. Wildlife and range research needs in northern Mexico and southwestern United States : workshop proceedings, April 20-24, 1981, Rio Rico, Arizona. Wildlife management Southwestern States Congresses; Wildlife management Mexico Congresses. Figure 1. —Mexico's Sierra del Carmen Range consists of a long, banded limestone escarpment and a much higher volcanic mass beyond. In the left foreground, the Rio Grande (International Border) cuts through the limestone ridges to form Boquillas Canyon. foothills. It is the start of the mountains. It is the bottom of the pyramid. On warmer south slopes the gr
. Wildlife and range research needs in northern Mexico and southwestern United States : workshop proceedings, April 20-24, 1981, Rio Rico, Arizona. Wildlife management Southwestern States Congresses; Wildlife management Mexico Congresses. Figure 1. —Mexico's Sierra del Carmen Range consists of a long, banded limestone escarpment and a much higher volcanic mass beyond. In the left foreground, the Rio Grande (International Border) cuts through the limestone ridges to form Boquillas Canyon. foothills. It is the start of the mountains. It is the bottom of the pyramid. On warmer south slopes the grassland belt may occur between 3,500 and 6,500 feet elevation, while it is somewhat narrower on the cooler northside slopes. These grasslands are relatively insignif- icant on the west side of the del Carmens, however, where the escarpment rises rather abruptly from the desert to the sheer cliffs of the mountain tops. The western escarpment ascends 7,500 feet in less than two miles (Figure 2). But on the east side of the del Carmens the same elevational change occurs in approximately 12 miles. The eastern side, therefore, provides easier access and has experien- ced much greater use from ranchers, loggers and hunters. Chisos Agave (Agave chisosensis) is found within these grasslands, although until recent years it was considered endemic to the Chisos Mountains of Big Bend National Park (McDougall and Sperry, 1951). And just above the grasslands, on rocky cliffs and ridges, is another agave that occurs only within the mountains of northern Coahuila—the del Carmens, Encantadas and Santa Rosas. This is Agave totrerana, a heavy-stem- med plant with a beautiful rosette leaf base (H. S. Gentry, pers. comm.), Yellow flowers appear in late July and, like all agaves, the plant dies at the end of the flowering season. It takes agaves from 15 to 35 years to bloom. A woodland of pinyon pine, junipers and oaks occur above the grasslands (Figure 3). This habitat is minimal on the western
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