Chihuahuan Desert Nopaleras: Defaunated Big Mammal Vegetation

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.