UCLA

Climate models predict increases in temperature and hydrologic variability for the remainder of the 21st century, threatening California’s fire-prone ecosystems. To gain a better understanding of future climate-fire-environment dynamics, it is important to study how biomass burning changed in ecosystems as temperatures varied and fuel types changed from Late Marine Isotope Stage (MIS) 3 through MIS 1 (the Holocene). Continuous sedimentary records of fire activity can provide such evidence, but are rare in Southern California. Here, I present fire and environmental dynamics over 32,950 cal yr BP as recorded in a high-resolution macroscopic charcoal record from Lake Elsinore, California. Results are compared to orbital climate forcings and previously reported proxy environmental interpretations for the lake sediments. The lake's charcoal record shows that fire activity was quiescent during late MIS 3. Lake Elsinore's most dynamic charcoal influx occurs during the MIS 2/1 transition from the B�lling Aller�d to the Younger Dryas chronozone. Moving into the Early Holocene, charcoal deposition decreased. During late MIS 1, fire frequency and variability increased as temperatures warmed, and human population density increased near the lake. The record shows millennial-scale variability in fire regimes corresponding to the climate changes associated with insolation changes. This study offers insights into fire, climate, and ecological dynamics from a lake in Southern California and may be key for projecting how ecosystems respond to disturbances under California’s projected climate change.