Abstract:
The southern portion of the Chihuahuan Desert of subtropical north central
Mexico (110, 186, 250, 254, 255, 262, 311) extends from the vicinity of
Zacatecas and San Luis Potosi north to the area of Saltillo, Torreon, and
Chihuahua (1100-2500 m elevation). It contains a number of vegetation types
in which large perennial plants (Opuntia, Yucca, Acacia, and Prosopis) are a
prominent part of the vegetation. Their names are often incorporated in the
names for Chihuahuan Desert plant associations (202, 250-256, 270, 272,
311). A spectacular example is the nopalera (Figure 1), the stimulus for this
eclectic review.
Nopaleras are dense stands of 1-4-m tall Opuntia cacti of several species,
dotted with emergent Yucca, Acacia, and Prosopis (181, 254, 246). The
name is local in origin and derives from the Mexican Indian (nahuatl) generic
name of 'nopa!' for the broad-stemmed species of Opuntia cacti. In a
nopalera, the cacti are so abundant that the habitat resembles the monotypic
forests of introduced Opuntia that grew in Australia [see figures in (69)] until
the introduction of neotropical insects that decimated them. The area between
the large plants in a nopalera contains numerous species and individuals of
annuals and smaller perennials (e.g. Agave, Larrea, Jatropha, Gramineae,
Leguminosae, Compositae, Cactaceae, Asclepiadaceae). The density and
proportions of all of these plants vary with contour, soil type, rainfall,
drainage, exposure, grazing regime, and recent historical events, but the large
plants remain conspicuous.
