A LAKE SEDIMENT RECORD OF PAST WILDFIRE AND ENVIRONMENTAL VARIABILITY IN THE EASTERN SIERRA, CA DURING THE HOLOCENE

In recent years, California has experienced the most destructive wildfires in its history. For example, consecutive record-breaking fire seasons in the state occurred in 2017 and 2018 with the latter being named the “deadliest and most destructive” season on record according to Cal Fire. It has been suggested that the toll from wildfires in California and elsewhere in the western U.S. will increase in coming decades as fires may become more common and more powerful in response to the impacts of climate change on hydrologic and vegetative conditions. The threat that future wildfire patterns pose to residents, infrastructure, and environments underscores the importance of geological records that can place recent and historical patterns in a longer-term context. Previous studies from around the western U.S. have been successful at generating paleo-fire chronologies during the Holocene (the past ~11,600 years) using lake sediments. In this study, we target lake sediments at Parker Lake, a small (~0.1 km²) and shallow (Z_max ~6 m) lake positioned at 2,540 m a.s.l. along the eastern range front of the Sierra Nevada Range, CA to investigate changing environmental conditions and wildfire occurrence for the past ~10,000 years. Sediment cores collected from multiple locations in the lake were analyzed for changes in sediment physical, biological, and geochemical parameters, including magnetic susceptibility, bulk density, organic matter content, elemental abundance, sediment accumulation rate, and charcoal abundance. Individual lake cores were correlated to each other using prominent tephra layers and distinct sediment laminations, and radiocarbon dating was used to establish age control for the composite sedimentary sequence. Preliminary results suggest that fire activity has varied substantially throughout the Holocene with associated changes in sediment physical parameters in response to changing environmental and hydrological conditions. These results contribute to a better understanding of how alpine and sub-alpine environments in the Eastern Sierra have experienced and responded to past wildfire events.