This proposal addresses JFSP announcement FA-FON-15-001, task statement #3 'Implications of changing fuels and fire regimes - selected regions'. The proposed project will quantify the probability of fire-facilitated ecosystem transition, defined here as the conversion from savannah, woodland, and forest (hereafter referred to as 'forest') to grass- or shrub-dominated ecosystems and fuel types (hereafter referred to as "non-forest"). This study will be conducted in California and the Southwest, where such transitions may already be occurring due to recent increased wildfire activity and severity as well as recent drought conditions that are increasingly limiting the ability of tree species to regenerate after fire. We posit that regeneration is limited at certain sites, even if adults of the same species are present, due to unfavorable climatic conditions and increasing drought conditions as a result of climate change. We further posit that this type of regeneration failure will be catalyzed by high severity stand-replacing wildfire because it removes forest overstory and associated microclimatic buffering as well as a seed source. We propose to quantify the risk of fire-facilitated ecosystem transition based on (1) the ability of tree species to regenerate as a function of climate, topography, and vegetation and (2) the expected severity of wildfire. Once we identify sites with a high probability of converting from forest to non-forest, we will evaluate several management scenarios aimed at reducing this risk; we will also evaluate how a warming climate alters this risk. We will conduct this study at two distinct scales: one at the 'plot scale' that characterizes the probability of fire-facilitated ecosystem transition for FIA plots, and one at the "landscape scale" that characterizes such transitions for forested pixels. These scales of analysis are complementary but will provide different levels of detail in both the factors driving ecosystem transition and in the analysis of management scenarios that may alter the risk of ecosystem transition. Input from resource managers will ensure our fire, climate, and management scenarios are relevant and useful for planning and decision-making purposes. The results of our study will help managers anticipate where fire-facilitated ecosystem transitions are most likely to occur within the next 20 years, and will help them evaluate options for either mitigating or adapting to these changes.