Some Amazon rainforest trees are over 1000 years old finds study
Rhett A. Butler, mongabay.com
December 13, 2005
Trees in the Amazon rainforest are older than originally believed according to new research published in the Proceedings of the National Academy of Sciences. A team of American and Brazilian researchers using radiocarbon dating methods to study tree growth in the world’s largest tropical rainforest found that up to half of all trees greater than 10 centimeters in diameter are more than 300 years old. Some of the trees are 750 to 1,000 years old says Susan Trumbore, a professor of Earth system science at University of California at Irvine and one of the authors of the study.
“Little was known about the age of tropical trees, because they do not have easily identified annual growth rings,” said Trumbore in a media statement. “No one had thought these tropical trees could be so old, or that they grow so slowly.”
According to Trumbore, the finding may have important implications for the role the Amazon plays in determining atmospheric carbon dioxide concentrations. Because Amazon forest trees are old and slow-growing says the researcher, they have less capacity to absorb atmospheric carbon than previous studies have predicted.
“In the Central Amazon, where we found the slowest growing trees, the rates of carbon uptake are roughly half what is predicted by current global carbon cycle models,” Trumbore said. “As a result, those models — which are used by scientists to understand how carbon flows through the Earth system — may be overestimating the forests’ capacity to remove carbon dioxide from the atmosphere.”
The growth rates measured by the team for trees in the Central Amazon are among the slowest in any forest on Earth. Trumbore says slow growth is likely due to the nutrient-poor soils of the Central Amazon combined with the low light conditions created by the shade of the forest canopy.
The slow-growing nature of Amazon trees may also mean that it takes longer for forests to recovery from logging.
Strangler fig tree in the Amazon.
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“The impact of logging activity in the Amazon region may be longer-lasting than we think,” Trumbore added, “because it may take centuries for these forests to grow back to their full size.”
The long recovery time after logging is a particular concern after a study released by the Carnegie Institution found that “selective logging” is degrading Brazil’s Amazon rain forest twice as fast as deforestation figures suggest. Using remote-sensing technology, the Carnegie Institution team determined that conventional analysis missed much of the degradation that occurs beneath the rainforest’s protective canopy.
The new research was conducted as part of the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA). Supported by NASA, the LBA is a Brazilian-led international scientific program with the goal of studying how the Amazon forest affects global climate and carbon dioxide. This specific study was a cooperative effort among researchers at the University of Sao Paulo, University of Acre and the Institute for Amazonian Research in Brazil, and UCI and Tulane University in the U.S. Radiocarbon measurements were made at the W.M. Keck Carbon Cycle Accelerator Mass Spectrometry Facility at UCI.
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This article used information from a news release from the University of California, Irvine.