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Worldwide, desert grasslands are undergoing change from a relatively uniform, non-fragmented structure to a more patch-dominated pattern (Schlesinger et al., 1990). This fragmentation results both in negative economic conditions where livestock forage is limited, and in substantial ecological consequences such as more heterogeneous concentrations of nutrients, moisture, and biomass, along with attendant changes in species composition (Whitford, 2002). Many believe that overgrazing accounts for substantial desert landscape modification, although climate change, fire history, and anthropogenic activity are also seen as partial causes of such changes (Buffington & Herbel, 1965; Grover & Musick, 1990; Whitford, 2002; Zonn, 1988). There is also increasing evidence that geomorphometric terrain variables (Franklin, 1987), especially reflected in soil and sediment properties, greatly modify the degree to which these factors influence desert vegetation (Schlesinger et al., 1990).
The concept that geomorphic landforms can have a significant effect on natural desert vegetation cover has been proposed and demonstrated by several workers including Buffington and Herbel (1965), Cole and Brown (1976), McAuliffe (1994, 1995), Montaña and Greig-Smith (1990), Parker (1991, 1995), Schlesinger et al. (1990), Sharma (1993), Valverde et al. (1996), Wondzell, Cunningham and Brachelet (1987, 1996), and Zimmerman (1969). Parker and Bendix (1996) provided a comprehensive review of geomorphic influences on vegetation pattern, or what has been called “physiographic plant geography” (Zimmerman & Thom, 1982). Most studies emphasized either spatial patterns (Satterwhite & Ehlen, 1982; Smith, Adams, & Gillespie, 1990), or the underlying processes creating those patterns (Glaser, Janssens, & Siegel, 1990; Malanson, 1993; Swanson, Caine, & Woodmansee, 1988).