PALEOECOLOGICAL RECONSTRUCTION OF HOLOCENE DROUGHT AND VEGETATION CHANGES USING LAKE SEDIMENTS FROM DOG LAKE, SOUTH-CENTRAL OREGON

Dog Lake is a perennial mid-elevation (1554 masl) freshwater lake located in south-central Oregon on the western periphery of the hydrologic Northern Great Basin. The 10,000 year old landslide-formed lake has a current mean depth of approximately 6 m and is surrounded by extensive wetlands and conifer forests. In 2016 a 13 m, highly organic sediment core was recovered. The core materials were used for isotopic and pollen analysis for the purpose of finding indicators of Holocene paleodroughts and their durations. Periods of increased aridity were determined using δ¹³C, δ¹⁵N, and TOC% serving as proxies for increases in water temperatures, which would result in increased diatom productivity and sedimentation rates. Pollen was used to identify decreases in mesic vegetation as a proxy for decreasing precipitation and measuring increases in wetland vegetation, an indication of increased wetland habitat as a result of lower lake levels. Our findings matched well with other regional paleodrought studies, but also show some variation in aridity timings unique to the Dog Lake basin area.