Nitrogen-Fixing Trees Help Tropical Forests Grow Faster and Store More Carbon


Planting fixers could benefit reforestation and climate mitigation plans.

Tropical forests are allies in the fight against climate change. Growing trees absorb carbon emissions and store them as woody biomass. As a result, reforestation of land once cleared for logging, mining, and agriculture is seen as a powerful tool for locking up large amounts of carbon emissions throughout the South American tropics.

But new research published in Nature Communications shows that the ability of tropical forests to lock up carbon depends upon a group of trees that possess a unique talent - the ability to fix nitrogen from the atmosphere.

The study modeled how the mix of tree species growing in a tropical forest following a disturbance, such as clearcutting, can affect the forest's ability to sequester carbon. The team found that the presence of trees that fix nitrogen could double the amount of carbon a forest stores in its first 30 years of regrowth. At maturity, forests with nitrogen fixation took up 10% more carbon than forests without.

Sarah Batterman, a Research Fellow at Cary Institute of Ecosystem Studies and coauthor on the paper, explains, "We want to use this work to guide tropical reforestation to optimize carbon uptake and resiliency. This requires understanding what mix of trees is needed to maximize long-term carbon storage while withstanding future climatic conditions. Our findings suggest that nitrogen-fixing trees are a key ingredient in the reforestation recipe."

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