Event Title

A 7000-year Wildfire Reconstruction from Southwest Utah Reveals Relations Among Climate, Vegetation, and the Timing of Arroyo Cut-fill Dynamics

Presenter Information

Kerry Riley
Tammy Rittenour
Justin DeRose

Location

USU Eccles Conference Center

Event Website

http://water.usu.edu

Start Date

5-4-2016 5:39 PM

End Date

5-4-2016 5:42 PM

Description

Changes in climate influence vegetation distributions and the frequency and severity of fire. This study uses 14C-dating of charcoal fragments from discrete arroyo wall deposits to reconstruct a 7,000-yr record of fire in the Grand Staircase region of the Colorado Plateau physiographic province, in south-central Utah. The Grand Staircase exhibits colorful cliffs and benches that are dissected by tributaries of the Colorado River and watersheds are underlain by alternating resistant and less-resistant sedimentary rocks that increase in elevation from south to north, rising from Grand Canyon. The increase in elevation influences precipitation and vegetation distributions. The precipitation regime of the region is generally bimodal, influenced by late summer and winter precipitation and is located on the northwest boundary of direct influence of the North American Monsoon characterized by increased precipitation from July through September. The study area spans an ecological gradient from the highest elevations composed of subalpine forests, transitioning into a mixed-conifer forest, then pinyon/juniper woodlands, and finally at the lowest elevations the vegetation is composed of desert scrub. Radiocarbon ages (n=124) derived from charcoal stored within arroyo-wall alluvium were used to reconstruct the fire history of the region. Preliminary results from three adjacent watersheds show peaks in fire activity between 2000-1500, 1250-950, and 700-450 cal yr BP. These periods correspond to similar peaks in fire activity throughout the western US. Preliminary results from superposed epoch analyses (SEA) comparing periods of multi-basin fires to reconstructed climate proxies including Nino3, Palmer Drought Severity Index (PDSI), and a reconstruction of Colorado River flow suggest that multi-basin fires commonly occurred during transitions from wet to dry conditions. We hypothesis that 1) fire spread in drier and (or) lower elevation ecosystems is limited by vegetation density (i.e., fuel accumulation) and 2) the drying of fuel accumulated during wetter periods would lead to subsequent large fires.

Comments

A poster by Kerry Riley, who is with Utah State University, Geology

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Apr 5th, 5:39 PM Apr 5th, 5:42 PM

A 7000-year Wildfire Reconstruction from Southwest Utah Reveals Relations Among Climate, Vegetation, and the Timing of Arroyo Cut-fill Dynamics

USU Eccles Conference Center

Changes in climate influence vegetation distributions and the frequency and severity of fire. This study uses 14C-dating of charcoal fragments from discrete arroyo wall deposits to reconstruct a 7,000-yr record of fire in the Grand Staircase region of the Colorado Plateau physiographic province, in south-central Utah. The Grand Staircase exhibits colorful cliffs and benches that are dissected by tributaries of the Colorado River and watersheds are underlain by alternating resistant and less-resistant sedimentary rocks that increase in elevation from south to north, rising from Grand Canyon. The increase in elevation influences precipitation and vegetation distributions. The precipitation regime of the region is generally bimodal, influenced by late summer and winter precipitation and is located on the northwest boundary of direct influence of the North American Monsoon characterized by increased precipitation from July through September. The study area spans an ecological gradient from the highest elevations composed of subalpine forests, transitioning into a mixed-conifer forest, then pinyon/juniper woodlands, and finally at the lowest elevations the vegetation is composed of desert scrub. Radiocarbon ages (n=124) derived from charcoal stored within arroyo-wall alluvium were used to reconstruct the fire history of the region. Preliminary results from three adjacent watersheds show peaks in fire activity between 2000-1500, 1250-950, and 700-450 cal yr BP. These periods correspond to similar peaks in fire activity throughout the western US. Preliminary results from superposed epoch analyses (SEA) comparing periods of multi-basin fires to reconstructed climate proxies including Nino3, Palmer Drought Severity Index (PDSI), and a reconstruction of Colorado River flow suggest that multi-basin fires commonly occurred during transitions from wet to dry conditions. We hypothesis that 1) fire spread in drier and (or) lower elevation ecosystems is limited by vegetation density (i.e., fuel accumulation) and 2) the drying of fuel accumulated during wetter periods would lead to subsequent large fires.

http://digitalcommons.usu.edu/runoff/2016/2016Posters/24