Although they have persisted for tens of millions of years, neotropical lowland forests have changed greatly in extent and composition due to climatic variation and to human impacts. In a symposium at the 2002 meetings of the Association for Tropical Biology, hosted by the Smithsonian Tropical Research Institute (STRI), Panama, scientists presented the latest results of research on neotropical forests and their transformations up to the time of Columbus.
Bruce MacFadden, of the University of Florida, has re-examined a mammal fossils of mid-Miocene age (18-16 million years ago) collected in central Panama in the 1960s, but not previously described in detail. At the time a deep oceanic channel across eastern Panama separated North and South America. Although the species are closely related to those of North America of the same age (instead of geographically closer South America), most appear to have been adapted to forested habitats, rather than being grasslands species like those that dominated North America. In particular, the low-crowned teeth of herbivores reveal that they fed on soft-leaved forest vegetation rather than grasses, and future analysis of carbon isotope ratios in enamel may further confirm this.
Lake cores are increasingly being used to obtain records of pollen, phytoliths, charcoal, and other evidence of forest distribution and composition from throughout the neotropics over the past 20,000 years. Dolores Piperno, of STRI, described how this data shows colder, drier conditions than those of the present prevailed in many areas in the late Pleistocene. In some areas forests persisted, although they often contained a mix of lowland species with those found only at higher elevations today, creating tree communities quite different from modern ones. In others, grassland replaced forest. Later, after the arrival of humans, forests gradually retreated with the spread of slash-and-burn agriculture, only to return again when indigenous populations were decimated after colonization by Europeans. Barbara Leyden of the University of South Florida presented data from lake cores from the Yucatan Peninsula. Although stable isotopes identified a severe drought at the end of the Mayan Classic Period, the pollen record showed the vegetation was not greatly affected except for maize and associated weedy species.
Dolores Piperno | EurekAlert!
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University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
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