Event Title

Historical Mountain Big Sagebrush Fire Frequency from Fire-Scarred Trees: A Multi-site Analysis for Utah and Eastern Nevada

Location

USU Eccles Conference Center

Event Website

http://www.restoringthewest.org/

Abstract

Knowledge of past fire regimes associated with mountain big sagebrush (MBS) communities is inadequate for science-based land management that requires assessment of departure from historical conditions. Widely used estimates of MBS fire frequency are based upon studies using fire-scarred proxy trees located at forest/shrubland ecotones. These studies fail to adequately address questions of fire behavior across plant community boundaries or independent estimates of post-fire MBS recovery. We developed 71 fire chronologies from 190 fire-scarred trees located within or in close proximity to MBS communities at 10 sites in the eastern Great Basin, upper Colorado Plateau and intervening highlands. Average chronology length was 246 years. Mean fire interval ranged from 7.8 to 144.5 years. Mean, minimum and maximum fire-free intervals were evaluated based upon spatial relationship of fire-scarred trees to study MBS communities and were compared to documented MBS post-fire recovery rates. Within sites, fire frequencies were mostly similar for shrub-dominated, ecotonal and tree-dominated chronologies, suggesting that, in spite of shifts in fuel structure, forest-shrubland ecotones were relatively porous to surface fire spread. Conversely, high fire-frequency chronologies associated with some landscapes were not consistent with the fire-free intervals required for full MBS recovery and dominance, inferring that either fires burned in patchy, incomplete patterns or that MBS was historically less abundant (or absent), or both. Hence, both reconstructed fire regimes and vegetation successional dynamics must be considered when comparing historical and modern MSB responses to fire.

Comments

Stanley Kitchen is with the US Forest Service, Rocky Mountain Research Station

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Oct 29th, 9:30 AM Oct 29th, 10:00 AM

Historical Mountain Big Sagebrush Fire Frequency from Fire-Scarred Trees: A Multi-site Analysis for Utah and Eastern Nevada

USU Eccles Conference Center

Knowledge of past fire regimes associated with mountain big sagebrush (MBS) communities is inadequate for science-based land management that requires assessment of departure from historical conditions. Widely used estimates of MBS fire frequency are based upon studies using fire-scarred proxy trees located at forest/shrubland ecotones. These studies fail to adequately address questions of fire behavior across plant community boundaries or independent estimates of post-fire MBS recovery. We developed 71 fire chronologies from 190 fire-scarred trees located within or in close proximity to MBS communities at 10 sites in the eastern Great Basin, upper Colorado Plateau and intervening highlands. Average chronology length was 246 years. Mean fire interval ranged from 7.8 to 144.5 years. Mean, minimum and maximum fire-free intervals were evaluated based upon spatial relationship of fire-scarred trees to study MBS communities and were compared to documented MBS post-fire recovery rates. Within sites, fire frequencies were mostly similar for shrub-dominated, ecotonal and tree-dominated chronologies, suggesting that, in spite of shifts in fuel structure, forest-shrubland ecotones were relatively porous to surface fire spread. Conversely, high fire-frequency chronologies associated with some landscapes were not consistent with the fire-free intervals required for full MBS recovery and dominance, inferring that either fires burned in patchy, incomplete patterns or that MBS was historically less abundant (or absent), or both. Hence, both reconstructed fire regimes and vegetation successional dynamics must be considered when comparing historical and modern MSB responses to fire.

http://digitalcommons.usu.edu/rtw/2015/Posters/9