131 A Continuous 60,000 Year Sediment Record Documenting Abrupt to Procession-Scale Climate Change and Ecosystem Response at Fish Lake Utah, Upper Colorado River Basin

Faculty Mentor: Andrea Brunelle (Geography, University of Utah)

Fish Lake, Utah’s geographic location provides a unique opportunity to explore the critical role of wildfire in high-elevation forested ecosystems in the Colorado Plateau. In light of extreme drought conditions in the western United States, we are investigating the linkages among vegetation communities, climate change and natural and anthropogenic disturbance. In addition, this study site is located proximal to the ancient “Pando” aspen clone, where we are studying this ancient clone’s specific history (believed to be 60,000 years old), and the overall aspen forest response to climate- and fire-driven events throughout the Holocene. This research demonstrates that wildfires have happened continuously throughout the Holocene, with a period of maximum fire frequency occurring during the last two millennia. In contrast, the early Holocene was a time of reduced fire activity, longer fire-return intervals and protracted climate-driven drought in response to seasonal forcing from maximum summer insolation. Pollen evidence suggests aspen persisted throughout the Holocene with higher and lower relative pollen abundance linked to increases and decreases in fire magnitude, respectively. For example, the largest fire episodes of the Holocene occurred ~4700 cal yr BP and was associated with an increase in aspen pollen within the Fish Lake record. This research is part of a larger timeline, exploring climate, vegetation and fire dynamics during Marine Isotope Stage 3 (25-60,000 cal yr BP) and is designed to provide land managers new insights into the long-term role of disturbances in aspen forests and potentially offer recommendations for future maintenance of healthy aspen ecosystems.