Desertscrub

Desertscrub communities.
Desertscrub communities can have a good assortment of plants even during dry periods when desert annuals are absent. Common sotol (Dasylirion wheeleri), ocotillo, pricklypear (Opuntia sp.), Mormon tea (Ephedra sp.), and velvet mesquite are all prominent in this photo. Photo by Charlie McDonald.

Desertscrub communities.
Desertscrub communities can have quite a few grasses in areas that are ungrazed or lightly grazed. Photo By Charlie McDonald.

“Desertscrub” is a general term that includes several desert plant communities occurring usually at elevations below 3,500 feet. These are the areas of hot summers, mild winters, and low (9 inches or less) and irregular rainfall. Going without rain for a year or more is not unusual in deserts. The vegetation is a mixture of shrubs, succulents, herbs, and a few grasses. The herbs often appear almost absent until above normal rainfall makes many bloom at the same time in spectacular wildflower displays. Some of the characteristic plants include creosote bush (Larrea tridentata), velvet mesquite (Prosopis velutina), yellow paloverde (Parkinsonia microphylla), ocotillo (Fouquieria splendens), fairyduster (Calliandra eriophylla), catclaw acacia (Acacia greggii), Palmer’s century plant (Agave palmeri), walkingstick cactus (Cylindropuntia spinosior), tulip pricklypear (Opuntia phaeacantha), jumping cholla (Cylindropuntia fulgida), saguaro (Carnegiea gigantea), and desert-thorn (Lycium spp.).

This desertscrub community at the base of the Santa Catalina Mountains.
This desertscrub community at the base of the Santa Catalina Mountains features saguaro and yellow paloverde. Photo by Charlie McDonald.

The invasion of non-native grasses introduced to the region for rangeland improvement threatens the integrity of some desertscrub communities. Lehmann lovegrass (Eragrostis lehmanniana) and buffelgrass (Pennisetum ciliare) are the main culprits. Both of these grasses produce dense stands of fine-textured fuels that burn much hotter than the native grasses. When these grasses burn, the hot fire kills many of the native shrubs and succulents leaving almost pure stands of the non-native grasses. Although fire is beneficial in native grasslands, it is very destructive in desertscrub communities that have been invaded by Lehmann lovegrass or buffelgrass.

Further Reading

Bean, T.M. and J.L Betencourt. 2006. Buffelgrass in the Sonoran Desert: Can we prevent the unhinging of a unique American ecosystem. The Plant Press 30(1):4-5. (PDF)

Bennett, P.S., M.R. Kunzmann and L.A. Graham. 2004. Descriptions of Arizona vegetation represented on the gap vegetation map. (PDF)