Dramatic changes in the type and amount of vegetation have occurred since the early 1900's. Examples of these changes since 1903 are provided in figures 2-16. In 1903 (fig. 2), draws were characterized by young stands of velvet mesquite, which matured and retained a woody aspect over time (figs. 3,4). However, uplands were generally devoid of woody plants (figs. 5,8) and characterized more by a grassland aspect. Burroweed was the dominant woody plant on uplands. Density of burroweed was documented to peak around 1908, 1935, 1959, and 1969, with each peak following one or more exceptionally wet winter-spring periods and with low densities following severe winter drought (Martin 1986a). Jumping cholla cactus was absent on uplands in 1905-1910 (figs. 5, 8, and 11) but locally abundant in the 1940's and 1950's (figs. 6, 9, and 12) and declined to low densities in the 1970's and 1980's (figs. 7, 10, and 13). Martin (1986a) reported the population cycle to be about 40 years. Velvet mesquite increased dramatically on more mesic uplands (figs. 5- 13) but some sites (rocky, clayey types) retained their grassland aspect (figs. 14-16). Some grassland sites retained their aspect and native vegetation (figs. 5-7), but sites where lehmann lovegrass was seeded and/or subsequently spread to other sites changed aspect to either a mesquite-lehmann lovegrass savannah or pure stands of lehmann lovegrass (figs. 8-16). Lehmann lovegrass has replaced many of the native herbaceous species on vast areas that once were native grasslands.