Twenty-Third Annual Meeting and Symposium of the
Desert Tortoise Council, April 3-5, 1998
Abstracts

In arid regions, where variability in growth rings reflects variability in climate, it is often difficult to age-date trees and shrubs by ring counting. This has required researchers interested in the demography of woody plants to exercise considerable ingenuity in determining how long various species can survive. One famous example is the so-called “King Clone,” a large clonal ring of Larrea tridentata (creosotebush) that has occupied the same site for an estimated 11,700 years. This estimate was made using radiocarbon dates from old wood combined with extrapolations from modern growth rates.

Repeat photography is another technique that has been used to determine longevity of shrubs in the Mojave and Sonoran deserts. In Grand Canyon, for example, photographs taken in 1872 and matched in the early 1990s show that Ephedra (Mormon tea), Acacia greggii (catclaw), and Lycium andersonii (wolfberry) can live for at least 120 years and that Ambrosia dumosa (white bursage), Atriplex confertifolia (shadscale), Opuntia erinacea (grizzly bear prickly pear), and O. basilaris (beavertail) can live for more than 75 years.

Long-term vegetation plots are a third source of information regarding longevity of desert shrubs; plots on Tumamoc Hill, Tucson, Arizona, indicate that Aloysia wrightii (oreganillo), Fouquieria splendens (ocotillo), Janusia gracilis, and Jatropha cardiophylla (sangre de Cristo) can live at least 72 years.

Estimates of longevity help us better understand the dynamics of desert communities and provide information that can be useful to management and restoration projects.

References

Bowers, J. E. 1997. Demographic patterns of Ferocactus cylindraceus in relation to substrate age and grazing history. Plant Ecology 133:37-48.

Bowers, J. E., R. H. Webb, & R. J. Rondeau. 1995. Longevity, recruitment and mortality of desert plants in Grand Canyon, Arizona, USA. Journal of Vegetation Science 6:551-564.