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Article Abstract – Yeaton et al. (1983)

Title:

Microhabitat differences between Opuntia parryiand O. littoralis (Cactaceae) in the mixed chaparral-inland coastal sage association

Authors and affiliations:

Richard I. Yeaton, Department of Biology, University of Pennsylvania, Philadelphia, PA
Ellen Layendecker
Kevin S. Sly
Robert Eckert

Citation:

The Southwestern Naturalist 28: 215-220 (1983)

Abstract:

Opunptia parryi,which has cylindroidal stems, and O. littoralis, which has flattened stems, are commonly found in the mixed chaparral-inland coastal sage association of Southern California. Both species occur with a similar set of shade-providing shrubs in this association but their position relative to these shrubs differs: O. parryi is found in open sites away from the canopy of the shrubs while O. littoralis occurs both in open sites and under the canopy of the shrubs. Internal stem temperatures for unshaded sites suggest that the platyopuntia, O. littoralis, may be exposed to excessive heat loads. However, the cylindropuntia, O. parryi, remains well below ambient temperatures in unshaded sites. In contrast both species follow ambient temperatures closely when they are found within the canopy of an associated shrub. The flattened stems of O. littoralis may, however, provide greater access to photosynthetically active radiation than the cylindroidal stems of O. parryi. The terminal cladodes of O. littoralis in the open grow so that they face east-west and minimize the heat load buildup that would be experienced by north-south facing cladodes.

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