April 6 (UPI) -- Until now, scientists thought plants got all their nitrogen from the atmosphere, but new research suggests Earth's bedrock supplies as much as a quarter of the planet's nitrogen.
The discovery, detailed this week in the journal Science, could change researchers' understanding of the carbon cycle.
"Our study shows that nitrogen weathering is a globally significant source of nutrition to soils and ecosystems worldwide," Ben Houlton, director of the Muir Institute at the University of California, Davis, said in a news release. "This runs counter [to] the centuries-long paradigm that has laid the foundation for the environmental sciences. We think that this nitrogen may allow forests and grasslands to sequester more fossil fuel CO2 emissions than previously thought."
Nitrogen is essential to the carbon sequestration process, but until now, scientists thought ecosystems were limited to the small amount of nitrogen plants and soil pull from the atmosphere.
In order for nitrogen to leach out of bedrock and into the ecosystem, weathering must occur. Tectonic activity could free up nitrogen, researchers suggest, as could chemical weathering, which occurs when rainwater reacts with a rock's minerals.
Mountains like the Himalayas and Andes are likely home to large amounts of nitrogen weathering, as are grasslands, tundra, deserts and woodlands.
Places with high levels of nitrogen weathering may warrant extra environmental protections.
"Geology might have a huge control over which systems can take up carbon dioxide and which ones don't," Houlton said. "When thinking about carbon sequestration, the geology of the planet can help guide our decisions about what we're conserving."
Scientists knew there was a missing nitrogen input somewhere because the atmosphere couldn't account for the levels researchers were measuring in soils. But scientists couldn't find it -- until now.
"We show that the paradox of nitrogen is written in stone," said researcher Scott Morford, a UC Davis grad student at the time of the study. "There's enough nitrogen in the rocks, and it breaks down fast enough to explain the cases where there has been this mysterious gap."