Effects of drought on shrub survival and longevity in the northern Sonoran Desert1

Abstract

Abstract Bowers, J. E. (U.S. Geological Survey, 1675 West Anklam Road, Tucson, AZ 85745). Effects of drought on shrub survival and longevity in the northern Sonoran Desert. J. Torrey Bot. Soc. 132: 421–431. 2005.—Permanent vegetation plots in the northern Sonoran Desert, USA, provided an opportunity to assess the effects of recent drought on desert shrubs and to examine survival in relation to rainfall variability during the past 76 years. Survival and maximum longevity of six species were determined for eight intercensus periods between 1928 and 2004. Average annual survival was Ambrosia deltoidea, 0.9167 ± 0.0415; Encelia farinosa, 0.7952 ± 0.0926; Janusia gracilis, 0.9334 ± 0.0247; Krameria grayi, 0.9702 ± 0.0270; Larrea tridentata, 0.9861 ± 0.0174; and Lycium berlandieri, 0.9910 ± 0.0077. The longest-lived species were Larrea, Lycium, and Krameria, with average maximum life spans of 330, 211, and 184 years. Janusia, Ambrosia, and Encelia were much shorter lived, with average maximum longevity of 53, 4...