For instance, the columnar cacti Carnegiea gigantea, Lophocereus schottii, and Stenocereus thurberi occupy different habitats along the topographic and edaphic gradients of the Sonoran Desert (Parker, 1988a).
This has been suggested for the columnar cacti Carnegiea gigantea and Stenocereus thurberi (Parker, 1993; Pierson & Turner, 1998), the barrel cacti Echinocactus polycephalus, Ferocactus acanthodes, and F.
Dubrovsky (1996, 1998) found that seeds of the columnar cacti Carnegiea gigantea, Pachycereus pecten-aboriginum, Stenocereus gummosus, and S.
McAuliffe and Janzen (1986) documented the effect of intraspecific competition for limited water in dense aggregations of young Carnegiea gigantea plants associated with the canopy of perennial shrubs; in this case, the effects of competition were decreases in water uptake, water storage, apical growth, and reproductive potential (McAuliffe & Janzen, 1986).
In contrast, high summer and low winter temperatures, soil-moisture availability, and pre- and post-summer dry periods are among the main environmental factors that affect the growth rate of Carnegiea gigantea (Steenbergh & Lowe, 1977).
With regard to allometry, there is some variation in the annual growth rate of Carnegiea gigantea related to changes in plant form associated with ontogeny (Hastings & Alcorn, 1961; Steenbergh & Lowe, 1977).