The birth of modern rainforests
The origins of modern rainforests can be traced to the aftermath of the bolide impact at the end of the Cretaceous. Carvalho et al. uses petrified pollen and leaves to characterize the changes that have taken place in the North-South American forests during this time (see The Perspective by Jacobs and Currano). They not only found changes in the species composition, but were also able to deduce changes in the forest structure. Extinctions were widespread, especially among gymnosperms. Angiosperm taxa dominated the forests during the 6 million years of recovery, when the flora began to look like that of the modern lowland neotropic forest. The leaf data also imply that the bush canopy developed from relatively open to closed and layered layers, leading to increased vertical stratification and a greater variety of plant forms.
Science, this issue p. 63; see also p. 28
Abstract
The Cretaceous event was disastrous for land communities worldwide, but its long-term effects on tropical forests are still unknown. We quantified the extinction of plants and ecological changes in tropical forests due to the Late Cretaceous event using fossil pollen (> 50,000 occurrences) and leaves (> 6,000 samples) from localities in Colombia. Late-critical (Maastrichtian) rainforests are characterized by an open canopy and diverse interactions between plants and insects. Plant diversity decreased by 45% at the Cretaceous – Paleogene boundary and did not recover for about 6 million years. Paleocene forests resemble modern Neotropical rainforests, with a closed canopy and multistratal structure dominated by angiosperms. The Cretaceous event caused a long interval of low plant diversity in the Neotropics and the evolutionary composition of today’s most diverse terrestrial ecosystem.