Authors: Helen Poulos; Andrew Barton; Alan TaylorThe Sky Island forests of Arizona are diverse and topographically complex ecosystems that have been maintained largely by frequent, low-intensity fire for centuries. Fire suppression and drought have triggered multiple, recent high-severity fires throughout the Southwest that have had major impacts on vegetation structure and function. We investigated the effects of the 2011 Horseshoe Two megafire on plant communities in Chiricahua National Monument by resampling a network of vegetation inventory plots that were established prior to the fire. Our results reveal that forest stand structure, species composition, and plant diversity have changed dramatically in response to the fire. While some areas remain unaffected, large portions of the Monument have changed from pine-oak woodland to shrub-dominated vegetation types in response to the fire. This shift is characterized by a loss of plant diversity in former pine-oak woodlands, as well as a loss of forest structural diversity due both to fire-induced mortality and low post-fire regeneration of pines. Such shifts in vegetation structure and function are a major landscape-scale conservation and resource management concern.