新澳门六合彩内幕信息

New Source of Global Nitrogen Discovered

Rocks Could Hold Key to Carbon Storage and Improved Global Climate Projections

News
Stone forest national park in Yunnan province
Weathering rocks, like the limestone at Stone Forest National Park in China, hold significant levels of nitrogen. (Getty)

Quick Summary

  • Not all nitrogen comes from the atmosphere
  • Up to a quarter of nitrogen on Earth comes from rocks
  • Discovery could greatly improve climate change projections and focus carbon sequestration efforts

For centuries, the prevailing science has indicated that all of the nitrogen on Earth available to plants comes from the atmosphere. But a study from the University of California, Davis, indicates that more than a quarter comes from Earth鈥檚 bedrock.

, to be published April 6 in the journal Science, found that up to 26 percent of the nitrogen in natural ecosystems is sourced from rocks, with the remaining fraction from the atmosphere.

Before this study, the input of this nitrogen to the global land system was unknown. The discovery could greatly improve projections, which rely on understanding the carbon cycle. This newly identified source of nitrogen could also feed the carbon cycle on land, allowing ecosystems to pull more emissions out of the atmosphere, the authors said.

鈥淥ur study shows that nitrogen weathering is a globally significant source of nutrition to soils and ecosystems worldwide,鈥 said co-lead author Ben Houlton, a professor in the 新澳门六合彩内幕信息 Davis Department of Land, Air and Water Resources and director of the 新澳门六合彩内幕信息 Davis Muir Institute. 鈥淭his runs counter 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.鈥

Weathering is key  

Ecosystems need nitrogen and other nutrients to absorb carbon dioxide pollution, and there is a limited amount of it available from plants and soils. If a large amount of nitrogen comes from rocks, it helps explain how natural ecosystems like boreal forests are capable of taking up high levels of carbon dioxide. 

Boreal forest, Canada
A boreal coniferous forest lies to the north of Canada's Fundy National Park in New Brunswick. (Getty)  

But not just any rock can leach nitrogen. Rock nitrogen availability is determined by weathering, which can be physical, such as through tectonic movement, or chemical, such as when minerals react with rainwater.

That鈥檚 primarily why rock nitrogen weathering varies across regions and landscapes. The study said that large areas of Africa are devoid of nitrogen-rich bedrock while northern latitudes have some of the highest levels of rock nitrogen weathering. Mountainous regions like the Himalayas and Andes are estimated to be significant sources of rock nitrogen weathering, similar to those regions鈥 importance to global weathering rates and climate. Grasslands, tundra, deserts and woodlands also experience sizable rates of rock nitrogen weathering.

Geology and carbon sequestration

Mapping nutrient profiles in rocks to their potential for carbon uptake could help drive conservation considerations. Areas with higher levels of rock nitrogen weathering may be able to sequester more carbon.

鈥淕eology might have a huge control over which systems can take up carbon dioxide and which ones don鈥檛,鈥 Houlton said. 鈥淲hen thinking about carbon sequestration, the geology of the planet can help guide our decisions about what we鈥檙e conserving.鈥

Mysterious gap

The work also elucidates the 鈥渃ase of the missing nitrogen.鈥 For decades, scientists have recognized that more nitrogen accumulates in soils and plants than can be explained by the atmosphere alone, but they could not pinpoint what was missing.

scientist samples soil and rocks
Co-leading author Scott Morford samples soils and bedrock to measure the geologic nitrogen input to forests. (Courtesy Scott L. Morford/新澳门六合彩内幕信息 Davis)

鈥淲e show that the paradox of nitrogen is written in stone,鈥 said co-leading author Scott Morford, a 新澳门六合彩内幕信息 Davis graduate student at the time of the study. 鈥淭here鈥檚 enough nitrogen in the rocks, and it breaks down fast enough to explain the cases where there has been this mysterious gap.鈥

In previous work, the research team analyzed samples of ancient rock collected from the Klamath Mountains of Northern California to find that the rocks and surrounding trees there held large amounts of nitrogen. With the current study, the authors built on that work, analyzing the planet鈥檚 nitrogen balance, geochemical proxies and building a spatial nitrogen weathering model to assess rock nitrogen availability on a global scale.

The researchers say the work does not hold immediate implications for farmers and gardeners, who greatly rely on nitrogen in natural and synthetic forms to grow food. Past work has indicated that some background nitrate in groundwater can be traced back to rock sources, but further research is needed to better understand how much.

Rewriting textbooks

鈥淭hese results are going to require rewriting the textbooks,鈥 said Kendra McLauchlan, program director in the National Science Foundation鈥檚 Division of Environmental Biology, which co-funded the research. 鈥淲hile there were hints that plants could use rock-derived nitrogen, this discovery shatters the paradigm that the ultimate source of available nitrogen is the atmosphere. Nitrogen is both the most important limiting nutrient on Earth and a dangerous pollutant, so it is important to understand the natural controls on its supply and demand. Humanity currently depends on atmospheric nitrogen to produce enough fertilizer to maintain world food supply. A discovery of this magnitude will open up a new era of research on this essential nutrient.鈥

新澳门六合彩内幕信息 Davis Professor Randy Dahlgren in the Department of Land, Air and Water Resources co-authored the study.

The study was funded by the National Science Foundation鈥檚 Division of Earth Sciences and its Division of Environmental Biology, as well as the Andrew W. Mellon Foundation.

Media Resources

Kat Kerlin, 新澳门六合彩内幕信息 Davis News and Media Relations, 530-750-9195, kekerlin@ucdavis.edu

Primary Category

Secondary Categories

Science & Technology

Tags