Sonoran Desert - Arizona Uplands

The Arizona Uplands subdivision of the Sonoran Desert is defined by having full sized trees in the uplands, as well as high diversity in structure and species. It is well vegetated and sees more moisture than other subdivisions, but also generally has longer and harder freezes. Abundant trees include Parkinsonia microphyllum and P. florida. Prosopis velutina and Olneya tesota are also common. Saguaros almost always occur in this subdivision as well as a variety of cactus, shrubs and sub-shrubs. Common are Opuntia, Lycium, Encelia, and Ambrosia among many others.

Large expanses of the nicest, most well developed Arizona Uplands occur on the Tohono O'odham nation and the Rio Plomo valley and nearby areas in Sonora. This subdivision is most often found on bajadas and rockier substrates closer to hills and mountains, even where Lower Colorado River Valley subdivision dominates, but can also be in valley bottoms and low mountains. Generally most of this subdivision is in south-central Arizona and north-central Sonora.