Global nitrogen availability consistent for past 500 years, linked to carbon levels

[OKIsItJustMe]

http://www.k-state.edu/media/newsreleases/mar13/nitrogen32113.html

[font face=Serif][font size=5]Global nitrogen availability consistent for past 500 years, linked to carbon levels[/font]

Thursday, March 21, 2013

[font size=3]MANHATTAN -- 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.

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http://dx.doi.org/10.1038/nature11916

[dipsydoodle]

1. I thought the supply of all elements was fixed.

[immoderate]

2. The amount is fixed. The "supply" not so much.

Whether an element is accessible or usable may depend on it's energy state, or its level of entropy.

Consider that carbon is available, but not so readily as carbon dioxide. Considerable energy must be applied to make that carbon usable again.

--imm

[eppur_se_muova]

3. Most of the nitrogen on Earth is elemental nitrogen (N2) in the atmosphere ...

it is not regarded as "available" nitrogen because only a tiny number of organisms have the ability to convert N2 to nitrogen-containing compounds, where it would be available to other organisms as well.

To most higher organisms, nitrogen is used primarily as ammonia and its derivatives. Most such nitrogen enters the environment thanks to nitrogen-fixing bacteria in the root nodules of certain plants.

Nitrogen fixation is a process by which nitrogen (N2) in the atmosphere is converted into ammonia (NH3).[1] Atmospheric nitrogen or molecular nitrogen (N2) is relatively inert: it does not easily react with other chemicals to form new compounds. Fixation processes free up the nitrogen atoms from their diatomic form (N2) to be used in other ways.

Nitrogen fixation, natural and synthetic, is essential for all forms of life because nitrogen is required to biosynthesize basic building blocks of plants, animals and other life forms, e.g., nucleotides for DNA and RNA and amino acids for proteins. Therefore nitrogen fixation is essential for agriculture and the manufacture of fertilizer. It is also an important process in the manufacture of explosives (e.g. gunpowder, dynamite, TNT, etc.). Nitrogen fixation occurs naturally in the air by means of lightning.[2][3]

Nitrogen fixation also refers to other biological conversions of nitrogen, such as its conversion to nitrogen dioxide. Microorganisms that can fix nitrogen are prokaryotes (both bacteria and archaea, distributed throughout their respective kingdoms) called diazotrophs. Some higher plants, and some animals (termites), have formed associations (symbioses) with diazotrophs. Biological nitrogen fixation was discovered by the German agronomist Hermann Hellriegel and Dutch microbiologist Martinus Beijerinck.

http://en.wikipedia.org/wiki/Nitrogen_fixation