PLANT DIVERSITY IN RESPONSE TO GLOBAL WARMING DURING THE PALEOCENE-EOCENE THERMAL MAXIMUM(PETM):EVIDENCE FROM FOSSILS AND MODELING
The Paleocene-Eocene Thermal Maximum(PETM)which occurred about 56 million years ago,represents the most significant global warming events in Earth's history.Within a short span of 100 ka to 200 ka,the global average temperature rose by approximately 4～8℃.This warming event was closely linked to fluctuations in the global carbon cycle,exerting profound effects on global climate and biodiversity.In this study,we synthesized and analyzed model simulations and fossil data from the global PETM period,summarizing the temperature and precipitation changes under different CO2 concentrations simulated during the PETM.Our comprehensive analysis focuses on the responses of plant diversity,floristic elements exchanges,and vegetation dynamics during this period.The results indicate that increased atmospheric CO2 levels led to widespread global warming and significant alterations of spatial and temporal distribution of precipitation.The temperature and precipitation increases were more pronounced in mid-to high-latitude regions compared to low latitudes.The impact of PETM induced climate change on terrestrial biodiversity exhibited regional variations with different plant groups responding in distinct ways.Certain plant groups,such as the Proteaceae and Araceae,experienced extinction or decreased diversity while others,such as Ulmaceae and Poaceae,were less affected.Additionally,the species diversity of tropical and subtropical groups,including Arecaceae and Fabaceae,increased during this period.This differential impact highlights the complex interplay between climate change and plant biodiversity.Furthermore,PETM climate change also facilitated global dispersal of angiosperms,leading to significant shifts in species distribution and accelerated the spread and exchange of plant communities.Consequently,global vegetation patterns underwent notable changes,with tropical and subtropical vegetation extensively spreading to higher latitudes.Compared to the overall warming,the rapid pace and fragmented environment posed more challenges to biodiversity:the former left short time for adaptation,while latter limited relocation to favorable conditions.Our findings underscore the complexity of the interactions between climate change and biodiversity during the PETM.The widespread global warming and changes in precipitation patterns had profound impacts on plant diversity and distribution.The varying responses of different plant groups to these changes highlight the importance of considering both regional and global perspectives when studying the impacts of climate change on biodiversity.Moreover,the PETM serves as a valuable analog for understanding the potential impacts of current and future climate change.The patterns of vegetation change and species redistribution observed during the PETM can provide insights into how modern ecosystems might respond to ongoing and future global warming.The rapid and extensive changes in vegetation patterns during the PETM suggest that current climate change could lead to similarly profound shifts in biodiversity and ecosystem structure.
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