Vegetation flammability contributes to alternative stable states in arid Australia

Background Alternative stable state theory holds that disturbance thresholds can drive transitions between distinct vegetation types that exist under otherwise similar environmental settings. Recent investigations in arid Australia have presented compelling evidence for the existence of fire-mediated alternative stable states (FMASS) in various shrubland–grassland communities. These studies have explored edaphic factors contributing to boundaries. However, research is lacking on vegetation flammability characteristics promoting or retarding fire. Aims Investigate whether the shoot flammability of two woody species associated with fire-sensitive vegetation, Acacia aptaneura and Aluta maisonneuvei, is lower than co-occurring fire-promoting hummock grasses Triodia basedowii and T. pungens. Methods Flammability assessments on a plant grill tested for statistically significant differences between species. Key results A. aptaneura ignited more slowly, burned at lower temperatures and self-extinguished more rapidly than the other species, consistent with a low-flammability strategy. In contrast, no significant differences existed between A. maisonneuvei and the Triodia species across flammability traits. Reduced flammability in A. aptaneura was associated with higher shoot moisture content, lower biomass and reduced dead material retention. Conclusions and implications The findings indicate that desert plants display contrasting flammability syndromes, supporting the hypothesis that fire acts as a selective force shaping shoot traits and reinforcing vegetation boundaries in arid ecosystems.