Context Treeless areas in forested landscapes are an enduring ecological puzzle globally. A fire-mediated alternative stable state (FMASS) model has been proposed to explain mosaics of forest and sedgeland in Tasmania, whereby shifts in fire frequency change vegetation and soil patterns. This model is controversial, and a key step in proving it demands elucidating post-fire vegetation dynamics at landscape-scales and over historical timeframes.

Objectives To quantify historical changes in extent of a large sedgeland patch surrounded by tall Eucalyptus forest and evaluate post-fire recovery after a large wildfire burned the area in 2019.

Methods We mapped historical vegetation changes by analysing sequences of aerial photography from 1947 to 2010, and in 2020 used UAS LiDAR to geolocate the current forest boundary. Satellite imagery, field measures of char: canopy height ratio, and stem mortality were used to gauge fire severity, while vegetative and seedling regeneration were used to assess post-fire recovery.

Results Forest-sedgeland boundaries were stable over the 73-year period. Sedgeland and scrub communities experienced high severity fires, reflecting their low stature compared to taller forest, which suffered minimal canopy impact. The dominant sedge and tree species in the three communities were post-fire resprouters, resulting in rapid recovery of vegetation structure, with prolific seeding of species killed by the fire.

Conclusion Forest-sedgeland boundaries in western Tasmania are resilient to fire because of keystone resprouter species, and geographically stable in historical time frames, a finding inconsistent with the FMASS model. Our study contributes to global question of treeless area in climate zones suitable for forest.