A Kansas State University research team has found that despite humans increasing nitrogen production through industrialization, nitrogen availability in many ecosystems has remained steady for the past 500 years. Their work appears in the journal Nature.
"People have been really interested in nitrogen in current times because it's a major pollutant," said Kendra McLauchlan, assistant professor of geography and director of the university's Paleoenvironmental Laboratory. "Humans are producing a lot more nitrogen than in the past for use as crop fertilizer, and there is concern because excess levels can cause damage. The mystery, though, is whether the biosphere is able to soak up this extra nitrogen and what that means for the future."
Nitrogen is a key component of the ecosystem and the largest regulator of plant growth. It determines how much food, fuel and fiber the land can produce. It also determines how much carbon dioxide plants remove from the atmosphere, and it interacts with several components of the climate system. Excessive amounts of nitrogen in ecosystems contribute to global warming and impairment of downstream ecosystems.
McLauchlan worked with Joseph Craine, research assistant professor in biology; Joseph Williams, postdoctoral research associate; and Elizabeth Jeffers, postdoctoral research associate at the University of Oxford. The team published their findings, "Changes in global nitrogen cycling during the Holocene epoch," in the current issue of Nature.
Changes in nitrogen availability
In the study the team also looked at how nitrogen availability changed thousands of years ago.
Roughly 15,000 years ago, the Earth began to warm, melting many glaciers and ice sheets that covered the landscape. Researchers found that Earth experienced an 8,000-yearlong decline in nitrogen availability as temperatures rose and carbon and nitrogen became locked up in soils. According to researchers, how the nitrogen cycle responded to these ancient global changes in carbon dioxide could be a glimpse into the future.
"What happened in the past might be a dry run for Earth's future," Craine said. "By looking at what happened millennia ago, we can see what controlled and prevented changes in nitrogen availability. This helps us understand and predict how things will change in the future."