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The birth of modern tropical forests
The origin of modern tropical forests can be attributed to the consequences of the impact of the fireball at the end of the Cretaceous period. Carvalho et al. used fossilized pollen and leaves to characterize the changes that took place in the forests of northern South America at this time (see Jacobs and Currano’s perspective). They not only found changes in species composition, but were also able to infer changes in 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 resemble that of the modern Neotropical lowland forest. The leaf data also imply that the forest canopy has changed from relatively open to closed and stratified, resulting in increased vertical stratification and greater diversity in plant growth forms.
Science, this issue p. 63; see also p. 28
Abstract
The Late Cretaceous event was catastrophic for terrestrial communities around the world, but its lasting effect on tropical forests remains largely unknown. We quantified plant extinction and ecological changes in tropical forests resulting from the Late Cretaceous event using fossil pollen (> 50,000 occurrences) and leaves (> 6,000 specimens) from localities in Colombia . The Upper Cretaceous (Maastrichtian) rainforests were characterized by an open canopy and various plant-insect interactions. Plant diversity declined by 45% at the Cretaceous-Paleogene border and did not recover for about 6 million years. Paleocene forests resembled modern Neotropical rainforests, with a closed canopy and a multistratal structure dominated by angiosperms. The Late Cretaceous event triggered a long interval of low plant diversity in the Neotropics and the evolutionary assemblage of the most diverse terrestrial ecosystem today.
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