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How the Chicxulub impactor triggered the modern rainforest


From forests full of ferns to forests full of flowers and plants: Plants begin to produce attractive flowers that contain sugary rewards for insects that carry pollen grains (basically the male sperm of the plant) to other flowers , Thereby helping plants to reproduce. This strategy is so successful that flowering plants have taken over tropical forests and the entire world. Credit: From: Hace Tiempo. Columbia Columbia University. The Alexander von Humboldt Institute of Tropical Sciences and the Smithsonian Institution. The Imágenes Bank (BIA) of the Istituto Alexander von Humboldt Institute.

Today’s tropical rain forest is a hot spot for biodiversity and plays an important role in the world’s climate system.A new study published today science Reveals the origin of modern tropical rainforests, and may help scientists understand how tropical rainforests will cope with the rapidly changing climate in the future.

This study led by researchers from the Smithsonian Tropical Research Institute (STRI) showed that the asteroid impact ended the dinosaur dominance 66 million years ago and caused the extinction of 45% of the plants in Colombia today, which is a modern tropical rain forest. The domination of flowering plants.

Mónica Carvalho, the first author and postdoctoral co-researcher of STRI and the University of Rosario in Colombia, said: “We want to know how tropical rain forests will change after severe ecological disturbances (such as the Chicxulub impact), so we are looking for tropical plant fossils.” ‘S team inspected more than 50,000 fossil pollen records and more than 6,000 leaf fossils before and after the impact.”

In Central and South America, geologists are busy searching for fossils that have been cut by roads and exposed by landmines, which are washed away by heavy rains, and the jungles hide them. Prior to this study, little was known about the effects of this extinction on the evolution of flowering plants that currently dominate the tropical Americas.

A short zoom interview clip with the first author and postdoctoral researcher from the Smithsonian Tropical Research Institute and the University of Rosario, Colombia. She answered the question: What is the most exciting part of the project for you? Image source: STRI Ana Endara

STRI paleontologist Carlos Jaramillo and his team (mainly from many STRI researchers in Colombia) studied pollen grains in 39 locations, including rock outcrops and cores for oil exploration in Colombia, to paint a large area picture of the previous forest . And subsequent effects. Pollen and spores obtained from rocks older than impact indicate that rain forests are also dominated by ferns and flowering plants. Coniferous trees such as Kauri (relatives of Kauri pine and Norfolk Island pine) sold in supermarkets (Araucaria family) at Christmas are common and cast shadows on dinosaur footprints. After the impact, the conifers almost completely disappeared from the tropical regions of the New World, and the flowering plants took over. After being affected, the plant diversity has not recovered in about 10 million years.

The leaf fossils told the team a lot about the past climate and local environment. Carvalho and Fabiany Herrera, postdoctoral researchers at the Negaunee Institute for Conservation Science and Action at the Chicago Botanic Garden, led the study of more than 6,000 specimens. The research team worked with Scott Wing of the Smithsonian’s National Museum of Natural History and others and found evidence that the tropical trees before the impact were so far apart that light could reach the forest floor. Within 10 million years after the impact, some tropical forests were dense, just like forests today. The leaves of trees and vines left deep shadows on the small trees, shrubs and herbs below. The sparse canopy of the forest before the impact has fewer flowering plants, and less soil water is transferred to the soil compared to the soil that has grown for millions of years.

“There were as many rainy days as the Cretaceous, but the way the forest worked was different.” Carvalho said.

Before the extinction event, the research team found no signs of legumes, but since then, the leaves and pods of legumes have gained great diversity and abundance. Nowadays, legumes have become the main family in the tropical rainforest, and through the combination with bacteria, they absorb nitrogen from the air and convert it into soil fertilizer. The rise of pulses will greatly affect the nitrogen cycle.

flowers! How the Chicxulub impactor triggered the modern rainforest

Representative leaf group. (A to K) Paleocene Bogotá taxa and (L to W) Maastricht Guaduas flora. (A) Half department (BF6). (B) Salicidaceae with midrib bile (BF5). (C) Small leaves of Compositae (BF38) with superficial eating damage. (D) Euphorbiaceae (BF37), with holes and edge feed. (E) ace family, Ca grass family (BF21). (F) Ferns, Salvinia bogotensis, Salviniaceae (BF22). (G) Malva. Malvaceae (BF4). (H) An example of a dripper from the Salicaceae (BF23). (I) Brachiaceae (BF13). (J) Compositae lobules (BF21, 5 mm), with holes and feed damage. (K) Arecaaceae (BF27). (L) Arecaaceae (GD47, 10 cm). (M) aff. Laurel Branch (GD54). (N)aff. Hamameliaceae (GD56). (O and P) Fertile and sterile fragments of Polypodiaceae (GD22). (Q) aff. Salicaceae (GD6). (R) Laurel Branch (GD7), with dripper. (S) aff. Urticaceae (GD52). (T) Zingiberales (GD46, 5 cm). (U) aff. Cucurbitaceae (GD8). (V) Bernhamniphyllum sp. Rhamnaceae (GD1). (W)aff. Dilleniaceae (GD3). Image source: Carvalho et al., Science (2021)

Carvalho also collaborated with Conrad Labandeira of the Smithsonian’s National Museum of Natural History to study the destruction of leaf fossils by insects.

Labandella said: “Insect damage to plants can be revealed in the miniature of a single leaf or a wide area of ​​a plant community. This is the basis of the nutritional structure of tropical forests.” “The energy that exists in plant tissues throughout the food chain. Eventually it will be passed on to pythons, eagles and jaguars. The energy starts from insects, which are skeletonized through plant tissues, chewed, pierced and sucked, mined, pests and bored. The evidence of this consumption food chain begins with insects All the diverse, dense and fascinating ways of consuming plants.”

Carvalho said: “Before being affected, we found that different types of plants suffered different damage: eating was directed at the host.” “After the impact, we found the same type of damage to almost every plant. This means eating more general.”

How did the after-effects of the impact turn the sparse, coniferous tropical forest of the dinosaur era into the rainforest of today-towering trees dotted with yellow, purple and pink flowers and dripping with orchids? Based on evidence from pollen and leaves, the research team proposed three explanations for this change, all of which are correct. One idea is that the dinosaurs kept the forest open before the impact by eating and walking through the landscape. The second explanation is that the fly ash from the impact enriches the soil throughout the tropics, which provides an advantage for faster-growing flowering plants. The third explanation is that the preferential extinction of coniferous species creates an opportunity for flowering plants to take over tropical regions.

“Our research follows a simple question: How does the tropical rain forest evolve?” Carvalho said. “The lesson learned from here is that under fast turbulent conditions (from a geological point of view) tropical ecosystems will not only rebound, they will also be replaced, and this process will take a long time.”

Fossils show insects that have eaten kauri trees for 66 million years

More information:
Mr. Carvalho and others, “The extinction at the end of the Cretaceous and the origin of the modern neotropical rainforest” science (2021). science.sciencemag.org/cgi/doi…1126 / science.abf1969

BF Jacobs of Southern Methodist University in Dallas, Texas, “The Influential Origins of Neotropical Forests”, science (2021). science.sciencemag.org/cgi/doi…1126 / science.abh2086

Courtesy of Smithsonian Tropical Research Institute

Citation: How the Chicxulub Impactor Triggered the Modern Rainforest (April 1, 2021) Retrieved from https://phys.org/news/2021-04-chicxulub-impactor-gave-modern-rainforests.html on April 1, 2021 Arrived

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