Zhou and the international research team sought to better understand how regional differences in soil nitrogen levels resulting from pollution or natural soil variation could be affecting how soils release carbon dioxide and impact atmospheric carbon dioxide levels.
"The interactive effects of nitrogen and carbon dioxide on soil respiration, a measure of carbon dioxide released from decomposition in the soil, is particularly important for our future climate, but are not all well understood, due to the lack of long-term manipulative experiments of these two elements together," said Peter Reich, a Distinguished McKnight University Professor at the University of Minnesota.
In the study, published in the journal, Proceedings of the National Academy of Sciences of the United States of America, the researchers found that in the last four years of the experiment, elevated carbon dioxide levels stimulated soil respiration twice as much under low as under high nitrogen supply, which was not observed in earlier years.
"Our study highlights that low nitrogen supply gradually accelerates the amount of carbon dioxide released to the atmosphere through decomposition of soil detritus," said Sarah Hobbie, a Distinguished McKnight University Professor at the University of Minnesota.
"Considering the worldwide nitrogen limitation in natural environments, heightened release of CO2 back to the atmosphere from soil may be pervasive under those conditions of persistent nitrogen limitation."