Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Clean forests prompt pollution rethink

24.01.2002


Nitrogen in unpolluted streams is more organic.
© Nature


Agriculture has added to the natural nitrogen cycle.
© Photodisc


South American streams call current nitrogen-cycle theory into question.

Pollution may have altered northern hemisphere forests dramatically. The surprise finding that clean forests use nitrogen differently to polluted ones emphasizes the effect that humans have on the planet’s nitrogen cycle1. It may even prompt a rethink of the way that this cycle works.

Humans have added vast amounts of nitrogen to the earth’s ecosystems. The element fertilizes plants. To understand what affect this has had already, and how the planet might fare in the future, we need to know how forests used nitrogen before this artificial influx began.



So Steven Perakis and Lars Hedin, ecologists at Cornell University, Ithaca, New York, searched the globe for an environment with as little nitrogen pollution as possible. They settled on 100 streams in temperate forests in Chile and Argentina, far from industry.

They found that more than three-quarters of the nitrogen in these streams is organic (combined with carbon). Nitrogen from pollution is overwhelmingly inorganic - chemically bound to oxygen, hydrogen or metals.

Over 70% of the nitrogen in woodland rivers in Europe and North America is in the form of inorganic nitrate. But in the 100 South American streams, nitrate was the least abundant form of the element, at only 5%.

So it looks as if northern nitrate is a legacy of human activity. "People have had an even greater effect than we thought," says Perakis.

"It’s an amazingly powerful message," says ecosystems researcher Knute Nadelhoffer of the Marine Biological Laboratory at Woods Hole, Massachusetts. "It changes the way we think about the nitrogen baseline in pristine environments."

It’s a good reminder of how much pollution has altered northern ecosystems, comments Bridget Emmett, who studies nitrogen pollution at the Centre for Ecology and Hydrology in Bangor, Wales. "Whether the baseline in Chile is the same as the baseline would have been in northern systems is debatable," she cautions.

Cycle path

Nitrogen makes up about 80% of the air, but only a few bacteria can turn the gas into a form that plants can use.

Over the past century, nitrate fertilizers and nitric oxides emitted from the burning of fossil fuels have roughly doubled the amount of nitrogen available to the biosphere. And farmers are still adding nitrogen to the land, particularly in developing countries.

Plants and microbes have taken up most of the slack. But large quantities of nitrogen are still washed into rivers and the sea, either because the element is not used or because it is released through death or leaf fall.

In many freshwater, estuarine and coastal environments, such as the Gulf of Mexico, this fertilization has changed the range of plants and animals that live there. Nitrogen-loving species swamp others more suited to poorer conditions (the same thing happens in a fertilized lawn). The extra nitrogen can also feed suffocating blooms of algae.

We need to think about nitrogen emissions in the same way that we consider the influence of sulphur on acid rain, or carbon on the climate, says Nadelhoffer.

"We have perturbed the nitrogen cycle much more than the carbon cycle," he says. "Most forests are still retaining more nitrogen than they release. The question is how much they can retain and for how long."

The theory that seeks to answer these questions currently hinges on nitrate. The new finding might force a rethink. "It seems that our models might be biased," Perakis concludes.

References

  1. Perakis, S. S. & Hedin, L. O. Nitrogen loss from unpolluted South American forests mainly via dissolved organic compounds. Nature, 415, 416 - 419, (2002).


JOHN WHITFIELD | © Nature News Service
Further information:
http://www.nature.com/nsu/020121/020121-10.html

More articles from Ecology, The Environment and Conservation:

nachricht Litter is present throughout the world’s oceans: 1,220 species affected
27.03.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

nachricht International network connects experimental research in European waters
21.03.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Researchers shoot for success with simulations of laser pulse-material interactions

29.03.2017 | Materials Sciences

Igniting a solar flare in the corona with lower-atmosphere kindling

29.03.2017 | Physics and Astronomy

As sea level rises, much of Honolulu and Waikiki vulnerable to groundwater inundation

29.03.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>