Event Title

Interpreting Fire, Vegetation and Climate for the Bonneville Basin, Utah During the Last ~36,000 Cal YR BP

Presenter Information

Kelsey Howard
Andrea Brunelle

Location

USU Eccles Conference Center

Event Website

http://www.restoringthewest.org/

Abstract

The Bonneville lake basin of northwestern Utah acts as a significant source of paleoenvironmental data due to the sedimentary and geomorphic evidence left behind from the late Pleistocene Lake Bonneville. Macroscopic charcoal and pollen from wetland sediments of North Redden Springs, Utah (40˚ 00’ 47.1” N 113˚ 41’ 59.9” W) were used to reconstruct a record of past fire and vegetation, along with local and regional climatic changes during the last 36.8 cal ka BP. Changes in charcoal (particles/cm²/yr), and high peak magnitudes (calculated from CharAnalysis), as well as the percentages of total pollen and pollen influx were used to interpret fire, vegetation and climate dynamics. During the latest Pleistocene (36.8- 29 cal ka BP), a cold and dry adapted sagebrush steppe surrounded Lake Bonneville, with no fire episodes due to the inundation of the 26 study site by Lake Bonneville. A subsequent increase in winter precipitation from the southward shift of the polar jet stream during the late Pleistocene (29- 16 cal ka BP) resulted in the expansion of a conifer forest and deeper lake levels. One fire episode occurred at 21 cal ka BP and is associated with a wet period followed by abrupt warming. Greater fuel sources correspond to increased fire episodes during the middle and early Holocene (16- 6.0 cal ka BP), when the climate was transitional between glacial wet/cold to interglacial warm/ dry climate conditions. As early as 16 cal ka BP, a xeric shrub steppe composed of halophytic Amaranthaceae (e.g. shadscale, saltbrush and greasewood) vegetation dominated large expanses of playa around the North Redden lake-wetland complex. The late Holocene (6.0 cal ka BP- present) was characterized as a period of increased aridity, interspersed with cool-wet episodes. A xeric shrub steppe (Amaranthaceae) expanded its range to become the dominate vegetation type on the landscape. Substantial increases in aquatics and other diversified vegetation types also occurred in response to increases in summer moisture. Fires continued to increase in frequency and intensity throughout the historical period. Mechanisms behind fire activity likely included wet climate episodes, which provided ample fuel sources, while subsequent dry climate episodes provided ignition sources. Additionally, anthropogenic burning, fire suppression, and invasive plant species may have contributed to increased fire activity.

Comments

Kelsey Howard attends the University of Utah, Department of Geography

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Oct 28th, 12:30 PM Oct 28th, 1:00 PM

Interpreting Fire, Vegetation and Climate for the Bonneville Basin, Utah During the Last ~36,000 Cal YR BP

USU Eccles Conference Center

The Bonneville lake basin of northwestern Utah acts as a significant source of paleoenvironmental data due to the sedimentary and geomorphic evidence left behind from the late Pleistocene Lake Bonneville. Macroscopic charcoal and pollen from wetland sediments of North Redden Springs, Utah (40˚ 00’ 47.1” N 113˚ 41’ 59.9” W) were used to reconstruct a record of past fire and vegetation, along with local and regional climatic changes during the last 36.8 cal ka BP. Changes in charcoal (particles/cm²/yr), and high peak magnitudes (calculated from CharAnalysis), as well as the percentages of total pollen and pollen influx were used to interpret fire, vegetation and climate dynamics. During the latest Pleistocene (36.8- 29 cal ka BP), a cold and dry adapted sagebrush steppe surrounded Lake Bonneville, with no fire episodes due to the inundation of the 26 study site by Lake Bonneville. A subsequent increase in winter precipitation from the southward shift of the polar jet stream during the late Pleistocene (29- 16 cal ka BP) resulted in the expansion of a conifer forest and deeper lake levels. One fire episode occurred at 21 cal ka BP and is associated with a wet period followed by abrupt warming. Greater fuel sources correspond to increased fire episodes during the middle and early Holocene (16- 6.0 cal ka BP), when the climate was transitional between glacial wet/cold to interglacial warm/ dry climate conditions. As early as 16 cal ka BP, a xeric shrub steppe composed of halophytic Amaranthaceae (e.g. shadscale, saltbrush and greasewood) vegetation dominated large expanses of playa around the North Redden lake-wetland complex. The late Holocene (6.0 cal ka BP- present) was characterized as a period of increased aridity, interspersed with cool-wet episodes. A xeric shrub steppe (Amaranthaceae) expanded its range to become the dominate vegetation type on the landscape. Substantial increases in aquatics and other diversified vegetation types also occurred in response to increases in summer moisture. Fires continued to increase in frequency and intensity throughout the historical period. Mechanisms behind fire activity likely included wet climate episodes, which provided ample fuel sources, while subsequent dry climate episodes provided ignition sources. Additionally, anthropogenic burning, fire suppression, and invasive plant species may have contributed to increased fire activity.

https://digitalcommons.usu.edu/rtw/2015/Posters/13