Study finds availability of nitrogen to plants is declining as climate warms

Study finds availability of nitrogen to plants is declining as climate warms
Study finds availability of nitrogen to plants is declining as climate warms. Credit: University of Maryland Center for Environmental Science/Andrew Elmore

Researchers have found that global changes, including warming temperatures and increased levels of carbon dioxide in the atmosphere, are causing a decrease in the availability of a key nutrient for terrestrial plants. This could affect the ability of forests to absorb carbon dioxide from the atmosphere and reduce the amount of nutrients available for the creatures that eat them.

"Even if is stabilized at low enough levels to mitigate the most serious impacts of climate change, many terrestrial ecosystems will increasingly display signs of too little as opposed to too much," said study co-author Andrew Elmore of the University of Maryland Center for Environmental Science. "Preventing these declines in nitrogen availability further emphasizes the need to reduce human-caused carbon dioxide emissions."

Although the focus on nitrogen availability is often on developed, coastal regions, such as the Chesapeake Bay, that struggle with eutrophication—runoff of from fertilized farms and lawns that feeds algae blooms and leads to the reduction in oxygen in the waters—the story is very different on less developed land, such as the mountains of western Maryland.

"This idea that the world is awash in nitrogen and that nitrogen pollution is causing all these environmental effects has been the focus of conversations in the scientific literature and popular press for decades," said Elmore. "What we're finding is that it has hidden this long-term trend in unamended systems that is caused by rising carbon dioxide and longer growing seasons."

Researchers studied a database of leaf chemistry of hundreds of species that had been collected from around the world from 1980-2017 and found a global trend in decreasing nitrogen availability. They found that most terrestrial ecosystems, such as forests and land that has not been treated with fertilizers, are becoming more oligotrophic, meaning too little nutrients are available.

"If nitrogen is less available it has the potential to decrease the productivity of the forest. We call that oligotrophication," said Elmore. "In the forested watershed, it's not a word used a lot for terrestrial systems, but it indicates the direction things are going."

Nitrogen is essential for the growth and development of plants. On the forest floor, microbes break down organic matter such as down fallen leaves and release nitrogen to the soil. The tree retrieves that nitrogen to build proteins and grow. However, as trees have access to more carbon, more and more microbes are becoming nitrogen limited and releasing less nutrients to the trees.

"This new study adds to a growing body of knowledge that forests will not be able to sequester as much carbon from the atmospheric as many models predict because forest growth is limited by nitrogen," said Eric Davidson, director of the University of Maryland Center for Environmental Science's Appalachian Laboratory. "These new insights using novel isotopic analyses provide a new line of evidence that decreases in carbon emissions are urgently needed."

In the U.S. and Europe, regulations on coal-fired power plants have reduced the amount of as a consequence of clean air regulations trying to combat acid rain. At the same time, increasing levels in the atmosphere and longer growing seasons are increasing the nitrogen demand for plants to grow.

"There are now multiple lines of evidence that support the oligotrophication hypothesis," said study co-author Joseph Craine, an ecologist with Jonah Ventures. "Beyond declines in leaf chemistry, we are seeing grazing cattle become more protein limited, pollen protein concentrations decline, and reductions of nitrogen in many streams. These dots are starting to connect into a comprehensive picture of too much flowing through ecosystems."

The paper, "Isotopic evidence for oligotrophication of " was published in Nature Ecology & Evolution by Andrew Elmore and David Nelson of the University of Maryland Center for Environmental Science and Joseph Craine of Jonah Ventures.


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More information: Joseph M. Craine et al. Isotopic evidence for oligotrophication of terrestrial ecosystems, Nature Ecology & Evolution (2018). DOI: 10.1038/s41559-018-0694-0
Journal information: Nature Ecology & Evolution

Citation: Study finds availability of nitrogen to plants is declining as climate warms (2018, October 22) retrieved 19 July 2019 from https://phys.org/news/2018-10-availability-nitrogen-declining-climate.html
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Oct 23, 2018
What a difference 2 years-and-change makes to climate 'science'.

Earth Is Getting Greener
Story by Samson K. Reiny Released on April 26, 2016 --NASA

"Scientists have found that a quarter to half of Earth's vegetated lands has shown significant greening over the last 35 years largely due to rising levels of atmospheric carbon dioxide. The findings are based on computer models and data collected by NASA and NOAA satellites. The greening represents an increase in leaves on plants and trees equivalent in area to two times the continental United States. ... "
_______
(ad hominem apologetics 'rebuttal' incoming, in 3...2...1)

Oct 23, 2018
What a difference 2 years-and-change makes to climate 'science'.

Earth Is Getting Greener
Story by Samson K. Reiny Released on April 26, 2016 --NASA
If you read the two articles, you can see that they do not contradict each other. This article discusses the effect that the greening of the planet due to CO2 uptake by plants is having on the available N2 needed by plants to grow.

It is unfortunate that you don't actually read the papers - or, based on your comment, even the articles in question.

Oct 23, 2018

It is unfortunate that you don't actually read the papers - or, based on your comment, even the articles in question.
You meant to write *didn't... read the papers?

"ad hominem apologetics 'rebuttal' incoming, in 3...2...1"
There, what did I tell you?
____________

Now, the abstract for the paper you are (presumably) referring to concludes as follows:
"These declines will limit future terrestrial carbon uptake and increase nutritional stress for herbivores."

It is carbon that is taken up, and incorporated into cellulose, lignin, and such, that is expressed as increased biomass (wood, foliage, etc.) for which chlorophyll (the 'green' in green) is a reliable proxy.


Oct 23, 2018
You meant to write *didn't... read the papers?
No, I meant to write what I wrote.

"ad hominem apologetics 'rebuttal' incoming, in 3...2...1"
There, what did I tell you?
It is not argumentum ad hominem to point out you do not seem to have read the papers, or the articles, you are commenting on.

____________

Now, the abstract for the paper you are (presumably) referring to concludes as follows:
"These declines will limit future terrestrial carbon uptake and increase nutritional stress for herbivores."

It is carbon that is taken up, and incorporated into cellulose, lignin, and such, that is expressed as increased biomass (wood, foliage, etc.) for which chlorophyll (the 'green' in green) is a reliable proxy.
Are you suggesting that nitrogen is not also taken up? The paper concludes that less carbon will be absorbed (ie "taken up") because of a dearth of nitrogen, an effect of higher CO2 concentrations in the air. I'm not sure what your point is.

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