A team of researchers led by a first-year UC Davis faculty member has resolved a longstanding paradox in the plant world, which should lead to far more accurate predictions of global climate change.

A paper describing the research, "A unifying framework for dinitrogen fixation in the terrestrial biosphere," was published online today by the journal Nature.

The paradox centers on puzzling aspects of the nitrogen cycle in temperate and tropical forests. Defying the usual laws of supply and demand, trees capable of extracting nitrogen directly from the atmosphere (a process called nitrogen fixation) often thrive where it is readily available in the soil, but not where it is in short supply.

Nitrogen is an essential nutrient for all life on Earth, and determines how much carbon dioxide plants (and entire ecosystems) can absorb from the atmosphere, said UC Davis assistant professor Benjamin Houlton, the paper's lead author. Because carbon dioxide is the principal greenhouse gas causing global warming, any process that changes the amount of nitrogen available for plant growth will affect global temperatures.

But any serious attempt to consider the impact of nitrogen on climate change has been limited by a lack of understanding of the global pattern of nitrogen fixation, Houlton said.

The researchers found the explanation lies in the key roles played by two other factors: temperature and the abundance of another element, phosphorus.

Houlton's co-authors are top international ecologist Peter Vitousek, the Clifford G. Morrison Professor in Population and Resource Studies at Stanford University; Christopher Field of the Carnegie Institution's Department of Global Ecology; and Yingping Wang of Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO).

The research was funded by the National Science Foundation, the U.S. Department of Energy, CSIRO, the Australian Greenhouse Office and the David and Lucile Packard Foundation.