The study was conducted in the southwestern Mojave Desert at the Sweeney Granite Mountains Desert Research Center, an ecological reserve of the University of California Natural Reserve System, using an integrated four-part field and laboratory design (Fig. 2). Experimental treatments and sampling took place within a cove in the Granite Mountains (ca. 1360 m elevation) dominated by Cylindropuntia acanthocarpa, C. echinocarpa, Larrea tridendata, and Yucca schidigera (34.7849° N, 115.6620° W). The terrain in this area is relatively flat with some gentle slopes and is characterized by abundant, large granitic boulders and seasonal washes. The climate is arid with a mean annual precipitation of 217 mm, a mean summer (May through October) daily high temperature of 29°C, a mean summer daily low of 18°C, a mean winter (November through April) daily high of 16°C, and a mean winter daily low of 6°C (data from UC Sweeney Granite Mountains Desert Research Center, Sweeney Granite Reserve Weather Station, RGSC1, 34.78° N, 115.65° W, 1304 m elevation).