Holocene climate, vegetation, and fire linkages in the Uinta Mountains, Utah

A 14,000-year lake sediment record from Heller Lake-Dry Gulch Meadow on the south slope of the Uinta Mountains provides evidence of large-magnitude disturbance events during the Holocene. The modern lake basin which catastrophically drained in the early 20th century provides a uniquely exposed sedimentary archive to examine lake sediments in situ and analyze sediment samples from the lake bottom. Analysis of this sedimentary record explores the climate, vegetation, and fire history, and their potential implications on land management. Pollen and charcoal evidence suggest a large-scale vegetation and fire regime shift at approximately 6,500 cal yr BP when fire activity increased dramatically and dominant vegetation changed from open spruce parkland to closed canopy pine forest. Average fire return intervals have remained relatively stable during the last ~10,000 years; however, frequency and magnitude have decreased during the last few millennia, suggesting the modern montane forest of the Uinta Mountains developed under an infrequent fire regime. The mid-Holocene maximum in fire frequency, with fires averaging one event every ~140 years, may provide a perspective on future trends of increased fires in middle and high elevation forests as snowpack decreases and summer temperatures continue warming. Increased fire frequency in the past has led to major vegetation changes in the Uinta Mountains, and recent trends in fire activity, such as the large fires in 2007, suggest understanding fire-climate linkages should be a management priority.