Tropical Forests Leak Nitrogen Back Into Atmosphere, Say Scientists

The bacteria, referred to as "denitrifiers," exist in forest soil, where they live by converting the nitrates fed upon by tree roots back into nitrogen gas, which is lost to the atmosphere. The researchers who recently discovered this behavior say the findings are important for our understanding of how tropical forests fit into the earth's climate system.

"Tropical forests play a major role in regulating the planet's climate, and these findings indicate that we are still working on our basic understanding of the nitrogen cycle," said Lars Hedin, a researcher on the team and professor of ecology and evolutionary biology at Princeton. "That a group of bacteria can have such a dramatic impact on forest nutrition debunks our previous theories about how nitrogen behaves in forests, and shows us that these microorganisms affect soil nutrients and forest growth."

The team, which also includes first author Benjamin Houlton, a student from Hedin's lab now doing postdoctoral work at Stanford, and Daniel Sigman, a Princeton professor of geosciences, will publish their findings in the May 22 issue of the journal, Proceedings of the National Academy of Sciences. Hedin is available for comment at (609) 558-9096.