Chemical variation in Amazon forest revealed

Eric Hopton for redOrbit.com – Your Universe Online

New techniques for studying the “chemical fingerprints” of Amazonian plants have given scientists a kind of “time machine” that can look back to the past and project the future.

Greg Asner from Carnegie Institution for Science used a high-tech approach to plot the hidden tapestry of chemical variation across the lowland Peruvian Amazon. The study showed how plants in different areas produce an array of chemicals that changes across the region’s topography.

“Our findings tell us that lowland Amazon forests are far more geographically sorted than we once thought,” Asner explained. “It is not simply a swath of green that occurs with everything strewn randomly. Place does matter, even if it all appears to be flat and green monotony at first glance.”

Mapping the chemical signature

The Amazonian forest covers more than three million square miles and contains thousands of trees and other plant species. Each of these synthesizes a complex portfolio of chemicals to capture sunlight, fight off herbivores, attract pollinators, and perform other functions to aid adaption to climate change.

Beneath the lowland forests of the Amazon lies a hidden mosaic of geologic and hydrologic variation. This mosaic affects the diversity of the plants’ chemical functions as the varying topography affects water, nutrients, and other plant resources. Understanding these geographical variations is crucial to understanding the way an ecosystem functions on a large scale.

Asner and his team took data collected from their Carnegie Airborne Observatory (CAO) to create the first high-resolution maps of the forest’s canopy chemistry. A high-fidelity imaging spectrometer and a laser scanner onboard CAO were used to map four huge forested landscapes along two river systems. The instruments enabled the team to capture previously hidden chemical fingerprints of rainforest canopy species.

“This is the first time that so many chemicals have been measured and mapped in any forest ecosystem on Earth,” Asner said. “No one has done the mapping we have achieved here, which enabled a discovery that the lowland Amazon is anything but monotonous or similar everywhere.”

The pattern of chemical properties in canopy trees changes along the paths of the two rivers, the Madre de Dios and the Tambopata, as well as across the landscape’s topography on a “microscale” level. Very small changes in elevation made all the difference to the plants living there.

Studies of this kind help scientists to better understand the Earth’s tremendous diversity and its geographic patterning, both of which are required to understand evolution or the future of species in a changing world.

“Looking at the lowland Amazon with this kind of detail, you can see back in time, from the way the topography was shaped millions of years ago, which still affects soils and mineral availability today, to the way that different species evolved to take advantage of this great variety of subtly changing conditions,” Asner explained. “And we can peer into the future and see how quickly human activity is changing the kaleidoscope of diversity that has been uniquely shaped over millions of years.”

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