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Distributional Associates of the Saguaro (Carnegiea gigantea)
Richard L. Hutto, Joseph R. McAuliffe and Lynee Hogan
The Southwestern Naturalist
Vol. 31, No. 4 (Nov. 10, 1986), pp. 469-476
Published by: Southwestern Association of Naturalists
Stable URL: http://www.jstor.org/stable/3671701
Page Count: 8
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The spatial distribution of the saguaro (Carnegiea gigantea) was studied with respect to its occurrence in open space or space covered by various perennial plant species at Organ Pipe Cactus National Monument, Arizona. Saguaros occurred significantly less often than expected in the open and significantly more often than expected under the canopies of perennial plants. Saguaros were associated with other species about as often as expected on the basis of their relative cover values, with two exceptions. They were found growing in association with Larrea tridentata significantly less often than expected, and with Prosopis juliflora and Cercidium microphyllum more often than expected. The degree of association with the varius perennial plant species did not change with age of the saguaro for saguaros exceeding about 19 years of age (10 cm in height). Abundance of saguaro seeds was recorded from directly beneath the canopy of C. microphyllum, at the edge of its canopy, and one m out from the canopy. Seed densities decreased significantly with distance from the base of the nurse tree. Such nonrandom seed dispersion resulting from differential seed predation or differential seed dispersal is a potentially important factor contributing to the dispersion patterns of adult saguaros.
The Southwestern Naturalist © 1986 Southwestern Association of Naturalists