The historical role of fire in shaping sagebrush ecosystems remains poorly understood, yet is important for informing the management and conservation of sagebrush landscapes and obligate species such as the threatened Gunnison sage-grouse (GUSG; Centrocercus minimus). To gain insight into the historical role of fire in sagebrush landscapes of the Upper Gunnison Basin (UGB), we reconstructed the historical (1424-2001) frequency of low-severity fire from tree-ring fire-scars at sagebrush-forest ecotones (10 sites, 111 trees), and conducted surveys of plant composition and structure at 100 sagebrush sites with and without recent (2001-2020) fire. Tree-ring fire-scars revealed a history of repeated (mean fire return interval of 18.2 to 79.7 years) low-severity fire at sagebrush-forest ecotones until ca. 1900, followed by over a century that was fire-free. Fires occurred synchronously at two or more sites on average every 23.6 years. Recent burns exhibited strong reductions in sagebrush (from an average of 36.5% to 5.7% cover) and concomitant increases in herbaceous cover (from 40.1% to 55.1%) relative to unburned sites. These shifts diminished with time since fire, but persisted for at least two decades. Together, these results indicate that portions of the sagebrush landscape of the UGB, including occupied GUSG habitat, were historically characterized by repeated fire and vegetation mosaics including patches dominated by grasses and forbs. These findings suggest that prescribed fire could be used to maintain and restore the important ecological process of fire, but also highlight the need for additional research on how such conditions might affect GUSG populations in the context of contemporary conditions.
