Holocene Fire History of Green Lake, Eastern Cascades, Washington, Determined Using Macroscopic Charcoal Analysis

Wildfires are common in the dry ponderosa pine forests of the eastern Cascades, and play a vital role in maintaining ecosystem health. However, fire activity in the region has generally been suppressed during the past approximately 100 years. As a result, forests in this region have recently begun to experience larger, more damaging fire events. One such event, the Carlton Complex Fire, burned during the summer of 2014. As the largest wildfire ever recorded in Washington State history, it burned more than 130,000 hectares, consumed 300 homes, and caused considerable infastructure damage before it was contained. In order to put recent fire activity in the eastern Cascades into perspective, long-term fire histories that span the past ~15,000 years are needed. Here, we present results from a study at Green Lake, Washington, which sits approximately 42 km from the Carlton Complex Fire. The lake was cored during summer 2012 and a 4.43 m long sediment core was recovered, providing an approximately 7,600 year-long record. High-resolution macroscopic charcoal analysis was used to reconstruct the fire history of the site, along with loss-on-ignition and magnetic susceptibility analyses. Ratios of herbaceous to woody charcoal were used to determine fuel types and fire severity. Preliminary results indicate that low-severity ground fires were frequent throughout the record, but increased substantially after ca. 1400 AD and remained high until ca. 1850 AD. Future research will involve reconstructing the fire history of a lake within the Carlton Complex burn zone to compare with the Green Lake record