Please note that the Museum will be closing at noon on Wednesday, September 9, 2026 for a staff appreciation event. (Art Institute classes are not affected by the closure.)

Biological Survey of Ironwood Forest National Monument

Lower Colorado River Valley gallery

Principal photographer: Mark Dimmitt


Tinajas Altas Mountains, SW Arizona. Photo: T.R. Van Devender
NW of Blythe, California
Above: Classical Lower Colorado River Valley Sonoran Desert (LCV) is characterized by trees growing only in drainages and saguaros, if present at all, grow on the flats, not hillsides. The mountain slopes support only small plants and appear barren from a distance. Most areas in IFNM (images below) mapped as LCV actually still have elements of Arizona Upland Sonoran Desert.
Above: The broad valleys characteristic of LCV are usually dominated by creosotebush (Larrea divaricata tridentata), as here in the Avra Valley (left) and Aguirre Valley.
Above: The vegetation of these valleys or lower bajadas fit the criteria for LCV (the trees are in drainages and there are saguaros on the flats), but the adjacent West Silver Bell Mountains (left) and Sawtooth Mountains in the backgrounds support sparse trees and saguaros, more typical of Arizona Upland. These two areas are in the transition between two subdivisions of the Sonoran Desert.

A sharp transition between LCV and AZU. The valley's dense jumping chollas and few trees (which are in drainages) are indicative of LCV. The dense woodland of trees and saguaros on the bajada and slopes of the Pan Quemado Mountains in the background are classic Arizona Upland.
This large tree-lined wash draining the West Silver Bell Mountains is a good example of LCV. The adjacent flats support only shrubs and sparse saguaros.

 

 
Silhouette Icon
Biological Survey of Ironwood Forest National Monument General Vegetation Vascular Flora Cacti Distribution and Status of Saguaros and Trees Natural History of the Desert Ironwood Tree (Olneya tesota) Rare Plant Inventory Exotic Plants Assessment Human Impacts Lesser Long-Nosed Bat Geologic Aspects of Ironwood Forest National Monument Avra Valley Gallery Aguirre Valley Images Pan Quemado Gallery Ragged Top Gallery Roskruge Mountains Gallery Samaniego Hills Gallery Sawtooth Mountains Gallery Silver Bell Mountains Gallery Waterman Mountains Gallery West Silver Bell Mountains Gallery Arizona Upland Gallery Lower Colorado River Valley Gallery Xeroriparian Habitats (Desert Washes) The Desert Ironweed Tree - Olneya tesota Cacti of IFNM Crucifixion Thorns of IFNM Gallery of Selected Noncactaceous Flora
CESD Homepage Adult Classes and Trips School & Youth Programs Teacher Resources Need-based Discount Application Community Outreach Digital Library Kids & Education Research & Conservation Natural History Tour of the Sonoran Desert Region Sonorensis magazine cover
Sonorensis Docent Program Green Initiatives

Support Desert Museum Education!

A donation of any size will help sustain our educational efforts. Simply select- Education, Conservation, Science, Research for your designation.

Donate