Twentieth century land use and management practices have increased the vertical and horizontal continuity of fuels over expansive landscapes. Thus the likelihood of large, severe wildfires has increased, especially in forest types that previously experienced more frequent, less severe fire (Allen and others 2002). Disturbances such as fire may promote nonnative plant invasions by increasing available light and nutrients, as well as by decreasing competition from native plants for these resources (Fox 1979; Melgoza and others 1990). Once established, nonnative species may further alter fuel bed characteristics and increase the likelihood of future wildfires (Whisenant 1990a). Land managers increasingly rely on prefire fuel manipulations to reduce wildfire potential, and these efforts have expanded significantly under the current National Fire Plan (USDI and USFS 2001).