Dwellers of the Sonoran Desert have done a good job of selling their homeland. Almost everyone thinks of it when thoughts turn to deserts, and its Saguaro Cactus has become the icon of the desert. That icon, though, is absent in the Great Basin, Mojave, and Chihuahuan deserts. But why? After all, aren't all deserts the same—marked by an absence of abundant water?
Well, no! Even though deserts are defined by low precipitation, each desert has its own character based on many differences. Apparently the Saguaro cactus is absent from the other three North American deserts in large part because those other three are too cold. Not too cold in summer, but in winter. Young Saguaros seem to be able to take a night of freezing temperatures, but if the temperature remains below freezing for a night, the following day, and the following night, mortality is high.
The Chihuahuan Desert, though as far south as the Sonoran, is a
high-elevation arid land, and thus extends into altitudes occasionally too cold in
winter for the Sonoran Desert's icon.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
Sonoran Desert scene near Tucson, AZ. A Saguaro stands in the mid foreground, while others are visible in the far background. Photograph by A.H. Harris.
Steenbergh, W. F., and C. H. Lowe. 1976. Ecology of the saguaro: I. The role of freezing weather in a warm-desert plant population. In: Research in the Parks: Transactions of the National Park Centennial symposium, National Park Service Symposium Series No. 1: 49-92.
Steenbergh, W. F., and C. H. Lowe. 1977. Ecology of the saguaro: II. Reproduction, germination, establishment, and survival of the young plant. National Park Service Scientific Monograph Series Number 8:1-242. National Park Service.