TRANSFORMATIVE EFFECTS OF THE END-CRETACEOUS EVENT ON THE EVOLUTION OF MODERN NEOTROPICAL RAINFORESTS
Maastrichtian rainforests were diverse assemblages of ferns, angiosperms, and conifers that formed open canopies and had diverse plant–insect interactions. Plant diversity declined by 45% at the K/Pg boundary, establishing a long interval (~6 million years) of unusual low plant diversity in the Neotropics. Paleocene plant communities became dominated by angiosperms, whereas conifers became (nearly) regionally extinct. By the mid–late Paleocene, tropical forests resembled modern-aspect rainforests in having closed canopies and a multistratal structure. Despite their low taxonomic diversity, Paleocene rainforests were ecologically diverse and had the same plant-family composition, dominated by legumes, as modern Neotropical rainforests.
The transformation in forest structure and plant composition across the K/Pg boundary likely is a byproduct of the ecological catastrophe at the end-Cretaceous, and indicates fundamental changes in carbon fixation, evapotranspiration and nutrient cycling.