Our overarching goals are to determine if past wildfires influence the severity of subsequent wildfires; to quantify and compare the effects on ecosystem structure and composition of single and repeat wildfires; and to effectively communicate our findings to natural resource managers. In particular, we ask if the ultimate effects on forest structure, composition, and fuels of short interval reburns depend on the severity of the initial fire (reburns are defined here as the two fires occurring in the same place within a 30 year). We will achieve these goals using a combination of detailed field measurements and remotely sensed data characterizing unburned, once-burned, and twice-burned areas in northern Rockies mixed-conifer forest; by constructing statistical models for our data; and by sharing our findings through multiple media, including peer-reviewed publications, scientific conferences, and workshops for managers. Specific objectives are to (1) quantify the effects of reburns on fuels and tree demography in western larch/mixed-conifer forests with a Before-After-Control-Impact study; and (2) determine if the severity and effects of reburns depend on the severity of the initial fire. An unresolved issue is if and under what circumstances the severity of reburns are moderated (negative feedback) or enhanced (positive feedback) by the initial fire. We hypothesize that in locations where the initial fire burned with low or moderate severity, reburn effects will be moderated (negative feedback), maintaining a low-density, multistory forest. But, in locations where the initial fire burned with high severity, reburn effects on the forest community will be exacerbated (positive feedback), creating a structurally and compositionally simplified forest, or even causing a transition to a non-forest community. While the work we propose here will take place in the Bob Marshall Wilderness where a resumed active fire regime provides the opportunity to investigate reburn effects in this forest type, our results will be directly relevant to management of adjacent non-wilderness lands. In particular, our work will inform landscape scale forest restoration and fuel reduction efforts within the Southwestern Crown of the Continent (SWCC) Collaborative Forest Landscape Restoration project by providing by providing data that will help managers evaluate if and how wildfires can be used to meet fuel reduction and ecological objectives in the SWCC.