Increased fire severity triggers positive feedbacks of greater vegetation flammability and favors plant community‐type conversions.

Questions: Increased wildfire activity is resulting in plant community‐type conversions worldwide. In some regions, fire‐sensitive forests are being replaced by flammable fire‐resilient communities, increasing the likelihood of reburning due to positive fire feedbacks. Here we evaluated whether fire severity affects post‐fire plant community flammability attributes that lead to community‐type conversions and changes in the likelihood of reburning. Specifically, we assessed how fire severity, the dominant pre‐fire vegetation, and distance to unburned remnant forest may shape post‐fire community properties and flammability trajectories in northwestern Patagonia. Location: Northwestern Patagonia, Argentina. Methods: We repeated sampling of Nothofagus pumilio, Nothofagus dombeyi, and Austrocedrus chilensis forests and native shrublands (composed of multiple shrub species) two and 18 years after fires that burned at low‐ to very high‐severity levels, and measured community structure and flammability attributes. Results: Eighteen years after fire, forests that burned at moderate to very high severity were unable to recover and were replaced by more flammable shrublands and grasslands. Following low‐severity fire, fine‐fuel density was lower and forest recovery was enhanced by greater survival of remnant seed trees. Burnt shrublands increased in abundance across all severity classes but attained highest fine‐fuel production after moderate‐ to very high‐severity fire. Conclusions: Low fire severity, by enabling regeneration of forests that are less flammable than shrublands, diminishes the likelihood of reburning, thus establishing a negative feedback favorable to forest perpetuation. Conversely, moderate to very high fire severity leads to a positive feedback by promoting conversion to shrublands and greater fine‐fuel accumulation. This increases the likelihood of reburning, reinforcing the persistence of pyrophytic communities and favoring landscape‐scale loss of fire‐sensitive forests. This fire severity‐mediated positive feedback may in many regions worldwide further amplify warming‐related wildfire activity increases, posing serious threats to the persistence of fire‐sensitive ecosystems. [ABSTRACT FROM AUTHOR]