Contrasting vegetation and climate regulation at the Permian-Triassic and Triassic-Jurassic hyperthermals

The Permian-Triassic (PTME, ~251.9 Ma) and Triassic-Jurassic (TJME, ~201.3 Ma) mass extinctions, both triggered by large igneous province (LIP) activity, represent two of the most significant extinction events in Earth’s history. Despite this similarity, there were contrasting impacts on land plants. Here, we compile global macrofossil records of Triassic-Jurassic flora and integrate them with lithological climate proxies, the HadCM3L climate model, and vegetation model FLORA to reconstruct vegetation dynamics across the TJME. Our findings suggest that, unlike the significant low latitude plant extinction during the PTME, the TJME coincides with floral compositional turnover and enhanced productivity, particularly in mid- to high- latitudes. High-resolution chemical weathering index, mercury, and plant biomarker records further suggest that global vegetation productivity and biotic weathering was enhanced after the TJME, stabilizing Earth’s temperature and facilitating rapid post-extinction cooling once LIP emissions ceased. This contrasts with the PTME when widespread deforestation trapped the Earth in a prolonged super-greenhouse climate. This study underscores the critical role of vegetation in modulating long-term climate and highlights plant thermal response and adaption as a key control on Earth's sensitivity to warming.