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Brian Enquist Amazon trees

Photo: Brian Enquist

Plant ecologist Brian Enquist in the Amazonian rainforest.

Scientists from the University of Arizona are part of an international research team looking at how climate change is affecting trees in the Amazon.

It's estimated that 20 percent of the world’s oxygen is produced by the Amazon rainforest, which is why it’s described as “the lungs of the earth.”

Brian Enquist, a UA plant ecologist and professor, is a principal investigator on the research project, funded in part by the National Science Foundation.

Over summer, he was in Peru collecting samples.

“This project is focused on an elevation gradient that ranges from all the way down from the Amazon basin, so the lowlands of tropical forest, all the way up to (the) tree line in the Andes," Enquist said.

His research is focused on studying the branching architecture of trees.

Enquist said that following a tree's branching pattern, going from one branch to another, can provide information to researchers, such as the flow of water within the plant or how much carbon dioxide it’s absorbing.

He said as an ecologist, what he is trying to do is link the measurements taken from a branch of a tree and use it to try and understand how a tree operates as a whole.

"...and then be able to say something about how changes in climate will then influence the functioning of that tree but then also how various ecosystems then function," Enquist said.

Lisa Patrick Bentley, a post-doctorate researcher with Oxford University and a former UA researcher, has been in and out of the Amazon since April.

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Photo: Connor O'Toole

Assistants Milenka Ximena and Jimmy Ronal with Lisa Patrick Bentley at a field site in Peru.

“What we are actually doing is we are cutting branches down from trees using a tree climber," Patrick Bentley said.

Once the branch hits the ground, researchers measure the length and width of each part of the branch.

"Using that information, we can predict how much carbon we expect the entire tree to be storing or releasing into the atmosphere," Patrick Bentley said.

Patrick Bentley said she and her fellow researchers are measuring other aspects of trees in addition to their branching architecture.

“We measure specific leaf area of the leaves, so that’s basically the relationship between the leaf fresh weight and the leaf dry weight and leaf mass," she explained.

The researchers also are measuring the pigment and chemical composition of leaves and the photosynthesis rate of the leaves.

"We also look at the whole entire canopy environment of a tree so we measure the light levels at different heights throughout the canopy,” she said.

The list of measurements the researchers take goes on.

“It’s actually the branching geometry that enables us to connect each of these different measurements, and enables us to connect our leaf level physiological measurements with the functioning of entire trees with...how these tropical forests and these different environments...function," Enquist said.

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Photo: Connor O'Toole

Researcher taking a leaf measurement.

He said global climate change models predict the Amazon will experience changes in temperature and precipitation.

“What we're really unsure of is how the role of changing precipitation, especially across the Amazon and across tropical forests..., influence their functioning," Enquist said. "...studying tropical forests along an elevation gradient, that then provides changes in both temperature and precipitation, enables us to began to assess the functioning of tropical forests.

The research team collected samples from 10 sites in Peru’s 2.5 million-acre Manú National Park.

The team wrapped-up the field portion of it’s research this week and will now process samples and compile data, Patrick Bentley said.

Rainforest audio provided by Topher Bentley