Masters Thesis

Sedimentary analysis of fire history and paleohydrology, Eagle Lake, California

This project used a high-resolution sedimentary technique to characterize the fire history of Eagle Lake, California from present to 18 kyrs BP, and considered the ecohydrologic interconnection of fire. In order to understand global fire history trends, and the influence of climatic and anthropogenic factors, continued mapping and analysis of fire history as an earth systems process is essential. A previous study analyzed the paleoenvironment of Eagle Lake and recommended a high resolution paleofire study be performed at Eagle Lake. Eagle Lake is an endorheic lake located in central Lassen County, California. Fire history and paleohydrology were analyzed using macro-charcoal, magnetic susceptibility data, chemostratigraphy (bulk geochemical data), radiochronology (14C), and lithology from a 1 m sediment core (ELNEC1-1). Fire history was characterized by entering macro-charcoal data and age-date information into CharAnalysis. Paleohydrology data was characterized using lithology and magnetic susceptibility data. Chemostratigraphy was used to enhance lithostratigraphy via zonation analysis. Radiocarbon age-dating was used to establish a geochronology of core ELNEC1-1. The fire history of the Eagle Lake can be divided into three periods: 18 to 10 kyrs BP, 10 to 2.8 kyrs BP, and 2.8 kyrs BP to present. Hydrologic activity during the first period (18 to 10 kyrs BP) was low, limiting fuel availability, and supporting small, frequent fires. Hydrologic activity during the second period (10 to 2.8 kyrs BP) was initially low due to limited fuel availability, supporting small frequent fire. The beginning of the second period marks the end of the glacial period. After approximately 8 kyrs BP, hydrologic activity increased to moderate/high levels, and fuel availability increased, supporting larger moderately frequent fires until 4.2 kyrs BP. From 4.2 to 1.5 kyrs BP, fire frequency and magnitude were low due to neoglaciation. Hydrologic activity during the third period (2.8 kyrs BP to present) was moderate and decreased to present, allowing for low to moderately frequent fires with moderate magnitude through to period end. The climate of Eagle Lake prior to 15 kyrs BP was cold and moist, from 15 to 8.5 kyrs BP it was warm and dry, from 8.5 kyrs to 4 kyrs BP it was warm and wet, and from 4 kyrs BP to present it was cool and wet. Indigenous populations clearly influenced the fire history of Eagle Lake, moderated fire frequency over the Holocene, and set fires for forest understory management, wildlife management, manufacturing, and agricultural purposes. Despite evidence of indigenous occupation, it is difficult to distinguish anthropogenic influences and climatic trends.

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