Reduced fire severity offers near-term buffer to climate-driven declines in conifer resilience across the western United States

Increasing  fire  severity  and  warmer,  drier  postfire  conditions  are  making  forests  in  the  western  United  States  (West)  vulnerable  to  ecological  transformation.  Yet,  the  relative  importance of and interactions between these drivers of forest change remain unresolved, particularly over upcoming decades. Here, we assess how the interactive impacts of chang-ing climate and wildfire activity influenced conifer regeneration after 334 wildfires, using a dataset of postfire conifer regeneration from 10,230 field plots. Our findings highlight declining regeneration capacity across the West over the past four decades for the eight dominant conifer species studied. Postfire regeneration is sensitive to high-severity fire, which limits seed availability, and postfire climate, which influences seedling establish-ment. In the near-term, projected differences in recruitment probability between low- and high-severity fire scenarios were larger than projected climate change impacts for most species,  suggesting  that  reductions  in  fire  severity,  and  resultant  impacts  on  seed  avail-ability,  could  partially  offset  expected  climate-driven  declines  in  postfire  regeneration.  Across 40 to 42% of the study area, we project postfire conifer regeneration to be likely following low-severity but not high-severity fire under future climate scenarios (2031 to 2050). However, increasingly warm, dry climate conditions are projected to eventually outweigh the influence of fire severity and seed availability. The percent of the study area considered unlikely to experience conifer regeneration, regardless of fire severity, increased from  5%  in  1981  to  2000  to  26  to  31%  by  mid-century,  highlighting  a  limited  time  window over which management actions that reduce fire severity may effectively support postfire conifer regeneration.