UC Davis researcher leads climate-change discovery

June 18, 2008

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 will be published online Wednesday (June 18) by the journal Nature.

The paradox centers on puzzling aspects of the nitrogen cycle in temperate and tropical forests. Defying 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 essential to all life on Earth, and determines how much carbon dioxide ecosystems can absorb from the atmosphere, said UC Davis assistant professor Benjamin Houlton, who tackled the problem with colleagues including top international ecologist Peter Vitousek, the Clifford G. Morrison Professor in Population and Resource Studies at Stanford University.

"You would expect that nitrogen-fixing species would have a competitive advantage in ecosystems where nitrogen is in low supply, but not where nitrogen is abundant, because fixation is energetically very costly to an organism," says Houlton, lead author of the paper.

"And in fact that's the way ecologists have found it works in the open ocean and in lakes. But in mature temperate forests, where the soils have limited amounts of nitrogen, nitrogen-fixing tree species are scarce. And in the tropical lowland forests, which are nitrogen-rich, nitrogen-fixing trees often are abundant.

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

Temperature, they determined, affects the activity of a nitrogen-fixing enzyme called nitrogenase. In cooler, temperate climates, more of the enzyme is needed to fix a given amount of nitrogen. This higher cost would offset the benefit of nitrogen fixation in temperate forests, despite low-nitrogen soils.

In tropical forests, it's the link between nitrogen and phosphorus that explains the abundance of nitrogen-fixing species.

"Many tropical forest soils are severely depleted in phosphorus, even where nitrogen is relatively abundant," said Houlton. "The extra nitrogen added to the soil by nitrogen-fixers helps mobilize phosphorus, making it easier for roots to absorb. That stimulates the growth of these plant species and puts them at a competitive advantage, despite the energetic cost of nitrogen fixation."

Source: University of California - Davis

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3.4 / 5 (9) Jun 18, 2008
It's a pretty far stretch to include 'climate-change' in the title...
3 / 5 (11) Jun 18, 2008
How can you say in the heading that this work led to a climate-change discovery when nowhere in the article is there any discussion of a link between this work and climate change. Just another example of the media hyping unproven Gore-bull warming.
2.7 / 5 (7) Jun 19, 2008
you don't have to believe "unproven Gore-bull warming", but the planet is warming, the climate is changing and it's because of the fossil fuels we've been pumping into the atmosphere with wild abandon for the last 100 years. You want scientific facts?, go to this site; http://www.ipcc.ch/
3 / 5 (4) Jun 19, 2008
Well Billybaroo, if you had bothered to check out the Nature article referenced,
you would have found in the opening paragraph:
"We propose that an analysis that couples biogeochemical cycling and biophysical mechanisms is sufficient to explain the principal geographical patterns of symbiotic N2 fixation on land, thus providing a basis for predicting the response of nutrient-limited ecosystems to climate change and increasing atmospheric CO2."

But that would have been too much to ask of you.
3.9 / 5 (7) Jun 19, 2008
The IPCC which was linked to is not a scientific organization but a cluster of UN clerics who manipulate, misrepresent and outright lie about the scientific data for political ends. There are scientists who have asked them to stop using their names to promote their cause but have been told to pound sand. The IPCC has no interest in science, only in forming the opinions of the public.
3.4 / 5 (5) Jun 19, 2008
Take your stupid global warming and shove it. Nobody wants to be a tool of some make-up wearing old bitty politician like Al Gore, except baby boomer apologetics who can't get anything right anyway. Anyone with half a brain can see the models are extremely over simplified.
Scientific objectivity is vanishing. Every observation somehow becomes "proof" of anthropogenic global warming.
3 / 5 (6) Jun 19, 2008
We should wait until they can predict next weeks weather, then it's maybe time to ask how the climate will be in 10 years.
2.3 / 5 (3) Jun 19, 2008
Lets not even go into the realm of fluid flow and turbulent mixing. Computer models of weather systems might be the greatest contributor to global warming, more so than the hot air coming out of politicians and celebrities alike. Now give the "scientists" something that's intractable and watch them sit and spin lies about nonsense to get more government money to do nothing.
1 / 5 (1) Jul 03, 2008
Too bad youi lot of anti-GW's can't figure out the scientific process, eg. READ SOME SCIENTIFIC LITERATURE OCCASIONALLY!

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