R. M. Turner
Janice E. Bowers
2001
<p>Past and current dieback of <i>Cercidium microphyllum</i>, a dominant, drought-deciduous tree in the Sonoran Desert, was investigated at Tumamoc Hill, Tucson, Arizona, USA. Logistic regression predicted that the odds of a <i>Cercidium</i> plant being alive should decrease with increasing circumference, association with the columnar cactus Carnegiea gigantea, and occurrence on steep slopes. Slope azimuth, parasitization by <i>Phoradendron californicum</i>, and distance to nearest <i>Cercidium</i> within 5 m did not significantly affect the odds of survival. <i>Carnegiea</i> was a source of background mortality rather than a primary cause of dieback. Of the >1,000 living and dead plants sampled, 7.7% had died within the past 5 to 7 years. An additional 12.8% died in the more distant past. Diebacks tended to occur during severe deficits in annual, especially summer, rain. More than half of the dead plants in the sample were <span>≥</span>50 cm in girth. In current and past diebacks on Tumamoc Hill, it seems likely that severe drought interacted with natural senescence of an aging population, weakening large, old trees and hastening their deaths.</p>
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10.2307/3088735
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Torrey Botanical Society
Dieback and episodic mortality of Cercidium microphyllum (foothill paloverde), a dominant Sonoran Desert tree
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