Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Forest canopies help determine natural fertilization rates

30.05.2008
Scientists clarify controls on boreal nitrogen resource that dictates long-term forest productivity

In this week’s issue of Science, a US and Swedish research team report on a newly identified factor that controls the natural input of new nitrogen into boreal forest ecosystems.

Nitrogen is the primary nutrient that dictates productivity (and thus carbon consumption) in boreal forests. In pristine boreal ecosystems, most new nitrogen enters the forest through cyanobacteria living on the shoots of feather mosses, which grows in dense cushions on the forest floor. These bacteria convert nitrogen from the atmosphere to a form that can be used by other living organisms, a process referred to as “nitrogen-fixation.” The researchers showed that this natural fertilization process appears to be partially controlled by trees and shrubs that sit above the feather mosses.

In the summer of 2006, the researchers placed small tubes, called resin lysimeters, in the moss layer to catch nitrogen deposited on the feather moss carpets from the above canopy and then monitored nitrogen fixation rates in the mosses. The studies revealed that when high levels of nitrogen were deposited on the moss cushion from above, a condition typical of young forests, nitrogen fixation was extremely low. In older, low-productivity forests, very little nitrogen was deposited on the moss cushion, resulting in extremely high nitrogen fixation rates.

Nitrogen fixation is an energy demanding process. Thus, when mosses are exposed to high concentrations of bioavailable nitrogen, the cyanobacteria will consume this resident nitrogen rather than expending energy on fixing new nitrogen. Thus the nitrogen content of canopy throughfall acts as a regulator of newly fixed nitrogen into these boreal forests. For this same reason, elevated nitrogen deposition from pollution likely reduces moss nitrogen fixation rates. The moss would initially buffer the forest against the effect of nitrogen added as pollution or fertilizer; however, chronic elevated nitrogen inputs would ultimately eliminate this natural source of forest fertility.

The feather moss-cyanobacterial association provides a unique model system in which to study nitrogen feedback mechanisms. The cyanobacteria reside on the leaves, thus the nitrogen status of the canopy throughfall directly influences nitrogen fixation in the feather mosses. This direct expression of a nutrient feedback mechanism could not be detected in other nitrogen fixing plant species, such as legumes, that house their nitrogen fixing bacteria below ground and where soils and decomposing litter intercept and modify the nitrogen from throughfall before it reaches the bacteria.

These findings are important from a global standpoint, because feather mosses (and associated cyanobacteria) are the primary source of biologically fixed nitrogen in the boreal forest biome. The dominating feathermoss Pleurozium schreberi is also found in arctic and temperate biomes and thus may be the widest distributed individual nitrogen-fixing plant species on Earth. Understanding feed back mechanisms among dominating organisms that regulate fundamental ecosystem processes are integral to our ability to predict long term outcomes of global carbon dynamics.

Sven-Olov Bylund | alfa
Further information:
http://www.sciencemag.org
http://www.slu.se

More articles from Ecology, The Environment and Conservation:

nachricht Preservation of floodplains is flood protection
27.09.2017 | Technische Universität München

nachricht Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen

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: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

Im Focus: New nanomaterial can extract hydrogen fuel from seawater

Hybrid material converts more sunlight and can weather seawater's harsh conditions

It's possible to produce hydrogen to power fuel cells by extracting the gas from seawater, but the electricity required to do it makes the process costly. UCF...

Im Focus: Small collisions make big impact on Mercury's thin atmosphere

Mercury, our smallest planetary neighbor, has very little to call an atmosphere, but it does have a strange weather pattern: morning micro-meteor showers.

Recent modeling along with previously published results from NASA's MESSENGER spacecraft -- short for Mercury Surface, Space Environment, Geochemistry and...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

Conference Week RRR2017 on Renewable Resources from Wet and Rewetted Peatlands

28.09.2017 | Event News

 
Latest News

A single photon reveals quantum entanglement of 16 million atoms

16.10.2017 | Physics and Astronomy

The melting ice makes the sea around Greenland less saline

16.10.2017 | Earth Sciences

On the generation of solar spicules and Alfvenic waves

16.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>