In many North American forests, post-European settlement fire suppression efforts have resulted in the excessive accumulation of forest fuels and changes to the historic fire regime, thereby increasing the risk of catastrophic wildfires (Cooper 1960; Dodge 1972; Covington and Moore 1994). To reduce this risk, it is necessary to develop treatments that will remove excess fuels while moving forests toward historical structural conditions and disturbance intervals, an approach currently being attempted in southwestern ponderosa pine (Pinus ponderosa) forests (see Covington et al. 1997; Fule et al. 2001). Both prescribed fire and mechanical fuel treatments have been used for restoration. However, it is not known if fire surrogates such as mechanical fuel treatment are sufficient to achieve historical forest structure in the place of fire, or how these treatments will affect ecosystem function.