Bobich, Edward , Wallace, Nick , Sartori, Keely .
Cholla Mortality as Related to Drought, Increased Temperatures, and Elevation in the Northwestern Sonoran Desert.
SOUTHWESTERN North America has received below-average rainfall for much of the new millennium and the rainfall total for the current winter season in the northwestern Sonoran Desert indicates a continuation of that trend. In addition to relatively low rainfall, the average yearly high temperature in the northwestern Sonoran Desert has also increased during the last decade. The combined influence of below-average rainfall and higher temperatures may reflect patterns in climate change and appear to have negatively affected most of the species of cholla cacti within the Philip L. Boyd Deep Canyon Research Center. At an elevation of 250 m, over 50% of the Cylindropuntia bigelovii (teddy bear cholla), 29% of the C. echinocarpa (golden cholla), and 19% of the C. ramosissima (diamond cholla) were dead, whereas none of the C. ganderi (gander cholla) were dead. At 820 m in elevation, 26% of C. bigelovii and 14% of C. ganderi were dead (the other two species did not occur at 820 m). It is hypothesized that the lower percentage of dead C. bigelovii at 820 m compared with those at 250 m was most likely due to more mild daily high temperatures and greater yearly rainfall at the higher elevation site. The greater percentage of dead C. ganderi at 820 m was most likely because the site is near its upper elevational limit. Differences in mortality among species at both elevations were attributed to several factors, including: intraspecies and intrageneric competition for water, susceptibility to xylem cavitation, particularly in the shoots, and shoot branching architecture. It is believed that this is the first evidence that climate change-type drought negatively affects survival of mature desert stem succulents.
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1 - California State Polytechnic University, Pomona, Biological Sciences, 3801 W. Temple Ave, Pomona, California, 91768, USA
2 - Whittier College, Biology, 13406 Philadelphia, Whittier, California, 90608, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Wednesday, August 2nd, 2006
Time: 11:00 AM