Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ozone, nitrogen change the way rising CO2 affects Earth's water

14.07.2009
Through a recent modeling experiment, a team of NASA-funded researchers have found that future concentrations of carbon dioxide and ozone in the atmosphere and of nitrogen in the soil are likely to have an important but overlooked effect on the cycling of water from sky to land to waterways.

The researchers concluded that models of climate change may be underestimating how much water is likely to run off the land and back into the sea as atmospheric chemistry changes. Runoff may be as much as 17 percent higher in forests of the eastern United States when models account for changes in soil nitrogen levels and atmospheric ozone exposure.

"Failure to consider the effects of nitrogen limitation and ozone on photosynthesis can lead us to underestimate regional runoff," said Benjamin Felzer, an ecosystem modeler at Lehigh University in Bethlehem, Pa. "More runoff could mean more contamination and flooding of our waterways. It could also mean fewer droughts than predicted for some areas and more water available for human consumption and farming. Either way, water resource managers need more accurate runoff estimates to plan better for the changes."

Felzer and colleagues from the Massachusetts Institute of Technology (MIT) in Cambridge and the Marine Biology Laboratory in Woods Hole, Mass., published their findings recently in the Journal of Geophysical Research – Biogeosciences.

Plants play a significant role in Earth's water cycle, regulating the amount of water cycling through land ecosystems and how long it stays there. Plants draw in water from the atmosphere and soil, and they discharge it naturally through transpiration, the tail end of photosynthesis when water vapor and oxygen are released into the air.

The amount of water that plants give up depends on how much carbon dioxide is present in the atmosphere. Studies have shown that despite a global drop in rainfall over land in the past 50 years, runoff has actually increased.

Other studies have shown that increasing CO2 is changing how plant "pores," or stomata, discharge water. With elevated CO2 levels, leaf pores contract and sometimes close to conserve internal water reserves. This "stomatal conductance" response increases water use efficiency and reduces the rate of transpiration.

Plants that release less water also take less of it from the environment. With less water being taken up by plants, more water is available for groundwater or runs off the land surface into lakes, streams, and rivers. Along the way, it accumulates excess nutrients and pollutants before emptying into waterways, where it affects the health of fish, algae, and shellfish and contaminate drinking water and beaches. Excess runoff can also contribute to flooding.

Sometimes rising CO2 has the opposite effect, Felzer noted, promoting vegetation growth by increasing the rate of photosynthesis. More plant growth can lead to a thicker canopy of leaves with increased transpiration and less runoff. However, this effect has been shown to be smaller than the effect of reduced stomatal conductance.

Aware of these cycles, Felzer and colleagues used theoretical models to project various future scenarios for the amount of carbon dioxide in the atmosphere and what it would mean to the changing water cycle in forests east of the Mississippi River. They found that runoff would increase anywhere from 3 to 6 percent depending on location and the amount of the increase in CO2.

Felzer and colleagues also examined the role of two other variables -- atmospheric ozone and soil-based nitrogen -- in the changing water cycle. Excess ground-level ozone harms the cells responsible for photosynthesis. Reductions in photosynthesis leads to less transpiration and cycling of water through leaves and more water added to runoff.

In most boreal and temperate forests, the rate of photosynthesis is also limited by the availability of nutrients such as nitrogen in the soil. The less nitrogen in the soil, the slower their rate of photosynthesis and transpiration.

"The increase in runoff is even larger when nitrogen is limited and environments are exposed to high ozone levels," said Felzer. In fact, the team found an additional 7 to 10 percent rise in runoff when nitrogen was limited and ozone exposure increased.

"Though this study focuses on Eastern U.S. forests, we know nitrogen and ozone effects are also important in South America and Europe. One region has seen a net increase and the other a net runoff reduction," said co-author Adam Schlosser of the Center for Global Change Science at MIT. "Our environment and quality of life depend on less uncertainty on this front."

Written by:
Gretchen Cook-Anderson and
Michael Carlowicz

Sarah DeWitt | EurekAlert!
Further information:
http://www.nasa.gov
http://www.nasa.gov/topics/earth/features/nitrogen_ozonestress.html

More articles from Earth Sciences:

nachricht Colorado River's connection with the ocean was a punctuated affair
16.11.2017 | University of Oregon

nachricht Researchers create largest, longest multiphysics earthquake simulation to date
14.11.2017 | Gauss Centre for Supercomputing

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>