Researchers monitoring tree canopy in Amazon rainforest

Researchers monitor Amazon rainforest-canopy processes such as photosynthesis, plant-water fluxes, leaf characteristics and growth.

How long the Amazon rainforest will continue to act as an effective carbon sink recently was investigated by an international team of scientists. Phosphorus-deficient soils in the rainforest reduced projected carbon-dioxide uptake by an average 50 percent compared to estimates based on previous climate models that didn’t take into account phosphorus deficiency.

“Most predictions of the Amazon rainforest’s ability to resist climate change are based on models that have outdated assumptions,” said Jennifer Holm, a research scientist at the Lawrence Berkeley National Laboratory and a co-author of the study. “One of the assumptions is that a sufficient supply of nutrients such as phosphorus exists in soils to enable trees to take in additional carbon dioxide as global emissions increase. But the ecosystem is millions of years old, highly weathered and is depleted of phosphorus in many parts of the Amazon.”

Researchers monitored tree growth and leaf development above-ground. They also tracked root growth and activity within soils at a study site north of Manaus, Brazil, where ambient carbon-dioxide concentration is planned to be artificially elevated. That is expected to enable a realistic investigation of how future carbon-dioxide concentrations will affect the ecosystem.

“Improved models now take into account these complexities and could help paint a more realistic portrayal of how the Amazon will be impacted by climate change,” Holm said.

The new models also could help provide greater understanding of the ability of trees to remove greenhouse gases from the atmosphere. The study recently was published in “Nature Geoscience.” Visit www.nature.com and search for "Amazon forest response" more information.

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