Document Type

Thesis

Date of Degree Completion

Winter 2019

Degree Name

Master of Science (MS)

Department

Resource Management

Committee Chair

Megan Walsh

Second Committee Member

Patrick McCutcheon

Third Committee Member

Steve Hackenberger

Abstract

Landscapes of the Pacific Northwest have been shaped by dramatic shifts in climate since the last glacial maximum and more recently, by human activity. However, it is unclear how past relationships between people, fire, and climate interacted on the landscape. The purpose of this research was to reconstruct the post-glacial fire history of a wetland known as Horsetail Fen, located in the Teanaway area of the eastern Cascades of Washington State. The goal was to evaluate how fire activity has varied under different climatic scenarios during the last ~16,000 years and in relation to human land-use actions. This lake was selected because it is one of only a few natural wetlands that exist in the Teanaway area below an elevation of 1220 meters (4,000 feet), and because the archaeological record contains evidence that people utilized mountain environments in the eastern Cascades like that around the site. In 2011, a nine-meter-long sediment core was extracted from Horsetail Fen using a modified Livingstone piston corer. High-resolution macroscopic charcoal analysis was used to reconstruct the fire history of the Horsetail Fen watershed. The chronology of the sediment was determined using radiocarbon (14C) dating and tephra layer identification. Results of this study show that fire frequency and severity have varied widely at Horsetail Fen during the post-glacial period. The early Holocene shows fire activity was low and steady and increased significantly during the middle Holocene. Fire activity remained relatively high during late Holocene. The archaeological record provides evidence that people were using these landscapes throughout the Holocene. Ethnographic and oral accounts suggest people were modifying their landscapes using fire. These results can be incorporated in future management plans of forest environments in the eastern Cascades as climate continues to change.

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