity to target community types representing the range of environmental conditions encountered across the Central Great Basin Ecoregion (Utah and Nevada). Fire-scarred trees are sampled (partial cross-sections) and samples processed and dated to construct location-specific chronologies of past fire. Estimates of episodic recruitment and stand age structure are developed by sampling (cores and cross-sections) trees (or shrubs) of all size classes, and by conducting seedling inventories. Taken together, these fire and stand recruitment chronologies provide the basis for evaluating the effects of fire and fire regime variability on these plant community types in the past, and for predicting plant community stability and response to fire regime change.

 

 

Fig. 2: Graph showing reconstructed fire history for the Swasey Mountain (BLM, Utah) bristlecone pine site.
Fig. 2: Graph showing reconstructed fire history for the Swasey Mountain (BLM, Utah) bristlecone pine site.

In Fig. 2, Solid horizontal lines represent individual trees or groups of trees. Inverted triangles are fire years. Vertical red lines show fire-year synchrony among trees or groups from the same site. Red-yellow bands show within-site synchrony between fire years and pulses of tree establishment. Species codes are PILO = Great Basin bristlecone pine and PSME = Douglas fir.

 

Key Findings

Mountain big sagebrush with pinyon pine encroaching. Over time, pinyon pine and juniper will displace some sagebrush communities in the absence of fire.
Mountain big sagebrush with pinyon pine encroaching. Over time, pinyon pine and juniper will displace some sagebrush communities in the absence of fire.
Great Basin bristlecone pine recovery can be slow after stand replacing fire. This site, which burned 100 years prior to this picture, is near tree-line in Great Basin National Park (Snake Range), Nevada.
Great Basin bristlecone pine recovery can be slow after stand replacing fire. This site, which burned 100 years prior to this picture, is near tree-line in Great Basin National Park (Snake Range), Nevada.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  • Utah aspen is well adapted to a wide range in fire regimes. Historically, fire regimes in aspen-dominant and co-dominant stands included high-frequency, low-severity fire; low-frequency, high-severity fire and intermediate-frequency, mixed-severity fire.
  • Contemporary increases in conifer dominance and aspen decline are due, at least in part, to reductions in fire during the Twentieth Century.
  • Fire-free intervals for mountain sagebrush communities varied historically from few to several decades.
  • Fire frequency for many mountain sagebrush communities has declined since 1900 resulting in expansion of conifers (especially pinyon pines and junipers) into mountain sagebrush communities. In many cases, conversion of shrubland to woodland has already taken place due to a complete loss of fire during the last 150 years.
  • Reconstructed fire histories reveal moderate to long fire-free intervals for Great Basin bristlecone pine even when intervals are much shorter in nearby stands dominated by other forest species.
  • Lack of synchrony among fire-scarred bristlecone pine trees in some stands suggests that many fires were small and patchy in nature.
  • Small-scale synchrony in tree recruitment and death suggests that mixed-severity fires were common on many sites.
  • Post-fire recruitment of bristlecone pine seedlings may begin soon after stand-replacing fire, however, full stand recovery may require 100-200+ years.

Publications

Nelson, Zachary J. ; Weisberg, Peter J. ; Kitchen, Stanley G. , 2014
Heyerdahl, Emily K. ; Brown, Peter M. ; Kitchen, Stanley G. ; Weber, Marc H. , 2011
Kitchen, Stanley G. , 2010
Keane II, Robert E. ; Agee, James K. ; Fule, Peter ; Keeley, Jon E. ; Key, Carl ; Kitchen, Stanley G. ; Miller, Richard ; Schulte, Lisa A. , 2008
Kitchen, Stanley G. ; McArthur, E. Durant , 2007


Project Contact: 

Principal Investigators:
Co-Investigators:
Peter Weisberg - University of Nevada-Reno
Emily K. Heyerdahl - FFS Reserch Forester
Peter Brown - Rocky Mountain Tree Ring Research

Collaborators:
Brian Van Winkle - USFS Dixie and Fishlake National Forest
Steven L. Petersen - Brigham Young University
Chad Reid - Utah State University Extension

Research Staff:
Funding Contributors:
Utah State University
Cedar Mountain Initiative Research Program
Joint Fire Sciences Program
Western Wildlands Environmental Threat Assessment Center