FIRE DISTURBANCE OF ALPINE VEGETATION IN THE EASTERN UINTA MOUNTAINS, UTAH, USA

A 10,250-year-long cal yr BP record of vegetation change and fire history from Reader Fen Basin (3205m asl) in the eastern Uinta Mountains provides a unique opportunity to investigate how disturbance regimes influence alpine systems. Previous research in the Uinta Mountains is limited and emphasizes long-term vegetation dynamics, but little information is available on the disturbance history of alpine ecosystems. As a result, significant gaps remain in understanding historical processes affecting biodiversity from this region. The pollen-based vegetation history at Reader Fen Basin suggests subalpine forest species (e.g., Picea engelmannii and Pinus contorta) expanded in the Uinta Mountains soon after glaciers retreated by 9000 cal yr BP. The charcoal record shows evidence of high magnitude fire events influencing vegetation composition during the Holocene. The fire history reconstruction from Reader Fen Basin suggests fires episodes occurred on average every 470 years during the last 10,000 years. Previous work by Morris (2010) on regional fire regimes for south-central Utah suggests climate-drivers, including El Nino/Southern Oscillation and the North American Monsoon, were responsible for the high variability in fire return intervals. Charcoal-based reconstructions of the American West suggest 20^th century fire shows evidence of decline when compared with predicted levels of biomass burning in response to climate (Marlon et al., 2012). In the eastern Uinta Mountains this may be contributing to changes in alpine ecosystems and vegetation composition. Understanding the frequency and magnitude of past fire disturbance is necessary for understanding the catalyst of vegetation change and for making informed management decisions on present and future ecological change in the Uinta Mountains.