"The availability of nitrogen is one of the key factors limiting vegetation growth around the world, but its release from plant litter can be very slow," said Mark Harmon, a professor of forest science at Oregon State University.

"For the first time, we studied this process at enough sites and over a long enough time period to really understand what's happening."

The results could help measure vegetation growth, carbon release and sequestration, as well as the potential impacts of climate change.

Researchers said they were surprised by the fact that the essential pattern of nitrogen release is nearly the same wherever it occurs, and depends mainly on the initial concentration of nitrogen present in the decaying plant material.

It has very little to do with location, soil types, microbes present, or other factors, the research found.

While the pace of the process is affected by climate -- temperature and precipitation -- the overall pattern, or "trajectory" of nitrogen release remains much the same regardless of the site, researchers found.

Plant growth is a main factor that affects the input or removal of carbon from the atmosphere -- an issue of growing importance during an era of global warming.

Plant decomposition releases more carbon each year than all of the fossil fuel combustion produced by humans, the researchers stressed in their study.

"If we hope to better predict carbon dynamics, climate change and other issues, we first must understand these basic ecological processes," Harmon said.

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