Increase of velvet mesquite (Prosopis velutina Woot.) on the Santa Rita Experimental Range between 1904 (A) and 2012 (B) where there is no record of fire during that period. Desert hackberry (Celtis pallida [Klotzsch] Liebm.) is the primary woody plant present in 1904 (Photo Station 33; http://cals.arizona.edu/photos/PS333/ps333.htm). Image courtesy of Santa Rita Experimental Range Digital Database (http://cals.arizona.edu/srer).